Re: [CAD_CAM_EDM_DRO] Duplicating (mostly) a real part - which CAD program ?

Hi Alan and others:
This is a Godawful way to get a part into CAD...usually way more work
than just measuring the part and drawing it from scratch.
I've tried the Corel approach...it does "kind-of" work but at the cost of
hours of fooling about and pitiful accuracy.
My approach now (and I do this kind of work quite a bit) is to measure
everything that's easy to measure accurately, and lay it out in Mastercam.
Then I get the trickier bits in and confirm their location by pulling
dimensions from the CAD drawing and cross checking them against the part.
Then I add the fillets and blends and the stuff that doesn't matter too
much.
I can get a moderately complex part into CAD and cross checked in about half
an hour.
My last step is to do a full size print and lay the part on top of it.
If it looks right, I assume it is right.
I've done some pretty complicated parts this way, and I haven't been burned
yet...the cross checking step seems to do the trick.
My last attempt with Corel Trace took hours and when I was done, the part
was no good and had to be re-done anyway.

I think we all tend to get too entranced by what the cool technology should
be able to do.
Bitmap toVector conversion is still pretty weak as far as I'm concerned, at
least with the kind of software tools most of us have readily available.
A "serious" company would have the part scanned and work from the CMM
co-ordinates for the major geometric features, and a point cloud for the
non-geometric ones.
No one that I'm aware of, uses bitmap to vector conversion for parts that
have any requirement for accuracy.
Even scanned-in drawings are hard to convert accurately...bitmapping them
degrades them so badly that the resulting vector trace is worse than
useless.
If you do insist on doing this, Corel is still your best low cost option so
far as I'm aware...so give it a go if you must, but check your final CAD
work very carefully before you start chopping metal.
Cheers

Marcus