question about circular interpolation

[warpedmephisto]

On my Taig (running TurboCNC and the stock controller box) when I do a circular interpolation move (G02, G03) it seems to ramp up/down in speed on each quadrant of the circle. Similarly, it ramps up/down in speed when doing multiple linear interpolations (G01). It just doesn't do a smooth transition from one move to the next and causes the infamous mark on the wall of the cut when it slows down in the cut. Is there some type of setting in TurboCNC that aleviates this, or is that just the way things are with the stock controller box and stepper motors?

[ravin]

did ur slides moter tuning is properly if not then tune the axis of the machine

[phil burman]

You would probably do better posting this question on the TurboCNC forum.

Regards
Phil

Originally Posted by warpedmephisto On my Taig (running TurboCNC and the stock controller box) when I do a circular interpolation move (G02, G03) it seems to ramp up/down in speed on each quadrant of the circle. Similarly, it ramps up/down in speed when doing multiple linear interpolations (G01). It just doesn't do a smooth transition from one move to the next and causes the infamous mark on the wall of the cut when it slows down in the cut. Is there some type of setting in TurboCNC that aleviates this, or is that just the way things are with the stock controller box and stepper motors?

[ger21]

If your G2 and G3 are written for 90degree arcs it will do this, and it will probably also do it if backlash comp is turned on. Are either of these the case?

[warpedmephisto]

Backlash compensation is turned on.

I've been writing my G02's and G03 by defining the new X and Y value, then tacking a Radius specification onto the end. Should I write them using the I & J parameters instead?

[lakeside]

When You Use I And J The Controller Reads It As One Move And On Feed With An R Vaule Your Controller Will Adjusted It Speed To Hit The End Location It The Look A Head Factor

[lakeside]

Originally Posted by ger21 If your G2 and G3 are written for 90degree arcs it will do this, and it will probably also do it if backlash comp is turned on. Are either of these the case?

ALSO LIKE GERRY ASKED IS COMP. ON TRY IT WITH COMP. OFF

[dammachines]

Originally Posted by warpedmephisto It just doesn't do a smooth transition from one move to the next and causes the infamous mark on the wall of the cut when it slows down in the cut. Is there some type of setting in TurboCNC that aleviates this, or is that just the way things are with the stock controller box and stepper motors?

It's not the controller or the steppers causing this, it's TurboCNC. It doesn't have a look ahead buffer or use constant velocity contouring so you get the ramp up/down for each move.

You'll have to switch over to something like Mach2/3 to get it to move the way you want...

Dave

[ger21]

Originally Posted by lakeside When You Use I And J The Controller Reads It As One Move And On Feed With An R Vaule Your Controller Will Adjusted It Speed To Hit The End Location It The Look A Head Factor

TurboCNC will treat I,J arcs exactly the same as R arcs. R arcs can give problems when doing 180 and 360 degree arcs, though.

Try writing your code using I, J and doing full 360 degree moves. With backlash comp off, you shouldn't see the stopping. With backlash comp turned on, the backlash comp is applied at every quadrant.

[warpedmephisto]

So then should I just try to tweak out nearly all backlash out of my X & Y axes and just run it without backlash compensation? That is, if I want to run "quick" arcs that don't pause at every quadrant. I guess that wouldn't hurt much tolerance wise while just doing arcs and circular interpolation moves.

I just want to start doing thread milling with G03 helical moves and not have it stop at every quadrant while milling the entire length of the thread.

[RotarySMP]

Constant velocity contouring has not yet been implemented in TurboCNC, so it will still Accel/decel every G01 sement.

Running high acceleration values (normally requires low starting velocity) normally leads to a faster machine in TurboCNC.

There is a test file on the yahoo groups file section.

[dkowalcz]

There are a few things you can do as a workaround for this:

- Turn off backlash comp.

- Increase the start vel and acceleration for the axes that are interpolating (usually XY)

- Program arcs as quadrants (some CAM programs have a checkbox for this), the backlash comp is faster if it happens first rather than in the middle.

I'm working on a fix for this, as it's plagued a lot of the users.