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Wierd behaviour on A

From the original Synthetos forum (2011–2025)

Started by JuKu on in TinyG Support. 3 replies, last activity Jun 25, 2013.

JuKu #

I'm pretty sure this used to work in earlier software... I'm running 377.08 now, and I'm getting 288 degrees revolution when I ask for one?

Here are my motor and axis settings. I have a 1:4.5 downgearing on A, so I get 80 degrees of tool revolution per one motor revolution. Here is log from my terminal:

tinyg [mm] ok>
$4
[4ma] m4 map to axis 3 [0=X,1=Y,2=Z...]
[4sa] m4 step angle 1.800 deg
[4tr] m4 travel per revolution 80.000 mm
[4mi] m4 microsteps 8 [1,2,4,8]
[4po] m4 polarity 0 [0=normal,1=reverse]
[4pm] m4 power management 1 [0=off,1=on]
tinyg [mm] ok>
tinyg [mm] ok>
$a
[aam] a axis mode 3 [radius]
[avm] a velocity maximum 80000.000 deg/min
[afr] a feedrate maximum 172800.000 deg/min
[atm] a travel maximum -1.000 deg
[ajm] a jerk maximum 12000000000 deg/min^3
[ajh] a jerk homing 5760000000 mm/min^3
[ajd] a junction deviation 0.0500 deg (larger is faster)
[ara] a radius value 0.1989 deg
[asn] a switch min 1 [0=off,1=homing,2=limit,3=limit+homing]
[asx] a switch max 0 [0=off,1=homing,2=limit,3=limit+homing]
[asv] a search velocity 600.000 deg/min
[alv] a latch velocity 100.000 deg/min
[alb] a latch backoff 5.000 deg
[azb] a zero backoff 2.000 deg
tinyg [mm] ok>
tinyg [mm] ok>
g0 a1
tinyg [mm] ok>
tinyg [mm] ok>
posa:18.121,vel:25070.881,stat:5
posa:236.185,vel:48416.883
posa:288.000,vel:0.000,stat:3
a0
tinyg [mm] ok>
tinyg [mm] ok>
posa:262.699,vel:31448.910,stat:5
posa:40.733,vel:43482.938
posa:0.000,vel:0.000,stat:3

And yes, the tool does rotate as much as TinyG tells me.

aldenStaff #

If your goal is to specify A rotation in degrees I would not use radius mode. Perhaps you have this worked out so it translates, but I have not worked through your math to see if this is correct. Presumably you have seen these topics, bit I list them here for reference:

https://github.com/synthetos/TinyG/wiki/TinyG-Configuration#1tr---travel-per-revolution
https://github.com/synthetos/TinyG/wiki/TinyG-Configuration#xam---axis-mode
https://github.com/synthetos/TinyG/wiki/TinyG-Configuration#ara---radius-value

To set up A for a 4.5 gearing I would do the following

$4tr=80 (as you have done)
$aam=1 (standard mode)
$ara --- don't care. It won't be used.

I also notice that your A feed rate max exceeds your max velocity, which is not normally the case.

aldenStaff #

OK. I think I might know what's going on. If you want a value of 1 for A to be 1 complete revolution (360 degrees) then the radius value should be 1/(pi*2) or 0.15915494. Try this for the $ara value. Then the value of 1 will move 360 degrees. Even though the 8 places of precision is not displayed is is kept in the system and will cause '1' to translate to 360 degrees exactly.

The $4tr value just translates the rotation for your gearing (4.5 : 1) They are independent of each other.

Oh... and apologies that the units displays are not correct for some of these values int the displays. That's a small bug that I need to fix.

JuKu #

Doh, user error. Too many settings for my simple brain. I was ignoring the aam setting. Setting that to 1 gets the expected behaviour. Thank you for your support!

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