Sheet Metal Manufacturing : The Definitive Guide

Sheet Metal Manufacturing : The Definitive Guide

 

Sheet metal is one of the fundamental forms used in metalworking and it can be cut and bent into a variety of shapes and that’s no secret!

Additionally, there is countless everyday of objects that can be fabricated from sheet metal.

The thing is, manufacturing with sheet metal involves many limitations associated with the process itself.

In fact, it’s a culmination of several different limitations.

Some type of complex geometries or parts can’t be produced by sheet metal.

Then, the bottom line is? If you want to master metalworking, knowing how to manufacture things out of sheet metal is a must (in most cases, we presume).

In these guidelines, we are going to show everything you need to know how to fabricate sheet metal into essential parts and will cover some of the best practices and tips in sheet metal fabrication.

By understanding and realizing these guidelines, you will be able to ensure that your sheet metal parts can be optimized for its uses, with durability and manufacturability, and fit various end-user applications.

Let’s dive right into it!

 

Contents

 

 

 

Chapter 1:

Facts About Sheet Metal Fabrication

facts about sheet metal fabrication

What is Sheet Metal Fabrication process?

 

For those who don’t know yet about sheet metal fabrication, the idea might intrigue them the same thing we are amazed the first time we encountered this process. This process involves the used of several types of metal (obviously in sheet form) in building machines, machine parts, and other structures.

Establishments or businesses engaged in the manufacture and fabrication of sheet metals are commonly called fabrication shops (or fab shops). The process usually involves cutting and burning sheet metals. The fabrication typically applies on metal sheets under 6mm (0.236 inches) thick using equipment from conventional to highly specialized tools depending on the thickness and the durability of the material.

Both engineers, fabricators, and other professionals are one in declaring that sheet metal fabrication is one of the essential processes of obtaining ideally conceived machine parts. The process entails the creation of parts via bending or stamping, cutting, forming, and punching sheets of metal for various applications.

 

 

Basic Principles of Sheet Metal Fabrication

 

Engineers and designers working on a different blueprint for sheet metal parts mostly end up redesigning their work. This is because of their negligence in observing one of the basic principles of sheet metal fabrication: the keen consideration for tolerances and allowances.

Tolerances and allowances play a vital role in the successful bid of the fabrication. These two parameters must be exact when designing in CAD systems and when executing the actual work on the shop floor to avoid costly repairs or time-consuming redesign.

As a simple illustration, specifying hole sizes and their spacing in sheet metal fabrication, including the holes’ location and alignment is crucial (Figure below).

 

sheet metal tolerances

 

Most experts advised that hole diameters with less than the plate’s thickness will yield longer buffing in the holes, extreme burr, and a higher punch loading.

Additionally, the holes should be placed in-between each other with at least twice or more than the sheet’s thickness (2T). Distances between holes and bends should also be considered while designing the sheet in the computer.

The spaces between bored holes and bends must give way to the bend’s radius (H) (Figure below) and must have a distance far from the bend. Common practice suggests that distance between holes and bend is 1.5 times the thickness of the plate then add the bend’s radius (1.5T + H).

 sheet metal bend radius

 

 

 

 Keeping in mind about the tolerances and allowances during your design process will make everything clear and cost-effective. Another thing is, when you are used to designing the right dimensions in theory and learning to apply them in the shop floor, we are seeing a work with minimal error.

 

7 most common types of metals used in Sheet Metal Fabrication

 

As we have mentioned above, sheet metal fabrication involves plates as thick as 6mm (0.236 inches) or almost 1/2-inch thick. The thickness of these metal sheets is also called as “gauge”. While some shops could manufacture parts from sheets as thin as 0.5mm (0.0196 inches), these materials require specialized tools and highly skilled fabricators to perform the task.

The industry uses common metals which are currently the most in-demand materials to date.

To give you a preview of the most types of metal used in this process, we are listing here 7 of the major metal types, their applications and specifications, and the level of their cost (cheap, low or high):

 

1/ Hot-rolled steel plate

 

Usually having a thickness of 3mm (0.118 inches), the hot-rolled steel sheet is one of the cheapest materials for this process. This material is used mainly for flat parts and is treated with spraying or electroplating to convert as SPCC steel (a commercial type of cold-rolled steel).

 

2/Cold-rolled steel plate

 

This cheap type of sheet has a maximum thickness of 3.2mm (0.125 inches) and commonly used for painted parts or in electro-plating jobs. This material can be used commercially for forming purposes.

 

3/ Copperplate

 

Copper plates have a high cost which can be used for electricity conducting parts. Copper sheets are typically treated with chrome and/or nickel plating on the surface.

 

4/ Stainless steel plate

 

Stainless steel plates are one of the costliest materials to used in metal sheet fabrications. This material is usually utilized in food, beverage, pharmaceutical, and other food manufacturing processes.

 

5/ Aluminum sheet

 

Also one of the materials with high cost, aluminum plates are nonetheless one of the most used metals in manufacturing. This material is basically treated with chromium, silver or nickel. It can also be anodized (either chemical or conductive anodizing).

 

6/ Galvanized or Electro steel plate

 

Electro-galvanized steel sheets are commonly used in office furnishings and light fixtures. This high costing material is a type of steel that is electrolytically treated with zinc for protection against the elements making it more expensive compared to other metals.

 

7/ Aluminum extrusion

 

Aluminum extrusions are widely used in various types of electronic equipment. The amount of manufacturing parts using this material entails a high cost when used extensively as machine parts or structures.

There are several other metals that could be made into sheets for fabrication. Brass, titanium, tin,

 

 

Design guidelines for sheet metal fabrication

 

Today, doing metal sheet fabrication is not just for engineers, designers, and professional fabricators. With user-friendly tools and equipment available in the market (whether online or in physical stores) and DIY instructions (like this article), skilled persons having the ability to comprehend on different designs and the urge to learn new things for personal or business use, nothing is impossible.

However, for a more complicated task, we advise you to solicit professional help until you master the craft. For seasoned engineers and designers who want to have additional knowledge on this activity, this article will provide more useful information.

Here is the guiding principle of sheet metal fabrication that we have prepared. This guideline is for those who seek more knowledge or to add something better about sheet metal fabrications that they already knew.

The following chapters (Chapters 2 to 9) will deal with the various steps in making sheet metal fabrication easier and non-elaborate (although some require extraordinary skills). The last two chapters (Chapters 10 to 11) are dedicated to other important facts, such as other sheet metal operations not performed on presses, and how to estimate costing in sheet metal fabrication, respectively.

 

 

 

Chapter 2

Choose a CAD software for sheet metal design

 

design guidelines for sheet metal

Finding the right CAD software for sheet metal design

 

There are various tools and software that you can use in designing your intended sheet metal parts, but they may not be an all-in-one solution. We have surfed the web and asked engineers about the tools they are currently using in designing sheet metal parts.

What we found are some of the most useful and frequently used CAD (Computer-aided Design) software in sheet metal fabrication available today for the job. Moreover, before this chapter ends, we shall advise you of the current 5 leading brands of CAD software in the market that you can choose from.

 

Why is an ideal CAD software necessary for sheet metal fabrication?

 

There are several products that offer to programme regarding the design of sheet metal fabrication and for similar businesses. Engineers and expert fabricators had been using specialized drafting tools that can generate design data.

