I believe its' a bug, Therefore, I put a bug report in the appropriate place, however, maybe any of you can open my eyes:

I have been running mach occasionally for a year now, all in all it went ok. however, I did mind that I had sometimes I needed to cancel the CV to get a proper corner. So, I went on and changed that on the config, for corners > 44.

The computer is a 2.5GHz, 2GB ram, winxp sp3.It is only running mach, commanding a router.

I used version 3.042.020 for most of the time. however, when I ran into problems with the steppers humming lately, I decided to upgrade to version 032.

Version 032 runs on my machine badly: it doesn't obey the velocity limit, and runs my steppers 1.4 times faster than the 020, and it didn't solve my stepper hum problem. so I downgraded to 029. the 029 obeys velocity limit, but still carries the same problem.

FINALLY: the problem description:

I run various g-codes. one of them is attached here below. the most run without any problems, however, this one caused humming. So I cut the velocity and accel in half, and still it humms. the funny thing is, it starts the humming when in full speed, without any apparent reason. when jogging it gives no hum at all, even though the jog is even faster.

IMPORTANT: I found that when I run the code with different lookahead(tried 1, 2, 5, 20, 50, 200, 400, 500, 1000), it does the humming on different program lines, but it is always the same line per lookahead value.

This humming causes loss of steps of course, and the programs keeps running from the supposed position, which is already wrong.

I really believe it has a strong relation to the lookahead, please help, I really have no solution, this experimental piece of code that is attached demonstrates all the problems. all it does is v-carve a rectangle, then with a 10 mm flat it makes a bottom, then a 25.4(1``) ball it makes another inner slope. supposes 19mm thick mdf.

G00 G49 G40.1 G17 G80 G50 G64 G90 G58

G21

(V-Carving 3)

M6 T1

M03 S4851

G00 Z60.0000

X96.0010 Y26.0010

G01 Z13.0000 F3000.0

X101.8451 F3500.0

G17

G02X96.0010Y31.8451I0.1549J5.9990

G01 Y26.0010

X95.9010 Y25.9010 Z13.1000

X96.0010 Y26.0010 Z13.0000

Z60.0000 F9000.0

G00

X102.0000 Y273.9010

G01 Z13.1000 F3000.0

X338.0000 F3500.0

G02X343.9010Y268.0000I0.0000J-5.9010

G01 Y32.0000

G02X338.0000Y26.0990I-5.9010J0.0000

G01 X102.0000

G02X96.0990Y32.0000I0.0000J5.9010

G01 Y268.0000

G02X102.0000Y273.9010I5.9010J0.0000

G01 Z60.0000 F9000.0

G00

X95.9010 Y274.0990

G01 Z13.1000 F3000.0

Y25.9010 F3500.0

X344.0990

Y274.0990

X95.9010

X96.0010 Y273.9990 Z13.0000

Y268.1549

X96.0151 Y268.4394

X96.0167 Y268.4555

Z13.0004

X96.0000 Y268.0000 Z13.0010

X96.0161 Y31.5507 Z13.0002

X96.0000 Y268.0000 Z13.0010

X96.0167 Y268.4555 Z13.0004

Z13.0000

G02X101.5445Y273.9833I5.9822J-0.4544

G01 Z13.0004

X102.0000 Y274.0000 Z13.0010

X338.4493 Y273.9839 Z13.0002

X102.0000 Y274.0000 Z13.0010

X101.5445 Y273.9833 Z13.0004

Z13.0000

X101.5606 Y273.9849

X101.8451 Y273.9990

X96.0010

Z60.0000 F9000.0

G00

X343.9990

G01 Z13.0000 F3000.0

X344.0990 Y274.0990 Z13.1000 F3500.0

X343.9990 Y273.9990 Z13.0000

X338.1549

G02X343.9833Y268.4555I-0.1546J-5.9983

G01 Z13.0004

X344.0000 Y268.0000 Z13.0010

X343.9839 Y31.5507 Z13.0002

X344.0000 Y268.0000 Z13.0010

X343.9833 Y268.4555 Z13.0004

Z13.0000

X343.9849 Y268.4394

X343.9990 Y268.1549

Y273.9990

Z60.0000 F9000.0

G00

Y26.0010

G01 Z13.0000 F3000.0

X344.0990 Y25.9010 Z13.1000 F3500.0

X343.9990 Y26.0010 Z13.0000

Y31.8451

G02X338.4555Y26.0167I-5.9983J0.1546

G01 Z13.0004

X338.0000 Y26.0000 Z13.0010

X101.5507 Y26.0161 Z13.0002

X338.0000 Y26.0000 Z13.0010

X338.4555 Y26.0167 Z13.0004

Z13.0000

X338.4394 Y26.0151

X338.1549 Y26.0010

X343.9990

Z60.0000 F9000.0

G00

X90.0010 Y279.9990

G01 Z19.0000 F3000.0

X95.9010 Y274.0990 Z13.1000 F3500.0

Z60.0000 F9000.0

G00

X349.9990 Y279.9990

G01 Z19.0000 F3000.0

X344.0990 Y274.0990 Z13.1000 F3500.0

Z60.0000 F9000.0

G00

X349.9990 Y20.0010

G01 Z19.0000 F3000.0

X344.0990 Y25.9010 Z13.1000 F3500.0

Z60.0000 F9000.0

G00

X90.0010 Y20.0010

G01 Z19.0000 F3000.0

X95.9010 Y25.9010 Z13.1000 F3500.0

G00 Z60.0000

(Engraving)

G53 X150 Y1740

M6 T20

M03 S4851

X102.0000 Y32.0000

G01 Z13.1000 F3000.0

X220.0000 F6500.0

X338.0000

Y150.0000

Y268.0000

X220.0000

X102.0000

Y150.0000

Y32.0000

Z13.0000

Y150.0000

Y268.0000

X220.0000

X338.0000

Y150.0000

Y32.0000

X220.0000

X102.0000

G00 Z60.0000

(Engraving)

G53 X150 Y1740

M6 T3

M03 S4851

X107.0000 Y37.0000

G01 Z13.0000 F3000.0

X220.0000 F6500.0

X333.0000

Y150.0000

Y263.0000

X220.0000

X107.0000

Y150.0000

Y37.0000

G00 Z60.0000

G00 Z155

M5 M9

M30