Using SolidWorks Sheet Metal for plastic parts

[Syncro5]

I have recently started working at a plastics fabrication company as a trainee CAD / CAM designer. The line bending process is widely used with in the company for parts such as polycarbonate and acrylic machine guards etc. Up to now the CAD / CAM designer has been modeling the part in solidworks to comunicate the idea to the customer. If the customer gives the go ahead then the CAD / CAM designer will work out the "net" or flat pattern on paper before drawing it in a 2D design program so it can be cut out by CNC and then line bent.

Since I have started working at the company I have created a couple of parts using the sheet metal toolbar in SolidWorks, flattened the part and exported the face as a DXF for CNC, before line bending. However, these parts have not been very dimension critical.

I am wondering whether any one has any tips and tricks for using sheet metal for plastic parts? Obviously there is shrinkage involved in the line bending process and the bend allowance wont be the same in plastics compared to metals. Has anyone succesfully created dimensionally accurate line bent plastic parts from sheet metal in SolidWorks?

Thanks, I look forward to your replies.

 

[MadMango]

You will have to create test strips for your various materials and figure out the proper K-factor to apply to your models. The easiest way to do this would be to create a model of a 1-2" wide strip of material with a bend at a specific distance from an edge that is easily measured. Then start with your K-factor at .50 and tweak that until the physical part equals the flat pattern model. It will take some time, but in the end it should provide for very accurate, in-house capabilities for using SW sheet metal for plastics.

"Art without engineering is dreaming; Engineering without art is calculating."


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[Syncro5]

Thanks MadMango, I done some research into "K-factor" and have managed to make a calculator-like spread sheet...this means I can key in flat length of material, thickness of material, angle of bend, inside bend radius, "length x" and "length y" and get the k-factor in return. I plan on bending a small test piece with similar geometry before each job, and making a log of results. Hopefully soon I will be able to look up the K-factor for any job in a data base and create an accurate part from that! The only thing I'm worried about is the different amount of shrinkage on different sized parts as they are heated...