4th axis speed limit

Hello, I've been going over the forums for a couple days to solve a speed problem with my 4th axis and am stuck. I imagine I've just done something wrong in the .ini and would appreciate a fresh set of eyes.

I recently added a 4th axis (b) to my machine (xyyz+b)

It appears to be accurate, however angular jog speed slider is limited to 3600 deg/min <- the motor can go faster than this. The default angular velocity doesn't appear to effect it as It always starts at 360deg/min <-painfully slow acceleration also slow.

G0 commands are limited to 60deg/min. even if only b is being addressed.
G1 b 15 F 360 is throttled to 60deg/min, G1b15F 45 does reduce the speed to 45.

Thanks, I'll make sure they agree.
The scale does seem odd to me, but my understanding was I was looking for number of steps for 1 degree.

200 steps per motor rev * 2 for half stepping 400
400 * 6/1 gear reduction = 2400 / 360 = 6.666 steps per degree.

I was suspicious but when I put an digital angle finder on the chuck and test it I get the correct amount of rotation.




Replied by Todd Zuercher on topic Formula to calculate the right SCALE
I thought I kind of did.
I'll try again.
Step motor's Steps/rev (including micro-stepping) = S (3200) (400)
Motor Revolutions / Rotary Axis revolution = R (12:1) (6:1)
Rotational Units(/rev) = U (360 degrees)
Steps per Unit = S*R/U = 3200*12/360 = 106.667 400*6/360 = 6.667

Yes, that is where you put it. I don't think you need to put it any where else."-

uploaded a cleaner .ini
problems remain the same.

In an effort to make sure I understand why and just not how I'm going to pose some questions about the INI setup.

1. I've been using linuxcnc.org/docs/html/config/ini-config.html as the official documentation for my version of linuxCNC 2.9.xxx . This is correct?

2. My calculation for scale is correct; assuming I have a 200 step motor, doing half stepping, and geared 6:1?

3. The only place MAX/ MIN/ DEFAULT_ANGULAR_VELOCITY entries appear is under the [DISPLAY] section?

4. The MAX_VELOCITY settings under [TRAJ] over-rule all of the AXIS_ and therefore [JOINT_x]s ?

5. We can't differentiate here between angular and linear axis? for example putting a MAX_ANGULAR_VELOCITY entry under the [TRAJ] doesn't work?

6. I need a MAX_VELOCITY under both [AXIS_B] and [JOINT_4]?

The slider not going above 3600 and not responding to default_angular_velocity in [display] appears to be a bug in gmoccapy.

If you edit the gmoccapy glade file /usr/share/gmoccapy/ you can input your desired values.
Thanks to cmorley in another thread for this insight.

still trying to sort out the g0 g1 commands being throttled at a painfully slow 60deg/min.

I thought this might be the problem, i've spent the morning and most of the afternoon attempting to find how to edit my post processor for fusion to output in g93. It appears possible but i've been unable to locate a good example. I have everything else in working order at this point. I'll keep looking but if anyone has a clue let me know.

attempting to follow this
forums.autodesk.com/t5/hsm-post-processo...ighlight/true#M14311

starting to feel like basic config undersold how complicated this would end up.

I have a working PP for fusion that can output g93 commands to my b axis. I followed the tutorial above and got it to output feed rates, although it wasn't putting the f in front of the feed rates. So it took some time to sort tha

feed rates still throttled at 60
commands like g93 g1 b360 f4000 don't have an effect.

Ok. I'm confused by this behavior,

I figured [AXIS_B] --> [JOINT_4] (angular) is being throttled by
MAX_VELOCITY = 2.25 [TRAJ] (scaled for max speed of my linear x,y,z)
Since MAX_ANGULAR_VELOCITY according to the documentation can only be used under [DISPLAY] I figured MAX_VELOCITY has to be the much higher (4000) for the b even though their scales are wildly different since one is representing 1 inch and the other 1 degree.

ok i said to myself well if [TRAJ] over-rules all other speed entries (coordinated moves) and {AXIS} has it's own throttle, then it shouldn't matter if that number is way higher. When I go above 2.25 in my [TRAJ] (i've tried a little above and a lot above) and restart the program, I can jog everything fine; aside from my y which is dualed and annoyingly can't be jogged before homing. Each axis correctly obeys it's specific speed limit.(joint mode) I home the machine, zero b manually and jog things. now linear axis still obey their limits but b is throttled to 60
I issue these MDI commands
g93
g0b360f4000

b remains throttled at 60

g93
g0x30y30f100

x and y move together and the velocity reads 190.92 which is higher than the max jog speed of the machine 135 but I don't think it's actually moving at 190. My machine might be able to go 190 just a bit risky so I check the jog again, and despite the linear slider now going ridiculously high(which seems weird since I didn't change the display max_linear_velocity) but it does report the velocity at 135 even as the slider is now centered around 300

ok so let's break it. If it reports 190 at a g93 f of 100 for 20 inches of travel what happens if i up it to 500
g0x10y10f500

throttled at 190.92 (which I believe is really 135)

*I should also note that on the gmoccappy screen the F under Feed override displays 0 and feed override is at 100%

Ok linear Axis appear to be working correctly even if reporting something odd.

Let's test the B again

g0 b360f500

slow accel throttled at 60 velocity

g0 b360f10 V= 60
g0 b360f1 V= 60

how about we go back to g94 and try


g94
g0 b360f10 V= 60
g0 b360f200 V = 60
g0 b360f1 V = 60

unhome all

B jogs at a high speed.

Home b alone B jogs at a high speed

home all but b
B still turns nicely!

g0b360f500
throttled
*but the F display appears to be working again

Anyway, aside from the fusion PP and fixing the slider in gmoccapy i'm pretty much where I started.

Any tests I should run or settings to experiment with? I'm at a total lost now that i've tried everything I could think of a dozen times.


actually wait, It's working less than when i started as giving it a g94 feedrate less than 60 used to work correctly, but now even slower speeds live at 60

**** gmoccapy uses [MAX_LINEAR_VELOCITY under [ TRAJ] nor display for it's slider

I can delete the [AXIS_B] and it's velocity settings and it makes no difference. b still jogs fine (reading from the joint) and feed commands remain fixed at 60.so it would appear that section is being ignored, and without being told a max velocity for b, a 1 is used as default