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FASCINATION OF SHEET METAL A material of limitless possibilities

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Sheet Metal Possibilities

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Page 1: Basics Sheet Metal Possibilities

FASCINATION OF SHEET METAL

A material of l imitless possibil it ies

Page 2: Basics Sheet Metal Possibilities

This work is protected by copyright. All rights reserved, including the right

to translate, reprint, or reproduce this book or any part thereof. No part

of this publication may be reproduced, stored in a retrieval system, or

transmitted in any form or by any means whatsoever, whether electronic,

mechanical, photocopying, recording, or otherwise, without the prior

written permission of the publisher.

While great care has been taken to ensure the accuracy of the contents

of this book, the author, the editor and the publisher do not assume any

liability for damages, direct or indirect, arising from the use of this book,

in part or total, except where prohibited by law.

ABOUT THIS PUBLICATION

Editor Dr. Nicola Leibinger-Kammüller, TRUMPF GmbH + Co. KG, Ditzingen, Germany

Author Gabriela Buchfink

Translation Matthew R. Coleman

Project coordinators Frank Neidhart, Gabriela Buchfink

Project associates Dr. Nicola Leibinger-Kammüller, Dr. Klaus Parey, Ingo Schnaitmann

Layout and design Felix Schramm, Karen Neumeister (SANSHINE GmbH, Stuttgart)

Text consultant Gurmeet Röcker

Translation coordination euroscript Deutschland GmbH, Berlin

Production coordination Jeanette Blaum (SANSHINE GmbH, Stuttgart)

Printing Rösler Druck GmbH, Schorndorf

Finishing Oskar Imberger & Söhne GmbH, Stuttgart

Binding Josef Spinner Großbuchbinderei GmbH, Ottersweier

Image editing Reprotechnik Herzog GmbH, Stuttgart

Publisher Vogel Buchverlag, Würzburg

ISBN-13 978-3-8343-3071-0

ISBN-10 3-8343-3071-X

1st edition 2006

Page 3: Basics Sheet Metal Possibilities

26 27

SHEET METAL – DISCOVER THE POSSIBILITIES

SHEET METAL – DISCOVER THE POSSIBILITIES

27

28 | THE DAYS OF THE DRAWING BOARD ARE OVER

30 | THE SHEET METAL PROCESS CHAIN

Putting it all together

Creating the finished product step by step

Data flow

34 | BEFORE DESIGNING BEGINS

When to choose sheet metal

Strategies for finding new solutions

36 | MAKING IT WORK

Creating functional designs

Creating economical designs

You designed it. Now can you produce it?

46 | CREATIVE IN CYBERSPACE

SHEET METAL DESIGN IS MORE THAN

JUST ENGINEERING – IT’S AN ART. IT

MEANS WORKING CREATIVELY WITHIN

STRICT TIME AND COST RESTRAINTS,

WHILE FORGING AHEAD IN NEW DIREC-

TIONS. PROVEN STRATEGIES AND

STATE-OF-THE-ART COMPUTER TECH-

NOLOGY ARE INDISPENSABLE TOOLS

FOR F INDING OPTIMUM SOLUTIONS FOR

FABRICATING INCREASINGLY COMPLEX

SHEET METAL PARTS.

Page 4: Basics Sheet Metal Possibilities

28 | Sheet metal – discover the possibilities 29

There was a time when the most important tools of a design

engineer were parchment paper, ink pens, razor blades for

erasing mistakes, a drawing board, and stacks of tables listing

standardized parts. As a manufacturing material, sheet metal

was not as flexible or versatile as it is today. For this reason,

parts were often constructed of individual prefabricated stan-

dardized components.

The last 25 years has seen a complete change in the way

design engineers work. Today’s manufacturing techniques

allow sheet metal to be cut, formed, bent, or joined in almost

any way imaginable. In the past, it was common practice

to construct a module of many simple parts. Today, design

engineers strive to use as few single parts as possible. The

parts themselves, however, can be extremely complex.

Once an indispensable tool, the drawing board disap-

peared from engineering firms long ago. Today, design engi-

neers can create 3D sheet metal parts directly at the computer

screen. All subsequent steps – from unfolding the part all

The days of the drawing board are over

the way to machine programming – are performed by the

computer. Even production can be simulated with the help

of special design and programming software. If the software

detects any problems, the engineer can make the appropri-

ate changes to the part. Electronic data flow bridges the gap

between design, programming, and production. As in the

past, design engineers work at the start of a process chain in

which they play a key role. An important part of their job is to

ensure that processes run smoothly and efficiently.

