drawing board drawings to cad drawings

[mike hide]

Trying to get a handle on this CAD stuff, I would like to produce a DXF cad drawing and using sheetcam get the G code for my machine .

I am attempting to copy a relatively complicated antique piece which involves many sweeping curves. I am a little long in the tooth so methods I am comfortable with are probably a little out of step with modern practice I was working on the board long before the advent of the PC and most other computers for that matter. So here is my procedure I am producing a drawing based on a photograph ,scaling each of the major components .When I have a reasonably similar scaled sketch I overlay it with ships curves and for the smaller details french curves. When this is completed I anticipate overlaying a grid on the drawing and read off the XandY coordinates and transfer these to produce a CAD drawing . A problem I may have is that sheetcam does not like splines and any splines would have to be converted to polylines. Most ship and french curves I believe are second degree curves so I am not sure if sheetcam will see them as that. any suggestions to simplify this precedure or answer the sheetcam recognition question would be appreciated. regards mike hide

[ger21]

Some CAD programs can convert splines to short straight segments, which should work OK if you use enough segments. Also, some CAD programs will do this automatically if you save as a version 12 or older .dxf.

[Kevin Taylor]

Mike I'v reverseenginered part's with the DRO on my mill and a pointed edge finder wright the X&Y of point's along the curve and in your cad program and eather arc conect the dot's or spline to generate the curves Pick out the points at the end of streight lines and line conect points Good luck kevin

[bostosh]

I've done a LOT of this type work
curves no problem, Art to Part
Yes I am an oldtimer also
On a drafting board in 1958,
Brian O

[warrenb]

I've tried a few raster to vector conversion programs and none of them produced the wanted results for manufacturing parts. i suppose it might be OK for architectural drawings but not for CNC manufacturing. There's been no substitute for reversing a raster image in a good CAD package in my experience. Cut a few parts and get the client to agree on accaptable tolerances.

[watchman]

I often have to reproduce parts which have sections knocked off or rusted away.. The easiest way to do so by far is to use a CAD program such as Rhino which allows you to use a photo/scan/drawing as a background image and to draw on another layer on top of it. I usually photograph the part, set the image as background in Rhino, scale it so that it is full size and draw over the edges, adding in the missing parts. Then I can save it as an Autocad-type DXF or DWG file and use one of the DXF-to-G-code converters to produce a script for my cnc machine.