Sheet metal parts are mostly fabricated from a 2D model using operations, such as bending, punching, and welding, in contrast with real objects (in solid form).

As sheet metal design widely differs from solid modeling, design engineers using a software must integrate certain provisions in their design. This will enable the fabricators to convert the programmed model into sheet metal elements propitiously.

Moreover, using the right design and modeling tools, you can minimize or eliminate the occurrence of mistakes and quickly bring the design to the shop floor. Delays and design flaws normally lead to loss of time, material wastage, and loss of profitability which will hurt the business tremendously.

Deciding the ideal CAD software to use is literally a matter of “life and death” situation on a company struggling to cope with dwindling sales. Having modern tools like this can minimize engineering change orders (ECOs), the reworking of design errors, and other mistakes designers usually make.

For a more resilient business so far, it still needs a sustainable CAD system that will help in the company’s journey towards a better future.

Moreover, selecting the right CAD system compatible with your needs may lead to more successful business opportunities and increase sales.

 

5 things to consider in choosing the right CAD software

 

Here are 5 tips to take into account in choosing the right CAD software in designing sheet metal:

 

1/ Capability in designing sheet metal

 

Engineers and designers must see to it that the CAD system that they are buying should be compatible with their current program. If not, there is a possibility that they will start from scratch.

The initial requirement is determining the sheet metal compatibility in the CAD setup you plan to purchase. Unfortunately, there is no single CAD system that can do all your design needs and that is the truth that we all have to accept.

Additionally, some of the most advanced CAD systems available today may not be compatible with your current tools. More CAD modeling platforms available now features sheet metal design capabilities which are so easy to utilize developing a 3D model. Moreover, there are various CAD systems that can convert solid models to sheet metal elements then supplement flat patterns from it.

 

2/ DFM provisions

 

CAD systems with a design for manufacturability (DFM) features will enhance productivity while minimizing lost time. The DFM functions are highly recommended in the design of sheet metal products as this system could bring assurance of the workability of a pattern before sending it on the shop floor.

There is new generation of CAD tools that can enable the designers to have a second look at the design and make final validation ahead of the actual fabrication.

 

3/ Capacity in handling different file formats

 

Designers and engineers must bear in mind that one of the essential reasons for picking a CAD system for sheet metal design is the software’s capability for storing and handling different file formats. Even the largest companies with this kind of business should observe the practice as they may be having lots of suppliers for this kind of software helping them to develop such numerous projects.

There could be possibilities that some design information might be coming from other CAD systems from other vendors. Transferring these models or images to your local program might lose they salient features when you are using multiple files. But always remember that this is a part of an evolving system, the whole team must learn to adapt easily.

 

4/ Designing tools that are more effective and longlasting

 

It’s an obvious reason to choose a software specifically designed for sheet metal fabrication. Most sheet metal designs usually comprised of 2D drawings although the program is detailed in 3D. However, 3D models do not completely reflect other specifications and dimensions (such as the tolerances, surface finish, etc.) and more details are needed after the groundwork.

In this regard, the 3D CAD system you should choose must have the capacity to competently design drawings in line with the basic programs that you follow. The standard functions, such as the BOM (bill of materials) listings, dimensions, lettering, and tolerances, must be compatible with the new system.

Additionally, see to it that your illustrations and other designs can be easily exported in basic formats (like DWG, PDF, and DXF). This will entail minute issues regarding your newly adopted software.

 

5/ Shorter time to learn the program

 

Choose a software that can be easily learned by users in the shortest possible time (also known as a “short learning curve”). Even the most advanced CAD system in the world could be less powerful when users will not learn how to implement it properly within your local system.

Consider a system that has a shorter learning curve with an interface most familiar with users. Select the one that has easy to understand programs from the establishment of the concept up to the manufacturing site.

 

5 Best CAD software for sheet metal manufacturing

 

Here are 5 CAD software brands that may help you in designing sheet metal components which can be integrated into your local system:

 

1/ Solidworks

2/ Rhino CAD

3/ Solid Edge

4/ AutoCAD

5/ AutoDesk Inventor

 

Useful Tips: Some CAD vendors are offering trial days with free subscription. You can check out their website and have a free trial version (most are for 30 days) and decide whether you want the stuff or not.

 

 

Chapter 3

How to choose sheet metal (materials, gauges, tolerances)

 

 

how to choose sheet metalKnowing sheet metal thickness and gauges

 

Since sheet metal is available in various materials, they also come in a variety of types and thicknesses. Whatever fabrication project you choose, picking the right sheet metal gauge is very crucial. Just like wire, the thickness of sheet metal is expressed in “gauge”.

Also, similar to wire measurement, the lower the gauge number the thicker the sheet metal is. The sheet metal fabrication industry frequently uses plate sizes ranging from gauge 30 (thinner) to gauge 7 (thicker). While a gauge is a non-linear (not denoting or arranged in a straight line) measurement, it had been used for so many years.

 

sheet metal gauge

 

The sheet metal gauge tool (Figure above) is used to measure both the thickness (in the thousandth of an inch) and the gauge number. The one pictured above is used for steel metal sheets. However, to make it clearer for those who didn’t know yet, there are different gauge thickness used for different metal types.

Additionally, there are distinct sheet metal tools used for ferrous and non-ferrous metals as they are manufactured with the same gauge but different in thickness.

To illustrate; a gauge 8 mild steel has a corresponding thickness of 0.1644 inches, while its equivalent gauge (gauge 8) for galvanized steel has 0.1680 inches of thickness. The same case with stainless steel, where a gauge 8 type has a thickness of only 0.165 inches.

Here is a useful chart you can use to distinguish the variation in sizes and gauges of different types of metals:

 

sheet metal thickness (gauge) chart

 

 

Understanding the 4 properties of metal

 

It is interesting to know how different metal behaves when heated, burned (when welded), bent, pierced, pressed, and punctured. With these characteristics of metal in mind, you will be aware of what will happen when you do something (like bending, pressing, etc.) to them. However, metals have several physical properties unlike any other matter on earth.

Metals have high melting and boiling points, good conductors of electricity and heat, and have higher density (they are heavier for their size). Metals are also shiny (lustrous), have high resistance to stress, and are malleable (the ability to be shaped in another form without breaking, also called “plasticity”).

But when you used sheet metal for fabrication, there are 4 specific properties of metal that you should bear in mind. Engineers have come up with these metal properties which they observed have the most effect on a successful sheet metal fabrication.

For a more convenient understanding, we will discuss here the 4 known properties of metal and find some interesting facts in choosing the right material for your requirement.

 

Tensile strength

 

When we say tensile strength, we are talking about the metal’s ability to withstand being subjected to stress without breaking. Steel is one of the leading candidates for having this property, next to stainless steel. While copper and aluminum have low and very low resistance to stress, respectively.

If you want strong machine parts or structure for your project, you might want to consider steel or stainless steel.

 

Machinability

 

This characteristic of metal pertains to the ease and convenience of cutting them (machined). Using inexpensive tools, if your choice of metal has this property, cutting them is easier and requires a little cost.

Steel with low carbon content is much easier to be machined than stainless steel (has poor machinability), while aluminum is the easiest to work with, especially aluminum alloys 2007, 2011, and the 6020 varieties.

However, due to its high malleability copper has the poorest machinability property among other metals.

 

Weldability

 

Weldability is the ease of joining (welding) metals. Steel is the easiest to weld. With a material that requires less skill and expertise from a welder, the preparation is quicker and needs inexpensive welding machine (arc welding is a good choice for this job on steel).

