Confused about the G54 command for resetting home position

[kristenanne77]

After I home device to x= -5, y= -5 and z= -5, I then jog the mill bit to where I want my new zero starting point on my workpiece. Lets say it is now at, -200,-250,-10. Then I would rezero and start work.
I would write these numbers down and if I have to go over the piece again after changing the bit I would home device and then jog it back to -200,-250,-10, then rezero , and start job again with the new milling bit.

I want to use the G54 command to to this.
How would I set this command , and then use it after homing without having to to write down new coordinates and rezero?
From what I have read there is a G10 command, aL20 command and some other stuff.
What does the G10 and L20 and P1 have to to with the G54 command?

Or maybe someone could show an example what would I have to do to set my device to the numbers I have listed above and then rezero it before running a file?
(I am currently using Universal G Code Sender)

Thanks
K

[WillAdams]

I just use the buttons in bCNC.

Remember that you can't use G54 if you're going to be using Carbide Motion, since it uses that to track machine position or some such.

Nice writeup on the wiki by Tim Foreman: http://www.shapeoko.com/wiki/index.php/ ... te_Systems

[kristenanne77]

I am not using bCNC yet.
The above question was for universal gcode sender.

I still have to find out where to get the bCNC zip file for the macbook. The github area seems a bit confusing.... It sort of details instructions in windows and Linux but not the macbook os

k

[RoguePirin]

I still have to find out where to get the bCNC zip file for the macbook.

As I understand it, bCNC is written in Python, which is OS independent. You just need to download the master.zip file from the main GitHub page. The "Download ZIP" button on the upper right points to https://github.com/vlachoudis/bCNC/archive/master.zip. I downloaded the same ZIP file for my Windows and Linux PCs and they both run fine.

That being said, I don't have a Mac, so I don't know how to go about ensuring that you have all the python prerequisites.

[twforeman]

The python pre-reqs should be installed with "pip" I think.

Code: Select all

pip install <package name>

[DRobs86]

After I home device to x= -5, y= -5 and z= -5, I then jog the mill bit to where I want my new zero starting point on my workpiece. Lets say it is now at, -200,-250,-10. Then I would rezero and start work.
I would write these numbers down and if I have to go over the piece again after changing the bit I would home device and then jog it back to -200,-250,-10, then rezero , and start job again with the new milling bit.

I want to use the G54 command to to this.
How would I set this command , and then use it after homing without having to to write down new coordinates and rezero?
From what I have read there is a G10 command, aL20 command and some other stuff.
What does the G10 and L20 and P1 have to to with the G54 command?

Or maybe someone could show an example what would I have to do to set my device to the numbers I have listed above and then rezero it before running a file?
(I am currently using Universal G Code Sender)

Thanks
K

I am not in front of a machine, so lets see if I can do this from memory.

Lets say you want to avoid G54 to accomodate whatever C3D has going on with that. Lets use g55 instead, which would be set by P2 in the g10 command. Also, i cant remember if grbl uses L2 or L20 to access g54 through g59. I think it is L20.

So to set g55 to be 0,0,0 at machine position -200,-250,-10 use this:
G10 L20 P2 X -200, Y -250, Z -10.
Now that sets that position to 0,0,0.
When I want to use that system I will enter G55, then all further commands will be based on tbat WCS. I would then enefn'

[cvoinescu]

That's a bit wrong. You describe the effect of L2, not L20. L2 sets offset relative to machine position, L20 is relative to the current position (and with opposite signs for the offsets). GRBL supports both. Also, Carbide Motion currently disallows all commands related to coordinates and offsets (G10, G54 to G59, G92...).

[DRobs86]

Thanks for clearing that one up cv. My memory lead me astray. That is a bumner on C3D and WCS.

[chamnit]

To be clear, CarbideMotion supports a single work coordinate system and allows you to set the G54(default) work coordinate offsets through its zeroing interface. It just prevents you from altering and using the others.

I think the argument here is whether or not additional work coordinate systems are useful for most users. Typically multiple systems are only used by more advanced users when they are doing production jobs. If that's the case, there are plenty of good Grbl senders available to give you that capability.

In terms of simplicity, CarbideMotion is a lot less fear-inducing to a new user than the glut of (awesome) features available in bCNC, which I would only recommend to users who have some CNC experience.

[cvoinescu]

There's value in having both simple but restrictive programs, and more complex ones that give more liberty.

It's also good to make the limitations of the simpler solutions known. To that end, I would change the error message in Carbide Motion from "unsupported command" (vague: unsupported by whom? why? especially confusing for users who are sure G10, G55 etc. are supported by GRBL) to something like "command not supported by Carbide Motion: interferes with zeroing interface", or "WCS commands not permitted (see 'WCS support' in online help)". That would eliminate some confusion.