Sporadic Erroneous Automatic Toolchange Behaviour

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02 May 2024 20:02 #299593 by Bassblaster
Hi Guys,

I have some trouble with my automatic revolver toolchanger on my lathe. If I set something like M6 T3 and then M6 T1 in MDI it should swich from tool 3 to tool 1. This works 80% of the time. However, randomly, sometimes it just doesn't move but still thinks that it changed the tool. However in my variable #4999 the tool has not been updated correctly in this erroneous case. I think that it maybe just somehow aborts in the middle of the change subroutine before moving or saving the tool, but I get no error messages or so... Also it actually never displays the current tool offset in Gmoccapy, but that is not my biggest problem.

For the toolchanger I just did a simple remap with this code:
REMAP = M6 modalgroup=6 ngc=sub_progs/toolchange

o<sub_progs/toolchange> sub
#4001 = 1 (distance to travel per tool pocket)
#4002 = 0 (calculated distance to travel)
#4003 = 0.4 (distance to lock turret)
#4004 = 0.2 (Aditional tolerance to clear the rachet)
M61 Q#4999 (stores the tool in spindle)
o100 if [#<_selected_pocket> GT 7]
    (DEBUG,STOP: Werkzeugtasche größer 7!)
    (DEBUG,Überprüfe eingegebene Tasche in der Werkzeugtabelle, maximal 7)
    M0
o100 endif
o101 if [#<_selected_tool> EQ #<_current_tool>]
    (DEBUG,Werkzeug bereits eingewechselt)
o101 elseif [#<_selected_pocket> GT #<_current_pocket>]
    #4002 = [[#<_selected_pocket> - #<_current_pocket> ] * #4001]
    G91
    G00 B-#4002
    G00 B-#4004
    G00 B#4003
    M6 G43
    G90
o101 else
    #4002 = [[#<_current_pocket> - #<_selected_pocket> ] * #4001]
    G91
    G00 B-[[8*#4001]-#4002]
    G00 B-#4004
    G00 B#4003
    M6 G43
    G90
o101 endif
#4999 = #<_current_tool>
o<sub_progs/toolchange> endsub
m2

Has anybody encountered similar problems or has an idea? I tried updating and writing a new hal and ini, but that changed nothing...
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04 May 2024 09:53 #299708 by andypugh
I don't advocate using a B axis for a toolchanger, I feel there is a danger of getting out of synch.

That said, is it possible that the B axis is configured to take the shortest path (WRAPPED_ROTARY) or that the G-code is setting the mode to incremental?

Your G-code sub probably needs to ensure that the mode is set to absolute, and then restore it after the change, even if this is not the problem.

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05 May 2024 15:06 #299815 by Bassblaster
Hmm, can you elaborate on what getting out of sync means? It is not set to shortest path, but I do use G91 for the movement of the revolver itself. In the end of the programm I set G90 again, but it is not executed in the erroneous case...
If not by a b-axis, then what is the common way to drive a stepper motor on the revolver? I thought this is necessary in order to use one of the pwmgen's on my mesa 7i96.

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