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Author Topic: Cutting Circles  (Read 11760 times)

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Offline docltf

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Re: Cutting Circles
« Reply #20 on: November 15, 2007, 04:36:40 PM »
rkjohn
lcam is having some problem with arcs,they are working on that.
you say your backlash will measure pretty good with a dial indicator,so you might have to consider this.
my machine fliped out 6 weeks ago,and was cutting a circle that looked like yours,but not as bad.
the problem was in my device drivers.when i upgraded mach some how it messed up some drivers and the machine started cutting weird.
the worst one was the video driver.then the printer port.try uninstalling and reinstalling drivers.

Offline docltf

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Re: Cutting Circles
« Reply #21 on: November 15, 2007, 05:23:47 PM »
rkjohn

loaded that circle program in two differant lcam programs here ,they loaded well.that makes it a stronger case to look at the video card and drivers.

vmax549

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Re: Cutting Circles
« Reply #22 on: November 15, 2007, 07:43:21 PM »
RKjohn, as a reference how did you measure the backlash?? Is backlash turned OFF in mach?  Is the CV setting as it was when installed?

(;-) TP
Re: Cutting Circles
« Reply #23 on: November 15, 2007, 07:53:56 PM »
Backlash is not enabled. I tested backlash like the photo on page 1 of this post.

Offline Graham Waterworth

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Re: Cutting Circles
« Reply #24 on: November 16, 2007, 06:15:43 AM »
Turn off backlash comp on Mach and restart Mach.

Now if you put a pen/pencil (not a felt marker type) in the spindle and draw a circle with it (code below). Do you still get an error in the circle?

G20 G40
G00 G90 X1. Y0 Z1.
Z.05
G01 Z0 F1.
G03 I-2. F10.
G00 Z1.
M30

If you say you have no backlash then it must be movement under load, the pen will have no load so should draw a perfect circle.

If the circle is still wrong, then you have got backlash.

Graham.
« Last Edit: November 16, 2007, 06:19:25 AM by Graham Waterworth »
Never give up, time will pass, the cloud will clear, the sun will shine once more.

Offline pumpa

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Re: Cutting Circles
« Reply #25 on: November 21, 2007, 08:36:07 AM »
Guys, just while we are on the subject regarding cutting a circle, when i load up gcode for cutting a circle from the wizards
the circle shows up way outside my table perimeters and i can not place it within the table perimeters for some reason, can anyone please tell me how this is done?  :-[

Cheers.

Offline Graham Waterworth

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Re: Cutting Circles
« Reply #26 on: November 22, 2007, 01:48:29 AM »
Try putting a G20 (Inch) or a G21 (Metric) at the start of your NC program.

Graham.
Never give up, time will pass, the cloud will clear, the sun will shine once more.

Offline lemo

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Re: Cutting Circles
« Reply #27 on: January 31, 2009, 02:17:46 PM »
Same problem here. One side of the circle ends with a flat. If the circle is about 8 inches, the flat is about 1 inch long. We generated code with lcam, cut2d from vectric and with Rhinocam. We used lines segments to create the circles, and we used arcs to create the circles. We used a stepper based machine and a servo based machine. Within small differences, the problem staid the same. We continue to look into paramaters here and willa lso try and run EMC on a PC to see if there is a mach problem. It seems that this issue is a tricky one...
Cheers
Rainer

PS:Nice meeting you in York Graham, Brian, and the rest of the gang!
Cut five times and still to short...

Offline Graham Waterworth

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Re: Cutting Circles
« Reply #28 on: February 01, 2009, 06:20:58 AM »
Hi Rainer,

when you used small line segments how long was a line segment move in X & Y ?

What is the resolution of your machine axis ?

If you put a long travel clock on the bed so it will show the last 1/4" of movement of the axis, watch to see if Mach is counting and the table stops in the area of the flat.

Are you getting a 1" flat in one place or 2 opposite each other.

It could be you are running out of resolution ?  :(

Graham

PS: I had a great time in York, it was nice to put faces to names. Funny I set off 20 miles outside York UK and 3500 miles later ended up in York PA
Never give up, time will pass, the cloud will clear, the sun will shine once more.

Offline lemo

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Re: Cutting Circles
« Reply #29 on: February 01, 2009, 08:33:27 AM »
I have a servo driven machine using 1000 line encoders and the axis is geared down 1:5. I use steel loaded timing belts which have no backlash. They are pre tensioned with 160lbs and sound like a guitar string. No movement there... per revolution of the drive shaft I get about 5 inches of travel. So I need 5000 ticks per revolution and that yields roughly 5 inches travel. And that's a theoretical 1/1000 of an inch resolution. Is there another resolution I have to be concerned about? The smooth stepper has a few settings regarding resolution and precision but due to a lack of documentation I have not bothered to dive to deep into it's settings. I run the default settings. However, the problem also shows up using Mach3. I'm in the shop today and will collect sample g-code and such. It's impossible to get closer to this without hard facts.  Ha, York, UK to New York, NY to York PA. That's a lot of York for one trip 8).
R
Cut five times and still to short...