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Sheet metal bend deduction tables for flat development.

Question asked by Evan Dlugopolski on May 25, 2016
Latest reply on May 26, 2016 by Dennis Dohogne

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Hello all,

I work for a high mix fab shop and my team and I are wondering if anyone has any tips for getting the most out of bend deduction tables in Solidworks. We are looking to try to use this functionality for developing flats for a panel bender. We are familiar with sheet metal, bend calcs, etc so setting up the table wouldn't be the issue but we want to integrate these things into SolidWorks and make it as seamless to use as possible.

That being said, is it possible to set up one single bend table to takes into consideration things like material or even bend length? In other words, what are the capabilities and limitations of bend tables? And are they the best way to develop flat patterns with a lot of variation in material type, thickness, and bend radius?

Thanks in advance,

Evan

Dennis Dohogne May 26, 2016 11:26 AM

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Evan,

Now I understand; you have a bend radius that is a function of length (or weight). I think your only option to get accurate flat patterns is to have some data that relates bend radius to length/weight and then use those radii in SolidWorks. (Once the bend radius reaches about 3+ times the material thickness the k-factor is very close to .5 so it could remain constant, however, that is a rule-of-thumb and should be verified.)

I've never used a panel bender, just press brakes. Our brakes always gave us coined 90 degree bends or air bends for bends less than 90, but we always had repeatable results so it was not that much work to develop the necessary data.

Unless the manufacturer of the panel bender can help you I think your only option is to get as much data as possible and develop your correlations. Even after you do this and start making parts from it I recommend you continue to measure the bend radius and the resulting flange lengths to see how they compare to your "predicted" values. You can then use this to further tweak your values.

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Toft Bill May 25, 2016 1:36 PM
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Mario Iocco wrote a very good set of tutorials on sheet metal and gauge table rules:
What Sheet Metal Gauge tables does SOLIDWORKS provide with its installation?
Spotlight on Features: Sheet Metal and Gauge table rules (Part I)
Spotlight on Features: Sheet Metal Bend and Gauge table working rules (Part II)
Spotlight on Features: Working with Sheet metal tables, understanding the measured parameters.
This should get you started on the right track!
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Dennis Dohogne May 25, 2016 2:49 PM
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Evan,

Don't limit yourself to bend deductions. Look at K-factors as well. See my response with informational files in this thread: K factor and flat pattern length
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Arthur McRae May 25, 2016 3:10 PM
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I personally created a pair of bend deduction tables for 2015. I had separated aluminium and steel into separate tables just for personal work flow but it is possible to include multiple types, radii, thicknesses and to name them in such a way to differentiate them.
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- ALUM Selkirk deduction.xls36.5 KB
- Steel Selkirk deduction.xls34.0 KB
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- Craig Schultz @ Arthur McRae on May 25, 2016 4:15 PM
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  I did the same thing separating out the different alloys, and then also adding in specific bend calcs for the panel bender. (Most of our forming was done on regular press brakes)
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  - Evan Dlugopolski @ Craig Schultz on May 25, 2016 8:37 PM
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    How did you calculate your flat length for the panel bender?
    We use Amada's "Sheet Works" for press brake flat development. Very powerful software & works great but it is meant for Amadas press brakes and lasers. But we cant use that for our panel bender. The bend info is very different so we thought we might use bend tables to achieve the flat pattern geometry we need. Ultimately we want to use the flat DXF that we create with solidworks to be the flat geometry used for the blank and panel bender geometry. However, we are having a hard time creating flats that will give us the proper formed geometry, and then to make the design flow efficient. We want to eliminate manual calcs or doing a bunch of extra work on the design end.
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    - Craig Schultz @ Evan Dlugopolski on May 25, 2016 8:57 PM
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      We back calculated.
      
