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Author Topic: Help Needed with MY 3040 cnc machine -Z axis Problems.  (Read 2707 times)

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Help Needed with MY 3040 cnc machine -Z axis Problems.
« on: January 27, 2016, 01:06:36 PM »
Hi
I have a 3040 chinese cnc machine , and I make my g Code on Cambam and use a licenced Mach 3 software.
I started cutting 3 mm perspex and managed to get pieces cut with very few noticable problems.

When I started to cut Aluminium it became apparent that the Z axis needed calibrating so after watching a video on YOUtube I set up the Z axis , but I still have problems.

When I start a program on Mach 3 after zeroing the z axis , It soon becomes apparent that each pass is deeper than the G code is stating. the DRO on Mach shows what should be happening but in actual fact the cuts are too deep.
When the DRO shows a depth of -1.8 to 2mm , the actual depth is 3mm. The settings page on Mach 3 confirms that the Z axis is set up correctly. I have had occassions when I get to pass number 15  or so (Each pass is 0.1mm) the tool digs in and drills though the remainder of the 4mm aluminium, breaking the tool in the process.
In hindsight I have always had this problem but as perspex is more forgiving I must have got away with it.
I would appreciate some help as I have run out of ideas.  The G code looks fine , I can see the coordinates being sent out and there is nothing strange that I can see.
The only thing I can say is that when I jog the z axis there appears to be some minor glitches in the sound of the motor which I cant hear on the x and y motors .

thanks Rob

Offline Tweakie.CNC

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Re: Help Needed with MY 3040 cnc machine -Z axis Problems.
« Reply #1 on: January 28, 2016, 03:35:54 AM »
I suspect that your Velocity / Acceleration for the Z axis is set too high in Motor Tuning.

If you attach your .xml file (the one from your Mach3 folder named <your profile>.xml [typically Mach3Mill.xml]) copy and rename it to snakesound.xml then use the 'Reply' tab and Additional Options to post it - I will see if I can spot any problems in your set-up that may be causing the issue.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Help Needed with MY 3040 cnc machine -Z axis Problems.
« Reply #2 on: January 28, 2016, 04:25:11 AM »
Thanks for the reply , i appreciate it .Ive just found out what my problem was, I thought it might be a motor issue so I started to swap over 2 motors to see if the problem transfered axes, and found that the coupling on the z motor had come loose. I sorted that and recalibrated the Z axis and the cutting depoth
is now perfect.
I understand keeping the accelleration and velocity low increases acuracy , but how do you get the rapids to be faster than the set velocity? and is the rapids speed the same as the jog speed as again with my motors set at the manufacturers recommended 150 ,rapids and jog speeds are painfully slow .

Thank you again, I told you I was a NEWBY

Offline Tweakie.CNC

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Re: Help Needed with MY 3040 cnc machine -Z axis Problems.
« Reply #3 on: January 28, 2016, 04:43:56 AM »
I am pleased you have found the problem.

You are not the first and you will not be the last to discover that a loose coupling is the root cause of many problems  ;)

You cannot get rapids faster than the set velocity, however, try holding down the shift key when jogging if this increases speed then the Tab key will bring up the pendant display where there is a Slow Jog Rate % which you can set.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Help Needed with MY 3040 cnc machine -Z axis Problems.
« Reply #4 on: January 28, 2016, 04:56:20 AM »
Thanks ,I will try that , I saw the slow jog setting  but didnt try it as i really want a fast jog, but if I set slow jog to say 10% does regular jog become 10 x faster? .
In motor tuning I have all 3 axes set at   400 150   (slow) If I set the velocity higher so the jog and rapids increase , the G code will still overight the velocity with the feedrates for cutting, Am I right?

Regasrds Rob

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Re: Help Needed with MY 3040 cnc machine -Z axis Problems.
« Reply #5 on: January 28, 2016, 05:15:39 AM »
Hi Bob,

In a word 'no'

Slow jog is by default set at 80% (I think - long while since I made a fresh install) increasing it to 100% will give maximum speed. The 'shift' key overrides the slow jog setting making it 100%.

In Motor Tuning, the Velocity of each axis should, ideally, be set 30% lower than the speed at which the motors nearly but just don't quite stall. Similar with Acceleration.

Within your Gcode the G0 / G00 moves are rapids and the axis will travel at the Velocity set in Motor Tuning - the G01 / G02 / G03 moves are at the Velocity determined by the Feed-rate which has been set (within the Gcode program) by the F#### command.

The Mach3 manual explains all this much better than I can. http://www.machsupport.com/help-learning/product-manuals/

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Help Needed with MY 3040 cnc machine -Z axis Problems.
« Reply #6 on: January 28, 2016, 05:27:14 AM »
Thank you
I understand now ,I'll try increasing the velocity in the axes, especially the x and y , and thanks for explaining what the G01 and G02 are for , the feedrate and the plunge rate , G code is making more sense by the day

Regards Rob