CRASH!
The ability of SolidWorks to do sheet metal design is both a blessing and a curse to sheet metal job shops. Understand this is no fault of the software but of engineers who don't really understand how bends are made in sheet metal. The example shown in the following figures is typical of what some of our customers will design. They even provide us with SolidWorks part files that they have have modeled. Can this part be made as modeled? Yes it can but it would required special costly tooling and extended lead times for the tooling. It has been our experience that making this in two pieces and welding two seams instead of one is more cost effective.
Figure 1 - the part
A simple part until you start looking at the bending operation. In the following figures you will see that I added typical press brake tooling and a section of the press brake ram so that you can see the problem with bending this part as modeled.
Figure 2
The first bend is no problem. you could start on either end of the flat blank with the same results.
Figure 3
The same holds true for the next bend. you will note that there is no interference between the sheet metal and the press brake.
Figure 4 - CRASH!
Now you can plainly see the problem. Even if the 4.00" dimension in the part sketch was increased the part would still crash. The only solution that would allow forming this part as modeled would be what we call a 'window punch'. This involves using a tool that would fit inside the part has modeled and extends far enough past both ends of the part so that 'extensions' could be placed between the press brake ram and the punch. When the last bend is made, one of the extensions would be removed so that the part could be removed. This only works for softer material of a lighter gauge because of the loading placed on the tooling.
I hope this explanation is clear to all those who design sheet metal with limited experience of the manufacture of sheet metal parts. I will continue in the coming days to share more instances where a small changes can save you money in your sheet metal designs.
Basic design course for sheet metal, lesson one:
ReplyDeleteFind a workshop and stay there until you understand how sheet metal behaves and what is physically posible to do, then go back to the computer.
/Bqt
Excellent advice. I was just saying to my co-worker this morning that **** needs to come over here and run a press brake for a week or two. Sadly I don't see that happening. In the next installment I will tackle unreasonable tolerances for sheet metal parts.
ReplyDeleteThanks for you comment,
The sheet metal shop I go to says "if you can model it, we can make it"... they're masters of custom tools.
ReplyDeleteof course anything can be made...but maybe there will be a weld seam instead of a bend? In the above example if the part was of any sizable length there is no way it could be formed unless your 'master shop' does roll forming.
ReplyDelete