W.E.T. [CAD_CAM_EDM_DRO] Checking-Duplicating (mostly) a real part - which CAD program ?

Hi Marcus and All:
When I used Corel Draw to transfer a copy off the copier to
AutoCAD I didn't trace it in Corel Draw. What I did was let Corel
Draw just dump the whole picture into AutoCad where you can copy and
scale as needed. The part I was working on came off of a hand built
die (about 20 years old) that cut teeth into the edge of a 1/8 inch
thick metal part. The problem was the teeth were not uniformly
spaced and I needed to find out how much the were off to make a
matching punch. It was easy to just draw a circle over the center
hole and a few angle lines to the main points of the teeth and then
dim's. Less then a 1/2 hour for the whole job. It worked better then
the ten power optical comparator they had in the shop. I wish I still
had access to the software as I have an ATV part that has a hex in it
that is badly beat-up with with only one or two corner radius that
are not damage to work from. I am in the process of placing the part
over the aluminium I am machining and working directly from the part
and estimating the damage.
GOD'S BLESSINGS
Bill

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