1 2

43

The end of the “white coat” For a long time, the word “design engineer”

conjured up images of a fussy, narrow-minded perfectionist dressed in

a white coat. Because of their outfit, design engineers were sometimes

called “white coats.” Despite their image, design engineers were the

same back then as they are today: inventive, creative minds striving to

meet a wide range of demands.

SERVING ’EM UP HOT WITH SHEET METAL

“What can I get you?” “I’ll have the spaghetti Bolognese.” An

extra large portion of spaghetti lands with a gentle “plop”

on a preheated plate. The Bolognese sauce is poured over

the noodles, and the plate is placed on the table in front of

Reinhold Portscheller. The spaghetti isn’t the only thing he’s

happy about. Reinhold Portscheller is a design engineer at

Rieber GmbH + Co. KG in Reutlingen, Germany, and knows

just how much work went into designing the plate dispenser

cart from which his preheated plate just came. The sheet

metal part used for pushing up the plates used to look very

different from the way it does now.

“The part holding up the plates used to be composed of

seven elements with 39 bends and numerous welding spots,”

recalls Portscheller. Manufacturing the part was extremely

complicated. All single parts were manufactured separately,

put into temporary storage, and then joined. The spot weld-

ing jig alone was, in Portscheller’s words “a real behemoth.”

No question about it: the sheet metal part was in dire need

of some serious production streamlining. Portscheller and his

colleagues were delegated the task of improving operation

while lowering production costs. With this in mind, the de-

sign engineer turned to an out-of-company workshop.

“This was a good decision,” says Portscheller looking back.

“You had colleagues from other companies and industries all

sitting at the same table. We were eager to exchange infor-

mation, and we approached things in an open-minded way.”

Instead of simply modifying aspects of the part, the workshop

participants started over from scratch. They asked them-

selves, “is this hexagonal form really necessary?” Indeed, this

turned out to be the crucial question. The sheet metal part

is now triangular in shape. “We reduced seven single parts

to two. Also, we now only need seven bends and a few weld

spots,” says Portscheller with a smile. But that’s not all the

new solution has to offer.

“The plates are pushed upwards much more evenly, the

part is more attractive than it used to be and our production

costs have been slashed considerably,” he explains. Port-

scheller’s colleagues now require much less time for laser

cutting, bending, and spot welding than they did before. Plus,

they no longer have to put the single parts into temporary

storage. This saves both time and space. A success story?

“It sure is,” confirms the design engineer and finally turns his

attention to his lunch.

1 Designing parts on a drawing board

2 3D design on a computer

3 Simple sheet metal part

4 Complex sheet metal part

The plate dispenser is used to hold and dispense heated plates. The plates

rest on an optimized sheet metal element.

Page 5: Basics Sheet Metal Possibilities

30 | Sheet metal – discover the possibilities

The sheet metal process chain

PUTTING IT ALL TOGETHER

From the idea to the finished part – to put it in a nutshell,

that’s what the sheet metal process chain is all about. The

company’s goal is to manufacture high-grade parts in a way

that is both fast and cost effective. For this to happen, in-

dividual stages of the process have to be coordinated as

precisely as possible.

Coordination begins at the design stage. For example, if

the engineer decides to create a part that will have round

punch holes, he or she will try to use only diameters that can

be produced with existing tools. In production, meanwhile,

speeding up the punch press does not make any sense if

a mountain of blanks is already waiting to pass through the

press brake and the programmer is still busy programming

the machine. Instead, the idea is to set up processes so that

they “dovetail,” or interlock into a unified whole. Companies

that take steps to ensure that their corporate organization

and technical infrastructure are well equipped to meet this

challenge will be prepared, even when a rush job comes

along. If a customer calls on Monday and wants 500 steel

angles by Thursday evening, this will only mean completing

an additional cycle and not a desperate race against time.

CREATING THE FINISHED PRODUCT STEP BY STEP

There are several process steps that have to be completed

from placement of the order to delivery of the product. The

main process steps are:

• Design

• Programming

• Production (flat processing, bending, joining)

• Final processing

Design Programming Flat processing

Design | Strictly speaking, the design stage does not start

with the idea for a part or module, but with the description of

the functions that the part or module is intended to perform.

These functions are specified in a document known as a

“requirements specification.”