Hard to weld metals (like stainless steel and copper) require specialized and more expensive tools (such as TIG/MIG or Plasma welding machines) and highly skilled personnel. Aluminum is easy to work with but it requires a gas to shield the material from atmospheric contaminants while the welding is being done.

When joining an aluminum, you must select the proper shielding gas in the right quantity while welding this metal. The correct amount of gas will minimize the chances of defects and cracks.

 

Ductile strength

 

The ductile strength or formability of a metal refers to its ability to be stretched, hammered thin, and formed into different shapes like a wire without breaking. Copper is an ideal material for this job (especially when annealed or the process of heating the metal at a specified temperature then allowed to cool slowly).

Aluminum has a poor ductile strength while steel has medium ductility. Stainless steel is highly ductile but is a poor conductor of electricity.

            

 

properties of metal tableproperties of metal table

 

 

 

 

Considering the material of sheet meta

 

Once you are able to identify the right material and gauges for your project, it is now time to choose the correct sheet metal type for the job. We are enumerating some of the pros and cons of the most common sheet metals used in the industry so you would be able to decide firmly on what is the best material for your needs.

 

Stainless steel

  • Will not corrode even when exposed to certain acids
  • Best for machines that have food contact
  • 100% recyclable
  • Thickness requirement could be reduced because of its high strength
  • Heavy and difficult to fabricate which warps easily on welding
  • Poor machinability

 

Aluminum

  • Lightweight material
  • Rust and corrosion-proof because of the oxide layer
  • Easy machinability with lower price compared to copper
  • Novice welders will have a hard time working on this metal
  • CNC cutting technology is not as abundant as for other metals

 

Copper

  • Can be formed easily and inert to other metals
  • A must for electronic type of machine parts
  • Has high corrosion resistance
  • High electrical and thermal conductivity

 

One of the most expensive metals to use

 

Steel

  • The cheapest metal to work on
  • Has properties almost similar to other metals
  • Has structural integrity (can withstand temperatures up to 1000C)
  • Needs protection from rust and corrosion
  • With difficulty in cutting compared to aluminum

 

 

Chapter 4

Cutting Operations

 

sheet metal cutting operations

Sheet metal cutting process explains

 

Sheet metal cutting involves the use of machinery, equipment, and tools that are designed to separate the metal on the sheet in pre-determined areas. Small fabrication shops often used manual tools in cutting metals for individual orders. Tools such as straight cutters, electric shears, Dovetail metal cutters, nibblers, and other cutting equipment are some of the most popular among shops and individual user.

But for companies manufacturing sheet metal products in mass production, they usually utilize press working operations. When press working is used on the floor shop, it dramatically eliminates the hazard of non-uniformity and errors (especially tolerances, etc.) on the workpiece, the job is faster, and enhanced productivity in actual fabrication. Wastage of material is also minimized using this technique.

The most common form of press working (also called cold stamping) is the punch and die assembly which is sometimes termed as “a die set” or simply die. The whole assembly is called a press machine.

Moreover, press working also make the job quicker and easier. Big manufacturers of sheet metal products used press machine in series with different punches and die that cuts, bends, pierce holes, forms, and other operations, to come out with fully working parts.

Here are some tips that are worth every cent: Sheet metal is under 6mm (almost 1/4 inch) in thickness, while those that are more than this thickness are commonly called “plate metal”. A press machine can be used in either sheet metal or plate metal.

 

 

die and punch setup of we work pressdie and punch setup of a work press

 

 

Sheet metal cutting processes

 

Here are some of the major processes that could be done on a working press. While this machine can cut, bend, etc., it could also perform other functions aside from cutting and separating (or parting), such as forming. In this chapter, we shall focus our attention on some of the basic cutting processes of sheet metal.

 

Straight cutoff (shearing) using an inclined blade

 

The straight cutoff (also called shearing) is so far one of the simplest press working operations in sheet metal cutting. This process involves cutting along a straight line (with shearing force) usually done in separating large sheets. The sheet metal is placed between two cutting edges with an inclined blade (between 4 and 15 degrees of inclination) to decrease the friction.

Most large manufacturing plants commonly used an angle of inclination of under 9 degrees allowing swift and quick cutting. Moreover, inclining the angle of the punch reduces the maximum force required in separating the metal. Using this method, the process can be repeated after each cutoff in fast and accurate manner.

 

punch and die setup on a straight cutting operation

 

Blanking

 

Blanking operation is a sheet metal cutting process in which a chunk (called blank) of the workpiece (or the product) is cut from a larger part of the stock (the slice of sheet metal where the product is cut). The blank part is the one which can be further processed into the desired design.

Blanking can be done together with a closed outline in one strike of the punch. However, like the majority of sheet metal cutting techniques, this operation will result in a certain amount of waste material. But the system’s designer could minimize the wastage by programming the right symmetry of the design before the actual operation on the shop floor.

The blanking and punching sheet metal cutting techniques have similar processes, but they must not be confused with each other. The distinction lies wherein in blanking, the cut piece is the work that is further processed, whereas, in punching, the cut piece becomes the waste. Blanking process can be classified as either conventional or fine blanking.

Here is the simple illustration of the difference between blanking and punching operations:

 

 

comparison between blanking and punching techniques

 

 

blanking process

 

 

 

 Cutoff and Parting (or separating)

 

The cutoff and parting operations in a sheet metal cutting process are two of the most significant techniques in the metal fabrication industry. Depending on the design, cutoffs are not necessarily in a straight line but might be in curves or other geometrical contours.

In cutoff processes, designers can be able to manipulate their design where there could be almost no wastage in the material. The cutting of sheet metal in cutoffs is almost always made within one direction minimizing material waste.

In parting, the shape may not fit precisely along the stock because the geometrical design of the workpiece may lie along two paths at the same time. This will result in a larger amount of waste material. The difference in laying out of design between cutoffs and partings is unique to this sheet metal cutting technique, however, they are basically similar in process.

 

 

cutoff and parting

 

 

parting operations

 

 

 

 Perforation

 

Similar to punching operation, perforation of sheet metal is usually done with circular holes {with sizes ranging from .04 to 3 inches (1 to 1.75mm)} and other geometric shapes in a decorative fashion and other amazing patterns. But these holes have industrial uses on sheet metal products while some are for cosmetic appearance.

The holes are often utilized for ventilation, filtration of fluids, and other industrial uses. Perforation of sheet metal in various machine and structural applications is also made to minimize weight or for garnishing.

 

Notching and semi-notching

 

The notching operation of cutting sheet metal entails removing waste material from a stock to form useful workpieces. The cutting starts from the edge then going inward yielding the finished product with a pre-determined profile.

The notching process is a progressive operation where each stroke of the punch removed another piece creating the correct contour. On the other hand, semi-notching refers to the removal of the material that is out of the edge of the workpiece.

These two identical operations almost always come together. The only difference between these two operations is that semi-notching is an element of a progressive cutting procedure creating a uniquely designed profile.

 

notching and semi notching

 

 

Difference between sheet metal cutting and forming

 

You should remember this tip when focusing on sheet metal forming operations: The forming operations that could be done on a work press includes bending, drawing, and squeezing. Here are some of the differences in sheet metal cutting and forming illustrated below:

 

 - Cutting Operations:

 

sheet metal cutting

 

- Forming operations:

 

sheet metal forming operations

 

 

 

Chapter 5

Laser cutting

 

Laser CuttingWhat is laser cutting of sheet metal?

