[dougie329]

Milling some pockets out of oak on a CNC router. Setup using mach3, it leaves one corner radius of the pocket exactly what it is supposed to be (12mm diameter cutter used). The other 3 corners are not correct.

I have tried multiple software and eliminated that, I have also tried 2 different machines and eliminated anything mechanical. tried foam thinking it may be the oak that is the issue, have also decreased the acceleration, slowed the speed, and tried larger size rectangles but it always leaves the corners incorrect. very strange!

A pic is attached to show what I mean. Code is also shown below, its very simple code.

Any help would be much appreciated. It hasnt been noticed up until now however inlays just wont fit correctly.

I must also say that the start and end points of the rectangular pocket are perfect and that it cuts perfect circles.

G90G17
T1 M06
S500
F3000
M03
G00 X18.686 Y14.462 Z20.000
G00 X18.686 Y14.462 Z0.000
F500
G01 X18.686 Y14.462 Z0.000
G01 X8.686 Y14.462 Z-3.000
F2000
G01 X76.686 Y14.462 Z-3.000
G01 X76.686 Y17.000 Z-3.000
G01 X76.685 Y17.061 Z-3.000
G01 X76.624 Y17.062 Z-3.000
G01 X8.748 Y17.062 Z-3.000
G01 X8.687 Y17.061 Z-3.000
G01 X8.686 Y17.000 Z-3.000
G01 X8.686 Y9.124 Z-3.000
G01 X8.687 Y9.063 Z-3.000
G01 X8.748 Y9.062 Z-3.000
G01 X76.624 Y9.062 Z-3.000
G01 X76.685 Y9.063 Z-3.000
G01 X76.686 Y9.124 Z-3.000
G01 X76.686 Y14.462 Z-3.000
F3000
G00 X76.686 Y14.462 Z20.000
G00 X18.686 Y14.462 Z20.000
G00 X18.686 Y14.462 Z0.000
F500
G01 X18.686 Y14.462 Z-3.000
G01 X8.686 Y14.462 Z-6.000
F2000
G01 X76.686 Y14.462 Z-6.000
G01 X76.686 Y17.000 Z-6.000
G01 X76.685 Y17.061 Z-6.000
G01 X76.624 Y17.062 Z-6.000
G01 X8.748 Y17.062 Z-6.000
G01 X8.687 Y17.061 Z-6.000
G01 X8.686 Y17.000 Z-6.000
G01 X8.686 Y9.124 Z-6.000
G01 X8.687 Y9.063 Z-6.000
G01 X8.748 Y9.062 Z-6.000
G01 X76.624 Y9.062 Z-6.000
G01 X76.685 Y9.063 Z-6.000
G01 X76.686 Y9.124 Z-6.000
G01 X76.686 Y14.462 Z-6.000
F3000
G00 X76.686 Y14.462 Z20.000
M05
M02

[ger21]

Increase your acceleration or lower your feedrate.
Or, try running in Exact Stop mode, instead of CV mode. (least desirable option)

[samco]

what are your acceleration and velocity set to in the config?

sam

[dougie329]

Velocity was 2000 and acceleration was 400. I changed the acceleration to 600 on all axis and it pretty much sorted the issue. I am not sure why this would work but it seems to be a fix

[ger21]

When you're running Mach3 in CV mode, you're telling Mach3 to try and maintain a constant velocity.
To make a 90° corner, you need to come to a complete stop (due to physics). But your telling mach3 not to slow down, so it has to start turning before it gets to the corner. The faster the acceleration, the longer it can wait before it needs to start turning. WHich gives you a sharper corner.

[dougie329]

I had to set the acceleration to 800 to get the best resolution to the corner problem however this has created other issues. When it is cutting text now (v carve especially) doing lots of small movements it really shakes and judders because of the high acceleration. Is there a way of balancing things out or any other settings I can change? . I have another machine with a handheld DSP controller and no such issues. That has the option of linear and curve acceleration settings, they are set to 500 each and it doesn't cause any of the problems experienced with mach3

[victorofga]

that called jerking..

go to general config
on the right side of panel you see a ""paragraph""" CV settings
enable exact stop on corners, and theres an input field, set value 90

another settings, cvmode on corners.. it is use to be 180 unit, you can set it lower but there the risk for jerk motion..


jerk motion occur when you try to get too fast the corner..

so simplest is, using mach built in function, and stop on sharp corners..

the handheld dsp a very advanced stuff.. there might youre not permitted to set everything..

while mach 3 lets you set even bad settings..

[dougie329]

I don't seem to have the option to choose enable exact stop on corners? All I have in the cv control box is cv distance tolerance which is currently 180, stop cv on angles which is set to 0, g100 adaptive nurbs and plasma mode. On motion mode in general config I can choose either constant velocity or exact stop. If I go on exact stop things like circles are extra jerky.

[ger21]

stop cv on angles which is set to 0

Set this to 89 and enable it.