On the basis of the specification, the design engineer

comes up with several initial designs and then sketches them

on paper. Often, several people will be working together on

one job, resulting in a wide variety of designs. Design en-

gineers frequently use paper models to see which design

will provide the optimum solution. After a design is chosen,

it is drawn using computer-aided design software. As the

design engineer models the part, the computer creates a

three-dimensional shape on the screen, while taking into

account material, tool, and machine data. Using the data,

the system checks whether the part can be manufactured. Design sketch

Ideas are first drawn on paper.

Bending Joining Final processing

31

Page 6: Basics Sheet Metal Possibilities

32 | Sheet metal – discover the possibilities 33

Common problems are:

• Missing tools | The part may have been designed with

oval holes but only round punching tools are available at

the time of machining.

• Overlap | Material overlapping results in the flat layout

of the part.

• Collisions during bending | The workpiece collides

with the machine or tool during bending.

• Bending flanges are too short | The bending line is

too close to the edge of the workpiece, causing the

flange to slip into the die.

• Holes are too close to the bending line | Holes may

be so close to the bending line that they undergo defor-

mation during bending.

The software detects these and other problems and then

warns the design engineer. The final product that the engineer

creates on the screen is three dimensional. The sheet that

will be used to make the part, however, is flat. For this reason,

the design stage is concluded by literally “unfolding” the vir-

tual three-dimensional part. The unfolding process produces

a flat sheet metal part showing how the initial sheet needs

to be cut or punched. Holes, formed sections, and bending

lines are also shown. This data is then transferred to the pro-

gramming software.

Programming | On the basis of the unfolded part, the

programmer creates NC programs for all machines used to

process the part. NC programs tell the machines what oper-

ations to perform in order to produce the part. Nowadays NC

programs are no longer programmed manually. Instead, they

are created semi-automatically, using programming software

that contains precise information about the machine and tools.

The programmer selects the machining strategy, specifies

the tools, and optimizes the parameters. Then, with a simple

click of the mouse, the programmer tells the programming

software to generate the NC program.

The programming software determines the optimum pro-

cessing sequence and generates error-free NC programs. In

the past, the only way to detect errors was to perform a test

run on a sample piece. Today, programmers can be certain that

the NC code does not contain any typos or invalid command

sequences that might disrupt the program.

Production | During production, each part must pass

through several stations. The first step in production is al-

ways flat processing. Blanks are punched out of the sheet,

or a laser is used to cut them out. The blanks are then bent

on a press brake. For assembled units, the final step is to

join the individual sheet metal parts. Fast and cost-effective 1

Thin but strong Tall power poles are able to withstand hurricane-

strength winds of over 120 kilometers per hour, even though the steel

sheet used to construct the poles is only a few millimeters thick. The

reason the poles are so strong is because of their design. They have a

large number of supporting elements that make them strong.

production means creating the final shape in as few steps

as possible. There are two ways of doing this. One way is

through targeted part design. For example, contours and

formed sections can be designed so that they can all be

produced using the punch press.

Another way is to use machines that combine various man-

ufacturing techniques. On combination punching and laser

cutting machines, for instance, it is possible to do forming

work, while, at the same time, producing complex contours

that can only be cut with the laser.

Final processing | When sheet metal parts come out of

production, the sheet metal itself is still unfinished. Scratches,

welding seams, and dirt are still visible on the part. The final

processing stage is when the steps still required to finish the

part are carried out.

Typical steps that are performed:

• Cleaning up welding edges

• Hardening / tempering

• Coating

• Marking

• Painting / varnishing

As in production, the time required for final processing should

be kept to a minimum. Through appropriate part design, the

amount of work needed for processes such as cleaning up

welding edges can be reduced.

DATA FLOW

The IT infrastructure has become a key factor determining

the productivity of both man and machine. Today, this is also

true in sheet metal processing. Without the electronic flow

of data connecting everyone involved in the entire process,

nothing would work. Orders are entered and created using

resource management or production planning systems. Design

engineers rely on computer-aided design software to model

the part. The data flows to the programming software, which

is used for creating the production programs. Once the job

is complete, the purchasing department may have to order

more material. The accounting department, meanwhile, pre-

pares and sends the invoice.

The entire process can only run smoothly when everyone

is able to access and utilize the required data at the proper

time. For the design engineer, for example, this means being

able to access machine, technology, and tool data during the

design stage. It is also possible to standardize the design

process to a certain degree. When this is done, the design

engineer only needs to modify existing designs to produce

similar sheet metal parts.

1 Flat blank and bent part

2 For flat processing: combination punching and laser cutting

machine with storage system

2

Page 7: Basics Sheet Metal Possibilities

34 | Sheet metal – discover the possibilities 35

WHEN TO CHOOSE SHEET METAL

So when does it make sense to use sheet metal parts? This is

a question that companies are often faced with. The answer?