 

The acronym LASER stands for Light Amplification by Stimulated Emission of Radiation. Lasers had been used to cut sheet metal and other objects for years now. Lasers are used in delicate medical surgeries, can cut diamonds and other thick metals, used in recordings and telecommunication systems, used in internet signals, barcode scanners, DVD players, laser printers, and various other uses that help mankind in achieving the “impossible” for the last 60 years.

In sheet metal cutting, laser plays a vital role in several industrial manufacturing applications, aside from press working. Lasers, which are mainly beam of lights, have the capability to heat, melt, cut, and even vaporize different materials. Lasers are a perfect tool for utilizing powerful energy which can be controlled.

Considering laser cutting, the operation primarily involves a thermal process in which a focused light beam (the laser) is manipulated to melt sheet metal in a controlled environment.

 

 

laser cutting diagram

 

How does laser cutting work?

 

Laser cutting typically involves the use of offline CAD/CAM systems that manipulate either a 3-axis flatbed system or a 6-axis robots for 3D laser cutting. The whole process is practically automated and requires minimal human intervention. The laser works wonders on the shop floor which is how large industry manufacturers were able to obtain quality products with almost zero deficiency.

Here’s how a laser cutter works. In a laser cutter, the laser beam is projected from a laser resonator through the machine’s beam path. The laser beam is composed of a column of a very high-intensity light with a single wavelength or color. The beam is then bounced off in different directions via a number of mirrors, called beam benders.

After passing through these benders, the laser is then focused on the sheet metal it is working on. However, the focused beam (laser) will pass through the bore of a nozzle before hitting the sheet metal. The beam is accompanied by a compressed gas (such as oxygen or nitrogen) in flowing through the nozzle that will help the laser in melting or cutting the metal.

The laser beam is also focused using a special lens (or curved mirror) which happens in the laser cutting head. On a CNC laser cutter, the head is moved over the sheet metal stock shaping the designed workpiece. The right distance between the cut piece and the laser cutting head must always be maintained to attain the desired piece without defect and burr.

 

 

laser cutter working diagramlaser cutter working diagram

 

 

Varieties of laser cutting

 

In laser cutting, a co-axial (sharing a common axis of discharge) jet of gas is used, much like when using an acetylene torch. The gas aids in heating up the laser beam to cut metal quickly under extreme temperature. So that you know what to use in laser sheet metal cutting, it is better that you are informed that there are 3 major varieties of laser cutting, namely: fusion cutting, flame cutting, and remote cutting.

  • Fusion cutting usually involves the use of inert gas (mostly nitrogen) in detaching melted material out of the kerf. Nitrogen is usually accompanied by the release of heat which reacts to the melted material hereby contributing to saving more energy.
  • The flame laser cutting technique preferred oxygen as the gas to use. However, contrary to nitrogen, oxygen gas contributes to the increased energy output of the process. Oxygen normally exerts more mechanical pressure on the melted material but has a lower error of tolerances.
  • The remote laser cutting technique utilizes partial evaporation of the material using a high-intensity laser beam. This operation does not use co-axial gas (as an assist gas) compare to other methods which can cut thin sheets of metal.

 

Kinds of lasers use in sheet metal cutting

 

The new generation of laser cutters used by large sheet metal manufacturers is the CO2 Lasers, the Fiber Lasers, and the Direct Diode Lasers. These three powerful laser cutters are the much preferred in the industry for safe and efficient manufacturing. Find out how these three kinds of lasers differ from each other.

 

CO2 Lasers

 

The CO2 laser (also called carbon dioxide laser) is best for cutting, engraving, and boring sheet metal. The laser is basically generated using a mixture of gas (like carbon dioxide, helium, and nitrogen) and is electrically stimulated via an electric discharge.

This type of laser is emitted at a wavelength of 10.6um while those utilized for material operations could prompt higher kilowatts of power. The CO2 lasers are mostly pumped into the system using electrical current passing through a gas mix (called DC-excited) or by using radio frequency (similar to a microwave) called RF-excited.

The RF-excited method is the newest version of the laser cutting technology which is being adapted by more industrial manufacturers. The CO2 lasers have higher efficiency (exceeding 10%) compared to other lamp-pumped solid-state beams (like the Nd/YAG, known also as the neodymium yttrium-aluminum-garnet variety). However, it’s efficiency is lower than diode-pumped lasers.

 

Fiber Lasers

 

The Nd/YAG laser is one of the variants of the fiber lasers. Fiber lasers are of that  variant of a laser included in the family called “solid-state lasers”. A laser of this kind is emitted from laser diodes then transmitted into an optical fiber where amplification is done. When the laser beam is amplified, the parallel light rays are then dispersed minimally while it propagates.

The collimated light is then focused by a lens or concave fixing on the sheet metal stock to be cut. This type of laser does not have moving parts, like cooling fans used in gas circulation, which makes the system more economical. Additionally, this method of a laser sheet metal cutting system is more energy-efficient compared to CO2 lasers of the same category.

 

Direct Diode Lasers

 

The direct diode lasers are the new generation of laser cutting technology (for solid-state lasers) available on the market today. Compared to fiber lasers, the direct diode process does not include a bright-enhancing stage allowing minimal optical loses and higher radiant efficiency.

In this cutting-edge technology of laser cutting, there are various light beams emitted from laser-enhancing diodes of variable wavelengths. This innovative technique is called beam combining. However, due to this technique, although more efficient in the wall-plug category, the direct diode laser has lower beam quality in comparison with fiber lasers.

 

Advantages/disadvantages of using a laser cutter

 

Most engineers and sheet metal designers agreed to a more convenient and advantageous use of laser cutting machines than any other method of sheet metal cutting.

Some of the more critical issues on laser cutting is its heat affected zone (or HAZ) along the edge of the cut. Since lasers have high-intensity light source, it melts metal quickly (in about a millionth of a second) resulting to HAZ. Another issue is the machine’s steep price.

However, the pros basically beat the cons in laser cutting of sheet metal. Some of the most admired results using this technique are the high processing speed, excellent quality of cut, high accuracy, has small kerf, cut complex geometrical contours, and other admirable feats of engineering.

 

 

Chapter 6

Bending operations

 

bending process

What is bending of sheet metal?

 

Bending is one of sheet metal industry’s most precious processes. In it lies some of the industry’s basic features in manufacturing, especially in forming operations of sheet metal. Sheet metal bending is primarily the plastic deformation of the workpiece along a straight line or over a certain axis. The bending enables a flat workpiece to transform into another shape or geometrical contour.

While bending changes the shape of the product, it does not change its volume but may alter the thickness a little bit in some cases. But for a majority of the process of bending sheet metal, the thickness is seldom affected. Aside from changing the geometric form of the work, the bending procedure is also utilized to bestow stiffness and strength to a sheet of metal while discarding the sharp edges of the piece.

 

 

simple bending process

 

As part of the metal forming operation, bending should be understood thoroughly by fabricators as not a simple process of construction. The metal’s elasticity and plastic deformation should be considered when designing a bending contour.

It is also important to know the basic fundamentals and different terminologies (which you will find in the Figure below). We will also discuss the various bending operations used in sheet metal manufacturing.

