Hey,

I'm new here and maybe in the wrong section but I searched a lot in this forum and could not find a better place to put my question on.
I have a mach3 (latest version Mach3 R3.043.066) installed and configured.

I draw a simple rectangle (200x200mm) in Cut2d and export the path as a Mach3 file (mm).
The rectangle has a depth of 4mm. Cut2d is set to 2mm per cut with a 3mm mill.

Now my problem:
First rectangle (2mm in the first mill) is OK (dimension). The second turn, the rectangle is not accurate at all. The second mill has an offset of about 1mm in X and Y.

I can say that it's not a mechanical issue because if I cut with another Tool (WIN-NC) both cuts are at the exact same position.
What i found out is that this is some how related to the cutting speed.

If i cut with 4mm/s the second cut of the rectangle is too wide.
If I cut with 8mm/s the second cut is too narrow.
With 6mm/s the second cut seems to be fine.

Does anyone have an idea what could cause this strange behaviour on mach3?

Thanks for your answer

Regards
Chris

Post the gcode file from Cut2d.
RICH

I'll post the code as soon as I'm back home... this could take a little while..

I'll backplot it to see if it's the code.
RICH

Here we go...

( 200x200 )
( Mach2/3 Postprocessor )
N20G00G21G17G90G40G49G80
N30G71
N40T5M06
N50G00G43Z20.000H5
N60S6000M03
N70G94
N80X0.000Y0.000F360.0
N90G00X48.500Y50.000Z6.000
N100G01Z-2.000F180.0
N110G01Y250.000F360.0
N120G2X50.000Y251.500I1.500J0.000
N130G01X250.000
N140G2X251.500Y250.000I0.000J-1.500
N150G01Y50.000
N160G2X250.000Y48.500I-1.500J0.000
N170G01X50.000
N180G2X48.500Y50.000I0.000J1.500
N190G01Z-4.000F180.0
N200G01Y250.000F360.0
N210G2X50.000Y251.500I1.500J0.000
N220G01X250.000
N230G2X251.500Y250.000I0.000J-1.500
N240G01Y50.000
N250G2X250.000Y48.500I-1.500J0.000
N260G01X50.000
N270G2X48.500Y50.000I0.000J1.500
N280G00Z6.000
N290G00Z20.000
N300G00X0.000Y0.000
N310M09
N320M30
%

Not the pathing. The pathing is the same for the 2nd cut.
Maybe drop your feedrate and and then play with the acceleration.
RICH

What code you're talking about ?. I could attach the crv file from Cut2d if this helps.
I've already played with acceleration and motor settings.

As I wrote before it seems to work, if i set the feedrate to 6mm/s. I can understand that it's causing problems with 8mm/s but it should work well with 4mm/s and it doesn't.
I think the motor settings are fine (used the same as in the other Application).
Dimension is OK
DRO positions are the same at both cuts.

note: renamed file extension from .crv to .txt for uploading

What code you're talking about ?.

The code you posted in reply #4

RICH

Hi Thomc, (Chris) I think RICH missed of an e from the end of not so you read the reply as not, instead of note meaning there is nothing wrong with your program. However I took the liberty of downloading your mach file, run it on my machine I had to scale it down to half scale so I could machine the shape, as expected it cut perfectly so your assumption of deflection due to the feed rate is correct. Cant remember if you said what you were cutting but sometimes the second cut is deflected because of the cut material left in the slot or the cutter deflection cuts more off one side of the previous cut. Anyway I think your problem is mechanical note electronic however sometimes too fast federate skip a few steps causing an offset when going round the same form especially when going round rounded corners. Try cutting a square without rounded corners. Chris I'm sure you will solve it keep experimenting mate but remember start with slow feed rates and work up until it goes wrong.

Thank's for your reply,

The major issue is that I've already tried with lower feedrates and the result is the same.
As I wrote in a previous post, I did the same thing in another application and it worked well. That's the reason why I think it's not a mechanical issue.
I'll try to cut without round corners and let you know if this works.

Thanks