More often than you think. Classic sheet metal parts typically

include covers, trim, brackets, profiles, and machine compo-

nents that have to be very lightweight so that they can be

moved at high speeds. In cases like these, using sheet metal

seems like the obvious choice. And, increasingly, sheet metal

parts are also being used in areas that were previously the

domain of other manufacturing methods.

Before designing begins

Sheet metal parts can be used as a substitute for:

• Cast parts made of molten metal, like radiators.

• Milled parts made from solid metal blocks. Parts like

these include holders with numerous holes and threads.

• Drop forgings made of red-hot metal that is pressed

into a mold. Parts such as these include collars used

in automobile transmissions to engage individual gears.

Instead of forging these parts, manufacturers can weld

together two sheet metal shells to form a hollow body.

There are two reasons for doing this. First, the manufacturing

techniques used to process sheet metal have become so pre-

cise that staying within the required tolerances is no longer

an obstacle. Second, steel has become more expensive. A

large amount of material is required to produce solid parts

from metal blocks. This, in turn, makes the parts more ex-

pensive. To reduce costs, companies have begun to explore

alternatives like sheet metal.

The advantage of sheet metal is its weight, price, and the

flexibility with which it can be processed. Sheet metal parts

are also more quickly available. For instance, considerably

less time is required to manufacture a sheet metal part than

a cast part, for which a model and mold must be prepared

before the first part can even be produced.

At the same time, the production quantity can be an im-

portant factor. For small to medium lot sizes, sheet metal is

less expensive. For quantities over 100,000, however, cast

parts are usually more economical and can also be manu-

factured more quickly. In the end, it is necessary to weigh

all the factors involved on a part-by-part basis to determine

whether sheet metal is the more economical alternative pro-

viding a solution that is of an equal or higher quality.2

1

It is always important to consider whether a sheet metal part

should be used instead of a solid part in the following cases:

• Whenever a part is developed from scratch

• Whenever modifying an existing part that has previously

been manufactured from solid material

Even if a part is already made of sheet metal, it is possible to

reduce costs through optimization. Combining several parts

into a single part is usually more economical on the whole.

Remember: small savings can mean big gains, especially

when it comes to standard parts produced in big quantities.

STRATEGIES FOR FINDING NEW SOLUTIONS

A new solution has to be innovative and more cost effective,

while providing a higher level of quality. These are the require-

ments that design engineers strive to meet. It can be a difficult

job, but there are three strategies that can help. The first

strategy is “always start at the beginning.” This is true even

if the goal is to optimize an existing part. This method opens

up your mind to new and unconventional ideas. The second

strategy is “start with the part’s function, not its present ap-

pearance or production method.” This ensures that the final

design includes only those elements that are actually needed.

Finally, the third strategy is “two heads are better than one.”

Inspiration frequently comes from other people in the team.

Because of its great flexibility, sheet metal allows the

development of many different solutions to a single prob-

lem. Maybe there’s a bend that can go somewhere else, or

a hole that could be shaped differently. Perhaps there’s a

90-degree angle that would be better as a 120-degree angle.

Sometimes a few minor changes are all that are needed. The

optimum solution usually combines an ingenious idea with

thorough testing and a concrete set of rules.

1 Device housings are typical sheet metal parts.

2 Lasers can even be used to cut contours on deep-drawn sheets.

3 Multilayer technique: multiple blanks form a complex component

3

Multilayer technique Solid sheet metal forms can be created by

stacking multiple layers on top of each other and joining their surfaces.

This technique is used for parts with complex internal structures. Each

layer is first processed individually. The finished parts are then placed on

top of each other and soldered together in a vacuum oven.

Page 8: Basics Sheet Metal Possibilities

Producing functional parts while minimizing costs and manu-

facturing times – it’s a goal that every sheet metal processing

company strives to meet. These are also the requirements

that design engineers must take into consideration when

creating a part. Using different strategies and rules of thumb

can be of great help here.

CREATING FUNCTIONAL DESIGNS

Every sheet metal part is designed to perform a specific task.

For example, the part may be used to support another part or

cover machine components, or it may have to move at very

high speeds. Creating functional designs means designing

the part so that it is able to fulfill its task. To do this, design

Making it work

engineers must have extensive knowledge of sheet metal

properties and take these properties into account when crea-

ting the part.