 

 

basic bending process

 

Various bending processes

 

There are several methods in bending sheet metal which is commonly done using punch and die and other bending machinery/device. But first, you must determine your workpiece’s material, size, thickness, and other important factors before choosing the method of bending.

Furthermore, take note of the size of the bend on your product, the bend radius, the angle of bend, the dimensions of the curve, and the spot (or location) where the bend should take place. Additionally, you must choose the most effective bending method available for the type of material that you are using.

Here are some of the bending processes being performed on the shop floor for sheet metal fabrication. These methods are proven effective when done properly and according to design and using the right tools for the job.

 

Air and bottom bending (V-bend)

 

Since various dies themselves are designed with different geometries, you can basically perform anything you want from them. Using a V-shape punch and a lower die while setting up the punch on the desired height, you can do air bending (freely) of sheet metal, just like in the figure below.

Bottom bending has similarities with air bending and coining. In this operation, the die angle must match the desired angle of the workpiece, with some minor adjustment for “spring back”. As such, to achieve a 90-degree bend, tooling should be fixed to 88 degrees.

 

air bending and bottoming

 

Roll Bending

 

In roll bending, sets of adjustable metal rollers are arranged where a large or a strip sheet metal is passed through, with every roller performing an incremental part of the bend. This technique usually involves 3 rolls to feed and bend the sheet to the wanted curvature. The rolling is continued until the desired cross-section contour is attained.

You can also bend panels, tubes, frames, channels, and other thick metal plates using this process.

 

roll bending process

 

Offset bending

 

Offset bending comes in two ways: upspring and horizontal. The upspring (or upsweep) method is primarily used in forming two bends which are very near each other conventional methods have difficulty achieving.

The horizontal offset tool is basically designed to offset the workpiece by one material thickness. However, the horizontal tool is not a bottoming one, instead, it is used, foremost, to “step up” one material thickness where angle and radius are usually not important.

 

offset bending ways

 

Corrugating bending

 

The corrugating bending process is one of the most stunning features of transforming sheet metal into something of a work of art. In this operation, the symmetrical bend is achieved across the width of the sheet with regular spacing along the entire length.

There are also diverse shapes that can be used in corrugating which elevate the cosmetic appearance of the sheet metal. Moreover, corrugating is done to boost the strength and rigidity of the metal while increasing its resistance to bending moments.

 

corrugating sheet metal

 

Edge Bending Process of Sheet Metal

 

Edge bending of workpieces is being done in industrial sheet metal fabrication plants where only a small section of the piece is bent using specialized tools (instead of bending a larger part of the workpiece). Here are some of those methods.

 

Beading

 

The beading (or curling) process pertains to the bending of a workpiece’s edge into a circular or other shapes of the die itself. The edge is bent into a curl using one or pair of die to improve stiffness by intensifying the moment of inertia at its extremities. One of the best examples of beading are hinges.

 

beading process

 

Flanging

 

Flanging process of sheet metal is the bending of the edge into a 90-degree turn to improve the workpiece’s stiffness or for integration with other pieces. If the angle of bend is less than 90 degrees, the bend is called flaring. This process gives the product a curve or a straight line depending on the desired contour.

The different flanging operations may subject the metal to different tensile strength, such as compressive hoop and tensile stresses.

 

flanging of sheet metal

 

Hemming

 

Hemming is one of the easiest bending processes you can do in sheet metal. However, utmost care should be observed when doing this operation to avoid cracks and lighten the stress the metal may endure. Hemming is a bending process where the edge of a sheet is bent into itself.

Bending a workpiece this way will increase the metal’s stiffness while protecting its edge. The process also eliminates sharp edges.

 

hemming on sheet metal

 

Seaming

 

 

Seaming is the assembly of two hemmed sheet metal ends to form another set of a usable workpiece. The pieces are joined together by a specialized machine by bending the edges of two parts over the other. This method will further strengthen the joint while the material is plastically formed into position.

Locking the parts together, each bend aids to resist the deformation of one another allowing a strong and rigid fortification of a well-joined structure. The sheet metal industry applies double seaming to products of this kind to come up with an air- and watertight workpieces commonly used in beverage containers.

 

types of seaming processes

 

Chapter 7

Deep Drawing Operation

 

Deep DrawingDeep drawing explained

 

Among the products manufactured using sheet metal are pots and pans for cooking, automobile parts (such as gas tanks, panels, and other car body parts), kitchen sinks, container cans, and other cup or box-like structures. But do you know what manufacturing process does a sheet metal undergo to produce these kinds of products? You guess it right, these things are made using deep drawing process.

Drawing is considered one of the most popular and widely used operations in sheet metal forming around the globe. The automobile industry, cookware manufacturing, and other similar industries are the most avid users of this process. The process is basically comprised of a punch with a circular comer and a die having a large radius.

Additionally, the punch-die space (or clearance) should be a bit larger than the thickness of the sheet metal to make deep drawing possible. Moreover, since deep drawing involves mostly cup or box-shape structures, the process is considered “deep” drawing when the drawn part has bigger depth than its diameter.

 

Common material of sheet metal used in deep drawing

 

The most widely used materials in deep drawing of sheet metal are brass, aluminum, cold-rolled steel, and stainless steel. Softer materials, such as aluminum, are easier to deform and drawn into a cup-like structure and therefore require less force when to undergo physical changes.

We will show you the table below to demonstrate the drawing force to percent reduction of popularly used materials in deep drawing.

 

drawing force and reductions

 

Note: 1 kN is a unit of force and is equivalent to 101.97 kgf (kilogram-force) so you can imagine how each sheet metal is forced to endure just to have its body elongated (drawn) to come up with a usable product.

 

Mechanical processes of deep drawing

 

There are 5 steps of deep drawing before sheet metal is converted into a fine workpiece. The primary tool in drawing is punch and die with the former designed to the desired shape of the base of the piece once the product is drawn. While the die’s hollow contour matches the punch with precise clearance and allowance to make a smooth passage of the workpiece (also called blank) for retrieving.

The deep drawing process for some products may involve progressive drawing wherein the work may be subjected to more than one stretching. Moreover, if the wanted product yield requires 50% reduction, the workpiece must undergo multiple operations. This way, the metal is drawn with minimal force to avoid cracks and other defects.

The setup in the deep drawing is also similar to cutting of sheet metal where there is a lateral distance between the edges of the punch and die. The manufacturing industry uses both mechanical and hydraulic presses in deep drawing. Here are brief explanations of the mechanics of deep drawing for your easy understanding.

 

deep drawing techniques

 

Touching of punch on workpiece

 

The process of deep drawing of sheet metal starts as the prepared punch and die assembly begins when the punch began to have contact with the work. Make sure that the punch is placed correctly and you have installed the right pattern. Also, ensure that the whole assembly is free from vibration as this will affect the quality of the draw.

 

Bending of the blank

 

For an initial application of the load (force) on the blank, it is first bent onto the contour of the die cavity. During the bending process, the force applied must not exceed the predetermined amount of pressure applied to the metal being press to avoid wrinkles on the metal. The Figure below further illustrates the bending process.

 

Straightening the work

 

The next step is to further increase the force applied in bending of the blank to straighten it without breaking. This process will sink the annular punch-die clearance. Straightening results to a short, straight, and the emergence of a vertical wall. At this point, you will notice the metal is being stretched out dramatically as the punch acts on the work.

