Fifteen years ago when we talked about “scanning” or “digitizing” on cmm, it sounds very fancy to most of cmm people. And not too many cmm guys had a chance to work on a cmm equipped with scanning probes even though the software that time has the scanning module already, for example, most Mitutoyo cmms were running Geopak with Scanpak as scanning module. But technology moves fast, today most cmm guys are familiar with terms like “reverse engineering”, which most likely involves scanning with an SP600 or SP25M probe, or even REVO probe. There’re so many cool things about scanning that I even see articles years ago talking about the total replacement of conventional triggering probes being a final solution.

 I myself am a scanning fan too. And I worked with SP600, SP25M and Vast gold xxt on cmms running pc-dmis, camio studio, calypso and umess with kum. Even though the software interface looks quite different, the way they define scanning path is very similar: start point, end point, direction point and increment, etc… What I like to share is some examples in which, if scanning method is properly employed, you can make your inspection process 3 times faster. Take a look at this part:

  

It’s a flat gauge and of course there’re lot of dimensions like diameter, radius, angle, distance, etc… I believe it’s not a difficult job to most cmm guys at all: create an alignment according to the drawing and then call up circles, lines, constructing intersection points… Now take a look at the two dimensions in the enlarged view: R1.264 and 0.713. How will you check them? Let’s try, for the R1.264 maybe you can just probe a few points to get a circle, but because you really have very little tiny area to probe how can you trust the result? I guess many people know a better method: using polar points from theoretical center, not too bad (actually the topic of “small arc, large radius” is my another one). But to get 0.713 is very difficult because the top is not something you can probe but you have to construct by intersecting a line with the circle you just did. You only have +/- .001” tolerance so if your circle is not accurate enough then you won’t get a good result.

 With scanning method, this job becomes really easy: because it’s flat, you don’t even need create your 

alignment, just make sure you scan (it doesn’t matter with analog or triggering probe) your –B- and –C- (the scanning path set up for this part should be really easy in any software) then output your scan to iges file. This should take no more than 30 minutes (you can tell it’s a relatively small part). The rest of work are all in your cad station, all you need is something like autocad (MDT), cadkey or mastercam. If you’re pretty good in cad then creating circles, lines, intersections off this spline is not a big job at all. Especially for those 2 dimensions, you can zoom in 100 times and construct a circle that fits your scan really good then you’ll get a very accurate reading for 0.713. And if someone challenges you on this dimension just print a nice graphical report to show him.

In this particular case, you use your cmm as a tool to collect points so you can capture the true profile of the whole parts and benefits are:

1, Minimize cmm occupancy and it’s so headache free when scanning, you don’t have to worry about any alignment, rotation, constructions, etc…

2, Data is saved permanently. You can go back to double check anytime.

3, When challenged, you have full confidence to defend with pictures which are worth thousands of words. 

4, It’s so easy to compare two parts or compare same part a year later when you make 2 scans different color and overlay them in cad.