Renishaw Lathe tool setter arm won't go up

Hello,

Maybe this is a bit off topic. But has anyone encountered a situation where the renishaw High-precision motorised arm (HPMA) won't come down upon the execution of the M code?

I have a HPMA installed on my lathe. I tried to use the arm to measure a tool today but after I entered the M code, the arm went down only half way and stopped. I run the other M code, trying to let the machine bring the HPMA back to its "home" position. It wouldn't work. I tried a couple more times and it wouldn't work either.

I contacted the machine builder and basically, they didn't have the solution.

Then oddly enough, just after I finished the call with the machine builder, I run the M code again to bring back the arm and it worked...

I am so confused now! LOL

What machine? How is the arm actuated?

It's a machine from Taiwan, with FANUC 0i-TD control.

How is the arm actuated... This, I don't really know. How can I get information on that? All I know is when we purchase the machine, I saw the machine builder's staff connects the wire of the motor to the machine's PMC. I guess that where it gets a signal from the control once I execute an M code.

Up or down prox could cause that, maybe an chip on one. The actuating device is also a reasonable suspect, open the cover and see what moves the arm.

On the manual, I found something like this

Two separate machine tool control outputs are required to command the arm to move to “machine ready position” (MRC) and “arm ready position” (ARC). The user must ensure that both outputs are never active at the same time. There must be a minimum time delay of 0.1 seconds (100 ms) between one command being de-activated and the other being activated.
If both outputs are active at the same time then the arm is unable to determine what to do and will stop. This condition can only be overcome by de-activating both outputs.

so can this also be a problem?

Not if it has ever worked before. That is speaking to the correct design of the ladder logic. If it is done correctly, it will never want to go up and down simultaneously.

okay, thx for the info.

So basically, I will have to use the air to clean out the drawfs or chips that block the arm. If that doesn't work, I may have to take apart the arm and check the actuator?

ifixcnc said:

Not if it has ever worked before. That is speaking to the correct design of the ladder logic. If it is done correctly, it will never want to go up and down simultaneously.

Click to expand...

Note that ifixcnc says "If it is done correctly....". Not all machine builders have stellar software folks writing their ladder logic.

If cleaning and other checks do not uncover the trouble, I'd have a look at the outputs from the PMC to verify that they are not being activated at the same time. There should be logic in the ladder to prevent both outputs form being on simultaneously.

Also, I'd look through the documentation for the arm. Seems like there should be a couple inputs from the arm to the PLC to indicate completion of arm out and arm retract. A good ladder will have logic to check that both signals are not on at the same time, and if they are raise an alarm. Many machines do not have these simple checks.

Stephan Spears said:

okay, thx for the info.

So basically, I will have to use the air to clean out the drawfs or chips that block the arm. If that doesn't work, I may have to take apart the arm and check the actuator?

Click to expand...

Probably.

First, though, I'd call up the builder again and have them walk you through the ladder logic for the arm. Take pictures of the ladder screen and email them to the builder if they don't know their own product. It's one thing if something is just broken, but working intermittently points to a simpler issue. Might just be a switch flickering.