Sheetmetal Method Question
Sheetmetal Method Question
(OP)
Hello all,
I do not do much in the way of sheetmetal so I would like to get some proper methods input for a simple part. I have a 10AWG flat plate about 18 inches wide that will have left and right flanges bent down 90° 1" in from each side. In the fixed face region I need to put some drilled holes and some tapped holes. Should the holes be put in prior to bending and should they be dimensioned from the edges before bending? Or should they be put in after bending and then dimensioned from the now bent face?
Thanks in advance,
BB
I do not do much in the way of sheetmetal so I would like to get some proper methods input for a simple part. I have a 10AWG flat plate about 18 inches wide that will have left and right flanges bent down 90° 1" in from each side. In the fixed face region I need to put some drilled holes and some tapped holes. Should the holes be put in prior to bending and should they be dimensioned from the edges before bending? Or should they be put in after bending and then dimensioned from the now bent face?
Thanks in advance,
BB






RE: Sheetmetal Method Question
ht
Add the holes after making the features, then flatten it.
Chris
SolidWorks 09 SP4.1
ctopher's home
SolidWorks Legion
RE: Sheetmetal Method Question
Youtube is banned here at work but I will look tonight. All of our holes have a 0.010" tolerance and I'm not sure if they can hold that on a plasma table or not. I would think that if the tolerance can be held that they would cut the shape and the holes and then bend to complete the part but I could be wrong.
RE: Sheetmetal Method Question
Chris
SolidWorks 09 SP4.1
ctopher's home
SolidWorks Legion
RE: Sheetmetal Method Question
RE: Sheetmetal Method Question
RE: Sheetmetal Method Question
If that is the case, I would treat one bend as the datum surface, dimension everything off of this, and then dimension the overall with a looser tolerance. The other option if using GD&T... is composite positioning. Using composite positioning, you can specify that a pattern of holes are "loose" relative to the surrounding features and "tight" to each other. This will allow you to tightly control the hole to hole spacing and loosely control the hole to bend spacing.
See the link http://tec-ease.com/tips/april-03.htm
In general, you always want to dimension you finished part. This will allow for inspection and not tie the hands of the fabricator. If you dimensioned the flat, but the flat was wrong... your finished part would be wrong.
-Dustin
Professional Engineer
Certified SolidWorks Professional
Certified COSMOSWorks Designer Specialist
Certified SolidWorks Advanced Sheet Metal Specialist
RE: Sheetmetal Method Question
RE: Sheetmetal Method Question
It is always advisable to dimension the final part dimensions. As if you do Flat pattern dimensions & the final part is not as per your expectation, then we have no method of finding out if the flat pattern was cut wrongly or the drawing was wrong.
One more suggestion ask your fabricator for thier favourite bend radius & try to make part around that information, as that is the biggest factor which can cause trouble between flat pattern & final part.
RE: Sheetmetal Method Question
Composite positioning as suggested by ShaggyPE will yield you the highest tolerances. Incoming inspection is going to inspect the final, bent shape, so dimension from the bent flanges. A locational tolerance of .010 from hole-to-hole should be easy to maintain, .020 from flange to flange is fairly easy on 10ga as well.
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RE: Sheetmetal Method Question
RE: Sheetmetal Method Question
You may also need to experiment with the correct K-factor that will yield the most accurate real world results for your bends. Take a piece of scrap sheet metal, measure accurately the length, then have your press brake operator bend one or two 90° angles. Measure the bent piece and duplicate it in Solidworks. Adjust the K-factor until what you are modeling is equal to what is being fabricated. The K-factor will vary with different material thicknesses.
Mad Dog McDurmott