Back or front tool

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26 Sep 2021 11:44 - 28 Sep 2021 14:31 #221626 by john11668
Back or front tool was created by john11668
My TCL 125 has no turret .
I was having problems due to "saddle lift" in back tool mode when screwcutting with tool reversed. Reversing spindle and using tool right way up will only give me LH thread unless I cut toward Z+ (away from the chuck)

Now I have made alterations to overcome the saddle lift problem , but it seems to be I would be better doing turning in back tool mode (spindle c/w) , and threading in front tool mode (spindle cc/w)(unless of course I want LH thread )

I have seen this  wiki.linuxcnc.org/cgi-bin/wiki.pl?BackToolLathe

What It seems to me that I need is the facility to change from back tool mode to front tool mode mid program.
Since Back tool mode is called up in the Ini file I cant see how best to achieve this.

Any suggestions folks ?
 
Last edit: 28 Sep 2021 14:31 by john11668.

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29 Sep 2021 10:44 - 29 Sep 2021 10:49 #221818 by john11668
Replied by john11668 on topic Back or front tool
So no takers over the last day or two 
Maybe I havent been clear enough about what my problem is .
maybe try and expand a bit on it 


So atttached is a pic of my is my lathe with two toolposts on the saddle


 

I had been having problems with saddle lifting / jamming (and missed steps ) when I used back tool configuration with cutting tools reversed and counterclockwise spindle.
I have resolved some of the lifting issues with higher voltage at the steppers which allowed me to tighten the gibbs a bit , but clearly better to use clockwise rotation and tools cutting forward taking away the tendency to lift ,
This mode allows me to do beautiful left hand threads but not Right hand unless I cut left to right , from the chuck towards Z+.

But if I use threading tool in the bottom position and spindle counter clockwise, (and in front tool mode) I have my cutting forces in the correct direction and can produce beautiful Right hand threads. Seems natural therefore to use back tool for turning down with reasonably heavy cuts, then go to threading in front tool mode . But how do I do this during execution of a program.

The front or back mode is called up in the Ini file and I cant see a way to change mode without restarting gmoccapy. Surely what I want to do is sensible enough whether for threading or even for parting off. No problems changing spindle direction. No problems specifying a tool offset for any of the front tools . but how do I change the direction of movement for the tools.

Is there a way to change from front to back tool mode mid cycle .
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Last edit: 29 Sep 2021 10:49 by john11668.

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29 Sep 2021 14:05 #221831 by tommylight
Replied by tommylight on topic Back or front tool
Sorry but i can not help, never had the time to retrofit a Mazak i have collecting dust ....
Did you try using Axis GUI and can it do what you want when changing the geometry in the .ini file?

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29 Sep 2021 20:22 #221852 by john11668
Replied by john11668 on topic Back or front tool
I can inhibit back tool in my ini file
If I then restart EMC without back tool mode I can reverse the spindle and traverses , then operate screwcutting (or parting ) in front tool mode .
Never tried in axis GUI . Have spent too much time setting up the hard buttons to simulate those in gmoccapy. Just feel the need to be able to change modes mid cycle .
Cant be an unusual request surely. Isnt it common practice to part off from the rear when front cutting?

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30 Sep 2021 09:40 #221878 by Aciera
Replied by Aciera on topic Back or front tool
Have you tried using G10:
linuxcnc.org/docs/html/gcode/g-code.html#gcode:g10-l1

I don't think you will be able to change the preview window display once it's loaded.

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30 Sep 2021 11:29 #221885 by john11668
Replied by john11668 on topic Back or front tool
have had a look at that Aciera and initially having difficulty making sense of it but will persevere .
Initial feeling is that it transposes the workspace with an offset.
My problem seems to be that when I go to front tools and I I need the tool to advance into the workpiece, I need to reverse the direction of X negative to move the saddle upwards , when with back tool x negative is downwards.
I dont see how G10 achieves this ( or am I missing something?)

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30 Sep 2021 13:19 - 30 Sep 2021 13:22 #221895 by Aciera
Replied by Aciera on topic Back or front tool
I believe the idea is to use the rotational word (R):

forum.linuxcnc.org/10-advanced-configura...athe?start=20#216769

[edit]
Not sure what the 'bug' is, he's referring to.
Last edit: 30 Sep 2021 13:22 by Aciera.

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30 Sep 2021 13:43 #221899 by anfänger
Replied by anfänger on topic Back or front tool
Ist the trajectory aware of the spindle direction?
If not simply use the right tool orientation and let the spindle run backwards.

Or one an negative spindle speed override.

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01 Oct 2021 09:39 #221941 by john11668
Replied by john11668 on topic Back or front tool
I need to reverse the direction of the tool progression during the generation of the thread Anfanger so simply reversing the spindle does not give me what i need .

Am making mods to the latching relay controls so that machine will respond to M3 and M4 .
Will then look at G10 R180 in the threading routine to see if that gives me what I want !
The following user(s) said Thank You: anfänger

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01 Oct 2021 11:40 #221944 by anfänger
Replied by anfänger on topic Back or front tool
OK when you use it with spindle synchronized motion its different.
I thought you were using the thread tool conventional and the normal tool in the back.

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