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Author Topic: Very slow feeds when cutting arcs  (Read 2512 times)

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Very slow feeds when cutting arcs
« on: February 04, 2015, 03:33:31 PM »
Hi All


 I have just set up a machine and I have done some test cuts, if I do a test with a square pocket the machines cuts fine but anything at all with any kind of radius or circle in it the feeds just drop down to an absolute crawl and I can work out why.

the maximum velocity in my machine is set to 750 and if specify a square pocket with a feed rate of 750 the machine will cut it fine and mach3 behaves as it should, if do say a circle and specify any feed rate at all it disregards it and cuts at a feed rate of about 5% so a 6mm hole in a piece of mdf takes about 10 minutes to cut

Originally I thought it was an issue with the code being output by bobcad but I have since run the circle cut wizard in mach and still have the same problem

 I really hope someone can point me in the right direction as I am pulling my hair out here

 Cheers
« Last Edit: February 04, 2015, 03:36:12 PM by plnewton »
Re: Very slow feeds when cutting arcs
« Reply #1 on: February 04, 2015, 03:52:14 PM »
Post your XML file.
Copy it to your desktop and rename it so it will attach.
Might see something there.
Russ
Re: Very slow feeds when cutting arcs
« Reply #2 on: February 04, 2015, 04:42:06 PM »
Hi Russ

Thanks for your input mate...

xml attached

Cheers
Re: Very slow feeds when cutting arcs
« Reply #3 on: February 04, 2015, 08:05:54 PM »
That file seems incomplete.
You sure it is the right one ?
Russ
Re: Very slow feeds when cutting arcs
« Reply #4 on: February 04, 2015, 08:45:40 PM »
Not sure what happened to that one but here it is again
Re: Very slow feeds when cutting arcs
« Reply #5 on: February 10, 2015, 01:53:04 PM »
This could be related to my problem:

http://www.machsupport.com/forum/index.php/topic,29052.0.html

The detail cuts I'm doing can't run quickly, which initially seemed like it's being naturally limited by the acceleration up and down the Z-height of the cut, but it's not- upping the acceleration to "impossibly fast" lowered the runtime by about 1/3rd but still 3x slower than the feedrate that specified in the file and the motors were told to do in Tuning.

If you set Exact Stop mode (G61) it'll definitely slow it down, but that's not likely you have it set.  Constant Velocity mode (G64) should be set instead, that's normal.
Re: Very slow feeds when cutting arcs
« Reply #6 on: February 10, 2015, 03:24:20 PM »
I actually have it tunning ok now but I am still unsure what was wrong to be honest, I basically configured a brand new profile from scratch and it is now running at normal speeds but for the life of me I can not see any difference between the two XML files