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Author Topic: Turn X axis swapping from + to - during cycle  (Read 3316 times)

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Turn X axis swapping from + to - during cycle
« on: July 23, 2011, 09:53:06 PM »
I have a random and reoccurring problem with Mach3Turn where the X axis DRO values swap from + to - during a cycle, causing the tool to crash into the stock.

Yesterday, I started Mach3, homed my Z and X axis to the back right of the lathe, turned down the X axis, measured and entered the value into the DRO and faced the Z axis and zeroed it. I'm just using a basic RH turning tool. Everything seems fine - I can jog and enter G00 commands into the MDI and it goes to the right place.

So I ran a turn wizard to turn the OD down. The first cycle goes smoothly. Then I ran a second wizard to turn the OD down some more (same settings, I just changed the X and Z start and finish values). I ran the cycle and the first few cuts went well and then all of a sudden, BANG, the stock flies out of the chuck (luckily I was using delrin, aluminium is more heart wrenching) and the tool moves through where the stock was, to the other side and keeps on going there (now - X values in the DRO). I restarted everything and ran the code three times cutting air and nothing happened.

Then I came to it today and did the same thing - trying to make the part I couldn't yesterday. A bit skeptical (after about a month of problems and trying to get things working smoothly, my trust in CNC is very low), I set the job up as before, but backed off 50mm on the Z axis to test the cycle in air. Same thing. At my wits end, I took screen shots of all my settings and compared them to my version on my laptop (never changed, just used for learning the screens). They are the same except that "Remove Tool Offset" under Pgm End in General Logic Configuration is unchecked, as I found that this caused a similar problem, where after running a cycle successfully, and starting another wizard, the DRO values were messed up (similar to the last screen shot).

This is not the first time this has happened and it happens randomly.

This is the crash. All the cuts are fine and then it moved to the other side and does the finishing cut.



Cutting on the wrong side...



Trying to make new GCode in the wizard afterwards:



This is the GCode generated from the wizard:

Code: [Select]
G18 G40 G49 G90 G94 G80
M3
G0 X26 Z2.5
F500
G0 X24.4
G1 Z-17.9
G0 X25.4 Z-17.5
G0 Z2.5
G0 X23.8
G1 Z-17.9
G0 X24.8 Z-17.5
G0 Z2.5
G0 X23.2
G1 Z-17.9
G0 X24.2 Z-17.5
G0 Z2.5
G0 X22.6
G1 Z-17.9
G0 X23.6 Z-17.5
G0 Z2.5
G0 X22
G1 Z-17.9
G0 X23 Z-17.5
G0 Z2.5
G0 X21.7
G0 Z2.5
G1 Z-17.9
G1 X26
G0 Z2.5
F100
G0 X21.5
G1 Z-18
G1 X26
G0 Z2.5
M5
M30

Thanks in advance for any help (please help!)

Offline DAlgie

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Re: Turn X axis swapping from + to - during cycle
« Reply #1 on: July 24, 2011, 02:27:53 AM »
I see no problems with the G code or the setup in the wizard page. And, the wizard is doing what it is supposed to do. I have to believe that your tools are not set right. If you jog to roughly X0.0, is the tip of the tool right at the center of the stock? Not missing steps, after the part run is the tool offset still where it was before you ran the G code? You have the steps per unit set correctly, a 10mm move in the X axis actually moves the tool 5mm, you are in diameter mode.
DaveA.

Offline Hood

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Re: Turn X axis swapping from + to - during cycle
« Reply #2 on: July 24, 2011, 03:17:35 AM »
Can you attach your xml and also tools3.dat file, the xml you will find in the main Mach3 folder and the tools.dat will be in the macro folder then in the folder of the profile you are using.
Hood
Re: Turn X axis swapping from + to - during cycle
« Reply #3 on: July 24, 2011, 06:50:08 AM »
Thanks for the replies. I thought it may be something to do with the tools - I bought a QCTP a few weeks ago and was trying to set up multiple tools, so there were tools entered in the table, but I was using the master tool with no offsets.

Missing steps were a problem recently where it was accelerating too fast when pulling the tool out so the part ended up 0.1mm undersize. I turned down the speed and acceleration and checked the gibs of the X axis and I can turn diameters to +-0.03mm comfortably. The Z axis is even better and I have never had problems with it - these issues have only been with the X axis. X and Z both move the correct distance.

I reinstalled Mach3 and entered in the same settings for the ports and motors, leaving everything else. After about 20 runs, it screwed up twice (+ x turning into - x) - I tried various GCodes, restarting Mach3, running wizards, everything to try reproduce the problem. I thought maybe I was pressing something like stop cycle, feed hold, rewind, reset etc. that required me to reset the co-ordinates - I tried to screw it up but nothing happened. The only pattern I can vaguely make out is that the problem tends to happen when the feed rate changes. I'm also not sure if being in radius mode is more reliable than diameter mode.

The Program co-ordinates and Part co-ordinates are equal before and after the crash, and the Machine co-ordinates are still correct. It still goes to the correct X value, just it turns -.

The two files are attached, Hood.

Thanks.

Offline Tweakie.CNC

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Re: Turn X axis swapping from + to - during cycle
« Reply #4 on: July 24, 2011, 07:02:57 AM »
Could this be related to the same problem we have just started to see occurring with Mach3 Mill ?    http://www.machsupport.com/forum/index.php/topic,18990.0.html

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline Hood

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Re: Turn X axis swapping from + to - during cycle
« Reply #5 on: July 24, 2011, 07:05:13 AM »
Very possible Tweakie ;)
Hood
Re: Turn X axis swapping from + to - during cycle
« Reply #6 on: July 24, 2011, 07:20:35 AM »
I'm also running the same version as miket161 in the other topic - R3.043.022

Offline Hood

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Re: Turn X axis swapping from + to - during cycle
« Reply #7 on: July 24, 2011, 09:50:22 AM »
Have sent you a PM.
Hood