 

Friction and compression

 

The next event that will happen will definitely put some excitement on your part. At this stage, the rest of the blank starts to flow radially as friction do its thing. There is now frictional forces acting on the lower surface of the work and the upper part of the die. The frictional force decreases as the workpiece continues to move along the die’s inner surface.

After experiencing a frictional force, the blank now undergoes compression stresses at this time. The larger diameter of the blank shrinks as it approaches complete sinking into the smaller diameter of the die, changing the shape of the piece from a flat one into a cup-like contour.

 

Tension release

 

During this last stage of sheet metal deep drawing, all of the stresses are liberated as the punch is no longer moving downward. At this stage, the blank is completely fitted into the die cavity forming a longer vertical wall.

By then, the remaining blank part takes the shape of a small annular flange. Furthermore, the new object is then treated to uniaxial tension as the newly formed workpiece is ejected by the machine.

 

sheet metal deep drawing

 

 sinking of the blank

 

Tool materials, lubrication, and cooling in deep drawing

 

Are you aware of the tools used in sheet metal deep drawing? And why they can endure pressing materials with such strong forces? The punches and dies used in the deep drawing process are mostly made of tool steel. But some manufacturers used cheaper carbon steel for the die assembly if the materials to be drawn have less severe applications.

Also, cemented carbides are sometimes used when there is high abrasive resistance. Alloy steel is sometimes recommended for the ejector system to spew out the drawn material. Additionally, this process, like most sheet metal operations, needs lubrication to reduce friction and heat between the punch, die, and the workpiece.

The lubricants also help in spewing out the piece from the punch easily. Some lubricants used by parts manufacturer include wax films, white lead, heavy-duty emulsifiers, and phosphates. However, to have a fine and smoother surface, the industry uses plastic film coverings together with lubricants.

 

Chapter 8

Other Sheet Metal Forming Operations

 

Knowing sheet metal forming processes better

 

 

As we have stated in the preceding chapters, there are more sheet metal forming operations that the industry is currently using to give us more user-friendly products or as parts of these manufactured articles. We learn to appreciate products that are mind-boggling and those that tickle our imagination because of their clever fabrication and brilliant designs.

However, there are more to discover and learn about these admirable processes. Sheet metal forming is definitely an engineering wonder consisting of a group of interdependent operations simplified by the availability of tools for the job.

Moreover, most of these undertakings are realized in subjecting malleable flat sheets of metal from mechanical forces to change these objects creating more usable products. The availability of various ways and means to achieve these changes on a stock of sheet metal will enable designers, fabricators, and engineers to pick the best processes to use.

On this chapter, we shall tackle 6 other sheet metal forming operations (aside from sheet metal cutting and drawing processes that we have discussed earlier in the preceding chapters). These other techniques in sheet metal fabrication are equally essential in the manufacturing process for various types of sheet metal. Here it goes!

 

Other sheet metal forming processes?

 

Bulging

 

The bulging technique in sheet metal forming is done by placing the tubular, curvilinear, or conical piece into a split-type die. This tube is expanded using a flexible plug (some manufacturers used polyurethane plugs) to a predetermined diameter.

When the desired diameter of expansion is reached, the punch is retracted while the plug returns to its original shape then the workpiece is removed from the dies. These type of manufactured sheet metal products are for pipe fittings, such as elbows and tees (for sewage treatment, water distribution system, and industrial boilers), plumbing, bellows, and other similar articles.

 

bulging process

 

Roll forming

 

The manufacturing industry utilizes several series of roller dies to bend and form a continuous length of sheet metal in a process called tube bending. This method of forming sheet metal is used widely for large production operations where the metal sheet is bent by passing the work through several stages of rolls.

Some of the characteristics of roll forming are that the finished product has a high-quality surface finish and the complex cross-sections remain uniform throughout the production run. However, the system has a high tooling cost compared to conventional roll forming methods.

This process is ideal for producing workpiece with constant-profile parts in bigger quantities having a longer length. Door frame manufacturers used this technique.

 

Tube Bending

 

Once the sheet metal is made of a tube or pipe and it needs deforming at various angles, the best to use process is tube bending. To make this operation possible, one of the oldest and most effective techniques is by using earthly particulates, such as fine sand. Yes, that gritty sand you can find on the beach when you are on vacation!

In the olden days and even today, fabricators fill the inside of a tube to be bent with loose sand particulates then bend it in the desired contour and angle. The sand keeps the tube from buckling. When the forming is finished, the sand is shaken out.

One other method is by using flexible mandrels. These mechanical mandrels come in various shapes (such as laminated, plug, balls, and cable shapes). Just like sand, these mandrels prevent the tube from damage, buckling, and collapsing during the bending process.

 

tube bending

 

Stretch forming

 

The stretch forming process usually involves two operations in one continuous production run. In this procedure, the sheet metal is stretched out and bent at the same time over sets of dies resulting to large bent parts. The sheet metal is fastened to its edges then stretched by a die or block.

The die moves in different directions (such as upward, downward, or sideways) depending on the design of the machine. This procedure is commonly used by automobile manufacturers (for door panels), window frames, and in the aircraft industry (specifically for airplane’s wing skin panel).

 

stretch forming process 

 Press brake forming

 

Sheet metal can be easily bent with simple equipment into long and narrow workpieces like using the press brake. This equipment used long dies installed in mechanical or hydraulic presses which is ideal for small manufacturing plants.

Even the tooling of a press brake requires only simple and quick setup and is convertible to various shapes and sizes of work. The process requires the sheet metal to be formed along a straight axis. The forming is accomplished by using a U-shaped, V-shaped, channel-shaped, and other shapes of the punch and die set to attain the desired contour of the workpiece.

 

press brake forming

 

Dimpling

 

In the dimpling operation of sheet metal, a hole is first punched in the work and then expanded into a flange. This operation involves the process of bending and stretching the interior edges of the sheet metal. In other types of dimpling, which is usually done on much thinner sheet metal, a shaped punch pierces the work and then the hole it makes is expanded by the same punch creating a flanged hole similar to a dimple (hence the name).

The second method of dimpling is not applicable to thicker sheet metal as the punch might not penetrate the workpiece easily which can result in abnormal deformation. The images below clearly illustrates the “magic” of the dimpling process.

  

dimpling process

 

The upper image shows the assembly of the punch and dies in dimpling where the workpiece has already a hole. The lower image shows the location of the punched and the expanded hole (also called dimple).

 

before and after dimpling

 

 

Chapter 9

Dies and Presses for Sheet Metal Processes

 

Importance of dies and presses in sheet metal fabrication

 

Sheet metal working is one of the most diverse industrial operations mankind had ever invented. In his pursuit to attain perfection in the shop floor, the humankind let the evolution of sheet metal processing to take its own course where sophistication never seizes to inspire them.

The die and press tandem largely play a significant role in forming, cutting, bending, drawing, and other metalworking procedures to create components for other machines or standalone parts. Die manufacturing covers even the production of the simple paper clips to more complex products that you could not ever imagine were the outcome of the collaboration of dies and presses.

The dies and presses used in sheet metal fabrication are also finding their way to a more reliable system which is now mixed with high-tech and computerized operations (called automation). The combination of these two tools (die and press) in metalworking operations and in the manufacturing processes create diversified functions in the realization of various shaping processes.

