1999 Hurco BMC 4020 - Calibration Problem

Hi Guys,

My machine randomly just doesn't calibrate. It make work for days or weeks and then sometimes I have to try 10 times.

The message: MARKER PULSE NOT DETECTED ON X Axis

I did some looking around and found this on Hurco site:
MARKER PULSE NOT DETECTED ON AXIS xxxx."
[FAULT] Î Encoder may be bad – requires “axis tuning” or “parameter
adjustment.” Telephone for technical assistance.

I can't find any information on how to "tune the axis". After a little research, I did find that the controller expects the limit switches to be a certain location (9 inches) by looking in CNC configuration. I'm not entirely sure what that means but I suspect that simply depressed the plunger on the limit switch isn't good enough. It's expected at a certain distance. Just not sure how.

One last thing, the encoder, that is inside the x axis drive or no? Not seeing it.

Thanks in advance for any help.
hk

Its on the back of the x motor. If this machine has scales, there is an external magnet that fails from coolant. No scales, just clean the switches up really good. They get sticky and won't spring return so the machine thinks the marker pulse is off.

Quote:

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Originally Posted by underthetire

Its on the back of the x motor. If this machine has scales, there is an external magnet that fails from coolant. No scales, just clean the switches up really good. They get sticky and won't spring return so the machine thinks the marker pulse is off.

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Thanks so much. I'll have a look today.

I'm not exactly sure what I'm looking at/for. Here are some pictures of the motor.

Thanks again in advance,
hk

Back cap come off, did you clean the switches? You may not want to dig too deep in the encoder, if it is bad, its a replacement only part, and being a seimens motor I don't know if they sell it by itself or with a motor. All our hurcos from that vintage have yaskawa.

Ah said the blind man. Gotta look a little deeper. I'll have a look.

Thanks again
hk

Quote:

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Originally Posted by hkenuam

Ah said the blind man. Gotta look a little deeper. I'll have a look.

Thanks again
hk

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There is dried coolant around the outside. Can I just spray contact cleaner in there?

I wouldn't, at least not till you get the debris vacuumed out. Not all contact cleaner is plastic safe either, ive seen it completely melt connectors and such. But, you don't seem to be listening to me anyways, since you still haven't responded to my question of cleaning the switches up. They are no where near the motor.

Sorry for the confusion. If you are referring to the limit switches, they are clean. I vacuumed and cleaned up the dried coolant from the motor. It was just laying on the bottom side of the motor when I removed the cover. I know it shouldn't be there but I'm not very confident that's going to help.

With that much dried junk in the motor, im guessing the connector to the motor filled with coolant and thats probably causing your issue. Really need a scope to check output signals from the encoder. Now days you can buy a decent scope for less than $350 from amazon.

Expose the X axis limit switch and then calibrate the machine. When the table begins to move to the switch, hold the negative travel switch down until the table begins to back away from the switch. Then quickly release it. If it doesn't find marker, try it a few more times. It may be it just needs the limit switch to marker parameter opening up a touch.

Thanks Bloke, I"ll give it a try.

Quote:

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Originally Posted by hkenuam

Thanks Bloke, I"ll give it a try.

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when I depress the switch the table stops and goes the other way but after many tries I still get marker pulse error.

it seems as if x and y are moving faster than z when calibrating. Not sure if thats Ok.

This is an Ultimax III and I see the following settings. Not sure how to slow the approach or distance.

Change the limit switch to marker distance on x to 20mm.
Change the cal to limit switch velocity for y to 2540.
Go to the next page and change the limit switch to marker velocity for x to 100 if it isn't already.
Save and exit and see if it'll calibrate.

Changed the settings and now when the table stops and starts back the other way, it's moving really slowly (marker velocity 100) and it still doesn't calibrate.

Is there a procedure for adjusting the location of the limit switch stops on the table? Or does that really matter. This has been going on for a long time and I've moved the x stop a time or two.

Thanks for help in advance,
hk

With the cal to marker distance opened to 20mm, if it doesn't find the marker, it's not being sent to the control. Reset the parameters to the original settings and now look tongetting the encoder repaired. The signals for the reference pulse go into the control at the MX4-J1 pins 5&6 for Z & -Z

Thanks everybody.

Hello everyone,

I thought I'd share some findings about my calibration problem. I went back into the motor and stared at the encoder for a while and noticed it had a hole with threads in the end of the cap. Using a bolt I was able to safely remove the cover from the encoder (has o-ring and just pressed on). Then, after more staring, I can kinda see whats going on in there. There is a very tiny eye on one side and a disc on the other (thought of cd player). Looking more closely I noticed there was something on it in places, but mostly shiny. Afraid to use any kind of solvent sprays I took a q-tip smashed it flat and put a small amount rubbing alcohol on the tip and rested it against the disc and turned the shaft. When I pulled it out, it was yellow, dried coolant dust I'm sure. Repeated the process and then carefully re-assembled. Calibrates every time now.

So, yes, encoders are scary, expensive pieces. But move slowly, think clearly and sometimes you can save yourself a ton of money.

Thanks to all who helped guide me to a solution.
hk