Quote:
Originally Posted by s_forbes
I'd also love to hear more about some of the details that need to be considered when dealing with sheet metal design. One of the things I find most perplexing is the tolerances involved with these kind of parts... Some things I've read online mention that large sheet stock (like 4'x8') can vary in thickness as much as .005" (thicker in the middle).
Separately, how tight of tolerances can the machines hold? For example, when bending a c-channel out of 0.125 thick sheet, how much does the outside flange to flange distance vary?
It seems like getting rivet holes to line up would be a nightmare.
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I've never had any problems with tolerances. The laser and punch tolerances are great. I had an argument with Paul a few years ago because the "promised" tolerances didn't meet his needs. I reassured him, they always under-promise and over-deliver. We're spoiled working with Metal Solutions.
Bend tolerances vary purely based on the skill of the break programmer and operator. I'm lucky to work with a group of absolute ARTISTS. For a long time I shied away from allowing for any bends to affect gearbox tolerances, but (in a typical role reversal) Paul has proved to me that these guys are getting things so close to nominal so consistently we shouldn't worry about it. For the first time ever 148 will be riveting our gearboxes together and spacing them with flanges instead of threaded standoffs.
When our holes don't line up it is 99% of the time a designer's error. I'm always amazed how smoothly things "drop together." We always get exactly what we ask for (now, whether that is what we actually wanted is another question...)
I've also never heard of thickness variances like you describe, though it is possible I just never notice it.
Hope this answers some of your questions.
-John