 

Classifications and types of presses

 

In order for a workpiece is formed, cut, or changed into another shape, a die assembly is installed in a power press or press machine. Before we discuss more dies, we will tell you more about the “other half” of the die: the press.

Furthermore, there are various types of presses which work and help with the dies in shaping workpieces. The press acts as the driving force in forming or shaping the product (workpiece) by the application of pressure.

Presses are classified according to their mechanism (mechanical, pneumatic, or hydraulic), controllability (conventional or servo-presses), structure (screw or Knuckle-joint presses), and function (punch presses, forging presses, stamping presses, press brakes, etc.).

Different types of presses are used in the manufacture of various parts for automobiles, aircraft components, plumbing systems, household items, and other structures. The most common types used in these industries are the press brake, forging press, stamping press, and the punch press. All these types of presses used dies as the primary tools in manipulating sheet metal.

 

 

Components of die assembly

 

Here are the major components of the die assembly with schematic diagram detailed in this chapter to give you more insights of the inner workings of this type of machine installed on a press.

 

die and punch setup of a work press

 

The punch and die assembly (or simply referred to as “die”), as we have pointed out in the preceding chapters, is the most commonly used tool in the metalworking industry. Here are the main components of a die assembly for your easy reference:

 

Shank

 

Shaped like a pillar, the shank is used to hold the top die (including the punch) of the relatively smaller die in a press.The shank should be aligned and placed at the center of gravity of the plate to make pressing smooth and effective. Shanks have standard diameters of 25, 32, 38, and 50 mm.

 

Die block

 

The main part where all the other parts or main components are attached. This part is usually made from high-quality steel and installed on the bottom segment of the die set on which the “female” section of the assembly is secured ( the “male” part of the system is the punch itself). 

 

Punch plate

 

The part that holds and supports the different punches. This segment of the assembly has the bore of the punch and is commonly secured with a special type of bolts.

 

Blank punch or blank holder

 

The blank punch, along with the blank die, produces the blanked part of the workpiece. A blank holder is also a part of the die used in drawing that prevents the formation of wrinkles.

 

Pierce punch

 

This chunk, together with the piercing die, removes parts from the blanked finished part. Whenever the punch is on its way up for another cycle of forming, the pierce punch ejects the work from the die.

 

Stripper plate

 

The stripper plate is the piece that is used to hold the material on the blank/pierce die and strip off the work on the punches. The stripper also guides the punch for an accurate alignment between the punch and die.

 

Pilot punch (or guide pin)

 

Act as a guide that will help in placing the sheet perfectly for the next series of the process. The pilot is typically a round hole and when there is an error in the system, it is corrected by inserting a shaft or metal stick (with a pointed tip) inside the hole.

 

Guide, back gauge, or finger stop

 

All these elements are used to ensure that the workpiece is placed in the same position within the die and as the last ones to be installed.

 

Stop block

 

This component, together with a bottoming block, is utilized in controlling the deepness (depth) which the punch goes into the die. The stop block can be adjusted to the desired depth of the punch as it is “buried” into the female die.

 

Classification of dies according to method of operation

 

As sheet metal products’ designs are becoming more and more sophisticated, engineers and designers also come up with ingenious solutions to make the workpiece easier to manufacture. There are various classes of dies based on their procedure of operation.

 

Simple die

 

As the term implies, this type of die operates in a single action or stroke of the punch. The operation might be cutting or forming of sheet metal. Simple die mostly perforate holes on a blank.

 

simple die assembly

 

Progressive die

 

In a progressive die, there are more than one operations that can be performed in a stroke of the punch when using this type of die. Progressive dies enable a series of operations where each workpiece transforms to another contour or shape.

 

progressive die

 

Combination die

 

The combination die, similar to progressive dies, can also perform several operations with a single stroke of the press. However, unlike other die assemblies, the combination die can perform forming and forging operations in one strike of the punch.

 

combination die

 

Compound die

 

The compound die is used to accommodate one or two operations on a workpiece with the press’ single strike. The dies can perform either forming or cutting operation and widely used in sheet metal fabrication for more accurate and cost-effective operations.

 

 compound die

 

Chapter 10

Sheet Metal Operations not performed on Presses

 

What if there are no dies and presses?

 

Dies, punches, and presses though are not the only means or tools in treating sheet metal to be transformed into other shapes or products. There are also a variety of methods to reshape or form sheet metal without using the press machine, only the well-loved die and punch tandem in some cases.

Aside from roll bending (discussed in Chapter 8), lasers (Chapter 5); and tube bending, roll forming, bulging, and stretch forming, which are all tackled in Chapter 8, there are still more sheet metal operations not performed on presses. And we shall discuss them in this chapter.

Moreover, these operations (non-press types) are also used currently in the manufacture of sheet metal parts being employed by large industrial fabricators. Most of these processes are also more advanced while the majority has CNC (Computer Numerical Control) operations.

On this chapter, you will be able to identify the processes in sheet metal fabrication using techniques other than presses. Here are 6 of the leading sheet metal processes not performed on presses.

 

Various Sheet Metal Operations Without Using Presses

 

Spinning

 

Spinning is one of the most effective ways of forming sheet metal without the aid of presses. This process involves the dramatic shaping of metal with an axially symmetric part of a spinning mandrel using a circular tool (or roller) in shaping the work. 

This process has 3 types, explained below.

 

Conventional spinning (or metal spinning)

 

In conventional spinning, the operation is largely based on an axis-symmetric part over a rotating mandrel where force is delivered via a rounded tool or a roller. The workpiece, sometimes come pre-formed (but are mostly flat), is held by a tailstock or clamped into a lathe machine in between the mandrel. When the work is properly in place, the machine can be rotated at slow speed. This process is similar to press drawing of small workpieces only on a larger scale, that is why the metal spinning process is done conventionally.

As the machine rotates, the tool applies limited pressure to the workpiece while the tool slowly moves up the cylindrical rod. The slight pressure is enough for the sheet metal to wrap around the mandrel mimicking its shape. Conventional spinning can be done cold, but in some processes, the metal is heated slightly to shape it off more easily.

Metal spinning is used primarily for large workpieces where sometimes diameter could reach 20 feet. The material used in metal spinning tooling is basically made from tool steel while the mandrel is made from wood (in some instances).

 

sheet metal conventional spinning

 

Shear spinning

 

Similar to metal spinning, shear spinning (also called as spin forging or flow turning) has the same setup of operation (in-between the mandrel and the tailstock). However, in conventional spinning, where the workpiece must have a larger diameter prior to the operation, in shear spinning, the work is usually started with a small diameter.

In shear spinning, the workpiece is also formed over the mandrel which causes metal flow over the piece. The metal flow enables the piece to be enlarged, initiating a reduction in its thickness. This process may use one or two rollers as tools which will allow an equilibrium of pressure within the piece to avoid fracture.

 

shear spinning

 

Tube spinning

 

The tube spinning process is commonly done on rounded workpieces. This operation is similar to shear spinning where metal flow also happens within the workpiece. Additionally, this metal flow enables the piece to have its thickness reduced, thereby increasing the length of the product (which is primarily what this operation is designed for).

The process can be performed inside the hollow tube using a mandrel and a rounded tool (a roller is also applicable) enclosed by a die. The operation can also be performed outside of the tube over a mandrel while the tool is also outside of the cylindrical piece to reduce the tube’s thickness and to elongate it.

