Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: M250cnc on October 26, 2009, 02:10:38 PM
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Ok so my machine has been working nice and today i have been threading
I am using the G76 for threading and the threads seem to be very good.
In between parts i re referenced the machine and this is where the problem lies.
I hit my home switch as normal but it behaved differently when it backed off the switch, i can only describe it as though the motors were re-tuned instead of the normal sound "Eee" i got lazy sound like "Whooa" ;D ;D
I quit Mach the restarted Mach and it was back to normal
And no this isn't a wind up thread ::)
Phil
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Don't have an answer for you. What version are you using? Do you have backlash compensation eneblaled?
RICH
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Can you do it again?
Hood
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Hood, Rich
No Backlash, and using Smooth stepper.
The machine seems to be working well, i only did a re reference to be on the safe side.
To test I just fired the machine up homed as normal it was normal.
Run the code with G76
Homed it again and now lazy back off.
Closed Mach, then restarted and homing back to normal.
I am using version 029 the lockdown.
I know if i use that home with the lazy backoff the machine will not be where it's supposed to be.
I found that in testing, the machine will home to within .0002" repeatedly but if i alter the motor tuning or the homing percentages
it will still home repeatedly but just in a different position. I only have one version of the M1076 Macro and it is dated Sept 25 2008
Maybe you could test yourself sometime you do a thread maybe you Rich as you seem to be doing a lot of threading at the moment. ;D
Phil
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I can't test I am afraid as I do the homing externally from Mach.
Hood
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I can't test I am afraid as I do the homing externally from Mach.
Hood
Hood are you trying to tell me something. ;D
I have just thought of something when the machine is threading the movements seem quite violent more so than just doing a G0 move
I have the motors tuned to 2000mm Velocity and 200mm acceleration which gives a G amount of .02395 etc
Phil
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Only thing I am telling you is Mach does not do the homing on my lathe ;D
Reason is I can do index homing with my servo drives and that in itself is deadly accurate but I also have it set so it gates the Index to the A and B channels so its even more accurate :)
Hood
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I don't even have limit switches installed on the lathe yet, and, don't use homing without switches.
SO can't try or help on that matter.
I have run the lathe at many different velocities and the G0 moves all seemed apropriate after each thread cycle.
Haven't even tried ver 029.
RICH
BTW: I don't use the G76 as i like to know what pass screwed something up in the thread testing.
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Hood,
Do you use G32 or G76
I think i may need to work on my post processor as i get what i would call a cnc thread in that the last thread is swept out if i use G76.
But if i use use G32 the thread stops at the designated Z position and is then cleared to the clearance X position and appears to be done by manual means in that the tool cuts full circle at the end of the thread.
Hood or Rich could you post some sample code ? so i can see what ia am aiming for.
Phil
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Yes G76,
Heres the threading snippet from the thread I did yesterday.
M4S1200
T303
G0X20.835Z7.758
G76 X13.39 Z-18.006 Q1 P2.0 H0.136 I29.0 R15.822 K6.228
G0X31.08Z7.758
Hood
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Phil,
The Chamfer at the end of the thread in G76 is specified with the "L" parameter and it is optional. So "L0" would mean no pull out and in the code below l45 would be 45 degree chamfer. The chamfer is specified in the wizard inputing a value for the chamfer. Note the Z differences in the second G32 line of the code.
You can look at the script to see how that it is is done.
THIS IS G76 CODE WITH 45 DEGREE CHAMFER
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G0 G40 G18 G80 G50 G90
G00 G53 X0 Z0
T202M6
G00 X1.1
G00 Z0.1
G00 X1
M03 S402
M08
G76 X0.9999 Z-1 Q0 P0.05 J0.0002 L45 H0.0001 I30 C0.1 B0.0002 T0
M9
M5
M30
THIS IS G32 CODE - 45 DEGREE CHAMFER
----------------------------
(Taper = 0)
(Infeed Angle = 30)
(Total_Depth = 0.0001)
(StartZ = 0.1)
(EndZ = -1)
(Seq = 0 )
(Min_Decrement = 0.0002 )
(Dia Mode )
G0 X1.1 Z0.1
G0 X1
(Min decremant being used)
(Last Pass ID_OD = 1)
(Decrement = -0.0001 pass 1)
G01 Z0.1
G32 X1.0001 Z0.1 F0.05
G32 X1.0001 Z-0.9938 F0.05
G01 X1.1 Z-1 F0.05
G00 X1.1 Z0.1
G00 X1
( Last pass at depth of 0.0002)
G01 Z0.1
G32 X0.9999 Z0.1 F0.05
G32 X0.9999 Z-0.9938 F0.05
G01 X1.1 Z-1 F0.05
G00 X1.1 Z0.1
G00 X1
G00 X1.1 Z0.1
THIS IS G32 CODE WITH 0 DEGREE CHAMFER
--------------------------------------
(Taper = 0)
(Infeed Angle = 30)
(Total_Depth = 0.0001)
(StartZ = 0.1)
(EndZ = -1)
(Seq = 0 )
(Min_Decrement = 0.0002 )
(Dia Mode )
G0 X1.1 Z0.1
G0 X1
(Min decremant being used)
(Last Pass ID_OD = 1)
(Decrement = -0.0001 pass 1)
G01 Z0.1
G32 X1.0001 Z0.1 F0.05
G32 X1.0001 Z-1 F0.05
G01 X1.1 Z-1 F0.05
G00 X1.1 Z0.1
G00 X1
( Last pass at depth of 0.0002)
G01 Z0.1
G32 X0.9999 Z0.1 F0.05
G32 X0.9999 Z-1 F0.05
G01 X1.1 Z-1 F0.05
G00 X1.1 Z0.1
G00 X1
G00 X1.1 Z0.1
RICH
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Hood thanks
Here is my G76 code X9.853 Z-12. Q02 P1.75 H0.1 I29 L29 C.100 B0. T0. J0.05
Apart from optional differences nothing major seems to be wrong ?
Phil
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Looks fine, you have the chamfer at 29 degrees so it will start the retract 29 degrees before the thread is due to exit. Only other thing I see is your spring pass is defined as 02, doubt if that would cause any problems but I would just have 2.
Hood
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Hood thanks for your help
Maybe the Holy Grail of Rev4 wil cure it. ;D
Phil
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Keep in mind, the retract or chamfer angle is in"angle of revolution".....or a "rotational angle".
Not actually a chamfer like I thought.
L90 would retract over 1/4 of a revolution, L360 would be 1 rev., 720, two revs. and so on.
Graham mentioned earlier that the only way to get a nice gradual radial retraction without gutting the groove all the way around the part is to run it sloooowwwww as the acceleration of the X axis retracting will "lag" causing the ringing.
Others mention cutting the threads to a relief groove.
I'll try to find the post.
RC
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Here is the topic:
http://www.machsupport.com/forum/index.php/topic,5250.msg36097/topicseen.html#msg36097
RC
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Rich your reply no 10 sorry did not see that till after Hood's.
Thanks
Overloaded thanks to you for that reply 14/15 that was a good explanation.
One thing i have learned is that there is a lot to learn. ;D :P ;D
Phil
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Everyday is a learning day. It never stops and when it does, well, it's cold 6' down! :D
RICH