G28 sequence

All things related to the Centroid Acorn CNC Controller

Moderator: cnckeith

Post Reply
vw_chuck
Posts: 45
Joined: Sun Sep 20, 2020 7:34 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: 0035FF8FEB5F-0708203490

G28 sequence

Post by vw_chuck »

I am working on a lathe and I am having issues with the G28 command. I used to have a drilling operation and the end of the operation it would G28 in the x direction first and then the Z direction. I recently setup ball screw mapping and also reset the Home position. Now when I run my drilling operation it attempts to G28 in the Z direction first and then the X direction. So it actually attempts to rapid right through the part to get to position. Is there a way to fix this in the code anywhere. So that is moves the X first and then the Z?
cncsnw
Posts: 1605
Joined: Wed Mar 24, 2010 5:48 pm

Re: G28 sequence

Post by cncsnw »

We would have to see your CNC program file.. If it is something you wrote with Intercon, then also post the .lth program file.

In general, "G28 W0" will move the Z axis directly to the G28 return position; "G28 U0" will move the X axis directly to the G28 return position; and "G28 U0 W0" will move both axes, diagonally if necessary, directly to the G28 return position.

A G28 with an X and/or Z coordinate (an absolution position) will move the specified axes to that position (measured from part zero) first, then from there to the G28 return position.

When you say you have a program that used to do one thing, and now does another, can you tell us what changed? Was it previously running on a different brand of control? Was it previously on a different Centroid control? Was it previously on this Centroid control, but you updated the software from one version to another?
vw_chuck
Posts: 45
Joined: Sun Sep 20, 2020 7:34 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: 0035FF8FEB5F-0708203490

Re: G28 sequence

Post by vw_chuck »

This NC code ran on this same machine and I did not end up with a broken drill bit. It used to move diagonally when finishing the operation. Now I run it and it breaks the drill bit because it rapids toward the chuck right through the center of the part and then it does it's x move breaking my drill bit.
What changed in the Acorn is I reset my software limits so I can use the ball screw compensation. I also changed the X,Z sequence back to home position. It used to home Z and then X but I had to change it to home x first then Z. No other changes between the two.
The code was posted by Fusion 360. The G28 lines are G28 W0 and the next line is G28 U0. So the machine is following the code but why did it not act this way before I made changes to the software limits and home sequence? It is quite strange.
cncsnw
Posts: 1605
Joined: Wed Mar 24, 2010 5:48 pm

Re: G28 sequence

Post by cncsnw »

Maybe your G28 Z position is to the left of where you are machining parts? I cannot tell, because you have not posted a Report.
vw_chuck
Posts: 45
Joined: Sun Sep 20, 2020 7:34 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: 0035FF8FEB5F-0708203490

Re: G28 sequence

Post by vw_chuck »

Yes it is to the left. I will get you a report.
vw_chuck
Posts: 45
Joined: Sun Sep 20, 2020 7:34 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: 0035FF8FEB5F-0708203490

Re: G28 sequence

Post by vw_chuck »

I found the issue. It seems to be the Centroid Turning Post Processor was getting confused thinking the tool was coming in from the other end. Some modifying the PP fixed it.
Post Reply