Renishaw Probe Problems

I've got an Okuma Howa V60R Vertical lathe with a Renishaw LT-02-T probe system with an LP2 probe. Here's the deal:

It will go through it's program fine (milling 0.25 mm off the face of a cast iron disc).
Brings probe over, good
Probe goes down to just above part, good
Green light in OMM comes on indicating probe is on, good
Probe comes down and touches part, good
Probe keeps going down about an extra three millimeters before I hit the emergency stop, bad

Anybody got any bright ideas? I replaced the battery (do the easy stuff first right?). The green light in the OMM comes on, makes me thing the thing is working. But when it touches anything (we tried it again with door open and reach up and touched it while trying to probe), it won't send a signal back to the OMM to tell the machine "hey, I've touched something here. Quit moving down on the Z axis and record this Z absolute value for later use."

Help me here. Need some things to try come first thing Monday morning. Extra good ideas will get tried tomorrow.

Can you pull the probe and put a meter across the wires and see if things change when you trigger it? You may as well first determine if the probe is working before tearing into the machinery.

cheers,
Michael

Yeah I guess we could. Thanks for the quick help Micheal. I really feel like it's the probe. Just wish I knew exactly what, cuz it seems like it's working just fine. And by working I mean I can reach up and move it around freely.

Is your probe connected by hard wire or does have an inductive pickup? I've seen some inductive types where the signal is enough to see the probe to run but doesn't get the contact signal across because the lens is a little dirty or cracked.

But Michael's thought is true too. Check to see if the trigger is working.

On another note, you want to look into modifying the probe programs for some safeties in case the pickup fails but it won't destroy the probe.

Its not wired or inductive. If it's got an OMM, its optical (infra-red). How did you program it? You should be using skip feed (G31 I think) if you want it to stop when it touches something.

I tried to do a bit of research on your model probe, but I couldn't find the model number you mentioned on the Renishaw website.

We used to develop software for touch-probes, and we've had experience with the Renishaw MP1 (wired) and MP9 (Infrared telemetry) probes. Since you said you had a battery in the probe, I assume that you have some type of telemetry probe. In any case, when the probe is enabled, you should be able to see an LED or hear a "Beep" when the probe touches anything. Sounds to me like the receiver isn't able to detect that the probe is deflected, and the CNC never sees the "Skip cutting" signal from the probe.

The Fanuc controls use a G31 command to move the probe and touch a surface. If you program a move of, say, one inch in G31, the machine will move that one inch just like it would in G01. The difference is that in G31, the machine will stop when the probe touches something. The axis will not stop IMMEDIATELY when the probe touches (due to servo following error), but it shouldn't compress the spring in the probe more than 1mm or so.

Try making a little program that just moves back & forth in G31 with a slow feedrate. When you run this program, you should be able to trip the probe with your finger and stop the motion.

I suspect that your probe is having trouble sending it's "Tripped" signal to the telemetry receiver. That receiver has the relay in it that actually sends the "skip cutting" signal to the CNC. If your receiver is beeping (or showing an LED change state when you trip the probe), then you might have a bad relay in the receiver. If you don't see anything happen on the receiver, you may just have a bad probe or the probe's infrared LEDs might not be pointed at the receiver.

Hope this helps.

If this control is Fanuc or Mitsubishi or similar, you can also look at the diagnostic screen and look at the skip input, on many controls like Fan. or Mits. the skip inputs are dedicated inputs, you can trip the probe at any time to see the input bit change.
I assume you might be using Renishaw supplied routines? Good practice is that you never do a move with a probe without a routine with a G31 in it.
Renishaw have what is called a protected move for just going to initial position before probing.
G31 cancels the present move on the line the G31 is on and falls through to the next line.
M.

I've got a G31 in my program it's something like:

M98 P9001; (skips to Probe ON / OFF program to cut probe on)
G31 Z35.08 F25.4; (probes to a depth of 35.08 mm at a rate of inch/minute)
#101=#5062; (stores Z location)
M98 P9001; (goes through probe ON / OFF program again, to cut probe off)

The lenses of the OMM and the probe are pointing to each other. This LP probe is new on me as well. We use MP probes elsewhere in the plant. I can make it turn the probe on, verify this by seeing a solid green light in the OMM. It will then go into it's G31 cycle and feed down slowly. During this time you can reach up and touch the probe all you want and it just keeps easing down.

Sounds like the probe and the receiver aren't communicating. If you're sure the battery in the probe is good, then I'd look to Renishaw for service or possibly a warrantee replacement.

touch the probe all you want and it just keeps easing down.

Click to expand...

bad contact inside the probe.

The OMM may not respond to the meter test, I believe they are all isolated I/Os.

When you start up the probe, how many lights come on the OMM?

There should be a red light, telling you the OMM is powered.

The green light in the middle comes on when the OMM commands the probe to turn on.

The green light on the end comes on when the probe is transmitting back to the OMM.


Which of those green lights is on?

If you only get the first green on, send the probe back to reneshaw to check it out. If the probe is OK, they will take $90 off your hands, but they will recalibrate it while it's there. No charge if the probe is broken and you have them repair it.

I went through this a couple of weeks ago - super fast service and great tech support.


