basics sheet metal possibilities
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Sheet Metal PossibilitiesTRANSCRIPT
FASCINATION OF SHEET METAL
A material of l imitless possibil it ies
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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
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.
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.
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
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
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.
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
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
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
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.
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.
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