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Sheetmetal Question – Different Forming Capabilities

Question asked by Brett Leland on Sep 21, 2018
Latest reply on Sep 26, 2018 by Scott Leacox

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Sheetmetal Question – We have different forming capabilities
for our sheet metal parts (Trumpf Press Brake - Trumpf Tooling / Amada Press
Brake - Amada Tooling / Cidan Panel Former- Cidan Tooling) The question or
issues is that when we are designing our product we do not know what machine /
machines our parts will be formed on. Each
machine / process requires different bend deduction / bend allowances and
generates (forms) different inside radii.
I am curios to how other handle these scenarios when it comes to generating
flats. Or initial thought was to pick
and process and design to it and then let manufacturing make the required adjustments
but that gets messy because they ultimately us our SW Files to generate flats. Any help will be greatly appreciated. Thanks, Brett

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Dave Bear Sep 21, 2018 10:03 AM
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Hi Brett,

Okay, so I make the assumption then that none of your designers have practical experience? I guessing at this stage that massive amounts of communication and education between the shop floor and your department is the best immediate fix.
An understanding of how and what your machining capabilities/processes are is the key answer to your question. Other things like bend deductions, K-factors, reliefs etc. can then be applied to each individual machine and/or process.

Dave.
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- Brett Leland @ Dave Bear on Sep 21, 2018 10:57 AM
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  Good Morning Dave, Thanks for the reply. The majority of our designers do have shop experience. The issue is that production programming likes to be able to open a SW File and generate a flat. When this flat is not accurate because the machine the part was modeled for is not used in the forming process it is a "design issue" because of the inaccuracy of the flat. Where in fact the flat is correct for a specific machine, it was just formed on a different machine. We tried for a while having our design group specify a machine but then we are dictating production and are not privy to machine loading. We also looked a different configuration but that became a mess as well.
  
  I hope this clarifies my question a bit more.
  
  Please add \your thoughts.
  
  Thanks,
  
  Brett
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Ruben Balderrama Sep 21, 2018 10:37 AM
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Buenos dias, no pierdas tiempo al principio donde vas a colocar la matriz, calcula bien los esfuerzos necesarios para luego colocarla en la prensa adecuada. Recorda que para formado de piezas podrias usar prensas mecanicas e hidraulicas por igual dependiendo de la complejidad del producto. Y si es punzonado deberias de usar una prensa mecanica Solamente.
Aqui nunca limitamos a una maquina en particular cuando diseñamos. Eso lo decide el que hace la programacion de produccion.
Lo que si hacemos es darle los valores que si necesita como
Dimensiones de Matriz abierta
Dimensiones de Matriz cerrada
Toneladas requeridas para garantizar el proceso
Te envio unas formulas para obtener las toneladas necesarias de acuerdo al proceso que elijas.

Good morning, at the beginning don't waste your time where you are going to put your die, make some math to obtain necessary efforts and then the place it in the appropriate press machine. Remember that to form parts you could use mechanical and hydraulic presses alike depending on the complexity of the product. And if it is punching, you should use a mechanical press only (simple rules).
Here we never limit to a particular machine when we design. That is decided by the one who does the production programming.
What we do is give you the values that you need as:
Open Die Dimensions
Closed Die Dimensions
Tons required to guarantee the process
I send you some formulas to obtain the necessary tons according to the process that you choose.
Attachments
- Math for Dies.xlsx436.9 KB
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- Brett Leland @ Ruben Balderrama on Sep 21, 2018 10:59 AM
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  Thanks for the reply Ruben, I will take a look further and may present it to production as an option. Have them specify what is needed to form the given parts. Thanks Again, Brett
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David Matula Sep 21, 2018 11:28 AM
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K factor of 44, is what our sheet metal man told us to set the k factor for on all models, at the user group meeting.

cure for the operations. 3 machines = 3 sets of dies, and 3 different drawings to get to the same finished dimensions.

make three different parts, with a 3 digit extension for each machine, then do a multiple page drawing one page for each machine.

or throw it back to manufacturing and say I don't care what machine you use, we need to have the parts come out the same if you do two bends on this one and three bends on this one. consistency in mfg is what you need.
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Frederick Law Sep 21, 2018 11:37 AM
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You have answered your own question.

Different machine, different tooling and different bend radius mean different flat pattern for each of the variations.
You cannot have a flat pattern that work on all machine.
Unless, you tolerance the part to work.
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Kevin Chandler Sep 21, 2018 12:33 PM
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Hello,

As Mr. Bear mentioned there are several factors involved, but another factor is what the final part requires to meet specifications.
Here are a few more:
- Do the bends have small (relative to gauge) or large radii?
- Do you coin? Air bend?
- What are the materials, including specific alloys?
- Are you using software from the machine vendor? (What are the capabilities in this software?)
- Who's programming the machines? And to what extent, just what's handed to them as complete?
- What tooling is available (die lengths, nose radii)?
- Where do the SW files originate?
- What are your standard production variances? (edge to bend, bend to bend, hole to bend, etc.)
- How much SW experience is in house? How much of it is sheet metal?
With the tooling you have/normally use and the materials you normally use at the gauges you normally use, I suggest creating precise coupons, measured before and after braking (and if you brake off 90°, then bend some coupons for +/-90° bends as well).
Compare the flat length to the measured bent flanges to see how well your bend allowance calcs are comparing to actual.

If you're using SW to generate blank sizes (which I don't recommend, it's an art and SW's precision isn't necessarily an advantage) then you will need to adjust your SW files for gauge, alloy, material, angle.

You will also need to determine which allowance method works for your parts and personnel.

I hope this helps.

Kevin
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Scott Leacox Sep 26, 2018 2:48 PM
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You have to make a choice.

Many parts can only be formed on one machine or the other. In those cases, use the details of those machines.

Determining what standard can be used for all the machines would be nice, then sticking to them in all cases would be ideal, but never quite works out.

You have to pick that battles that are important. It's never perfect with sheet metal. Don't start making runs of 100 parts until you test the flats of one or two. If the shot will not take the time to do such things, then you are are the limit of your info.

Tell the shop this: "Flat patterns are the result of CAD" To have CAD do it right, you have to know the radius, Thickness, Neutral factor, spring back, and dimensional limits of each machine.

Most use the Thickness as default R.

Here are the specifics I tend to use
The folder we use ended up needing R=1.4T, and K=0.26. (18 gauge through 10 gauge)
The default for break machines is R=5/64 and K=0.33 (Up to 7 gauge)
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Sheetmetal Question – Different Forming Capabilities

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