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G53 & G28
« on: April 09, 2016, 05:01:13 PM »
Can anyone tell me why my Mach3, G53 & G28 are doing the same thing. I have another thread called gcode mishaps so you can see what is happening. I can cut anything because may x scale is out and my z seems to act crazy at the first of a gcode run and unpredictable at the last. Can anyone help?

Offline mc

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Re: G53 & G28
« Reply #1 on: April 09, 2016, 05:07:26 PM »
Re: G53 & G28
« Reply #2 on: April 09, 2016, 05:38:12 PM »
This still doesn't explain why my machine, when I run a gcode run the y axis goes to the proper dro and the x axis dro is short by approximately -.0025. At the first of my run when I start the gcode run you don't know where the z is going to go. The y is fine the x is out a bit. At the end of the run the z axis mite go to zero or try to cut away down into my table. You have to baby sit it all the time and it is inaccurate to say the least. I am just about to take the cutting torch to it and send it for scrap I am pulling my hair out. Help Help.

Offline RICH

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Re: G53 & G28
« Reply #3 on: April 09, 2016, 06:05:18 PM »
How about just one fix at a time.

The controller is only doing what you told the controller about YOUR machine and what you tell it to do, so, if the x axis is off, then test the X axis.
Before you do that, calibrate the X axis so the steps per unit are  correct. The calibration is done with axis backlash removed before moving the axis
in the same direction. You can use the calibration feature of Mach to do it or calculate the steps per. Now check for backlash, and if there is any, fix the machine, use BC,
or live with it.

In the mean time, have a read about G28 & G53 in Mach's Manual on how the code is interpreted by Mach.

For now,
RICH
« Last Edit: April 09, 2016, 06:07:52 PM by RICH »
Re: G53 & G28
« Reply #4 on: April 09, 2016, 06:32:20 PM »
Thanks I'm new to all of this but I am trying hard to learn

Offline RICH

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Re: G53 & G28
« Reply #5 on: April 10, 2016, 07:45:45 AM »
kevin,
Understand.  The gcode for different controllers are similar, but like language there are dialects.
So consult the Mach Manual when reviewing something based on a different controller.

You need to understand machine coordinates, homed / referenced machine, work offsets,
and G90  & G91. G53 works in machine coordinates and G28 works inclusive of work offsets
and distance mode (ie G90 / G91). So defined controller configuration has an affect
on what happens when using G28. May also want to have a look at G30 and G55 commands.

Home can also be the same as Machine zero.

So if one does not understand some of the cnc basics and uses commands ( G53, G28, G30,
G5x, G0, G1) to move the axis...... the axis may not go where the user thought it would.

Note: The controller only knows what it is told and that includes current configuration
      and implements commands as instructed.

So it can be confusing if the basics and the big picture of setup is not understood.

A few command examples:

G53 X0 Y0 Z0 -  Makes a straight traverse run to Machine Zero

G30 - Makes a straight traverse move to machine zero

G28 - G28 without defined axis all axis goes home in the order of Z then all the rest.
 USED with a defined axis ONLY the defined axis goes home via the intermediate point.
 In g28 you can call a single axis to home, in G30 ALL axis go home reguardless and G28/30 in MACH3 is backwards to FANUC.

G0 & G1 used relative to PART
 
G55 G0 Z0 X0 Y0 - Changes  the Fixture / work offset then goes to X0 Y0 Z0 as straight traverse move at rapid speed

When you ask........
  
Can anyone tell me why my Mach3, G53 & G28 are doing the same thing.

I now ask you......
Under what conditions and how G commmand is coded will they work the same?

RICH
Re: G53 & G28
« Reply #6 on: April 10, 2016, 08:55:08 AM »
Thanks Rich, it's all new to me. 1 of me home switch wires broke so I disabled them. What I was doing with the original gcode run was just milling my bed top flat. I had run the codes several times with no problems. On my very last run at the end of the program instead of the cutter coming up .100 it started to cut down into the table. This was for no reason as my gcode was telling it to come up +1.00. And I had noticed throughout the entire x movement  every 3rd x dro was a litter off in the minus for no reason as the x was only traveling in the + so backlash should not have be a issue. What are your thoughts.
Cheers Kevin
Re: G53 & G28
« Reply #7 on: April 10, 2016, 08:59:59 AM »
What I am trying to say is I can run the program 6 or 7 times it works fine but when I run it again it doesn't

Offline ger21

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Re: G53 & G28
« Reply #8 on: April 10, 2016, 09:35:54 AM »
Quote
n my very last run at the end of the program instead of the cutter coming up .100 it started to cut down into the table. This was for no reason as my gcode was telling it to come up +1.00.

What did the DRO show?
If the DRO showed it moving up, then it's probably an electrical issue.

Quote
And I had noticed throughout the entire x movement  every 3rd x dro was a litter off in the minus for no reason as the x was only traveling in the + so backlash should not have be a issue.

I don't understand what you're saying here?
Gerry

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Re: G53 & G28
« Reply #9 on: April 10, 2016, 09:38:15 AM »
Why does the same gcode run good for me for 6 or 7 times but no for the next time I run it