Hello,

I'm pretty new to Mach3 but coming from LinuxCNC, so there's "some" knowledge of the CNC stuff.
I set up my machine which is a pretty rigid construction and it is constructed for precise milling of soft materials (brass, etc.).

First I calibrated my motors via "Motor Tuning" with the following specs:

- NEMA 23 with TRIPLE BEAST board
- Microstepping 1/10 = 200*10 steps per rev = 2000 steps per rev = 400 steps per mm
- Ballcrew spindle (d=16mm) with 5mm pitch

Steps per: 400
Velocity: 850
Acceleration: 350

2us / 2us

Motors sound good with these specs. Backlash is set to 0.008mm but no difference to 0mm.

Axis problem No.1
I started the Axis Calibration. I told Mach3 to go for 1mm and adjusted the steps until precisely 1mm was reached. I tested this several times and Mach3 always reached the 1.000mm.
I then tried the same for 5mm. Surprisingly, the Axis would go 5.015mm. When I adjusted the Axis with these values and tried 1mm again, the 1mm would be off 0.018mm.
Any ideas where to problem might be?

Axis problem No.2
For my other axis I was able to get stable precise results for 1mm, 5mm, 7mm and so on. I then restarted, homed again and tested the axis at the same position with the same distances again and were off by almost 0.01mm. Any ideas on that miracle?

Thank you guys in advance!
Best regards,
Hancock

What grade of precision are your ball screws , are they double nut or single nut

sounds like it's the ball nuts ,
Are they fixed tight , has the screws got any end float in them

All the about will cause the symptoms you describe

Have fun
Stuart

Hey Stuart,

thanks for your reply. The ball screws are grade C2 with a single nut.

They are pretty tight and I just disassembled the axis and tested it by using the my Mitutoyo (.000) and pressing against the nut. Max. 0.002mm movement of the nut on the spindle.

Best,
Hancock

One tip - when tuning go for a long travel - as much as you can measure, get this right and then the small steps should be good too.
1mm is not a good distance to tune on.
i used a 1000mm rule on my plasma and the mini-mill was calculated and checked over 400mm.

well that only account for a bit of lost motion

just a thought ( you know its a dangerous thing to do  ) try reducing the acceleration to see if it helps

on my small mill ( metric setup ) i use 100 acc with 4 mm pitch ball screws

just bored a 3 mm dia hole with a 2mm end mill just goes on a 3mm ground steel rod

Good point, try a rule i have used for a while and thats 1/10 for speed and accel.

So if your speed is 850 then set acceleration to 85 and so-on.

Even if its not a perfect target, it does seem a very good setting to start on.

Thanks for all the suggestions! It took me some time to try a few things out, recalibrate and test again.

I adjusted the steps via Mach3 and get repeatable results for 80mm, 100mm, 5mm, 1mm, 0.5mm - everything lies within a tolerance of 0.005mm.
The results are constant with speed/acc: 850/350 or 2400/600

But here comes the problem: When I mill circle, it's way too large. At this point I have absolutely no idea anymore why I can go a specific distance precisely but can't mill a circle with the correct size.

Did anyone had this problem before or still has an idea?
Thanks a lot in advance!!

If your movements are good, the difference is probably a code problem, put some code up and show what is wrong with it.

Also, what happens when you try a square? Is the issue related only to circles?

Here's the code for the circle. It's two pockets but only the second one is for measuring.

Thank you for your help!!

