Problem with circles

Discussion about the arduino based g-code interpreter, grbl
pacaj2am
Posts: 9
Joined: Mon Mar 10, 2014 8:46 pm

Problem with circles

Post by pacaj2am » Wed Apr 16, 2014 8:14 am

Hello,

I have problem with GRBL - it doesn't matter, how big the circle is, but it makes allways two tooths on a circle. You can see it on image below
CIRCLES.jpg
CIRCLES.jpg (188.69 KiB) Viewed 11544 times
.

The .nc file is also attached
mlynky.nc
(107.62 KiB) Downloaded 218 times
.I tested it on simulators, but there is nothing like this in NC file.

Where could be problem? If i do straight lines, i have no issue with GRBL.

Thank you.
Last edited by WillAdams on Wed Apr 16, 2014 10:31 am, edited 1 time in total.
Reason: stickied

lordmundi
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Location: Friendswood, TX
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Re: Problem with circles

Post by lordmundi » Wed Apr 16, 2014 9:47 am

Well, you're right... i ran it through a simulator also and it looks fine. Posting the picture for others to see. Could it be a belt slipping somewhere?

Image

pacaj2am
Posts: 9
Joined: Mon Mar 10, 2014 8:46 pm

Re: Problem with circles

Post by pacaj2am » Wed Apr 16, 2014 9:59 am

Belt is nost slipping.

The outer route went two times in exactly same manner.

If i look closly on circles while doing pocket, i see tooths in every small circle. In both pockets.

It is really strange... :-(

WillAdams
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Re: Problem with circles

Post by WillAdams » Wed Apr 16, 2014 10:30 am

Too long lines.

Part/MakerCAM exports extremely high precision, while Grbl will only accept 50 (or 70 for newer versions) characters per line:

http://www.shapeoko.com/wiki/index.php/ ... leshooting
Symptoms: Stairstepped diagonals, jagged circles/curves, loud squealing or 'ker-chunka' thuds, gantry chattering, mis-aligned edges
Possible software cause: Lines in G-code file are too long.
Co-ordinates have too many decimals
GRBL is limited in the number of characters per line it can handle, which causes it to ignore the end portions of too-long lines. If your job is previewing correctly, but not running properly, check to see that line lengths are w/in its limits (50 for older versions, 70 for 0.8c dev or later) as discussed in the forums[2] [3].
See:

http://www.shapeoko.com/forum/viewtopic.php?f=3&t=1161
http://www.shapeoko.com/forum/viewtopic.php?f=33&t=1536

http://www.shapeoko.com/wiki/index.php/ ... y_decimals

http://www.shapeoko.com/forum/viewtopic ... 72&p=23069
https://github.com/jhessig/metric-gcode-truncator
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets
Nomad 883 Pro #596 (bamboo)

pacaj2am
Posts: 9
Joined: Mon Mar 10, 2014 8:46 pm

Re: Problem with circles

Post by pacaj2am » Wed Apr 16, 2014 10:37 am

Hello,

i know about the problem (I am using makercam in mm). This generates long lines.

I am using GRBL Controller v 3.5.1 which can truncate nc file on the fly. This should not be the issue. But will try to get the code actually sent to grbl and check.

Thank you

Jan

WillAdams
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Location: Pennsylvania --- south of the Turnpike, East of US-15
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Re: Problem with circles

Post by WillAdams » Wed Apr 16, 2014 10:51 am

In that case, the problem is some difficulty of feeds, speeds, machine rigidity (or lack thereof), deflection and cutting orientation.

What are your settings for:

- feed rate (in Grbl)
- cutting speed (how fast are you running your tool)
- plunge rate
- plunge depth
- are you cutting clockwise or counter-clockwise? Have you tried the other direction?

How tightly do you have your Z-axis adjusted? The Delrin V-wheels should not easily rotate when one tries to turn them, and they should all move when one turns the coupler or jogs the machine up and down.
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets
Nomad 883 Pro #596 (bamboo)

pacaj2am
Posts: 9
Joined: Mon Mar 10, 2014 8:46 pm

Re: Problem with circles

Post by pacaj2am » Wed Apr 16, 2014 10:58 am

Hello,

feedrate (grbl): 250 mm/min
cutting speed: 500 mm/min
plunge rate: 500 mm/min
plunge depth: 500 mm/min

direction doesn't matter.

But when i looked more closly to log i see a prbolem:
GRBL Controller.jpg
GRBL Controller.jpg (196.67 KiB) Viewed 11538 times
Seems the truncation of number is wrong in Grbl Controller. Could this ocuse the error?

Thank oyu

Jan

pacaj2am
Posts: 9
Joined: Mon Mar 10, 2014 8:46 pm

Re: Problem with circles

Post by pacaj2am » Wed Apr 16, 2014 11:05 am

Now i see in log of the application, that it is not runcating correctly>

Code: Select all

2014-04-16 12:45:46.473 ERROR (DIAG) - Unable to remove enough decimal places for command (will be truncated): G3 X41.19035532994924 Y106.4746192893401 I-5.2030456852791875 J0
2014-04-16 12:45:46.473 INFO (STATUS) - Precision reduced 'G3X41.19035532994Y106.47461928934I-5.20304568527J0' 
And it sends J to 0.

I will report to GRBL Controller.

Thank you

lordmundi
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Location: Friendswood, TX
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Re: Problem with circles

Post by lordmundi » Wed Apr 16, 2014 11:07 am

interesting. FWIW, if you truncate the file yourself, you can probably send it with no issues using the stream python script that comes with grbl. It works great on the command line for me.

pacaj2am
Posts: 9
Joined: Mon Mar 10, 2014 8:46 pm

Re: Problem with circles

Post by pacaj2am » Wed Apr 16, 2014 11:44 am

I truncated in python script and really found no issues :-) The implementation in GRBL Controller is not working.

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