      Cut some test pieces and measure the blank sizes. Form the pieces up. Measure the ODs. Adjust you SW model to match the ODs you got, and adjust your k-factors and bend radiu so that the blank matches up with the blank size you cut.
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    - Arthur McRae @ Evan Dlugopolski on May 26, 2016 9:28 AM
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      We are using a RAS bender out of Germany and basically made a ton of blanks at 6" x 8" and bent them did the bend calculations and entered the info into the spread sheet. If you want accurate calculations for your specific process there is basically no way around doing the manual calculations first to make sure that everything matches properly. Yes I spent nearly a week at our break on test pieces of all thicknesses, radii, and material. I also haven't had a problem with my blanks in months now, invest your time into doing it right, it's worth the initial time investment.
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      - Craig Schultz @ Arthur McRae on May 26, 2016 10:29 AM
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        "I also haven't had a problem with my blanks in months now, invest your time into doing it right, it's worth the initial time investment."
        
        That was the hardest thing to convince people of. The shop manager and the sales guys "We don't have time to do this $%#" Me: "So we have don't have time to figure it out, but we have time to redo parts when doing actual jobs?"
        
        There's a reason I'm not there any more. Never enough time to do things correctly, but there was always time to screw things up and redo it multiple times. So bass ackwards.
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        Dennis Dohogne @ Craig Schultz on May 26, 2016 10:47 AM
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        Amen, brother! When we invested just a small amount of time we had beautiful information to work with. Our sheet metal was punched and bent accurately to within .002" after we had our K-Factor and actual thicknesses determined. Prior to that it was "Go! Go! Go!" I was the new Director of Engineering and held a mirror up to them and had them watch their reaction when I got them to realize that "Speed without accuracy is just making $hit faster."
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Evan Dlugopolski May 26, 2016 10:52 AM
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I don't disagree with either of you. But before we turn my thread into a rant about doing things 'the right way' let me clarify my issue.

We had to do testing for our press brakes to set up Sheet Works so yes we are fully aware and understand that testing will need to be done with our panel bender too. My question was more on the end of how could we set up a bend table specifically for a panel bender. Because sure we can figure out our k-factors or whatever other bend info we want for each material but our experience is that panel bending is very dependent on the length of bend.

Basically as the length of bend increases the radius increases because the machine doesn't have the tonnage to hold the tooling tight. The radius changing on a length of bend basis is very different than simply testing for each of your materials, thicknesses, and tooling radii. K-factor or bend deduction for a certain material type and thickness doesn't do a whole lot of good when your radius changes depending on how long the bend is.

It doesnt seem like bend tables have the capabilities I am looking for. I might have to look into developing a macro unless someone has another work around.
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- Craig Schultz @ Evan Dlugopolski on May 26, 2016 11:00 AM
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  Separate bend tables for each alloy. Alu, 304SS, 430SS, Galv, CRS,.......
  
  The bend table contains all of the thicknesses of that alloy. TRUE thickness that you order.
  
  You can have as many variations of the thicknesses you want. So I set up an ".080 ALU", and an ".080 ALU Panel" row of variables. That way we could get the correct flats for however we were going to form the pieces.
  
  And the reason why I separated them out was for ease of selecting in the drop down for material. Simple is better in my opinion.
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  - Evan Dlugopolski @ Craig Schultz on May 26, 2016 11:13 AM
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    I understand that the tables can contain different material thicknesses.
    
    Let me give an example and you can tell me if you think a bend table can accommodate our issue. Bend tables look at thickness, radius, and material correct? What do you do when the radius is dependent on length of bend?
    
    I know that when I bend .060" material that is 12" long it will bend with roughly a .060" radius on our panel bender. So I can model this accordingly. But when I bend .060" material that is 120" long the radius will be more like .120". I don't see a way for bend tables to handle this.
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    - Dennis Dohogne @ Evan Dlugopolski on May 26, 2016 11:26 AM
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      Evan,
      
      Now I understand; you have a bend radius that is a function of length (or weight). I think your only option to get accurate flat patterns is to have some data that relates bend radius to length/weight and then use those radii in SolidWorks. (Once the bend radius reaches about 3+ times the material thickness the k-factor is very close to .5 so it could remain constant, however, that is a rule-of-thumb and should be verified.)
      
