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Author Topic: Mach3 steps per mm ...some decimal places don't work  (Read 3343 times)

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Mach3 steps per mm ...some decimal places don't work
« on: January 25, 2015, 08:30:53 AM »
Hi guys,

I'm using a pokeys 57E with newest firmware
and Mach3 Version  R3.043.066

calibrating my machine...
setting steps per mm and backlash...

actually my x y and z axis should go by 640 steps /mm

I started with the X axis and did 100 times the same stuff... homing the machine, moving it towarts the dial indicator via G0 x52 (for example)
(the dial indicator axis is quite parallel to the X axis)
write down digits move another 5mm write down digits and go back to the first position to get the backlash...

when moving the 5 mm the x axis seems to moves average 0,002 mm to much...so i tried to set new steps per mm.

MY PROBLEM: in Motor Tuning I can not set steps per mm as I want to, cause else my motor wont move properly or not a bit...

The strange thing is 639.4 works 639.5 as well 639.6 doesn't and so on... Mach3 seems to be picky about the digits, which makes no sense to me...

When I do the procedure with the settings screen and "Set steps per Unit", Mach suggests me 638.3233533 and asks me if I want to store this value.
After I stored it, the motor doesn't move anymore.

I wanted to set steps per mm first before I start dealing with the backlash.
But when I tried to change it to x 0,01 for example, 100% speed,
checked backlash enable and set shuttle accel. in general config to 0.005 there was no effect on it.

What am I doing wrong?

Thanks for your help

Offline Hood

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Re: Mach3 steps per mm ...some decimal places don't work
« Reply #1 on: January 25, 2015, 03:32:58 PM »
Two things may be connected and that is the plugin for the Pokeys.
I have never heard of Mach not accepting certain decimal place for steps per unit, so I think that is most likely a Pokeys plugin thing.
The Backlash may also be a PoKeys thing, with Backlash, when using an external controller, it is the controller that needs to do it rather than Mach, if your PoKeys does not support backlash then you can not use it. If it does support backlash then it may be that it needs configured in the Plugin rather than Mach, best ask PoLabs if it supports backlash.
Hood
Re: Mach3 steps per mm ...some decimal places don't work
« Reply #2 on: January 25, 2015, 03:49:44 PM »
hmm, they told me:
"Unfortunately, this looks to be Mach3 issue."
Re: Mach3 steps per mm ...some decimal places don't work
« Reply #3 on: January 26, 2015, 07:13:27 AM »
does it matter that I'm running the demo mode of mach3?

Offline Hood

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Re: Mach3 steps per mm ...some decimal places don't work
« Reply #4 on: January 26, 2015, 01:42:46 PM »
Would not think so.

Hood

Offline Jeff_Birt

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Re: Mach3 steps per mm ...some decimal places don't work
« Reply #5 on: January 26, 2015, 04:48:21 PM »
Reality check: you are talking about a difference of 0.02mm over 5mm for folks that still use inches that is 0.000197". I would suspect that you can't really measure down to the hundredths of a mm range accurately and your chasing faulty measurements. To get an accurate believable measurement you must be able to measure at 10x that resolution. So to be quoting measurements of 0.01mm you need to be able to accurately measure 0.001mm. When you get to that scale you have issues with the measurement tool construction, springiness of the tool needle, dust under the needle, etc. etc.

If you know your steps/unit is 640 based on your lead screw pitch, drive reduction etc. then type in 640. You are NOT going to make it more accurate overall by trying to measure distance traveled to one point and altering the steps/unit. As you move an axis along inaccuracies from the lead screw pitch, drive reduction pitch errors, the table shifting slightly in the gibs all come into play. Let's stay you have a table with 200mm of travel so you tell your machine to move 100mm and measure the distance travels with an uber accurate measurement device. Now if you only move from your starting location to that same position that you calibrated to you will be very accurate as long as the temperature never changes, and nothing ever wears, etc. Your calibration did not make your machine more accurate overall.

What I'm trying to say is don't chase your tail trying to achieve accuracy you can't even measure. When you are actually machining you will have far more inaccuracy dies to tool flex, your machining strategy, tool wear, etc.
Happy machining , Jeff Birt