Rounding corners

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19 Jul 2017 12:56 #96060 by NikolayShopov
NikolayShopov created the topic: Rounding corners
Hello, i have problem with the new version of linuxCnc !!! I use the program for plasma cutter.At high speeds (4000mm / min) curvature is obtained at the edges of the details. I used G64P01 and еxecutes the curves as small segments and stops at each point. Please help !!!!
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19 Jul 2017 13:58 #96075 by PCW
PCW replied the topic: Rounding corners
What version of LinuxCNC? Versions > 2.6 Have a quite capable trajectory planner
that can follow paths and maintain speed at corners as well as your machine acceleration limits allow

G64P01 sets the path following limit to 1 mm which is quite large
so this would definitely result in unwanted path deviation at sharp curves

I dont see how you would stop at ends of segments unless you have a G61 in your file
The following user(s) said Thank You: NikolayShopov
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19 Jul 2017 21:14 #96101 by rodw
rodw replied the topic: Rounding corners
This may not be relevant but it is possible this is a bug.

I am using Master V 2.8. When testing my plasma machine without cutting at a G0 speed of 18000 mm per minute with some gcode that basically traced rectangles and diagonals around 1200mm long (eg to the corners of the machine), I observed significant rounding of travel with a radius of maybe 200mm or more and the programmed point was missed by a long way. The machine appeared to speed up during travel around the arc.

Not knowing anything about gcode, I put this down to expected behaviour but thought it was strange. I programmed a Z axis movement at each point and the machine visited each point.

Anyway, it sounds like an amplified version of your problem (maybe becasue I was travelling 4.5 times faster) so it is worth mentioning.
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19 Jul 2017 22:11 #96108 by PCW
PCW replied the topic: Rounding corners
A bug is possible but If you have rounded corners its much more likely that you don't have G64 P Q set properly in your GCode
The following user(s) said Thank You: NikolayShopov
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20 Jul 2017 02:42 #96118 by Todd Zuercher
Todd Zuercher replied the topic: Rounding corners
Could you post a copy of the offending g-code program?
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20 Jul 2017 09:55 #96131 by NikolayShopov
NikolayShopov replied the topic: Rounding corners
Thanks for the fast reverse !!!! On the first picture I have not used G64, and you see the program round the corners. But it does well with the arc. On the second picture i use G64 аnd does not round the edges, but when it reaches the arc the machine starts and stops for a few seconds and so to the end of the arc. I apply the G-code.
Attachments:
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20 Jul 2017 09:55 #96133 by NikolayShopov
NikolayShopov replied the topic: Rounding corners
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20 Jul 2017 14:02 #96148 by PCW
PCW replied the topic: Rounding corners
You are using a quite ancient version of linuxCNC (2.4.3), I would update to the current = 2.7.10
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20 Jul 2017 14:07 - 20 Jul 2017 14:12 #96149 by Todd Zuercher
Todd Zuercher replied the topic: Rounding corners
That isn't completely unexpected, especially on a machine with lower acceleration settings, because your curves are actually a series of line segments (lots of little corners). You may have experiment some to fine tune your G64 P setting to find the most optimal compromise between rounding the corners you want to keep and smoothing the corners of the line segments in your curve.
Try setting it to G64P0.05 and G64P0.1 to see if the corners are square enough for your taist and if the curve movement is smooth enough. Or you could change the G64P setting in the file. There is no rule that says you can't change it while the file is running, setting a large P for areas where you need smoothing and a small P where you need the path followed precisely.

Edit:
I didn't see the Linuxcnc version you were running. Good catch Peter Changing to 2.7 with the new trajectory planner should greatly reduce the slowdowns while running your curve, even with a smaller G64P setting.
Last Edit: 20 Jul 2017 14:12 by Todd Zuercher.
The following user(s) said Thank You: NikolayShopov
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21 Jul 2017 07:05 #96209 by NikolayShopov
NikolayShopov replied the topic: Rounding corners
On 2.7.10 we met the same problem ;/
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