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Author Topic: Machine coordinates in wrong units  (Read 3256 times)

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Machine coordinates in wrong units
« on: January 23, 2016, 04:40:40 PM »
Hello. I'm having some trouble with my little CNC machine. I have a generic ebay 3040 crap machine that was working perfectly. If I traveled the spindle 1 inch, then it showed one inch on the coordinates display for whatever axis I was using. Well, yesterday it randomly started showing different units. If I travel 11 inches on my table, it shows 355 whatevers on the coordinates display. I've installed and reinstalled mach3 about 4 times, including trying out an older (2.x?) demo. About half the time it shows the correct units, then goes right back to the wrong ones. All my settings in motor tuning, inputs, motor outputs, etc are exactly as they've always been. The native units are set in mm, as they've always been. Now, when I load up some g-code, the coordinate display is accurate again and the part cuts fine. Changing between native units has no effect. Anyone know what's happening here? It's driving me nuts. Technically, I guess it's fine because my programs run fine, but jogging around is irritating because it says I'm moving like 25 whatevers for every inch.

My settings are as follows:

Native Units - mm

Port 1 enabled 0x378

X axis enabled - step pin 2 - dir pin 3 -dir low active x - step low active check - step port 1 - dir port 1
Y axis enabled - step pin 4 - dir pin 5 -dir low active x - step low active check - step port 1 - dir port 1
Z axis enabled - step pin 6 - dir pin 7 -dir low active x - step low active check - step port 1 - dir port 1

e-stop port 1 - pin number 10 - active low check

motor tuning:
X steps per 400 - velocity 2000 - acceleration 200 - step pulse 3 - dir pulse 0
Y steps per 400 - velocity 2000 - acceleration 200 - step pulse 3 - dir pulse 0
Z steps per 400 - velocity 700 - acceleration 100 - step pulse 3 - dir pulse 0

According to the little sheet that came with the CNC machine, the dir pulse is supposed to be 1, but it resets to 0 every time I save the settings.

This is driving me insane, any help would be much appreciated. If this is in the wrong spot, mods feel free to move it.

Thanks.
Re: Machine coordinates in wrong units
« Reply #1 on: January 23, 2016, 05:27:04 PM »
G20 inches, G21 mm, look in your G-code.
Re: Machine coordinates in wrong units
« Reply #2 on: January 23, 2016, 06:34:14 PM »
It's G20, but it's always been G20. The problem is before I  load any g-code.

Offline BR549

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Re: Machine coordinates in wrong units
« Reply #3 on: January 23, 2016, 07:12:08 PM »
Look in the config I think you will find a setting to LOCK/UNLOCK  the DROS to the setup units.

YOU are using Metric units but running in INCH mode . FOR best results IF you are going to normally  RUN in inches you need to setup the machine for inches.

(;-) TP
Re: Machine coordinates in wrong units
« Reply #4 on: January 25, 2016, 11:04:58 AM »
If the machine has metric components like ball screws then I would set it up as metric and work in inches if you like.

Offline ger21

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Re: Machine coordinates in wrong units
« Reply #5 on: January 25, 2016, 11:38:23 AM »
If the machine has metric components like ball screws then I would set it up as metric and work in inches if you like.

That's a bad idea, as you'll run into situations where the units don't get converted and you'll get a crash.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Machine coordinates in wrong units
« Reply #6 on: January 25, 2016, 04:39:24 PM »
Why would this cause a crash? Most CNC machine tools are metric screws as is mine. The steps per rev is an exact steps per mm of travel. Its just math after that and computers are pretty good at that!

Offline ger21

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Re: Machine coordinates in wrong units
« Reply #7 on: January 25, 2016, 08:45:51 PM »
If you set up the machine in mm's, then Mach3 will be converting all your g-code to inches. Sooner or later you'll find that Mach3 doesn't convert everything to inches, and the machine will not go where you expect.

It's always been recommended to setup the machine in inches if your g-code will be in inches, or in mm's if your g-code is in mm's.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html