We're talking about part set up in part (1), which I think is definitely worth your spending time on because you don't want to get stuck half way and realize that you have to change your set up to get work done. The next thing I'd like to discuss is probe configuration. If you get on any 5-day training course I'll bet you that probe calibration will normally covered on day 1. But I don't want to talk about probe calibration here since everyone knows how to do this on his own cmm very well, instead, I'd like to share some opinions about how to select your probe configuration efficiently.

Step Two: Probe configuration

1, Non-index probe vs. index probe

If you're running a Zeiss cmm equipped with Zeiss ST probe system (usually with tool rack) then building different kind of probes for your work piece will possibly your regular job depending on the complexity and similarity or your products. This kind or non-index probe system is really good for most of complicated machined parts or castings (especially engine components) because you can easily custom-build special probes to check deep bores or groove features. But since most people use index probes like PH10 or RDS we'll focus on these types of probes here and also I won't talk about Revo head simply because many people haven't even seen it physically.

2, Probe size and total length

You're lucky if you have a TP20 or TP200 because that gives you flexibility to switch between different sizes of probes easily and you're luckier if you even have a tool changer. But it still makes good sense to select proper ruby size so you can finish your inspection work more efficiently. Usually you should make sure that you can probe your smallest internal features but try not use 1mm probe for measuring large parts because it can easily shank out without being noticed. One way to work around small holes is to put a pin in so you can measure it externally. 2mm, 3mm and 4mm rubies are most popular ones.

Use your extensions (TP2 extension, styli extensions) wisely so you don't build a very long probe configuration. Usually you want to try A90 B-90 and A90 B90 at each of your left and right side to make sure you can access those features.

3, Probe angles

I find that some cmm operators like to build a large probe database so they can always calibrate to that large database and then pick whatever probe angle they want to do the inspection job. I personally don't recommend that because improving work efficiency should always be part of our job. So take some time to study the part geometry and drawing requirement and select probe angles that will access those geometries most effectively. From my experience, probe angles like A45 B45 is very flexible for measuring because you can reach the top, left and rear face without angle change and in case of crashing it takes less impact for your TPs than those A90 angles.

4, Special probes

Sometimes it's very challenging to find a proper probe angle to get into certain features, e.g. a very busy checking fixture with many pins and pads pointing downwards. In this case, star probe is my favourite tool to solve the problem. If you never use it before you should really try it. Combined with different A and B angles you'll be amazed to see that you can reach some very tight area where you can never get without a star probe.

Try not use cylinder probes all the time. I know many people really like it for thin sheet metal parts but you can easily get wrong size and wrong location readings because your cylinder probe picks burrs or wrong edge of a slot. Cylinder probe is good tool for thin material only when your probe is really perpendicular to the measurement feature.

Disk probe is another nice tool for groove measurement, but calibration is always tricky and depending on different software you have to be careful when calibrating the disk probe. In most cases, you should be able to use star probe to solve the problem.