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Joggle of Offset Bend Allowance?

Question asked by Bernie Daraz on Apr 21, 2011
Latest reply on Apr 22, 2011 by Bernie Daraz

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Hey People!

OK, I've been doing sheet metal for more than 30 years, along comes Solidworks and it's just the best tool! I was born 30 years too early! Anyway when we do models or designs for flats to import into Fabriwin I always struggle with applying a bend allowance to the part. I know for instance that I want to "fix length" but adding in the plus .045 bend allowance is a nightmare. I always end up tweaking the numbers to arrive at my correct flat. What is the proper way to apply my "known" bend allowances to one joggle or offset bend? Normally we take the overall of the part and add the joggle allowance.

Best! Bernie

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Wayne Tiffany Apr 21, 2011 9:22 PM

I prefer to use k-factor as my designs frequently change. By applying a k-factor, if the bend angle changes, my flat will still be correct. Every bend in a SW sheet metal part can have its own k-factor assigned.

So, design the part as a sheet metal part and set the k-factor in the sheet metal feature.

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Bernie Daraz @ Wayne Tiffany on Apr 21, 2011 9:44 PM

Wayne,

Sorry the only place I use k-factors is in rolling tubes or sections of tubes where the bend radius is 8-10 or more times the material thickness. We have really accurate bend deductions for our forming depatment and it's no sweat to hold plus or minus .005. I understand that the neutral axis taks a wild trip through tight joggles so absolute numbers are required in my line of work. We sell quality! Maybe it's just that I don't like the way SW (2010 and 2011) does it.

Thanks for your reply!

Bernie

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Bernie Daraz @ Bernie Daraz on Apr 22, 2011 1:41 PM

To clarify, using my actual bend allowance (.060 for 18 ga CRS) for a .125 offset it is a k-factor of .275. Yet changing the height to .187 I should obtain a .110 bend allowance, yet using the same k-factor it becomes .122. It is not somewhat linear as normal bend deductions and allowances go. So rather than vary the k-factor I would rather enter actual, obtainable and repeatedly reproducable bend allowances from our charts. Normal bends are not an issue, just joggles.

My desire is to generate usuable models whether for me and our shop or a subcontractor. Having worked in fab shops that have received 'good' models we find we cannot use them. We import them as 3D IGS and use our software (Fabriwin) to change the bend radii and deductions. Since some choose to model to tangent dimensions we cannot just change the radius as the model can change, sometimes drastically.

This is the real world of precision sheet metal and varies slightly from shop to shop. IMHO the technology presented by SW is great, but not yet complete.

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Wayne Tiffany Apr 21, 2011 9:22 PM
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I prefer to use k-factor as my designs frequently change. By applying a k-factor, if the bend angle changes, my flat will still be correct. Every bend in a SW sheet metal part can have its own k-factor assigned.

So, design the part as a sheet metal part and set the k-factor in the sheet metal feature.

WT
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- Bernie Daraz @ Wayne Tiffany on Apr 21, 2011 9:44 PM
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  Wayne,
  
  Sorry the only place I use k-factors is in rolling tubes or sections of tubes where the bend radius is 8-10 or more times the material thickness. We have really accurate bend deductions for our forming depatment and it's no sweat to hold plus or minus .005. I understand that the neutral axis taks a wild trip through tight joggles so absolute numbers are required in my line of work. We sell quality! Maybe it's just that I don't like the way SW (2010 and 2011) does it.
  
  Thanks for your reply!
  Bernie
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  - Bernie Daraz @ Bernie Daraz on Apr 22, 2011 1:41 PM
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    To clarify, using my actual bend allowance (.060 for 18 ga CRS) for a .125 offset it is a k-factor of .275. Yet changing the height to .187 I should obtain a .110 bend allowance, yet using the same k-factor it becomes .122. It is not somewhat linear as normal bend deductions and allowances go. So rather than vary the k-factor I would rather enter actual, obtainable and repeatedly reproducable bend allowances from our charts. Normal bends are not an issue, just joggles.
    
    My desire is to generate usuable models whether for me and our shop or a subcontractor. Having worked in fab shops that have received 'good' models we find we cannot use them. We import them as 3D IGS and use our software (Fabriwin) to change the bend radii and deductions. Since some choose to model to tangent dimensions we cannot just change the radius as the model can change, sometimes drastically.
    
    This is the real world of precision sheet metal and varies slightly from shop to shop. IMHO the technology presented by SW is great, but not yet complete.
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Joggle of Offset Bend Allowance?

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