Machsupport Forum

G-Code, CAD, and CAM => G-Code, CAD, and CAM discussions => Topic started by: javalin00 on August 27, 2023, 05:01:54 AM

Title: doesnt mill the correct size
Post by: javalin00 on August 27, 2023, 05:01:54 AM

Hi All

Trying to mill a 5mm x 150mm slot, easy eh?  Well if I write the g-code manually it works, if I use V-Carve's output it comes out ~4mm x 149mm.  Code looks the same for both.  Thought about tool compensation but as far as I can see its not "active".  Stuck.  Machine is calibrated ok, using the correct 1/8" bit.  Help?

Example code attached as picture for comparison - left is working manually written, right is vCarve GCode mm arc's output - not working.

thanks!
James

Title: Re: doesnt mill the correct size
Post by: MarshaJ847 on August 27, 2023, 04:34:35 PM

Some of the math is skewing the results.

In the hand written code, the 1/8 inch bit is shown having a radius of 1.58 
In reality 3.175/2 = 1.5875, or keeping the same precision 1.588
Also the X axis only seems to move 100mm, not the 150 mentioned.

In the generated code, X moves from -73.412 to +73.412 and adding the 2 radii of the bit adds up to 149.999mm
The Y moves from -0.913 to +0.913 adding in the bit again results in 5.001mm

As far as I can tell maybe your machine may need a little more adjustment.  Or measurement of the bit.

Title: Re: doesnt mill the correct size
Post by: javalin00 on August 30, 2023, 03:12:08 PM

thanks for looking.

I checked the calibration and its fine at 40cm when jogged.

Edited the files to use the same numbers and I still get two different results, which I'll post if the forum page lets me! (third time writing this!)

Help?

Title: Re: doesnt mill the correct size
Post by: javalin00 on August 30, 2023, 03:15:07 PM

picture

Title: Re: doesnt mill the correct size
Post by: javalin00 on August 30, 2023, 03:15:34 PM

ah.  code.  Left hand one gives 4mm, not 5mm :-(

Title: Re: doesnt mill the correct size
Post by: Graham Waterworth on August 30, 2023, 09:42:04 PM

My guess is something is loose or slipping.

Title: Re: doesnt mill the correct size
Post by: TPS on August 31, 2023, 01:42:03 AM

so, same coordinates but different speeds:

-loose or slipping like Graham mentoined
-loosing step's - devide your speed and acelleration in motortuning by 2
-G61/G64 setting - try to use G61