%
(KREIS 3,53)
(T22  D=1.49 CR=0. - ZMIN=-2.1 - SCHAFTFRSER)
N10 G90 G94 G17 G91.1
N15 G21
N20 G53 G0 Z0.
(2D-TASCHE3)
N25 M9
N30 T22 M6
(1.5MM VHM FRSER)
N35 S42000 M3
N40 G54
N45 M9
N55 G0 X0.095 Y0.149
N60 G0 Z15.
N65 Z5.
N70 G1 Z2.5 F150.
N75 Z-0.151
N80 G19 G2 Y0. Z-0.3 J-0.149 K0.
N85 G17 G3 X0.605 I0.255 J0. F400.
N90 X-0.605 I-0.605 J0.
N95 X1.305 I0.955 J0.
N100 X-1.305 I-1.305 J0.
N105 X2.005 I1.655 J0.
N110 X-2.005 I-2.005 J0.
N115 X2.005 I2.005 J0.
N120 Y0.011 I-0.149 J0.
N125 X2.003 Y0.021 Z-0.298 I-0.149 J-0.011
N130 X2.002 Y0.031 Z-0.297 I-0.147 J-0.021
N135 X1.999 Y0.041 Z-0.294 I-0.146 J-0.031
N140 X1.996 Y0.051 Z-0.291 I-0.143 J-0.041
N145 X1.992 Y0.06 Z-0.287 I-0.14 J-0.051
N150 X1.988 Y0.069 Z-0.282 I-0.136 J-0.06
N155 X1.984 Y0.077 Z-0.276 I-0.132 J-0.069
N160 X1.979 Y0.084 Z-0.27 I-0.128 J-0.077
N165 X1.974 Y0.091 Z-0.264 I-0.123 J-0.084
N170 X1.969 Y0.097 Z-0.256 I-0.118 J-0.091
N175 X1.964 Y0.102 Z-0.249 I-0.113 J-0.097
N180 X1.96 Y0.107 Z-0.24 I-0.108 J-0.102
N185 X1.955 Y0.111 Z-0.232 I-0.104 J-0.107
N190 X1.951 Y0.115 Z-0.222 I-0.099 J-0.111
N195 X1.947 Y0.118 Z-0.213 I-0.095 J-0.115
N200 X1.944 Y0.12 Z-0.203 I-0.091 J-0.118
N205 X1.942 Y0.122 Z-0.193 I-0.088 J-0.12
N210 X1.939 Y0.124 Z-0.183 I-0.086 J-0.122
N215 X1.938 Y0.125 Z-0.172 I-0.083 J-0.124
N220 X1.937 Z-0.162 I-0.082 J-0.125
N225 G1 Z-0.151
N230 G0 Z15.
(2D-TASCHE4)
N240 M9
N245 G0 X0.314 Y-0.149
N250 Z15.
N255 Z5.
N260 G1 Z2.5 F150.
N265 Z-0.151
N270 G19 G3 Y0. Z-0.3 J0.149 K0.
N275 G17 G3 X-0.314 I-0.314 J0. F100.
N280 X1.014 I0.664 J0.
N285 X-1.014 I-1.014 J0.
N290 X1.02 I1.017 J0.
N295 X-1.02 I-1.02 J0.
N300 X1.02 I1.02 J0.
N305 X-1.02 I-1.02 J0.
N310 X1.02 I1.02 J0.
N315 X0.908 Y0.065 I-0.074 J0.
N320 G1 X0.426 Y-0.214
N325 G2 X0.314 Y-0.149 I-0.037 J0.065
N330 G1 Z-0.451 F150.
N335 G19 G3 Y0. Z-0.6 J0.149 K0.
N340 G17 G3 X-0.314 I-0.314 J0. F100.
N345 X1.014 I0.664 J0.
N350 X-1.014 I-1.014 J0.
N355 X1.02 I1.017 J0.
N360 X-1.02 I-1.02 J0.
N365 X1.02 I1.02 J0.
N370 X-1.02 I-1.02 J0.
N375 X1.02 I1.02 J0.
N380 X0.908 Y0.065 I-0.074 J0.
N385 G1 X0.426 Y-0.214
N390 G2 X0.314 Y-0.149 I-0.037 J0.065
N395 G1 Z-0.751 F150.
N400 G19 G3 Y0. Z-0.9 J0.149 K0.
N405 G17 G3 X-0.314 I-0.314 J0. F100.
N410 X1.014 I0.664 J0.
N415 X-1.014 I-1.014 J0.
N420 X1.02 I1.017 J0.
N425 X-1.02 I-1.02 J0.
N430 X1.02 I1.02 J0.
N435 X-1.02 I-1.02 J0.
N440 X1.02 I1.02 J0.
N445 X0.908 Y0.065 I-0.074 J0.
N450 G1 X0.426 Y-0.214
N455 G2 X0.314 Y-0.149 I-0.037 J0.065
N460 G1 Z-1.051 F150.
N465 G19 G3 Y0. Z-1.2 J0.149 K0.
N470 G17 G3 X-0.314 I-0.314 J0. F100.
N475 X1.014 I0.664 J0.
N480 X-1.014 I-1.014 J0.
N485 X1.02 I1.017 J0.
N490 X-1.02 I-1.02 J0.
N495 X1.02 I1.02 J0.
N500 X-1.02 I-1.02 J0.
N505 X1.02 I1.02 J0.
N510 X0.908 Y0.065 I-0.074 J0.
N515 G1 X0.426 Y-0.214
N520 G2 X0.314 Y-0.149 I-0.037 J0.065
N525 G1 Z-1.351 F150.
N530 G19 G3 Y0. Z-1.5 J0.149 K0.
N535 G17 G3 X-0.314 I-0.314 J0. F100.
N540 X1.014 I0.664 J0.
N545 X-1.014 I-1.014 J0.
N550 X1.02 I1.017 J0.
N555 X-1.02 I-1.02 J0.
N560 X1.02 I1.02 J0.
N565 X-1.02 I-1.02 J0.
N570 X1.02 I1.02 J0.
N575 X0.908 Y0.065 I-0.074 J0.
N580 G1 X0.426 Y-0.214
N585 G2 X0.314 Y-0.149 I-0.037 J0.065
N590 G1 Z-1.651 F150.
N595 G19 G3 Y0. Z-1.8 J0.149 K0.
N600 G17 G3 X-0.314 I-0.314 J0. F100.
N605 X1.014 I0.664 J0.
N610 X-1.014 I-1.014 J0.
N615 X1.02 I1.017 J0.
N620 X-1.02 I-1.02 J0.
N625 X1.02 I1.02 J0.
N630 X-1.02 I-1.02 J0.
N635 X1.02 I1.02 J0.
N640 X0.908 Y0.065 I-0.074 J0.
N645 G1 X0.426 Y-0.214
N650 G2 X0.314 Y-0.149 I-0.037 J0.065
N655 G1 Z-1.951 F150.
N660 G19 G3 Y0. Z-2.1 J0.149 K0.
N665 G17 G3 X-0.314 I-0.314 J0. F100.
N670 X1.014 I0.664 J0.
N675 X-1.014 I-1.014 J0.
N680 X1.02 I1.017 J0.
N685 X-1.02 I-1.02 J0.
N690 X1.02 I1.02 J0.
N695 X-1.02 I-1.02 J0.
N700 X1.02 I1.02 J0.
N705 X1.016 Y0.033 Z-2.096 I-0.149 J0. F400.
N710 X1.006 Y0.063 Z-2.085 I-0.145 J-0.033
N715 X0.992 Y0.087 Z-2.067 I-0.135 J-0.063
N720 X0.977 Y0.105 Z-2.044 I-0.121 J-0.087
N725 X0.964 Y0.117 Z-2.016 I-0.106 J-0.105
N730 X0.955 Y0.123 Z-1.984 I-0.093 J-0.117
N735 X0.952 Y0.125 Z-1.951 I-0.084 J-0.123
N740 G0 Z15.
N750 M9
N755 G53 Z0.
N760 M30
%