Sheet metal offers certain advantages. It weighs less

than solid metal blocks and is easy to shape. At the same

time, this means that sheet metal is not as sturdy or rigid. If

stressed improperly or subjected to excessive loads, it can

bend or buckle. Special design techniques, however, can

be used to lend greater strength and rigidity to the parts. In

addition to resilience, appearance can also play an important

role. The surfaces of external parts like covers and paneling

have to be flawless. Here, too, design engineers have a few

tricks they can use.

Distributing loads | If a strong load is applied to an

unfavorable spot or if it is concentrated on too small an area,

the sheet metal part may become deformed. That is why

parts are designed to distribute stresses to different areas

of the component. This reduces the amount of force applied

at each point. If the load is still too great, features such as

braces can be used to reinforce certain areas.

Using tension instead of compression | Long com-

ponents with small cross sections can bulge or buckle easily

when subjected to pressure. This is because the force and

counteracting force collide within the metal. The same com-

ponents, however, remain stable when subjected to tensile

force. This is due to better distribution of forces. For this

reason, components are designed so that parts with small

cross sections are stretched instead of being compressed.

Different thicknesses | The thicker the sheet, the greater

the load it can withstand without becoming deformed. Put

simply, if you need more stability, use a thicker sheet. Greater

sheet thickness, however, also means more weight. Large

parts often need to be lightweight and are only stressed in

a few spots. That is why thicker material is used only and

exactly at the stressed points.

In large-scale production, “tailored blanks” can be used.

“Tailored blanks” are made up of different pieces of sheet metal

that are welded together into a single sheet. This means

thick and expensive materials are used only in areas where

they are needed most.

For small and medium-sized quantities, making tailored

blanks is not a cost-effective solution. Here, another approach

is used. In areas where the part needs to be thicker, another

sheet is simply welded on to it.

As great force concentrated on a single spot causes the sheet to deform,

it needs to be distributed. Energy absorbing areas are reinforced.

If pressure is applied to a long component, it may buckle. The component

fares much better, however, when subjected to tension.

“Design engineers are often not aware of the full range of possibilities

that sheet metal has to offer. That’s why I present a variety of examples,

tips, and tricks in various workshops. A lot of the people who take part

in the workshops are amazed to discover just how easy it is to cut and

bend a 10-millimeter thick sheet. Others, meanwhile, are impressed by

the complexity of some of the sheet metal parts. These workshops give

people inspiration and insight that they can apply in their daily work.”

Jörg Heusel, Design

Making it all work: design engineers have to meet a wide range of demands.

3736 | Sheet metal – discover the possibilities

Page 9: Basics Sheet Metal Possibilities

38 | Sheet metal – discover the possibilities 39

Formed sections for added stability | Forming is the

most common method of making sheet metal more stable. On

tin cans, for example, corrugated areas or beading around the

can make it sturdier. These corrugations can have different

configurations or spacing and are used on other products as

well – not just tin cans. You can spot corrugations on cars or

on the brackets holding up a row of shelves at the hardware

1 Corrugations make cans stronger.

2 Folds are used to reinforce ducts.

Edge variations

Edges can be made more robust by bending or folding them over or joining the edges at the corner.

store. Parts with large surfaces such as ventilation or heat-

ing ducts can be made more stable by adding intersecting

creases. When this is done, the walls of the ducts resist bulg-

ing and, at the same time, are less susceptible to vibrations.

A greater degree of stability can also be attained by forming

the edge of the sheet metal part. Oftentimes, simply bending

or folding over the edge is all that is needed.

1 2

Closing of cross sections | Closed sheet metal struc-

tures are much sturdier than open ones. This is especially

true of parts that are subjected to torsion, or twisting. For

this reason, box-shaped forms should be closed wherever

possible, for example, by welding together the edges.

Composite structures | Ribs, rods, braces and reinforce-

ment plates can also be used to add stability to parts made

of thin sheet metal. Corner or center plates are frequently

used on open box structures made of profiles (tubes having a

variety of cross sections) like those used to construct stands

at exhibitions or trade shows. Evenly spaced ribs are used to

reinforce large-volume parts.

Joining from the inside | On sheet metal parts requiring

a flawless appearance, processing marks must not be visible.

On parts like these, visible edges that are welded from the

outside can prove to be problematic. To avoid having to polish

them by hand, special joining methods are used to create a

clean seam. Such methods include TIG welding for stainless

steel or laser welding. Another alternative is to weld the edges

from the inside. Here, the edges of the sheet are bent over

so that the welding seam is on the inside.

Tension Forces act in opposite directions, stretching the part.

Corner or center plates can be used to reinforce open box structures.

Pressure Forces converge on a single area, compressing the part.

