[plasmator]

This post deals with the topic of reverse engineering, for example the reproduction of a machined part that's no longer available.

In short, I would like to be able to undertake something like this. I know that there's more to it than slapping a set of calipers on a part, particularly if 3D contours are involved.

I also know that there are service bureaus that do this sort of thing, but I'm not interested in that option.

So my question is, can anyone give a rundown on the process, including which measurement techniques are the best, how to handle/determine tolerances, et cetera?

One caveat: I will not have access to anything more sophisticated than Tormach's CNC USB microscope gadget. So no laser scanners or optical comparitors please. This is reverse engineering on a budget.

I know this is a pretty big request so thanks a ton for any replies!

[HuFlungDung]

Pretty tough question without seeing what part you want to draw up. But generally, you look around for the most important surface on the part, whether it be a hole or a planar surface. The most important surface will be a machined feature, not a cast or molded feature. Sometimes, the most important feature has a phantom location, meaning you must deduce where the geometric center is relative to a mating part. Then you take measurements from the most important surface and begin the process of deducing where the other features of the part are located.

A bit of familiarity with common fasteners, bearings and seals would be a big help. Obtain catalogues from bearing and seal suppliers. This can help you figure out the exact diameter of important bores, rather than slavishly copying what might be an out of tolerance or worn out hole in the sample part.

Hole patterns can be complex to figure out (sometimes). Think of an engine bell housing as an example. You'd need a caliper to measure the distances between holes accurately. Pick any two holes to serve as a baseline.

Pick one hole and take measurements to various the other holes on either side of each hole. Deduce the center distance (because hole diameters may vary). You need as many hole distance combinations as you can make.

Then plot the measured distances in CAD as a series of circles, using the intersections to determine the location of the unknown holes. For example, from your baseline hole pair (the datum holes), you would take a measurement from each datum hole to the next hole. Plot those measurements as circles, and the intersection will locate the first unknown hole center. Obviously, the more combinations of measurements you make, the more circles you can plot, and the more sure you can be of the actual hole location.

Some sort of a flat plate (a surface plate) and a height gauge is also a good way to reverse engineer some stuff. But you'd need to spend a bit of money to get there

[diyengineer]

http://www.nextengine.com/

About 9 grand with all the software that is a must for importation into solidworks.. I dream of it nightly. lol

Anyways, how does this microscope work for you? It can obviously do 2D patterns and objects but what about 3d? if it were on a 3 axis cnc how can it measure the depth of a pocket Do you have to take that measurement by hand and enter it? If you had a 4 axis can it do full 3d? Seems like a pretty cool tool for less than $1000!

[mcphill]

I have had a NextEngine since they came out, and love it. I finally got RapidWorks for it a couple weeks ago, and WOW! I have a steep learning curve on that one, but it will make reverse engineering and recreating solids a snap...

[diyengineer]

I have had a NextEngine since they came out, and love it. I finally got RapidWorks for it a couple weeks ago, and WOW! I have a steep learning curve on that one, but it will make reverse engineering and recreating solids a snap...

You are a lucky!! =)