Renishaw officially released REVO 5 axis scanning probe about 10 years ago then a few years later PH20, the touch trigger version. However not until last couple years, CMM community starts to see real user questions in various forum. Many CMM users, even though thrilled by many of those well created videos on youtube about 5 axis REVO/PH20, don’t really have 1st hand experience on how much differently this new technology works from all other probing systems.
Everyone knows that REVO is fast and accurate, for which there’re many videos on the internet. Myself I did a test with REVO scanning a ring gauge at various scanning speed from 100-500 mm/s and then comparing the results. Nothing extremely exciting but the video I made has real data: https://www.youtube.com/watch?v=PCYphkbuG9Q
Interestingly I got a very tricky job recently, in which case the 5 axis probing is probably the only resolution to get measurement done properly. Have a look at this part:
The manufacturing process is this: the small tube (about 6-7” long) is welded to the main body (40” long machined cylinder), then drill a 1/8” hole at centre of small tube into the main body thru. Then there’s concentricity call out for this small hole. So the measurement task is very simple and clear, but as an experienced cmm programmer I guess you’ve already seen the problem: how can you built a probe that can access the small hole at very bottom without SHANKING?! My client has high end Zeiss CMMs, so building custom probes with scanning capability is not a problem, problem is how do you your probe is actually touching that little hole? To make it worse, there’re multiple tubes welded on the same body with slightly different angles. I’m sure we can still comp up with a solution such as fixturing, gauging, etc. to get it done, but if we use REVO then it’ll be much easier. 5 axis probing system (REVO/PH20) works quite differently than conventional indexing probes or fixed probes. In this case 2 key characteristic makes REVO the prefect tool to check the 1/8” small hole at a very deep position:
1, Headtouch (or PCS touch) with unlimited probe angles removes possibility of shanking. For this small hole, REVO can easily uses a probe angle roughly at around 0.2-0.3 deg. to ensure the probe will make a “clear” hit and same time have just enough clearance at the top of the tube (see image below)
2, You might wonder how about part variations? After all the tube is welded onto the body, it can be easily off 0.5 deg. then the 0.3 deg. only works when the tube is perfectly upwards. But that’s not true for REVO because it can align itself to the Part Co-ordinate System (PCS) so all we need to do is set primary axis and origin at the tube then REVO will automatically adjust probe angle accordingly if PCS point measurement is created for each hit:
So you don’t really need any fixturing to align the part physically because once REVO measures the tube it will be able to figure out the probe angles needed so it won’t shank. This is a huge time and money saver.
I have to admit that jobs like this are not that often depending on what kind of industries you’re working with. But in almost all cmm programming tasks, choosing the right probe (ruby size/probe length/probe angle) is always a major part that you spend much time on. I have many clients whose CMM systems has many modules/ports/plates just because they need all these different probes to deal with complicated jobs, then the calibration time increases dramatically. With REVO you really only need just a few different probes. I can write a long list on benefit of using REVO/PH20, but this particular case study should give you a good idea about why 5 axis is superior to conventional probing system.
CMM Application Specialist
GDTP S-0605 (ASME Y14.5)
RX Metrology Solutions Inc.
A "1Source Metrology" partner