Torsion Forces pass in different directions, causing the part to twist.

Bending Forces act in the same direction, causing the part to bend.

“You know you’ve achieved perfection, not when you have nothing more

to add, but when you have nothing more to take away.”

Antoine de Saint-Exupéry

Page 10: Basics Sheet Metal Possibilities

CREATING ECONOMICAL DESIGNS

The maximum allowable cost of a sheet metal part is deter-

mined before work begins on designing the part. Naturally,

the more economical the part is, the better. There are two

ways of achieving this. You can either save on material or cut

costs in production. “Economical,” however, is not the same

as “cheap.” The goal is to combine the various production

factors – the type of material, material consumption, time,

machines, and tools – in the best way possible.

Production factors influence each other. One change can

oftentimes have a positive effect on a number of different

areas. For example, a reduction in the number of single parts

used to create a module not only saves material, but also

reduces production time. The following methods have proven

to be successful in creating economical designs:

Minimize sheet thickness | Save material by select-

ing the smallest sheet thickness possible. This means lower

material costs, reduced part weight, and faster production.

Use the same sheet thickness | Wherever possible, the

single parts making up a component should all have the same

sheet thickness, so that they can be produced from a single

sheet in one work cycle. When this is done, an entire sheet

can be used for flat processing instead of portions of several

different sheets. This is especially important for small sheet

metal fabricators who handle each job individually. It not only

makes purchasing and storage easier, but also cuts down on

transport between the storage bay and the machine. Also, it

takes less time to set up the machine.

Maximize nesting potential | Everything left over after

the parts are punched or cut out of the sheet is scrap. This

includes the sheet skeleton remaining between the parts

and the cutouts that are produced when holes are cut in the

workpiece. Design engineers can fit more parts on the sheet

by designing the parts so that they “nest” inside each other.

Depending on the design, it may be possible to fit smaller

parts inside some of the larger cutouts. Enlarging a notch

on the outside contour may also allow parts to be nested

closer together. Parts with straight contours can be placed

right next to each other and separated with a single cut. This

helps to reduce scrap.

The benefits of these methods are particularly apparent

when manufacturing parts in large quantities or producing

sets of parts for use as components in sheet metal modules.

One part, many functions | In many cases, the sheet

metal part can be designed to fulfill two or more functions.

Often, these parts only need some additional holes or larger

recesses in order to perform a different task. Advantages:

larger quantities can be produced and only one storage loca-

tion is needed.

“If it isn’t there, it doesn’t cost anything. This applies, above all, to sheet

thicknesses and the number of single parts that make up a component.”

Lutz Hartmann, Design

Using design to reduce scrap: designing parts so that they nest closer

to one another is a way to maximize sheet utilization.

Minimize the number of single parts | As a general

rule, it is better if components comprise a small number of

complex parts than a large number of simple parts. This is

because joining processes are usually very time consuming.

Today’s manufacturing techniques and programming software

make it easy to produce even complex single parts.

Why weld when you can bend? | Welding not only takes

up valuable time, but also generates heat that could poten-

tially warp the workpiece. For this reason, it is always a good

idea to check whether an attached part can be substituted

by simply bending another section. This eliminates the need

for welding along with all the associated prep work such as

setting up, aligning, and clamping the parts.

Minimize cleanup | Cleanup work can be reduced by

eliminating welding seams entirely, by welding sections from

the inside, or by designing edges so that they are straight

and smooth after welding. New manufacturing techniques

such as laser welding also help to reduce cleanup work.

1 The visible edges of this cover are welded together using a laser.

The welding seams are clean and smooth, eliminating the need for

extra cleanup work.

Alternatives to welding: flanges can be bent and side elements can be secured in place using pegs that fit into holes.

1

4140 | Sheet metal – discover the possibilities

Page 11: Basics Sheet Metal Possibilities

43

YOU DESIGNED IT. NOW CAN YOU PRODUCE IT?

When designing a part, design engineers not only have to

keep in mind the function and cost of the part, but also how

it is going to be manufactured. Here, there are a number of

different strategies that engineers can rely on.

Allow extra space for bending zones | When a sheet

is bent, the metal on the inside of the bend is compressed.

This causes the material at both ends of the bend to be

pushed outward, which, in turn, may lead to inaccuracies.

To prevent this from happening, small recesses are designed

into the ends of the bending zones so as to provide extra

space for deformation.

Extra space is frequently provided for bending zones,

regardless of whether two edges meet at a corner or whether

a flange is bent upwards. This produces much better cor-

ners, while permitting greater freedom in the selection and

arrangement of bending tools.

