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Z axis incorrect
« on: February 06, 2015, 08:06:20 AM »
hello everyone
iv dusted off my old machine and am going to have another go at trying to get to know it better
with a few trial runs iv found that i am loosing depth of cut to what i have programmed. ie programmed to cut to a depth of 6mm but actual final cut was only 4.24mm
process of elimination.

 i first check the Z movement (distance) in mach to the actual movement (distance) of the spindle.

i set the base of the spindle 55mm from the bed zeroed the Z axis and then lifted the spindle 45mm on the z counter on mach
that should have ment that the spindle should be a total 100mm from the bed, it wasnt, it was 89mm off the bed, a loss of 11mm
the machine is a 6040 chinese cnc
according to the specs sheet the ball screws are dia 16mm with a pitch of 5 mm
the motors are 387 oz motors from Homann supplies (with a lot of outside help i changed the moter rewired and fitter G540 stepper controlers to it)
the info/help i am after is what should the correct configeration be, for this setup, and were in mach do i change the settings
thankyou in advance for any feed back that maybe provided.
cheers Tony
Re: Z axis incorrect
« Reply #1 on: February 06, 2015, 10:47:21 AM »
Check to make sure steps/unit is correct in motor tuning.
Re: Z axis incorrect
« Reply #2 on: February 06, 2015, 06:43:43 PM »
but what would the correct steps settings be
cheers Tony

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Re: Z axis incorrect
« Reply #3 on: February 06, 2015, 07:17:20 PM »
How to figure out the steps per unit is in the Mach3 Manual.

Re: Z axis incorrect
« Reply #4 on: February 06, 2015, 07:22:13 PM »
I assume the motors are 200 steps per revolution (there are some old 180 step motors still around but it's not likely you have one) the Gecko G540 is x10 microstepping. The ball screws are 5mm pitch. So doing the math, 200 x 10 = 2000 pulses per rev, divided by 5 mm = 400 steps per unit.  Go into Mach 3 motor tuning and enter 400 in the steps per unit for each axis (X,Y,Z). This will equal 400 steps to travel 1mm.

This is only the calculated values and in a perfect world would be exact, but the actual distance traveled may vary slightly due to ball screw precision. Next use Mach 3 calibration function and follow the instruction on the popup window... enter a distance value and then measure the travel with a digital caliper. This will correct the steps per unit numbers.

« Last Edit: February 06, 2015, 07:27:09 PM by geh7552 »
Re: Z axis incorrect
« Reply #5 on: February 06, 2015, 11:26:21 PM »
Geh 7552

thanks heaps with that info problem has been solved
again thankyou
cheers Tony