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Author Topic: Run From Here: strange Z axis plunge to zero ruining jobs!  (Read 5115 times)

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Offline Frank1959

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Run From Here: strange Z axis plunge to zero ruining jobs!
« on: January 22, 2015, 06:44:14 AM »
I do big rotary A axis milling jobs in polystyrene, and sometimes want to / have to stop halfway into a job and resume the next day.
I´m trying to use the Run From Here function, to save time, some jobs can take hours… but with disastrous results.
What I do is this (obviously I´m doing something very wrong):
I open the Gcodes for the job that’s half done, I manually advance to the Line number I stopped at, (I have tried to key in the line number, instead of manually scrolling down…but to no effect) , and when I get to the line, in this case 36297, manually, I click on the Run From Here button.
After a brief pause, I get a prompt to Press Cycle Start, I do this, and a “Preparational Move To” window emerges, so far so good.
The data shown in this window is (see pdf):
X 1314.004 (I presume this is because the last X instruction was at line 36203 “G1 X 1314.004”)
Y 3.4879121; (this I don’t understand, as I´m doing rotary milling an Y is stationary at Y=0)
Z 153.83 (this Z height would clear all the geometry without crashing into material)
A -109440. This divided by 360 degrees is 304, the number of revolutions I suppose the A axis has made, so in effect it’s the same as A axis going to Home/0 degrees.
BUT…AND HERES THE PROBLEM…the Z axis, on clicking on OK,  dives and crashes into the material, far below the 153.83 value given in the “Preparational Move To” window.  Job ruined. I then E Stop, but when I haven’t had time to EStop, once the Z axis  gets to (probably) Z = 0 level, it starts to move (probably) to the X axis position indicated…job ruined totally.
This has always happened, in my year or so use of  MACH3,  to the extent that I´ve avoided using the Run From Here function, but now I´ve some big jobs to do and using it will be inevitable.
What am I doing wrong? By the way, I use DESKPROTO for g-codes, which I´m very happy with.
All help greatly appreciated!
Frank.
The pdf is a screen shot of those  Prep Moves over the MACH screen
 
Re: Run From Here: strange Z axis plunge to zero ruining jobs!
« Reply #1 on: January 22, 2015, 07:39:41 AM »
I have suffered the same issue with job destruction.
I think I know what you're doing wrong.
If, like me, in your CAD you set the Z zero to be at the centre of the job, that being the center line of the rotary axis.
When you OK'd the preperation move in the pdf, you needed to type in a rapid clearence height. The screen capture shows '0' in the rapid height box and that is the centre of the job, thus plunging into the job and then running from there.
Not sure what the other DRO numbers indicate, but I would say that you need to reference the machine to the start position of the job before running to the line number.
Do you use a saved offset for your rotary work so that the machine knows where the centre line of the A axis is?

Offline BR549

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Re: Run From Here: strange Z axis plunge to zero ruining jobs!
« Reply #2 on: January 22, 2015, 10:42:46 AM »
Are you saving all the fixture and tool offsets when you shut down Mach3 ??

You will HAVE to RefHome the Machine to an exact spot AND then when you set teh Work Zero you are changing the offests. When you restart Mach33 to continue you MUST refHome again then Move to the exact spot that you set the Work Zero to to begin. 

If you do NOT save the offsets then Mach3 assumes you do not want to restart in the exact spot and simply goes where you tell it to go.

Then is the option in Gen Config to save the offsets make SURE it is set.

(;-) TP

Offline Hood

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Re: Run From Here: strange Z axis plunge to zero ruining jobs!
« Reply #3 on: January 22, 2015, 05:10:05 PM »
Do you have Safe Z enabled and if you do what is it configured for?
Hood

Offline Frank1959

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Re: Run From Here: strange Z axis plunge to zero ruining jobs!
« Reply #4 on: January 24, 2015, 03:25:25 AM »
Thanks Ozymax, TP, and Hood, as Ozymax said " The screen capture shows '0' in the rapid height box and that is the centre of the job, thus plunging into the job and then running from there." So I changed this to a safe height, and it works perfect!!

I´m away from the machine now, but will check to see if the Safe Z setting is enabled, and to what. Is this the same as the setting that should appear in the Rapid Height box?

Regards to you all and happy milling; )

Frank.

www.franknorton.com

Offline Hood

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Re: Run From Here: strange Z axis plunge to zero ruining jobs!
« Reply #5 on: January 24, 2015, 08:03:08 AM »
If you have a safe Z set then yes it should appear in the window. If you have it set as Zero in Machine Coords it will rise fully in the Z axis before moving X or Y. That is assuming you home the machine and have Z0 as fully up in Machine coords.
If you had safe Z enabled and had 0 set but in Work coords then it would go to the Z0  in your work coords.
If you had Incremental and had 0 set then it would not move at all.

If you do not have safe Z set then you must enter a value into that box before you press OK, unless of course Z0 is fine.

Hood
Re: Run From Here: strange Z axis plunge to zero ruining jobs!
« Reply #6 on: September 09, 2016, 03:53:34 PM »
Why does Mach3 EVER plunge the z axis first for a preliminary move? It should just move x and y first. I have ruined a bunch of jobs and broken expensive bits for carbon fiber trying to restart with "run from here" with this same problem. I've even moved the spindle manually above this spot but it still plunges and tweaks the job. Can you please point me to some tutorial on how to setup Mach 3 to never move Z axis first in a preliminary move?

Offline Hood

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Re: Run From Here: strange Z axis plunge to zero ruining jobs!
« Reply #7 on: September 09, 2016, 03:58:22 PM »
There can be many reasons it moves to that Z position, it could be in your code, it could be you have a safe Z set up but incorrectly or it could be there is a Zero call in the Prep move box that appears.

Hood
Re: Run From Here: strange Z axis plunge to zero ruining jobs!
« Reply #8 on: September 09, 2016, 04:09:18 PM »
Thanks for your help. I use Cut2D and zero my work z-axis at the surface of the material. So cuts plunge in the negative. I attached my machine config from the manufacturer (Zenbot 24 x 24 machine).

Offline Hood

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Re: Run From Here: strange Z axis plunge to zero ruining jobs!
« Reply #9 on: September 09, 2016, 04:13:34 PM »
Sent you a PM.
Hood