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Author Topic: Problem just appeared with G91/G41 combination  (Read 4101 times)

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Problem just appeared with G91/G41 combination
« on: May 12, 2009, 06:55:06 PM »
A strange problem just appeared today.

To circular interpolate a series of C-Bores, I program a G41D7 (D7 = 0.5) then G1 and G3 moves in G91 then cancel G91 to move to the next location.

Example:

------cut from program-----
M6T7
G0G90X-1.Y-1.M3
G43H7Z.1
G1Z-.9F20
G41D7
G1X-.616F3
Y2.714
G2X-.616Y4.472R1.09
G1Y5.
G0G40X-1.
Z1.

X0Y3.594
G1Z-.9F20
G41D7
G91
G1X.872F3
G3X-1.744Y0R.872
G3X1.744Y0R.872
G0G40X-.1
G90
Z.1
-------------------------


I have used this with success on many occasions however today, Mach won’t read the D offset. I can get it to read the offset in G90 but not in G91!

I have many programs that use this method just fine but all of a sudden I can’t get any of them to work today!.

If there a setting in Mach(R3.042.021) that might have got messed up?

Thanks!.

Offline jimpinder

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Re: Problem just appeared with G91/G41 combination
« Reply #1 on: May 14, 2009, 12:54:40 PM »
Have you got the XY plane active - if you read the notes attached to the GCode explanation on Mach 3, it says the D command will not work unless the XY plane is active (G17).

G17 should be included in the prelim of your program
Not me driving the engine - I'm better looking.
Re: Problem just appeared with G91/G41 combination
« Reply #2 on: May 15, 2009, 11:24:08 AM »
G17 made no difference.

Something I should have mentioned before but I didn't think was relevant, This computer was recently used to test another mill. I backed up the .xml file, modified the configuration to run the second mill (testing to make sure the retrofit on it was correct) then I copied the backup .xml file back to the mach directory.

I had assumed this file stored all the configuration values but I read in another post that isn't always true.

Is it possible that this messed it up? If not, any other places to look?

Offline jimpinder

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Re: Problem just appeared with G91/G41 combination
« Reply #3 on: May 16, 2009, 03:44:44 AM »
Second try -

When applying tool offsets, there must be some lead in from the line applying the offset, to the next cutting line, so the tool can move to the correct position (left or ringt of the design line)

On your G90 code, this will be allowed (although I don't think it would be fully applied on the first G1 after the G41.

On the G91 code, G91 moves in increments fronm a previous position, and therefore Mach would take the last known position from the DRO's and apply the increments to them. You have no tool movement between applying G41 and G91 therefore the G91 will take its start position from the DRO's as they were after the X0Y3.594.  
Not me driving the engine - I'm better looking.

Offline Chip

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Re: Problem just appeared with G91/G41 combination
« Reply #4 on: May 16, 2009, 02:11:00 PM »
Hi, Timmy

Hears a G Code file I use to set Mach back to a standard configuration, I usually use it as an m1s file.

; Start UP Re-Set Mach3 G Code

;' ( M1111.M1S Macro )
;' ( Needs to be installed in C:\Mach3\Macros\"Profile" You Are Using Folder)
;' ( Basic Default Location would be "Mach3Mill")
;' ( Change it as you need to )
;' ( For MM Units Replace G20 with G21 )
;' ( For CV Mode Replace G61 with G64 )

G15 ;Code "G15" '            Cancle X,Y Polar Mode
G17 ;Code "G17" '            Set X,Y Plane
G20 ;Code "G20" '            Set INCH Units Mode, G21 for MM
G40 ;Code "G40" '            Cancle Cutter Radius Comp. 
G49 ;Code "G49" '            Cancle Tool Length Offset
G50 ;Code "G50" '            Re-Set All Scale Factors To 1.0
G61 ;Code "G61" '            Set Exact Stop Mode
G69 ;Code "G69" '            Cancel G68 Rotate Coordinate System
G80 ;Code "G80" '            Cancle Canned Cycle Mode
G90 ;Code "G90" '            Set ABS Mode
G91.1 ;Code "G91.1" '          Set IJ's INC Mode
G94 ;Code "G94" '            Set Feed Per Minute Mode

G92.1 ;Code "G92.1" '          Set G92 5211-5216 to Zero

G52 x0 y0 z0 ;Code "G52 x0 y0 z0" '   Re-Set Temp Offset Mode

F100 ;Code "F100" '           Set Default F Speed To 10

M30 ;Code "M30" '            Program End and Rewind G-Code
%

Load it and run it, Then load your problem code and see if it run's.

Hope this Helps, Chip