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Z-axis problem
« on: October 25, 2010, 11:01:30 PM »
Last summer I built a home CNC machine for use in my garage.  orig ionally I built and assembled a home made z-axis assembly.  I could never get the z-axis to operate over 20-inches per min compared to the x&y axis which could operate at near 50-inches per min.  I scraped the home made z-axis assembly and went with a K2 CNC prefabbed assembly rated at 100 inched per min.  I still cannot get the z-axis to exceed 25-inches per min.

Other than that problem my machine works great and my tolerances are acceptable for the type of wood working I am doing.  I purchased the stepper motors and 3-axis controller from Xylotex.  Is there a setting in the Mach3 software I need to check?

Sorry for the lack of pictures, I will try to get some posted shortly.

Dglasco

Offline Hood

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Re: Z-axis problem
« Reply #1 on: October 26, 2010, 03:14:32 AM »
Are the steps per unit for the Z axis a lot more than the other axis?
Hood
Re: Z-axis problem
« Reply #2 on: October 26, 2010, 11:14:55 PM »
Yes the X & Y axis are set at 3200 and the z axis is set at 16000.

I have 1/2" 2 or 4 start threaded rods for the X & Z axis and 1/2" single start rod for the z axis

any suggestions would be greatly appreciated.

Right now it cuts and travel accurately but slowly.

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Re: Z-axis problem
« Reply #3 on: October 27, 2010, 03:36:49 AM »
Ok well I wa thinking maybe the kernel was set to low for your steps per unit on the Z but that is not the case as even at  25KHz kernel you could theoretically get a rapid speed of 375IPM.

Ok so now thats been ruled out what are the actual problems when you try and set faster?
 It could be that your pulse stream is extremely bad and as such 7KHz is the max you can reliably output, have you run the driver test to see what it looks like?

Hood

Re: Z-axis problem
« Reply #4 on: October 27, 2010, 05:05:35 PM »
When I try to run the machine faster than 25 ipm the z-axis stepper motor will intermittently pause or just stop (almost like it is hanging up on something) while the program is trying to tell the stepper motors to lower or raise the router and it screws up the depth of cut on my machine.

How do I check my pulse stream?  Is there a diagnostic I can run using the mach3 software?

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Re: Z-axis problem
« Reply #5 on: October 27, 2010, 05:38:59 PM »
Yes, close Mach and go to the mach folder, you will see a file called drivertest.exe double click that and let it run and see what the line in the graph looks like.

What kernel speed do you have Mach set to?

Hood
Re: Z-axis problem
« Reply #6 on: October 28, 2010, 07:27:48 AM »
Results of Driver Test you requested

The graph is pretty much a straight line and it said system excellent.

Pulses 24999
CPU Mhz 2940
short time 34.483 varies
long time 47.271  varies
Apic time constant 5346
Interupt 0
Max. Variation 12.709  varies

Version 550
PCI second lo 3579545
PCI second Hi 0
Window 1 second 2940000000
Avgerage interupt 40.0030 varies
Long Interupt 66.214 varies


Re: Z-axis problem
« Reply #7 on: October 29, 2010, 07:24:01 AM »
I tried playing with my motor tuning yesterday in Mach3.  The fastest speed I could obtain without the z axis hanging up was 25 IPM.  If I set it at 26 IPM I would start having problems.

 I think I need to change my lead screw with a 2 or 4 start.

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Re: Z-axis problem
« Reply #8 on: October 29, 2010, 07:28:16 AM »
Sorry must have missed your driver test reports :(
If you look on the diagnosics page in Mach what is the frequency at and is it varying quite a bit?
What do you have the kernel on Ports and Pins main page set to?

Hood