 

tube spinning

 

High-Energy-Rate Forming (HERF)

 

This process (HERF) of sheet and plate metal fabrications concerns about the shaping of work shuttling great amount of energy quickly in a short amount of time. There are three main methods of HERF which are mainly based on the source of power or energy for acquiring high velocities. Here are the different HERF methods explained.

 

Explosive Forming (EF)

 

As the operation implies, the EF process of sheet metal forming uses controlled explosives to shape the workpiece. Compared to conventional sheet metal forming which uses a punch in the operation, EMF uses an explosive charge to realize forming. The charge used are high-explosive chemicals, propellants, and other highly efficient gaseous mixtures.

This power from an immense explosive charge can manufacture industrial parts in a controlled environment. However, the mold and the workpiece are submerged in water before explosion commence which adds up to the safety of this process. The figure below schematically shows the principle of this sheet metal forming process.

 

explosive forming technique

 

Electro-Hydraulic Forming (EHF)

 

Also known as the electro spark forming, EHF is the process of shaping sheet and plate metals using electrical energy by converting the same into mechanical energy. Utilizing a bank of capacitors in the first stage of the operation and charging them with high voltage, the energy is discharged across between electrodes creating an explosion.

Just like the EF process, the EHF technique is also utilized underwater in a controlled environment. The explosion creates shock waves traveling radially in all directions where they form the metal when obstructed. However, the process used external obstructions in the form of a die with the shape of the desired contour.

 

electrohydraulic forming

 

Electromagnetic Forming (EMF)

 

EMF is a high-speed velocity process involving a pulsed magnetic field in forming tubular workpieces. The work is usually made of copper and aluminum alloys with higher electrical conductivity compared to other metals. This characteristic (high conductivity) makes these sheet metals to achieve increased deformation, lower corrosion rate, high hardness, increased flexibility, and stronger formability.

The principle of application for EMF is shown in the figure below where the sheet metal tube is placed enveloping a coil. Then, a high energy charged (high voltage current) is actuated in an instance creating the desired contour of the workpiece.

This method is used primarily in the aerospace (such as rocket engine nozzle and space shuttle skin) and aircraft industries (for airplane parts), especially using aluminum and its variety of alloys. Other industrial applications include automobile parts and other high-tech industries. These sheet metal types are preferred because of their higher ductility, low density (lightweight), good corrosion resistance, and high strength to weight ratio.

 

electromagnetic forming

 

 

Chapter 11

Estimating sheet metal fabrication costs

 

Why costing on sheet metal manufacturing matters?

 

Just like any other businesses, costing in sheet metal fabrication is a crucial part of the enterprise to make it more successful and a sustainable money earner. In this ever-growing competitive market, having a product that cost less to the consumers but with unquestionable quality will make your business prosper and last for generations.

As an entrepreneur involved in sheet metal manufacturing, knowing what you are doing matters most, especially the costing of your product. But how could you determine the right pricing for your workpieces before they arrive at the end-users?

In this chapter, you will be able to learn the loops and hoops of estimating sheet metal fabrication costs using a simple guide that is proven effective in the industry. Even larger sheet metal manufacturers are relying on this type of estimation (or widely based on this guide) for calculating pricing for their products.

 

Parameters to consider in estimating sheet metal costs

 

The production runs of sheet metal products are composed of several phases, depending on the type of the workpiece. From the sheet’s raw material stage, the product undergoes numerous process, which might include the following: cutting, bending, roll forming, punching, welding, laser cutting, assembly with other accessories, painting, and lastly, packaging.

But whatever your process of choice or the needed operations to manufacture sheet metal parts, you (or your most trusted staff) must make an effort in establishing your machines’ efficiency, the hourly cost to operate the machinery (including the cost of manual labor), and other parameters that you can base your decisions on determining the correct costing.

Additionally, as we pointed out before, the production processes or cycles could be distinct from each other. We pictured below a useful chart that shows simple production cycles where you can base your calculations.

 

6 simple steps in estimating sheet metal fabrication costs

 

Step 1: Calculation of quantity/material of sheet metal

 

Considering a production run for a single part, you could base your calculation on the number of the sheet that you will use depending on the quantity of the order for a single item (or workpiece). Decide also for the material of the sheet metal to be used (or what the customers want).

The minute you decide on the number of sheets to procure and its material, you can determine the budget for the raw materials. Mark this material cost as “A”.

 

Step 2: Solicit for a quote on the job

 

If you have machinery on you hand needed to undertake the different processes on the production of your articles, have your fabricator quote on the cost of the job. This also applies if you don’t have the means (like machinery and personnel) available to you. But you must select the most efficient fabricator having the lowest cost with the highest quality of finished products.

You can quote labor cost outside by contacting your fabricator/s if the situation calls for. Moreover, some suppliers of raw materials have their own fab shops, which you can utilize to manufacture your goods. Once you settle for a more cost-effective quote, brand this as cost “B”.

 

Step 3: Determine shipping/transport cost

 

Some suppliers deliver raw materials free of charge, some put additional charges on them. This also holds true if you decide to fabricate your products elsewhere. The costs that your suppliers and manufacturers are charging you should be ascertained and keep recording them occasionally.

If you observed that some suppliers and fabricators are overcharging their materials and services, you have all the freedom to outsource from other providers. Once you determined the cost of shipping or transport fees and other charges associated with moving the raw materials, label this as cost “C”.

 

Step 4: Calculate for miscellaneous expenses

 

You must also include the cost of other expenditures associated with the manufacture of your sheet metal products. One example is the cost to obtain a quality certificate, or the cost of machining, and other expenses. Let the items be marked as cost “D”.

 

Step 5: Sum up the total estimated cost

 

After calculating all the necessary cost required to finish a single type of product in its entirety, add all the estimated costs you have established in the above steps. Therefore, summing up cost A+B+C+D = Total cost. After arriving at this estimate, you can determine the overall cost to fabricate your product and you are now ready to find out your profit in the next step.

 

Step 6: Calculating profit and overall cost

 

Most manufacturers put a 20% marked up price on each piece of the finished product as their profit margin. However, you may opt for a lower or higher mark up depending on the viability of your product. Once you decide for the right marked up, you can determine your total profit percentage.

Here’s the idea. If you decide to have a profit percentage of 15% on your total cost, consider this example:

If you have a total cost of $2000 (from A+B+C+D above) and the profit percentage of 15%, then the profit would be:

Profit = 15/100 x $2,000 = $300

Determining the total cost of your product,

Overall cost = Profit + Total Cost = $2,000 + $300 = $2,300

Therefore, you can price your product depending on this information you obtained. However, most manufacturers based their pricing on the outcome of a particular product’s inventory. That is, dividing the Overall Cost by the number of pieces the operation yielded. Just simple as that!

 

Some healthy tips for the starting/veteran entrepreneurs

 

  • Some sheet metal manufacturers do not count the profit they make out of selling the scrap metal (as waste) from the fabrication. But unless the scrap material is so enormous, you may consider your profit on it and reduce the selling price of your finished product to make you more competitive.
  • You can order raw materials in large volume as some suppliers lower their price depending on bulk purchases. Additionally, you can also save a lot in shipping charges if you order in large quantities and lessen the overall price as well as the fabrication services.
  • You can also narrow down your suppliers into the most efficient and cost-effective ones by getting quotes from numerous providers. The lots of choices will help you grasp with the different costs corresponding to the fabrication processes.