Renishaw CMM probes- Why angle type head versus star probe tip ?

Milacron · Mar 23, 2013

In other words, if you need for example to confirm accuracy of the outside of a horizontal hole on your CMM, why would a head that rotates to horizontal position be more desirable than a simple probe head that does not angle, but with a tip that has horizontal capability ? Does it come down to depth possibilities or are there other reasons the angle head would be more desirable ?

And speaking of angle capable heads, why any angle other than 90 degrees ? To check hole tolerances of holes that are bored at an angle.....or other reasons ?

To put some definitive models out there, why would the Renishaw PH1 be more desirable than the TP-ES and why would the MIH be more desirable than either of those ?

http://www.helmel.com/Probe/ProbeHds.htm

CarbideBob · Mar 23, 2013

Mostly depth and getting inside an angled feature.

For example, checking a V-6 engine block.
You need to get deep inside from the ends to check the inner main cam and crank bearing surfaces.
Then you need to be on the angle of the vee to get deep inside the cylinders and clear the valley when probing the lifter bores to check that these holes are square to the crank and cam.

You have to calibrate the probe tip back to the scales for each angle position.
The PH1 lets you setup to get inside an angled feature but if you change it to a new angle you have to recalibrate. The M1H has known positions it can return to so you can calibrate all the positions you will use and bounce back and forth without having to retouch off the master ball.
Think 5c collet spin fixture with and without an indexing plate and you want to grind a square.
Bob

Milacron · Mar 23, 2013

CarbideBob said:
Mostly depth and getting inside an angled feature.

For example, checking a V-6 engine block.
You need to get deep inside from the ends to check the inner main cam and crank bearing surfaces.
Then you need to be on the angle of the vee to get deep inside the cylinders and clear the valley when probing the lifter bores to check that these holes are square to the crank and cam.

You have to calibrate the probe tip back to the scales for each angle position.
The PH1 lets you setup to get inside an angled feature but if you change it to a new angle you have to recalibrate. The M1H has known positions it can return to so you can calibrate all the positions you will use and bounce back and forth without having to retouch off the master ball.
Think 5c collet spin fixture with and without an indexing plate and you want to grind a square.
Bob

Interesting. So if the horizontal hole dimensions or positions you need to confirm are no deeper than a typical cross or "star" type tip the simple TP-ES probe head would be fine ? What about calibration with those "star" style stylus on the master ball...how is that done exactly...i.e. do you touch off all 5 tips at various positions on the master ball, or just the ruby tips that might actually get used on the part you are checking ?

WILLEO6709 · Mar 23, 2013

ever tried getting down a deep slender bore with a star probe? I have a renishaw MP10 power head on my cmm. One part we use 5 rotations to check 56 features.... I considered a star probe but I think it would get in the way on this part.

CarbideBob · Mar 23, 2013

If the star will get in your feature there is no need to change the probe angle.
You only need to calib the tips you are going to use but if you are not going to change the tip I calibrate all of them so that I can jump to new one if needed.

Your pictured part is interesting as there are three slots which with a fixed 4 point star probe forces you to use two balls on the dimension on one of slots.
I do not like doing this as you add the tip to tip calibration error on top of the machines natural error, effectively doubling the measuring error.
Bob

Milacron · Mar 23, 2013

WILLEO6709 said:
ever tried getting down a deep slender bore with a star probe? I have a renishaw MP10 power head on my cmm. One part we use 5 rotations to check 56 features.... I considered a star probe but I think it would get in the way on this part.

Does the MP10 only rotate via program or will it angle the stylus also ? I guess the PH10 head does it all, but takes up a lot of Z real estate and costs $$$$ (plus you need a specific Renishaw drive box to interface with CMM control as well, right ?)

Milacron · Mar 23, 2013

Does there exist a web page somewhere that goes into great detail as to which Renishaw probe head model is best for different DCC CMM applications ? The Renishaw site itself has a page that goes into some detail on the subject but is a bit lacking IMHO.

This video I just found for example... I had no idea there was a non motorized probe that could change angles without human intervention.
http://www.youtube.com/watch?v=4ybAmu53BvI

WILLEO6709 · Mar 23, 2013

Milacron said:
Does the MP10 only rotate via program or will it angle the stylus also ? I guess the PH10 head does it all, but takes up a lot of Z real estate and costs $$$$ (plus you need a specific Renishaw drive box to interface with CMM control as well, right ?)

My mp10 has a special interface box aka external 4th/ 5th axis control. It spins 360 and tilts up 90, so you can have a " right angle head that rotates 360 degrees", but its increments, if you wanted 11.299 degrees you settle for 10 or 15. It takes some real estate and I only rotate it by telling it to move... and you still calibrate every probe position before use.

Milacron · Mar 23, 2013

OK, here's another mystery. Why is a used PH8 head is $300 but used MH8 is $1,550 ? From same company, same warranty.

Renishaw PH8 Manual Indexable cMm Touch Probe Head Fully Tested with Warranty | eBay

I presume PH8 is older model but are there any functional advantages to the MH8 ?

http://www.ebay.com/itm/Renishaw-MH...566?pt=LH_DefaultDomain_0&hash=item2ebdf7d5ce

And will the TP6 probe I already have fit into either of these heads and work ok ? Curious that TP6 is not specifically mentioned in their ad copy. And speaking of the TP6...why the heck are there so many different TP6 type probes anyway ? So confusing...

Milacron · Mar 24, 2013

Milacron said:
OK, here's another mystery. Why is a used PH8 head is $300 but used MH8 is $1,550 ? From same company, same warranty.

Below is the answer, from the seller. Also, the TP6 will work fine with either head. I wondered as I happen to have two TP6's already.

Speaking of which, I was looking to sell one or both of the TP6 units back a few years ago but simply forgot about them. I figured by now their value had gone down considerably but the interesting thing is if eBay is any guide the value seems to have gone up on them. Recession vs better times I guess.

The difference between an MH8 and PH8 is that the MH8 has 168 repeatable positions that can be pre-calibrated and stored in your software for future use. A PH8 basically has a friction mechanism that allows the probe to be moved in both A and B axis in any orientation and then locked with an Allen screw. Once the probe has been moved you would have to recalibrate the position.

Bruce Nelson · Mar 24, 2013

On my Renishaw touch probe for my B & S Microval, I simply have a adjustable knuckle to accommodate other construction planes. Simply use the same probes in the knuckle, make a new construction plane, re-qualify the probe for the tip diameter, and go to town. If you don't move the part that you are digitizine, everything remains lined up. You are simply drawing in a new construction plane. I can't see where the star probe would help, as it would get in the way.

Possibly the use of the star would save the bother of requalifying the probe for a different construction plane, but would certainly get in the way for most digitizing purposes.

Lord Byron

Milacron · Mar 24, 2013

Bruce Nelson said:
On my Renishaw touch probe for my B & S Microval, I simply have a adjustable knuckle to accommodate other construction planes. Simply use the same probes in the knuckle, make a new construction plane, re-qualify the probe for the tip diameter, and go to town. If you don't move the part that you are digitizine, everything remains lined up. You are simply drawing in a new construction plane. I can't see where the star probe would help, as it would get in the way.

I think I know what you mean...a simple bracket with one locking knob to manually adjust the angle of the entire probe head, right ? No angle scale, just eyeball the angle you want, lock 'er down, re qualify the ruby tip on the master ball in the new position.. and go, right ?

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Renishaw CMM probes- Why angle type head versus star probe tip ?

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