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Messages - xray_man

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General Mach Discussion / Re: Noisy Axis problem.
« on: July 10, 2011, 10:38:49 AM »
Good to hear, or not as the case may be ;D


Thanks again for your help!

BTW - I looked back through all of my posts over the past five or so years, and YOU (Hood) have given me more help with my CNC problems than anyone else. You are truly one of the "good guys" because not only are you very knowledgeable, but you are very willing to share your knowledge with others. And for that, I (and I'm sure many others whom you helped) give you a BIG THANKS!

xray_man (Mike)

General Mach Discussion / Re: Noisy Axis problem.
« on: July 09, 2011, 09:24:31 PM »
UPDATE:  I was wrong.  I didn't think that the drive current would make a difference, but when I adjusted the Vref pot for the Y axis, which now provides a little more drive current to the motor, it cleared up the noise!  Apparently, my Y axis was struggling to move the table at high speed, and so the drive became unstable. Now I can jog the Y axis in either direction and it moves without growling at me!  :D


General Mach Discussion / Re: Noisy Axis problem.
« on: July 08, 2011, 02:54:28 PM »
I was wondering if the vibration is in the motor or the way its being driven rather than in the axis.

Good point!  I'll play with that and see what I can come up with.  I was hoping that Mach-3 had some sort of filter parameter that I can adjust (like some industrial CNC controllers have).

General Mach Discussion / Re: Noisy Axis problem.
« on: July 08, 2011, 02:29:44 PM »
Have you tried the motor disconnected from the axis? Also might be worth a try swapping motors.

I don't understand how disconnecting the motor can prove anything because the vibration doesn't occur unless the axis is moving fast enough. I certainly can't spin the ball screw fast enough with my fingers!  As far as swapping motors, I'll only do that after trying every other possibility because that would be a major job.

General Mach Discussion / Re: Noisy Axis problem.
« on: July 08, 2011, 02:10:15 PM »
Have you checked the mechanical side of things? Loose bearings, tight ballscrew, loose mounts etc could allow for things to start to vibrate.

Hi Hood,
Yes, that was the first thing that I looked into. I made sure that there wasn't any backlash in the lead screw, and that it was properly lubricated, etc.  The -Y axis movement is smooth as silk! It's only in the +Y direction that the noise occurs.


General Mach Discussion / Re: Noisy Axis problem.
« on: July 08, 2011, 02:08:12 PM »
Just from memory because it is a long while since I looked at the Xylotex instructions but if it has a PFD (percent fast decay) pot (adjacent to the current adjust pot) associated with each axis you could try a slight adjustment of this on the axis that is causing trouble.


Hi Tweakie,
There is only one pot adjustment for each axis on the Xylotex board that I have, and this adjustment is called "Vref" which affects the maximum current that the drive will supply to the motors. Those pots should have no effect on the vibration that's occuring.


General Mach Discussion / Noisy Axis problem.
« on: July 08, 2011, 12:27:05 PM »
Hi guys,
A few years ago I converted a New Hermes engraver to CNC using Xylotex drives and Mach-3 controller (my post describing details is on this forum).  Well, I recently noticed a "growling" vibration coming from the X/Y table when I move it in the +Y direction at high speed. All other axes and directions are smooth and quiet. My Y axis carries the X axis motor and lead screw, therefore it carries the biggest load (if that makes any difference). When I jog the Y in the positive direction, the table starts out smooth and quiet but then starts to growl and vibrate after a second or two of movement, becoming louder and stronger over a short distance. It seems to me like something is mechanically resonating, but I'm not certain. I tried retuning the Y axis using different velocity and acceleration numbers, but that did not help unless the table moves very slowly (which is unacceptable).  So, my questions is, Is there some way to filter the resonance/vibration in the Mach-3 software? All axes use standard stepper motors.


General Mach Discussion / Re: G92 Offest Problem (maybe)
« on: November 28, 2010, 12:16:35 PM »
Don't forget to cancel with G52 X0 at the end of the code section. There are lots of examples on here of how to use the command.


Okay, thanks again Graham!  ;D

General Mach Discussion / Re: G92 Offest Problem (maybe)
« on: November 26, 2010, 12:49:13 PM »
Use G52 instead it is a local shift and will offset as you expect, G92 is to be used instead of G54


Hi Graham -- Yes, I will use G52 from now on because it makes more sense for what I need it to do. Thanks very much!


General Mach Discussion / Re: G92 Offest Problem (maybe)
« on: November 26, 2010, 12:37:15 PM »
I think it may be right if I am understanding what you are saying. Here is snippet of what the G-Code button says
Here is an example. Suppose the current point is at X=4 in the currently specified coordinate system and the current X-axis offset is zero, then G92 X7 sets the X-axis offset to -3, sets parameter 5211 to -3, and causes the X-coordinate of the current point to be 7.


Hood -- Thanks for your reply.  Even though I have read the description of how G92 is supposed to work, I was not able to understand it until I "played" with it under a number of different situations. Now I understand it, and it makes sense.

This is what confused me before. As an example, my current physical X position is at X0.0. I want to offest the current zero position 3 inches (approx 76mm) in the plus direction so that I can call a subroutine to repeat a pattern in the offest position. Originally, I inserted "G92 X3.0" into my Gcode, but when the program executed a "G0 X0.0" the X-axis moved 3 inches in the minus direction, which was opposite to what I expected. But now I realize that the G92 offset made my X position shifted to X3.0, and when I executed the "G0 X0.0" it made the X-axis move in the minus direction. That's what confused me, but now I understand it. 

Thanks again,


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