There are a number of ways to create extra space for bend-

ing zones. A punch press can be used to punch round holes

at both ends of the bending line. Or a laser can be used

to cut fillets, which are more complex. This makes corners

more attractive after the parts are bent.

Use existing tools | Especially when it comes to small

and medium-sized quantities, acquiring new tools is not a

worthwhile investment for a company. In most cases, it is

not even necessary. For many shapes and functions, there is

more than one alternative. It is the design engineer’s job to

find the alternatives that make do with existing tools.

A good example is the ventilation holes on a PC housing. A

punch press that permits tool rotation can be used to arrange

simple oblong holes in a radial pattern. An alternative would

be to arrange small squares in rows or use a louver tool to

produce ventilation slots.

Use positioning and joining aids | Where was the part

supposed to go again? Was it on the left or the right? Ques-

tions like these can be avoided by designing the parts so

that there is only one way to put them together. This is done

by using matching holes and pegs to assemble parts. At the

Certain areas can be notched in order to obtain better corners.

1

same time, there are certain joining techniques that reduce

the amount of prep work involved in processes such as weld-

ing. Instead of using a device to position multiple parts and

secure them in place, you start by fitting the matching parts

together. Now all that is needed is a simple welding jig to hold

the parts securely in place.

Microjoints | The idea of using microjoints was a solution

initially developed for laser cutting. Microjoints are narrow

tabs located between the workpiece and the sheet. They

hold the workpiece in the sheet and keep it from becoming

displaced. After the sheet has been processed, the parts are

snapped out of the sheet by hand.

There are other ways that microjoints can be used. For

example, they can serve as production aids in the manufacture

of small angles. The blanks remain connected by microjoints.

They are bent together and then separated by hand. Another

example is creating bends in parts where accuracy is not

crucial. Microjoints are placed along the bending line, making

it possible to bend the parts by hand.

Everything on the punch press | When solid parts are

substituted by sheet metal parts, these parts often still require

machining of some kind. Holes still have to be drilled, and

threads have to be cut. The most cost-effective solutions,

however, do not require any cutting at all. This can be done,

for example, by using the punch press to form threads instead

of cutting them.

Life after production | The true life of a sheet metal

part actually begins after production. For this reason, it is

important for design engineers to take into account aspects

such as transportation, storage, assembly and disassembly.

For example, parts that are transported and stored in large

numbers should be designed so that they can be stacked on

top of each other to save space.

1 Housing with different ventilation openings

2 Microjoints: thin support pieces keep punched parts from falling

out of the sheet skeleton.

2

42 | Sheet metal – discover the possibilities

Joining made easy: there is only one way of joining the parts together.

Page 12: Basics Sheet Metal Possibilities

44 | Sheet metal – discover the possibilities

Production simulations | Many types of design and

programming software enable users to simulate production.

This allows design engineers to test sheet metal parts as

often as necessary to identify problems. Today, computer

simulation has become an indispensable pre-production tool,

particularly for the manufacture of complex parts.

The use of simulations ensures that workers in production

no longer have to stand next to the machine for hours trying

to figure out the optimum production sequence for a sample

piece. Company directors will also be pleased to see that

the machine is being used to produce something instead of

completing endless test runs.

Knowledge transfer | Design engineers who have exten-

sive experience in the field are able to rely on their expertise

to tackle each new task. Working together with colleagues

in production, they have gained knowledge of the attainable

tolerances and learned which hole spacings, edge formats,

side lengths, and bending radii work and which ones don’t.

To ensure that this knowledge can be used by others, it has

to be documented. Ideally, this is done using the design

software, which helps to integrate individual experience and

safeguard company standards.

FIVE WAYS TO PRODUCE AN ANGLE

Design is an art. Designers not only have to know plenty of

good tricks, but also when to use them. Sheet metal is so ver-

satile and the parts are often so complex that engineers may

not immediately recognize all the possibilities. Jörg Heusel,

design engineer and instructor at TRUMPF Werkzeugmaschi-

nen GmbH + Co. KG in Ditzingen, knows just how challenging

this can be. He conducts workshops in which participants

search for new solutions for their existing parts. “The people

in my workshops frequently ask me to demonstrate the many

possibilities available using only a simple example,” says Jörg

Heusel. His response is to show them five ways to produce

an angle. Angles are always positioned in areas where two

surfaces meet. They hold the surfaces in place and help sup-

port them when they are stressed. If the angle is subjected to

extreme loads, it may need to be reinforced. There are many

different ways of doing this.

