I've read a ton of posts trying to figure out why my 4th axis isn't smooth. I've eliminated smoothing (fusion 360 option), CV settings in Mach3, computer performance, disabled toolpaths to see if that helps. I think the issue is acceleration differences between A and the XYZ axes. My XYZ are set to 100 IPM, my 4th axis is set to 2500. If I set my A axis to 100 IPM its impossibly slow. Are there any tricks smooth this out?

https://youtu.be/Cz8HDmt4FTA

Trying to figure out why my 4th axis isn't running smoothly. Every video I've seen shows people configuring the 4th axis and off it goes.

I've tried changing speeds, disabling backlash compensation, and changing several settings in mach3, but nothing seems to help.

I've look at the Gcode and there doesn't seem to be any particular pattern in the code and the pausing.

Any ideas?

https://www.youtube.com/watch?v=Cz8HDmt4FTA

In your motor setup do you have the steps/per set for 1 degree or for 360 degree.

Also is the move in the video 1 move or several moves?

It's per degree I guess? I know dimensionally everything is very dialed in.

That's probably a couple hundred lines of code. Some of the code is below.



ROTARY1)
M5
T1 M6
S4000 M3
G54
G0 A0.
M8
G0 X5.193 Y0.1102
G43 Z1.5451 H1
A0.
Y0.0552 Z0.7737
G1 Y0.0522 Z0.7323 F3.3
Z0.6938
Y0.0517 Z0.6864 F10.
Y0.0499 Z0.6788
Y0.0468 Z0.6712
Y0.0424 Z0.6641
Y0.0368 Z0.6577
Y0.0302 Z0.6523
Y0.0228 Z0.6483
Y0.0151 Z0.6455
Y0.0074 Z0.6441
Y0. Z0.6439
G93 Z0.6444 A-0.905 F933.752
Z0.6464 A-2.002 F696.164
Z0.6505 A-3.591 F451.8999
Z0.6547 A-5.291 F422.7951
Z0.6581 A-6.858 F467.2529
Z0.6615 A-8.558 F433.8702
Z0.6641 A-10.051 F502.2252
Z0.6667 A-11.771 F442.008
Z0.6686 A-13.141 F561.1862
Z0.6704 A-14.855 F457.9756
Z0.6718 A-16.432 F502.2218
Z0.6727 A-17.981 F523.8417
Z0.6733 A-19.427 F566.6257
Z0.6737 A-21.11 F497.0237
Z0.6735 A-22.949 F459.5164
Z0.673 A-24.788 F451.0638
Z0.672 A-26.369 F511.8767
Z0.6707 A-28.16 F447.4703
Z0.669 A-29.76 F489.1512
Z0.6666 A-31.671 F404.9184
Z0.6642 A-33.267 F476.5405
Z0.661 A-35.06 F417.513
Z0.6574 A-36.88 F407.3277
Z0.6539 A-38.448 F463.6209
Z0.6499 A-40.112 F436.4893
Z0.6456 A-41.764 F432.8346
Z0.64 A-43.701 F365.378
Z0.6349 A-45.389 F416.2034
Z0.6285 A-47.302 F362.3115
Z0.6224 A-49.037 F399.259
Z0.6164 A-50.649 F423.8037
Z0.6099 A-52.33 F407.022
Z0.6033 A-53.93 F424.1621
Z0.5959 A-55.655 F390.7474
Z0.5884 A-57.339 F400.4215
Z0.5779 A-59.572 F299.2493
Z0.5703 A-61.126 F428.5042
Z0.5622 A-62.723 F416.1878
Z0.5539 A-64.278 F425.7003
Z0.5438 A-66.103 F360.0496
Z0.5326 A-68.027 F339.7208
Z0.5221 A-69.745 F377.6411
Z0.5123 A-71.281 F420.5518
Z0.5033 A-72.654 F470.2919
Z0.4899 A-74.654 F322.2894
Z0.4769 A-76.638 F334.2914
Z0.4646 A-78.638 F345.0893
Z0.4529 A-80.651 F356.5038
Z0.4417 A-82.674 F368.5998
Z0.4312 A-84.704 F381.4469
Z0.4207 A-86.832 F377.7341
Z0.4108 A-88.97 F390.6529
Z0.4063 A-89.997 F839.3133
A-90.004 F208001.4655
Z0.416 A-92.174 F391.7739
Z0.426 A-94.263 F391.8613
Z0.4346 A-96.023 F455.4113
Z0.4399 A-97.174 F708.7327
Z0.4481 A-99.094 F430.2127
Z0.4567 A-101.186 F396.7344

You are running inverse time mode and tiny moves so every move has a different feed rate so it will look jerky.

Try running it with a fixed feed rate, remove the G93 and the feed commands and use G94 and see how that looks.

Thanks! I'll give that a try.

It's still jerky, almost exactly the same. Fusion creates different feed rates, even if inverse time is not selected. I tried manually going through several lines and giving them the same feed rate, but its still the same results. I tried changing a bunch of settings from exact position to CV, editing CV paramters, changing the radius under the settings tab, but nothing seems to really affect the start/stop motion. It doesn't do that with 2D or 3D milling, but the 4th axis is causing some sort of hesitation.