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View Full Version : Z Axis is not working correctly.



Rich05
09-14-2008, 09:58 PM
Z-Axis is not reliable. Sometimes it stops for no appearant reason.

This is especially so when mill is cold first booted up in morning. gets better during day but still may stop. Thanks R.

sandefuj
09-15-2008, 08:05 AM
I had similar problems to you, and for me it was the gecko each time. Have you tried swapping the Z drive with X or Y and see if the problem follows the drive? Also with my mill it was hard to get the gibb adjustment just right, it was very easy to get it to tight. Is you Z axis motor running hotter than your X and Y? I also have to readjust my drive on a regular basis to keep the motor tuned for the Z. Hope this helps a little. Also the owners at IH are very helpful; you should give them a call.

Jay

Rich05
09-15-2008, 09:32 AM
I had similar problems to you, and for me it was the gecko each time. Have you tried swapping the Z drive with X or Y and see if the problem follows the drive? Also with my mill it was hard to get the gibb adjustment just right, it was very easy to get it to tight. Is you Z axis motor running hotter than your X and Y? I also have to readjust my drive on a regular basis to keep the motor tuned for the Z. Hope this helps a little. Also the owners at IH are very helpful; you should give them a call.

Jay

Hi Sandefuj,

Can you just leave the gibs fairly lose? I dont think mine is very tight? I am praying its just the Gecko, this is encouraging news thanks.

Tommy and Gene have provided me with the best (over the top) technical support. They have held my hand re-wiring the whole mill, advised on the operation of the mill. Talked with me on Sundays, evenings you name it. Possibly 20+ hours in total. Covering a range of problems on a mill they did not sell me. The CNC kit was provided by Arron and built by a friend of mine.

There is allot of unknowns I am dealing with. The new even Z Servo and Gekkos have been through hell, due to wiring issues and user errors made here and there.

I will call Gecko today and order a new drive. I quess. I did swap the geckos a few months ago and the Z axis had the same problem. but maybe all my gekkos are a bit weak now? I am a newbie at this stuff.

IS there another source for Z servos out there? That might be as good as the IH ones? can not afford $500 again

mcarvey
09-15-2008, 10:00 AM
Its tough to diagnose the problem without physically being there, but it does not sound like a problem with the components. It sounds like the computer is not outputting the pulses correctly for whatever reason. This is namely due to the problem of "rapid retract followed by a dive" that you were mentioning. The G320's only have an 8 bit counter in them, so they can't actually lag behind the computer pulses by very much without getting an error.
That being said, here are a few things that I would try.
-try wiring the X or y step/dir outputs from the Computer to the z axis controller. If there is a problem with the z axis motor/drive you should expect to see the same intermittent failures. If you can't get it to fail, they the problem likely has to do with the computer outputting the step/dir pulses.

-I had an issue with the x,y, and z axes due to the inability of my computer to output pulses correctly at higher speed (I was using an old computer) I reduced the maximum speeds of the axis to 10ipm, and then started bumping them up until they stopped working correctly, then set a comfortable number. (my x and y do 60ipm, the z only does 25ipm with a 450mhz computer). There is a chance you may be having similar problems.

-If an axes suddenly stop working, and you get the message in mach "limit switch triggered" even when it obviously isn't the problem is likely due to electrical interference. To minimize this problem, you need to make sure you have a fairly strong pullup resistor (.5K-1K or so). Putting shielded wiring on the motor wires also helps tremendously- the relatively high current 20khz PWM drive puts out tons of EMI on those long motor leads.

Sorry for the not-so-greatly worded response- I'm in a bit of a rush.

Hope this Helps.

-Matt

Rich05
09-15-2008, 02:12 PM
talking with Gecko right now they think the 20 amp power supply might do be too light for the z-servo.

does anyone know the datasheet on the z-servo and for the encoder?

Rich05
09-15-2008, 02:24 PM
Its tough to diagnose the problem without physically being there, but it does not sound like a problem with the components. It sounds like the computer is not outputting the pulses correctly for whatever reason. This is namely due to the problem of "rapid retract followed by a dive" that you were mentioning. The G320's only have an 8 bit counter in them, so they can't actually lag behind the computer pulses by very much without getting an error.
That being said, here are a few things that I would try.
-try wiring the X or y step/dir outputs from the Computer to the z axis controller. If there is a problem with the z axis motor/drive you should expect to see the same intermittent failures. If you can't get it to fail, they the problem likely has to do with the computer outputting the step/dir pulses.

-I had an issue with the x,y, and z axes due to the inability of my computer to output pulses correctly at higher speed (I was using an old computer) I reduced the maximum speeds of the axis to 10ipm, and then started bumping them up until they stopped working correctly, then set a comfortable number. (my x and y do 60ipm, the z only does 25ipm with a 450mhz computer). There is a chance you may be having similar problems.

-If an axes suddenly stop working, and you get the message in mach "limit switch triggered" even when it obviously isn't the problem is likely due to electrical interference. To minimize this problem, you need to make sure you have a fairly strong pullup resistor (.5K-1K or so). Putting shielded wiring on the motor wires also helps tremendously- the relatively high current 20khz PWM drive puts out tons of EMI on those long motor leads.

Sorry for the not-so-greatly worded response- I'm in a bit of a rush.

Hope this Helps.

-Matt

interesting idea about moving the output of the pc x or y to z. imagine if it was just the parrel cable..

i have had the motor shutdown at very low speeds, I think even like 10 ipm, but need to check that and see if that helps, i have reduced it to 40ipm however. this pc is 3.4 pentium 4 with 1 gig of ram. but might be worth another try.. to check on this.

as far as mach, it does not give any error when the z-servo stops it just keeps scrolling through the g-code as if everything is fine.

Rich05
09-15-2008, 02:59 PM
just switched the Gecko Y and Z drives, works worse, this time completely untune-able. Z axis erratic.

IHCNC
09-15-2008, 10:53 PM
Hi Rich05;
As we stated in the prior post. We still consider you an IH customer and will help you any way we can. please feel free to contact us.

Rich05
09-15-2008, 11:02 PM
Thanks Gene and Tommy for your tech support. Looking forward getting back to cutting. You guys are the best.

McAhron
09-18-2008, 08:43 PM
If its a matter of power from the motors you can either add an hydraulic shock to take some of the weight off or build a counter balancer.There are several good posts here on different ways to add counter weights.

Rich05
09-20-2008, 12:38 PM
IH got it all working. They corrected a bunch of dumb errors. Thanks Gene and Tommy!!

Runner4404spd
09-21-2008, 08:00 AM
can you post what the errors were so others may have a chance at fixing theirs if need be.

Rich05
09-22-2008, 10:29 AM
The encoder was dirty. Not sure how stuff got in there but it was not clean.

Also I replaced the parallel cable length with a shorter one, from 15' to 6' just as a precaution.