Method 1 | Using cross braces The first way to make

angles sturdier is to weld a cross brace down the middle of

the angle. What this means for production: two parts have

to be punched or cut with a laser; the angle is bent; and the

cross brace is positioned and welded to the angle, producing

two seams. Not bad, but how can we find a better solution?

Method 2 | Using joining aids This method is aimed at

reducing the amount of positioning and welding work. The

cross brace has two tabs, and the angle has two rectangular

slots. The tabs are inserted into the slots, and the joint is

welded from the outside at two points.

1 Virtual manufacturing: the movement of the laser cutting head

is simulated on a computer.

1

Method 3 | One part only Two parts generally mean more

work than one part, because they are often produced sepa-

rately and then put into temporary storage. So let’s try using

one part instead of two. Two supports on the sides of the

angle now replace the cross brace. As before, these sides

are also designed with joining aids that facilitate welding.

The angle is punched or laser cut and then bent three times.

The sides are then welded. Although we have not significantly

reduced the amount of work required to produce the angle,

we now have a part that is very robust.

Method 4 | The answer is just around the corner So what

do you do if the brace absolutely has to be positioned down

the middle of the angle? The solution is easier than you might

think. This time, two bends are made to bring the brace into

position. Here, too, a tab is used to fit the brace to the angle.

This results in a single part that requires only three bends.

Now, all that’s left to do is to weld the brace at one single

point.

Method 5 | Don’t forget what the part’s made for Let’s

look back for a moment at the function of the angle. It has

to be sturdy and be able to support a load. Wait, does the

angle even need a cross brace? Or would a simple, well-

placed corrugation do the trick? If cross beading is enough,

you could consider first punching or cutting the rectangular

parts from the sheet. Afterwards, the edge and corrugation

can be produced in a single bending process. This approach

not only minimizes production time, but also makes it possible

to stack and store parts to save space.

3

One-piece design: sides

instead of cross brace.

4

Three bends are used to

produce a center brace.

5

One bend only: cross bead-

ing instead of cross brace

1

Angle with welded cross

brace for reinforcement

45

2

The cross brace has tabs

that help to join parts.

Page 13: Basics Sheet Metal Possibilities

Creative in cyberspace

The changing nature of the job | The job of a design

engineer is constantly changing. Each new material, tool, and

manufacturing technique adds to the ever-growing array of

design possibilities for sheet metal parts. At the same time,

new design software and virtual modeling methods are

changing the way design engineers work. Even so, it usually

takes years before new technology becomes known among

professionals in the field and is then applied.

Many companies feel that the engineering design programs

offered by various schools do not give enough attention to

sheet metal design. To fill the gap, an effort has been made

to provide workshops and special training courses.

Virtual space | A number of companies are already using

virtual space to present and elaborate their product models.

Multiple projectors are used to display the image of a part

on several screens at the same time. People in the room

wear special glasses that combine the different images into

a three-dimensional model, just like in a 3D movie. People

in the automotive industry have found a way to project an

entire vehicle interior around a simulated driver’s seat. The

virtual interior makes it possible to see how well the different

elements of the design fit together or whether the steering

wheel is properly positioned. The simulation makes it easy to

move any elements that don’t fit.

Mechanical engineers can also use virtual space to present

components or entire machines. This allows them to discuss

the models with other departments.

As the technology becomes easier to use and the costs

become lower, use of virtual space will continue to grow.

Even so, computer-aided design software will remain crucial

for the design of the part. This is because most of the work

involved in designing a part is actually drawing it.

Automated design? | Computer technology has come a

long way, and is still advancing every day. Nevertheless, com-

puter software is no substitute for human creativity. Design

software will remain a tool that design engineers use to make

modeling easier, while enhancing the precision and efficiency

of their work.

At the same time, the data interfaces between the resource

management system, computer-aided design software and

programming software continue to undergo optimization. The

goal and essence of the design process, however, remains

the same: creative, intelligent people working to find innova-

tive solutions. 1

Virtual space or “cave” Complex computer and projection technology

make it possible: multiple projectors are used to display the image of

a part on several different screens. The people in the “cave” wear special

glasses that combine the images on the various screens into a single

three-dimensional image. Cameras, meanwhile, are used to monitor the

position of the observer. If the observer moves, the image changes accor-

dingly. This allows the observer to examine the part from different angles:

from above, from below – even from the inside!

1, 2 Still in the design stage and yet incredibly real: developers discuss

their designs in virtual space.

2

4746 | Sheet metal – discover the possibilities