Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Sly Cobra on January 08, 2016, 12:00:50 PM
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I have a problem with my y axis. If I drill a series of holes on 2" centers the first hole always starts at 1.75". Then the 2nd is 1.875. All others after are spot on. The X axis works fine. Both axis are setup identical as far as motor, and pulses.
I ran the same program with 2 different post processors with the same result
Can anyone help?
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I would first check your Gcode file to make sure IT is correctly coded.
Then work out from there.
Yo may want to post the Gcode you tried so others can test it.
(;-) TP
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this is from the Mach3 postprocessor in mastercam
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O0000 (TEST3)
(MASTERCAM - V13.)
(MC9 FILE - C:\DOCUMENTS AND SETTINGS\ALL USERS\DOCUMENTOS\TEST3.MCX)
(POST - )
(MATERIAL - WOOD INCH)
(PROGRAM - TEST3.NC)
(DATE - JAN-07-16)
(TIME - 17:34)
(POST DEV - NovaLab)
(NWDTOOL N" 1/4 STRAIGHT BIT" T1 D0. F2. L3. CD2. CL1. SD2. C0)
(NWDSTOCK X0. Y0. Z0. OTC OX0. OY0. OZ0.)
N100 G00 G17 G20 G40 G49 G80 G90
N110 T1 M06 ( 1/4 STRAIGHT BIT)
N120 (MAX - Z.75)
N130 (MIN - Z-.3)
N140 G00 Z.75
N150 G00 X.97 Y0. S18000 M03
N160 G99 G83 Z-.3 R.75 Q.05 F200.
N170 Y2.
N170 Y4.
N180 Y6.
N190 Y8.
N200 Y10.
N210 Y12.
N220 Y14.
N230 Y16.
N240 Y18.
N250 G80
N260 M05
N270 G90
N280 M30
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this is the default postprocessor
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O0000(TEST4)
(DATE=DD-MM-YY - 08-01-16 TIME=HH:MM - 08:24)
(MCX FILE - C:\DOCUMENTS AND SETTINGS\ALL USERS\DOCUMENTOS\TEST4.MCX)
(NC FILE - \\CNC-MINI\GCODE\TEST4.NC)
(MATERIAL - WOOD INCH)
( T1 | 1/4 STRAIGHT BIT | H0 )
N100 G17 G20 G90 G40 G80 G64 G49 G0 M05
N102 G8 P1
N104 G90 M05 Z0
N108 T1 M6
N110 G0 G90 G54 X.97 Y2. C0.
N112 S18000 M3
N114 G43 H0 Z.75
N116 G17 G99 G83 Z-.3 R.75 Q.05 F180.
N118 Y4. Z-.3
N120 Y6. Z-.3
N122 Y8. Z-.3
N124 Y10. Z-.3
N126 Y12. Z-.3
N128 Y14. Z-.3
N130 Y16. Z-.3
N132 Y18. Z-.3
N134 G80
N136 G90 G49 Z0. M05
N140 G8 P0
N142 G17
N144 M30
%
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Both run fine here.
Are you watching the Y DRO to see that it is indicating the proper position ?
If it is, and your part is measuring differently, you might be missing steps at the beginning.
Does it return to the exact same physical 0 Y position after the file is done ?
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i will add a g00 x0 y0 z0 to the code see if it does
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it does go back to zero
the 1st the x0y0 fine the next hole 2" drills at 1.702. the following holes are on 2in centers.
the DRo show as follows
0
1.9997
4
5.9997
8
9.9997
etc
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here is the modified code
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O0000 (TEST3A)
(MASTERCAM - V13.)
(MC9 FILE - C:\DOCUMENTS AND SETTINGS\ALL USERS\DOCUMENTOS\TEST3.MCX)
(POST - )
(MATERIAL - WOOD INCH)
(PROGRAM - TEST3A.NC)
(DATE - JAN-08-16)
(TIME - 12:56)
(POST DEV - NovaLab)
(NWDTOOL N" 1/4 STRAIGHT BIT" T1 D0. F2. L3. CD2. CL1. SD2. C0)
(NWDSTOCK X0. Y0. Z0. OTC OX0. OY0. OZ0.)
N100 G00 G17 G20 G40 G49 G80 G90
N110 T1 M06 ( 1/4 STRAIGHT BIT)
N120 (MAX - Z.75)
N130 (MIN - Z-.3)
N140 G00 Z.75
N150 G00 X0. Y0. S18000 M03
N160 G99 G81 Z-.3 R.75 F200.
N170 X.97 Y2.
N180 Y4.
N190 Y6.
N200 Y8.
N210 Y10.
N220 Y12.
N150 G00 X0. Y0.Z0 S18000 M03
N160 G99 G81 Z-.3 R.75 F200
N230 G80
N240 M05
N250 G90
N260 M30
%
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That last file is a bit different.
The first hole is at 0,0 then the rest are at .97, 2-4-6-8-10-12 making the first two 2.223 apart and the resr 2" apart. And you're drilling the first hole twice.
I don't understand what is happening with yours. It runs as programmed here.
Maybe someone else can see a problem.
Russ
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What controller are you using ? LPT or other ?
(;-) TP
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Actually in the last example the hole spacing is in Y and it starts at Y0 then spaces 2 " each step from there.
Are you saying that teh spacing is wrong and it is not following the Gcode or is ONLY the first two positions wrong and the rest are exacly where they should be based on 0,0 because that does not make sense . Look at teh exact location points not just the spacing. This code is abs code not incremental. So all positions should be an abs value.
(;-) TP
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my breakout board is cnc4PC C1G and using smooth steep uc3000
forgive me, for not clarifying myself the moving to the first position it drills at 1.7" but thereafter it drills at 2" center. However all holes are off by .281" from the 0,0
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Actually in the last example the hole spacing is in Y and it starts at Y0 then spaces 2 " each step from there.
(;-) TP
starts at x0,y0 then goes to x.97,y2 and so on by 2
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That would indicate that you are loosing steps on the first move from 0,0 and coming up short. It stops at 1.7" instead of 2". Now the important Question does teh DRO should the correct values of teh first move from Y0 to Y2 ?
(;-) TP
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You are correct I was concentrating on the Y and ignored the X (;-)
(;-) TP
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That would indicate that you are loosing steps on the first move from 0,0 and coming up short. It stops at 1.7" instead of 2". Now the important Question does teh DRO should the correct values of teh first move from Y0 to Y2 ?
(;-) TP
Page 1
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it shows as follows
1.9997
4
5.9997
8
9.9997
12
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why would i lose step on the first move and not on the rest?
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Try it by moving up on teh table in Y about about 2-3" from where you started originally. It could be a stiction problem on tha table at that point OR it could be a controller problem OR you are right on the verge of loosing steps on teh Y axis config setup (Vel,acel) Try reducing teh Vel and Accel settings by 50% and rerun the Gcode.
Have you tried it with different Drill cycles ? G81 , G83, G73 ? I would all 3 to see IF it made a difference. Also I would try a manually programed cycle to help rule out some things.
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i think i have may have found the problem, by reducing the velocity i noticed that tere is some play in the rack and pinion gear. i will review and get give you an update.
thanks for all the help
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yup that was it. the lock nuts were loose on the pinion gear which caused backlash whenever the axis change direction. that is why it was losing step only on the first position
thanks for all your help you guys are GR8T
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Glad you got it sorted out.
(;-) TP
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Me too.
I don't see how it could have returned to 0,0 ..... but anyway, hope you are good to go now.
Cheers,
Russ
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It returned to zero because it had the same backlash offset in the negative movement