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DRO Axis Values (?)
« on: January 17, 2015, 12:39:41 AM »
new to hobby cnc and just finished by first build based on the open builds ox, with a bob/motor kit consisting of the JK02 5 axis and DIV168 stepper drivers. However, when I load my Meshcam generated GCode the machine hits limit switches when doing the initial positioned despite my secondary offsets. Mind you, the road runner example GCode runs just fine. Comparing the GCode there are some significant differences, though some in the Meshcam generated file seem correct. One thing I have noticed is the when setting my soft limits (mach3 is set to default to mm) is the the DRO of the axis position is nowhere near what the value should be if it is supposed to be reading mm from machine zero (have verified I am homing to the correct positions, motors appear tuned correctly and home/limit switches are 100%). THe DRO would be correct (or much closer) if it I were to be expecting inches. Is there a setting other than defaulting to mm to display in mm? Also, when motor tuning it appears to only tune in inches (?) which seems odd if you are expecting a system to work based on mm. I'd prefer not to go back and forth and forget that imperial measurement even exist if possible.

note: this is the trial version of the product until I can decide between it and GRBL

Offline Tweakie.CNC

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Re: DRO Axis Values (?)
« Reply #1 on: January 17, 2015, 03:16:52 AM »
Hi Leeawilson,

Perhaps check your MeshCam generated Gcode to make sure it does not contain a G20 code which would make the machine operate in Inch units instead of your desired mm units.
Motor tuning is in units so if Mach3 is set up for mm then that is what is displayed.

Hope this helps,

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline ger21

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Re: DRO Axis Values (?)
« Reply #2 on: January 17, 2015, 08:10:37 AM »
Are you using the Meshcam Mach3 MM post processor?
Gerry

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

JointCAM Dovetail and Box Joint software
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Re: DRO Axis Values (?)
« Reply #3 on: January 17, 2015, 11:38:40 AM »
Thanks for the replies all. I will check for the G20 instruction, but I am using mm in Meshcam and the Mach3 finishing processor. Though, I neither would explain why my values on the DRO are incorrect (or misunderstood). When starting from machine zero and jogging all the way over to the limit switch I get a value of positive value of 16 and some change. If that is supposed to be in mm it is horribly off. Again in machine tuning when I enter 1.0 it moves one inch exactly (or 2 or 3). Same behavior on y and z. I feel like I am missing a Mach3 setting somewhere and that I should get this corrected/understood before diagnosing the GCode.

Offline ger21

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Re: DRO Axis Values (?)
« Reply #4 on: January 17, 2015, 11:51:10 AM »
Quote
Again in machine tuning when I enter 1.0 it moves one inch exactly (or 2 or 3).

If you're creating your g-code in mm's, than your machine should be setup in mm's, not inches. When you tell the machine to move 1 unit, it should move 1mm, not 1inch, if you intend to run g-code 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
Re: DRO Axis Values (?)
« Reply #5 on: January 17, 2015, 02:20:40 PM »
agreed, and it was set to mm as the default unit with a fresh reinstall yesterday. However, it still seems to be defaulting to imperial on the DROs and motor tuning feature under settings, and why I suspect that there is something that I am overlooking. Is there a line in the mach3.xml file that dictates the default machine units or something I can check? It seems clear that it is set to use inches somewhere other than the select native units option.

Offline ger21

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Re: DRO Axis Values (?)
« Reply #6 on: January 17, 2015, 02:29:43 PM »
Check the status bar for G20(inch) or G21(mm) to see which is active. If it's G21, then your steps/unit are probably set for inches.
Gerry

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

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: DRO Axis Values (?)
« Reply #7 on: January 17, 2015, 02:57:16 PM »
its set for G21, but above you say G20(inch) G21(mm) and then that if G21 its inches. Based on the second post I assume G21 is correct and it set for mm? I did retune the motors, though and think I may have been thinking of the steps per unit incorrectly. I was thinking it was steps per revolution, and started with 2000 as suggested in documentation, however rather than going higher with that as increased microstepping (1/16th) I went lower as I now think I realize it is steps per unit (or mm), so adjusted the steps per unit to 53.333 per the settings wizard and now my part seems to be running correctly. well, at least running. I'll adjust the speed of the GCode and put some material under it on the next run. Does the assumptions/adjustments above make sense or am I digging a deeper hole?

Offline ger21

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Re: DRO Axis Values (?)
« Reply #8 on: January 17, 2015, 03:57:49 PM »
Sorry if I wasn't clear.
What I meant was if you see G21, then you are in mm mode, but your machine is configured to travel in inches due to an incorrect steps/unit setting.
Gerry

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

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: DRO Axis Values (?)
« Reply #9 on: January 17, 2015, 05:48:30 PM »
thanks for the info all, I think adjusting the steps per unit corrects all previous concerns. now let me see what else screw up in this endeavor.