I often create parts from cardboard cutout pieces provided by R&D. The shapes rarely contain many straight edges, are usually fairly irregular in nature, and not necessarily accurate.
Currently, I trace the parts onto some high accuracy graph paper, manually plot points along the perimeter, and create a spline with a reasonably close fit. I then create the part using a 1 to 1 print and the actual material to be used, then check fit. Most times small changes are made, some for funtionality and some for asthetics ( R&D doesn't care what it looks like, if it works ), then another prototype part is made.
When the shape is verified, I then create an identical part using tangent arcs/lines rather than splines. I do this because most machine tools ( mills, lasers, ect ), have an easier time processing arcs/lines rather than the many small line segments a spline produces when converted to NC code for most, but not all, machines. My vendors really appreciate this effort.
Rather than tracing/plotting I have had some limited sucess using a scanned .bmp at the proper scale inserted as an object and laying sketch points along the perimeter. Other formats don't work for me, some because I don't have the appropriate software installed to view them, and some, like jpegs, I can't seem to get an image to appear ( all I get is a small square box ). Scanned .bmps become massive in file size and cause a significant slowdown on my comp even though I have much more physical memory than is required.
Is there a better method of obtaining the needed points from a scanned image? If so, what format/software have you had the best luck with? Also, is there a macrom or small utilitym out there than can convert splines to tangent arcs/lines within a given accuracy? The manual conversion is a time consuming PITA.
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