How would you copy a part

[CNCadmin]

If I had a flat plate with lots of holes and complicated shapes let's say and wanted to copy it, how would I go about it. In the past I would scan it and convert raster to vector.

[cadcam]

Are you stating a hand drawing persay or cad file?

[CNCadmin]

No a physical part.

[Wjman]

Hi,
In answer to your question (How would you copy a part)
Basically I would measure the plate and all the apertures on the plate on our CMM, getting all the positions of the apertures as points from a known datum. then I would draw in all these points on the cad system and then literally join up the dots. Then its just a case of making a program from the resulting DXF or DWG file. It might seem a long way to do it, but we regularly do this when a customer needs a new die or something else making and we did not make the original, and we have no information about it.
Mark...

[Klox]

You "digitise" the component. It is a machine that measures the component either using a laser or with a (very) sensitive probe.
Then the info is printed out point by point. You can use these points to generate a cad drawing then.
I know that Hu can tell you more than me on this topic.

Klox

[HuFlungDung]

I wish we all had CMM's! Shouldn't this be a human right?

I usually do the "reverse engineering" with a vernier caliper, measuring the hole diameters and distances from adjacent edges to various features.

If there are a lot of holes, then typically a lot of them would be in some kind of regular spaced pattern. If possible, I try to reason out what the part is being used for, whether it is a component from a "metric-scaled" machine or "inch-scaled". This can help a lot to determine what a measurement should be.

A quick overview of the part to gain this kind of perspective is liable to pay off, rather than slavishly copying what may not have been laid out all that accurately to start with.

[cbcnc]

I think that Hu's answer brings up a good point. That the part can only be accurately measured to it's largest tolerance. In other words, the part falls within the tolerances that it was made to. But that measurement may or may not be the exact size it was designed to.
So an overview or some reasoning must be applied also.

Chris