      I've never used a panel bender, just press brakes. Our brakes always gave us coined 90 degree bends or air bends for bends less than 90, but we always had repeatable results so it was not that much work to develop the necessary data.
      
      Unless the manufacturer of the panel bender can help you I think your only option is to get as much data as possible and develop your correlations. Even after you do this and start making parts from it I recommend you continue to measure the bend radius and the resulting flange lengths to see how they compare to your "predicted" values. You can then use this to further tweak your values.
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      - Evan Dlugopolski @ Dennis Dohogne on May 26, 2016 11:43 AM
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        I agree with you. It will require a lot of testing. The only problem I see now is that we will have to manually calc and set the radius in solidworks for each bend depending on the length. The bend tables can handle the rest but this still is less than ideal it looks like it will require a lot of extra work on the design end unless I can build a macro to do it.
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        Arthur McRae @ Evan Dlugopolski on May 26, 2016 11:50 AM
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        I would agree you have your work cut out for you. Best of luck to you.
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        Dennis Dohogne @ Evan Dlugopolski on May 26, 2016 12:44 PM
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        Evan,
        
        As I read your situation more clearly I would agree that the overhung load (weight or more accurately the torque) is the direct influence on resulting bend radius rather than just the length. Unless everything you do on these long legs is the same width then you might have to do some preliminary steps to determine the values affecting your situation.
        
        I'm thinking of the modeled part, complete with its bends. You might have to make a temporary cut at the bend for a long leg to leave the long leg only. You can get mass properties of this section which will show the weight and its location. Using this information you can get the torque due to its weight measured from the bend. Of course, if the leg is mostly rectangular then you could easily have a calculation in the spreadsheet based on the length, width, thickness and density to determine this torque. Whether the bend is modeled as .06" or .3" isn't going to matter if the leg has a lot of torque so just model the part with a bend radius that is in the ballpark at this point. It is this torque I would then use in the table, not length. So now you will be accumulating data based on this leg torque and the resulting bend radius. You should also be collecting measurements as accurately as you can on the resulting flange lengths. Using the spreadsheet in my other post you can easily calculate a K-factor.
        
        The nice thing about SWX sheet metal is that you can set different bend radii and different K-factors for different bends. So if you have a part with a short/light leg and you get a coined bend with a tight radius and the part has another leg(s) with different bend radius and K-factor you can set those values and get an accurate flat pattern.
        
        This process actually works in an iterative fashion. You can start out modeling a part with your best guess of these values and then make measurements to see how the predicted values compare to the actual. However, if you have a part with multiple bends of different types you could be chasing your tail. You would be well served to do some coupons of sample bends ranging from short legs to long legs. You'll need to measure the flat length before bending. For bends that are adequately coined you wouldn't need to do the torque calculation. Eventually I see a table that would list the torque (however you get there) and the resulting bend radius and K-factor. This will likely be a flat line for leg torques up to the point where the bends are no longer coined, then following a smooth curve. Once completed your new designs will be able to pick values from the curve or interpolate from a lookup table.
        
        Yes, it will be a manual calculation and it will take some time to set the values in the part prior to making the flat pattern, but you will end up with an accurate flat and an accurate part. The iterations to get there will not be that bad once you really get into it. Once you have evolved your data you'll then be able to figure out how to automate it or at least make it a simpler routine. Your alternative is to cuss a lot and to learn a few additional words as they are aimed at you from your boss and customers.
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        Evan Dlugopolski @ Dennis Dohogne on May 26, 2016 4:56 PM
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        The length shown here is what we believe the radius is dependent on. Is this what you were talking about as well?
        
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        Dennis Dohogne @ Evan Dlugopolski on May 26, 2016 5:42 PM
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        Actually I was thinking of the length of the long flange. But this tells me your panel bender doesn't have much clamping force. If you are finding that your bend radii varies with the length you are showing then that is the parameter you'll have to correlate to bend radius and K-factor.
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Sheet metal bend deduction tables for flat development.

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