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Author Topic: G28 in Turn causing problems?  (Read 3164 times)

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Offline Fastest1

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G28 in Turn causing problems?
« on: February 26, 2012, 02:40:22 PM »
I am using Turn and my understanding is that a G28 command should return all axis home (of course I could be wrong). However upon inserting G28 into the MDI line and pressing enter, my Z starts homing as it should, my X dros start moving but the carriage does not and I hear my toolchanger's stepper stalling against the pawl. Crosstalk? There are no home or limit switches in my toolchanger.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Graham Waterworth

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Re: G28 in Turn causing problems?
« Reply #1 on: February 27, 2012, 02:33:39 PM »
G28 needs an axis too e.g.

G28 Z0 (Go rapid to known Z home)

or

G28 X0 (Go rapid to known X home)

or

G28 X0 Z0 (Go rapid to known X & Z home)

or

G28.1 X0 Z0 (Search for X & Z home)

Graham
Without engineers the world stops

Offline Fastest1

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Re: G28 in Turn causing problems?
« Reply #2 on: February 27, 2012, 04:27:57 PM »
Graham. Thanks for any advice you can impart as I am not well versed at all. I dont remember if I assigned an axis or not. I will have to repeat the procedure to verify. I do know that the A axis tool changer has no homing or limit switches so to hear it attempting to rotate against a pawl is suprising. Well maybe not suprising, not expected or intended. I inherited a tool change macro that seems to work well, though his machine might have been slightly different in regards the switches etc. Could the tool change macro include info for a G28 move? Should a G28 alone cause movement? Thanks
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Fastest1

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Re: G28 in Turn causing problems?
« Reply #3 on: February 27, 2012, 05:47:45 PM »
Graham, I just went back, restarted my computer, replugged in my Smoothstepper and opened Mach. I homed my machine. I then jogged off of both Z & X axis a few inches. I then put "G28"not followed by any axis designation and pressed enter. The machine started to move in Z first and then in X (I wonder if this is due to an M6End file Hood was reffering to?). In my usual pressing of home, X retracts first and then Z. Oddly enough, the first 3 times I attempted a G28, it retracted as it should (or how I perceive it to work). Then on my 4th attempt the stepper for the tool changer was screamiing against the pawl. Quite odd. What do you think my next course mof action should be besides not using a G28?
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Fastest1

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Re: G28 in Turn causing problems?
« Reply #4 on: February 27, 2012, 06:07:05 PM »
I diid some more testing. I come to find, I can home and move of axis then hit G28 alone and it returns to home (many times, 10 or more). However if I jog my tool changer or ask for a tool change thru MDI and then hit G28 it causes the toolchange stepper to back up (everytime). I am now removing any trace of M6End files on that particular computer as it will be used for a lathe only. Hood was suspicious it might be causing some issues.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Fastest1

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Re: G28 in Turn causing problems?
« Reply #5 on: February 27, 2012, 06:14:52 PM »
Ok now it really gets weird. I repeated the above after all M6End files were removed (unfortunately I didnt try it before), if I do complete the G28 as in G28 Z0 X0 F6 it will go home at a reasobly high speed disregarding the F speed. It also homed the X in the wrong direction on 1 tool but not another?
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline BR549

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Re: G28 in Turn causing problems?
« Reply #6 on: February 27, 2012, 07:43:27 PM »
Homing occurs at rapid rate UNLESS you set the Homing rate in GenConfig/ Homing. The rate is a % of max velocity

(;-) TP

Offline Fastest1

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Re: G28 in Turn causing problems?
« Reply #7 on: February 27, 2012, 10:10:24 PM »
BR549/Juniors Auto Sales, That makes sense as I do have my homing speed at about 75% of max. I would have thought the F# would have overridden the setting. At least now I know what is responsible for the choice of speeds. Still a few concerns, why does it home at different speeds seemingly dependent on which tool is selected? Also why does the toolchanger get affected only when a tool change or move was made prior to the G28?  Why does G28 with no other command cause motion? My understanding was that it shouldnt move without an axis being specified. Also since the homing speed is set on the homing/limits page, F wouldnt be necessary in the Gcode would it. So G28 Z0 X0 would be a viable command? Again thanks for your input.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)