4-th Axis running bad

[SpaceCat]

Hi, new here but been using Mach for many yrs. I have Build a new welded steel machine and this is performing absolutely great with Gecko drive. I can run the machine smooth and quick with good accurancy.

Now i am building a rotational axis and have just connected the 4th motor into Mach3. After Creating a 4 axis toolpath in PowerMILL i have test runned this in the machine. Now the machine moves smooth when XYZ movement, but if a A-axis movement the machine starts to stop at every block, this makes my machine jumping around..

Is it possible to tun simultaniously 4 axis quick and smooth in Mach-3 ? 

I normaly machine with a feedrate at max 2500mm/min, but machine handles up to 3500mm/min in feed. I tried to change lookahead, G64, and alot of settings, but machine runns about the same..

Any idee?


Machine travels 300x300x300mm and is build with 80x80 steel frame. Using THK linear rails makes this very stable. I have machined in CoCr without any prob, so it is a nice machine..
BR/R

[Graham Waterworth]

What do you have set in your steps per for the A axis.  You need to have it set for a one degree movement.

Graham

[SpaceCat]

Hello,

I have only the 4th stepper motor conevted without the rotary axis ready yet, so the setting is 5.5555 for step/...  ((200step*10 microstep)/ 360) = 5.5555... and this is correct

Tried to remove al G64 in code and also CV function turned off.

In mach and motor tuning Velocity = 367020 Acceleration = 94500

Code looks like :
(Just a stupid test of milling on a cylinder with rotational lead in..


     ( TOOLPATH RANGE )
     ( XminX-50. )
     ( XmaxX0 )
     ( YminY0 )
     ( YmaxY50. )
     ( ZmaxZ50. )
     ( ZminZ-49.72 )
(" VerktygsTyp :  BALLNOSED ")

G1 G49 G40  G17 G80 G50 G90
G21 (mm)
G1Z50. F500

     ( G43 = Längdkompensering på )
     (  Toolpath : 1 )
G1 G43G0X0Y50. A0 T1 H1 F3000
X-.28Y49.34 A1.96
X-.56Y48.68 A3.91
X-.85Y48.03Z49.99 A5.87
X-1.13Y47.37 A7.82
X-1.41Y46.71Z49.98 A9.78
X-1.69Y46.05Z49.97 A11.73
X-1.98Y45.39Z49.96 A13.69
X-2.26Y44.74Z49.95 A15.64
X-2.54Y44.08Z49.94 A17.60
X-2.82Y43.42Z49.92 A19.55
X-3.1Y42.76Z49.9 A21.51
X-3.38Y42.11Z49.89 A23.46
X-3.67Y41.45Z49.87 A25.42
X-3.95Y40.79Z49.84 A27.37
X-4.23Y40.13Z49.82 A29.33
X-4.51Y39.47Z49.8 A31.28
X-4.79Y38.82Z49.77 A33.24
X-5.07Y38.16Z49.74 A35.20
X-5.35Y37.5Z49.71 A37.15
X-5.63Y36.84Z49.68 A39.11
X-5.91Y36.18Z49.65 A41.06
X-6.19Y35.53Z49.61 A43.02
X-6.47Y34.87Z49.58 A44.97
X-6.75Y34.21Z49.54 A46.93
X-7.03Y33.55Z49.5 A48.88
X-7.31Y32.89Z49.46 A50.84
X-7.59Y32.24Z49.42 A52.79
X-7.87Y31.58Z49.38 A54.75
X-8.15Y30.92Z49.33 A56.70
X-8.43Y30.26Z49.28 A58.66

[ludiheum]

Hi spacecat, i think i have the same problem, where you able to fix it? i think i could be the acceleration

[olf20]

Here is a post over on the Vetric forum. Greg has done lots
with rotary / 4th axis with Mach
Hope this helps!1
http://www.vectric.com/forum/viewtopic.php?t=6449
olf20 / Bob

[Greolt]

There is not much info on this but,

Mach has problems with CV and a 4th axis, if the acceleration settings are wildly different to the other axis.

I have mine set to much the same as X, Y and Z

This may, or may not, be possible or desirable with your setup.

Greg

[ludiheum]

Thanks olf im going to check the link right now.

Greolt: but if you set the speed and acceleration of the X, Y and Z axis similar to the rotary A axis, the will move to slow, im having this problem and dont know how to fix it

[Greolt]

Acceleration,not velocity.
 
You may not be able to set it close to what the other axis are, but that is what is needed to get CV to actually work.

As far as velocity and feedrate are concerned, have you set up "Use Radius for Feedrate" to compensate the rotary axis velocity?

Greg

[ludiheum]

i didnt knew that Greg, i have activated it and seems that nothing happens. I went to config ---> toolpath and then check the box use diameter for feedback and A-rotations enabled, then over the settings tab--> rotational diameters i change the value for the A, and the jog the A axis with the hotkeys, but it runs always at the same speed. How is this supposed to work? i thought that if i put a big diameters it will slow the speed and with little diameters it will spped up, but i change this and dont see any chage, im doing something wrong?

[BR549]

I don't think you will see a difference UNTIL you run code. That is when it should blend the feedrates.

Just a thought, (;-) TP