Circle problems

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Leeroy6392
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Circle problems

Post by Leeroy6392 » Wed Jul 10, 2019 1:14 am

I am having issues with flanges I am cutting out. The first 60 or so did not have any issues other than my programming on the first couple now after 50+ it has started making a egg shaped flange and bolt pattern follows the same egg. I have checked the steps/ calibrated the axis. I have ground rod attached to the table to limit interference, matched speeds on acceleration and travel speed between x and y. I’m just lost any help is appreciated.

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robertspark
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Re: Circle problems

Post by robertspark » Wed Jul 10, 2019 1:27 am

something mechanically worked loose (pinion) check your axis in the direction of the smaller (squashed ) circle.... gcode does not change.... the machine will still be "trying" to output the same steps to both axis
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Leeroy6392
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Re: Circle problems

Post by Leeroy6392 » Wed Jul 10, 2019 1:56 am

All three motors are tight, guides, y axis and torch mount. I thought it might have been torch lead pulling so tightened and still draws in and out on the 45 degrees but it does measure out to only be on one side.

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Re: Circle problems

Post by robertspark » Wed Jul 10, 2019 7:38 am

Picking at straws now..... what cnc software are you running? (Mach3, Linuxcnc???)

Have you shut down the PC, restarted and tried again to see if the issue is consistent?

It may be a memory thing not being flushed and something is wrong with the planner.... (like I said its just a guess.... but it can be only one of a few things..... mechanical, signal transmission (is what is being sent being recieved correctly), drives or motors (have you tried swapping axis / motors around if that is possible .... does the problem move (may be a motor thing / axis thing then), or its a planner thing (unlikley.... but who knows)

Try to break the problem in 1/2.... swap the motors around on the drives ./.... does the problem move? Swap the drives around..... does the problem move....?

Sorry out of ideas maybe someone else will have a brainwave...
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weldguy
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Re: Circle problems

Post by weldguy » Wed Jul 10, 2019 9:20 am

Have you done a dry run with the plasma off and the shop quiet to see if you notice a hiccup, strange noise, or jerky motion at some point in the design?

Leeroy6392
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Re: Circle problems

Post by Leeroy6392 » Wed Jul 10, 2019 10:15 am

I have ran with everything off in the shop including the plasma it still seemed to run fine never noticed any issues. The part are not jerky it’s still smooth all the way around (not like motor I popping out of the gear).
Yes I have turned it off since the issue occurred bad thing was cut 3- 6x12’ sheets over 2 days went to make the parts then realized they were misshaped. They are all consistent in location direction the south east side is long while the north east side is short. I will see what I can do on swapping motors.

Bucket8577
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Re: Circle problems

Post by Bucket8577 » Wed Jul 10, 2019 10:29 am

I would do some more testing before swapping motors.

The first thing I would do is do some test cuts in some of the scrap pieces. Simple squares. Measure them and see where the error is.

I would also re-check everything mechanical for the axis that has the error.

One more thing. Has anyone edited the g-code by hand? Maybe re-compile it and give a run.
Newbie to plasma cutting.

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acourtjester
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Re: Circle problems

Post by acourtjester » Wed Jul 10, 2019 11:58 am

You do have slippage in the mechanics, when cutting large circles the transition between the X and Y is very small and hard to see it happen.
this will not get better :Sad
slipping.JPG

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WyoGreen
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Re: Circle problems

Post by WyoGreen » Wed Jul 10, 2019 12:36 pm

You might try sending commands to move the torch in the 2 directions and measuring the distance moved versus what was commanded to move. Perhaps one of the axis is getting tight and can't accelerate as fast as it used to and is losing steps.

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Re: Circle problems

Post by robertspark » Wed Jul 10, 2019 1:19 pm

are you running servos or stepper motors?
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Leeroy6392
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Re: Circle problems

Post by Leeroy6392 » Wed Jul 10, 2019 2:40 pm

I’m running stepper motors. But the circle is half correct then I has one qtr pushed in 1/8”-3/8” and the other pushed out 1/8”-3/8” I did drop to the inside of the scrapped piecesand it was only out 1/8”

Leeroy6392
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Re: Circle problems

Post by Leeroy6392 » Wed Jul 10, 2019 8:17 pm

Ok now I just ran a program parts not horrible but has done a lot better. Traversing the table and brining it back to front of the table the y and a motor out of alignment 5/16” could one be getting weak? Thanks for all the help so far by the way.

Bucket8577
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Re: Circle problems

Post by Bucket8577 » Wed Jul 10, 2019 8:28 pm

Leeroy6392 wrote:
Wed Jul 10, 2019 8:17 pm
Ok now I just ran a program parts not horrible but has done a lot better. Traversing the table and brining it back to front of the table the y and a motor out of alignment 5/16” could one be getting weak? Thanks for all the help so far by the way.
Sounds like you have a gear or pulley spinning slightly on a shaft.
Newbie to plasma cutting.

Leeroy6392
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Re: Circle problems

Post by Leeroy6392 » Wed Jul 10, 2019 8:44 pm

Just slid the motors back gears are tight could something not be communicating to both motors throwing off the steps? Or do I have a weak motor that needs changed.

weldguy
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Re: Circle problems

Post by weldguy » Thu Jul 11, 2019 10:07 am

Try cutting a giant L in the lower left corner of a sheet and using a large square be sure the L you just cut is square. If the left and right side of the gantry are not even you cannot cut square and can cause all kinds of problems like this. May need to re-align the left and right sides.

If your losing steps then you will not return back to the exact same position you started at. Mark your starting position on the rails with tape or sharpie and do a dry runt to see if your returning to where your starting.

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acourtjester
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Re: Circle problems

Post by acourtjester » Thu Jul 11, 2019 10:12 am

I have found the motors having a hardened shafts can be a problem I file or machine 2 flats that match the set screw location on the pulley/gear used in the drive assemble.
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