Now then again if you have both green lights on, perhaps you have a problem with the MI12 (or similar) inteface between the OMM and the machine control.

In my installation, I used an OMI which is essentially a OMM + MI12 in the same package, and a heck of a lot cheaper.

Don't know much about the probe, but I do write software for probes on our equipment. Sometimes we are looking for a change of state. If the initial move causes the probe to make contact before entering the detection routine, the change of state will never occur. Can you back off the probe or use a shorter probe contact?
The only thing that bothers me about a lost signal is that an initial handshaking should be taking place with the probe to preclude exactly this kind of problem.

And this bad contact should be up inside the probe (or possibly the OMI, not the OMM)? There seemed to be only two wires between the probe and the OMI.

What really irks me is that this thing just quit. One part is runs great and the next part it won't go down and probe. I really don't think the operator had anything to do with it. All he knows is hit the cycle start button. You think this wire just all of a sudden came loose? We've only had this machine a week. Maybe 100 parts have gone through it. Just goes to prove the new ones will break as easy as the old ones I guess.

Im not familiar with the LP2 - but if you have a OMM, there shouldn't be any wires between it and the probe since the OMM relies on infrared transmission.

I think you'll need at least 6 wires from the OMM to the interface or controller ?

On my setup (MP8 & OMI) if *anything* goes awry the table stops. Like if the MP8 stops transmitting (wrap a rag around the LEDs) the OMI will detect the error and report it back as a 'touch' to stop the machine.

Well the machine will definately still move. That's the main problem I have I guess. The probe touches the part and the machine just keeps on mashing it down. Oh well, I guess I'll take the probe and OMI apart and tug on the wires to see if any are loose.

I'm planning on calling Renishaw at 7:45 Monday morning and run all this by them and get their advice. Then I'll take their advice and do all I can do with it between then and about 9:30 or so (UPS truck comes at 10:30). At 9:30 or so I'll have to make a decision to either order a rebuilt unit ($660), send ours back in for a $90 inspect and repair, or keep working on what I've got.

From the information given it is clear that the probe and OMM communicate, but the skip signal is either not generated or not conducted to the control (assuming your program is OK). I believe you have OMM (6 LEDs) which is connected to another unit (interface - Renishaw call it MI-12). This unit is probably situated inside the electric cabinet.
Open the cabinet, turn on the machine and run the program untill the green light in OMM turns on. Push feed hold and look on the interface. As long as the probe is not deflected the "Probe Status" light should lit. Ask somebody to deflect the probe and observe if the "Probe Status" light goes out. If positive - the probe, OMM and receivig part of the MI-12 are ok. Now check if the signal from interface accesses the control. If it is Fanuc, the signal inputs on X4.7 or X1004.7. Go to diagnostics and look for inputs status under one of the above numbers. It normally is signed SKIP and should change from 0 to 1 when deflecting the probe (as long as the green light on OMM is on). If this is not changing - probably the fuse on the skip output of the MI-12 is gone. You will have to look into MI-12 manual in order to locate it (http://www.renishaw.com/UserFiles/acrobat/UKEnglish/H-2000-5073.pdf).
Good luck.

If the OMI is mounted on anything other than a fixed surface relative to the machine cabinet, i'd put my money on a broken wire from the pickup. I've repaired a few of these in the past. The Renishaw wiring is really thin gauge stuff.

Dang PROBE, do you work for Renishaw or something? That's pretty much what they told me to do this morning. Go to my parameter diagnostics and check X4.7 and F122 for skip signal bits. I had zeros, and time was getting tight, so I bit the bullet and got Renishaw to send me a rebuilt probe body.

After lunch today I was digging around and found a Renishaw accessory kit with the necessary hardware to attach a 1" spindle (which just so happens to be the same shank size as the VTL probe). So I borrowed a buddy's MP10 and put it into the lathe. Worked like a charm.

So this has me thinking, I've pretty much got MP probe all over the shop, and they cost about $3K new from Renishaw for the whole deal. The new LP2 probe only costs around $1500 new. So should I be looking at phasing out the MPs for the cheaper LPs? Or should I pay more for the MPs just to have standard probes throughout the shop? What do you guys think?

High CatMan,
Pay attention when comparing your system with MP10. First of all the MP10 is not suitable for use in harsh environment.
Your system - LTO2 includes the LP2 and the OMP (Optical Module Probe). You can find very easy if the problem is LP2 or the OMP. Unscrew the LP2 and look on its backside. You will see 2 concentric rings which are in fact contacts of the inner microswitch. This contacts are electricaly shorten when probe is seated, and open when deflected. Use simple conductivity meter to find out. If the LP2 is ok then your problem is the OMP. Its price is also much less then complete MP10. Ask also Renishaw for the RBE (Repair By Exchange) service. This also will spare you a lot of money.

PROBE, thanks for the good tips. The MP10 lives in service on a Devlieg HMC, but no coolant. Those puppies are like $3,300 new. The LT03T we have back in the lathe gets subjected to some coolant and only costs $1600 new. We use mainly MP12s throughout the rest of our CNCs.

Funny about that repair by exchange though. No matter what the probe (I've had to replace a few) it always seems to be about $650 to swap it out. I don't know how they figure that, but I don't really care either. I'm very happy with the company.