I’ve been experimenting with OnShape sheet metal models to produce patterns for etching parts. Being designed for ordinary bending processes, OnShape is not directly applicable, but I think it is close enough for my purposes.
Here are the sheet metal model parameters that I have found work in OnShape to produce drawings that match the recommendations for etching.
- Thickness = material thickness
- Bend radius .0004″
- Bend K Factor: .625
- Rolled K Factor: ?
- Minimal gap: 0.0008
- Corner relief type: Closed
- Bend relief: Rectangle – Scaled
- Bend relief width scale: 1
- Bend relief depth scale: 1
This produces a flat part with the appropriate allowances for bends. You then select this part in the Flat Model context and download it as DXF, Release 13.
OnShape and InkScape don’t play nicely together, but QCADcam is able to intermediate. So open the .dxf in QCADcam and Save as R27  DXF Drawing [Teigha]. This can then be imported into InkScape, using one of the following parameters in the import dialog:
- Manual Scale 25.4
- Method of Scaling = Read from File
The part then appears in the InkScape drawing, almost perfectly to scale. The part shown above, which is three inches long, stretched by 01″ through all the transformations; I don’t know who introduced the error, but it is easy to correct in InkScape.