Hi all,

Finally got my machine integrated and I started testing it. (ESS, Integrated Servos, M4)  I noticed that there is a significant lag while jogging (it is very easy to overshoot and hit a limit).  I have 2 ways to jog my machine and they both have the lag (an XHC USB pendant and a joystick style 4 position switch that is connected directly to ESS inputs).

I would expect the USB input to be laggy, but the I/O pin switches should be instant, right?  They have about the same delay (1-2 sec!).  This leads me to think that there is a delay setting hidden somewhere that I'm unaware of.

Where should I look first?   

There are two jog modes and they behave differently.

If you are in Incremental jog mode, you can expect jog movement to begin promptly, but possibly overrun on stop if your input has caused lots of incremental moves to queue up.

In Continuous mode the jogging will act more like the accelerator in a car. Response to stopping will occur faster but motion will not be directly tied to the number of increments.

Ok, thanks.  I’ve been using incremental with the pendant and continuous for the joystick.  That makes sense for the stop.  What about the start?

Start should normally be immediate in any mode.

I would check your acceleration rates on the motor tuning tab.  The higher the accel value, the faster the machine responds without having to "spool up and down". 

Also on the MPG tab. 

My xhcMPG is smoking responsive.

Steve

Ok.  I’ll take a look at that.  One difficulty when working in metric units is that many of the default values are still set in imperial units (ft/min is very different from mm/min!) and i haven’t found them all.

My servos are set to 30,000 pulse/rev with a 6000 counts/mm, a velocity of 5000 mm/min and an acceleration of 250 mm/sec^2. 

I haven’t played too much with the acceleration, but the ESS can’t keep with much faster movement.  (Which is pretty scary as it gives the gantry leadscrew some serious whip, even after pre-tensioning)

What do you think is a realistic place to start with the acceleration?

The G force field is calculated based on your accel entry and should be units agnostic.  Mine ends up being 0.19426428 for comparison.  So keep raising your accel until you get around that number.  Should be around 1900 mm2 per second if my math is correct.  If not, just keep raising the accel value.  Now, it may not be right for your machine.  My machine has 400 watt DC motors that are pure torque monsters and 35mm ball screws capable of super high accelerations.  But basically, you will want as much accel as your motor/drives/machine will let you have.  If you are getting screw whip, then that may be your limitation. 

Steve

Yea, i have 180w integrated servos in this build.   Dual Y axis, built to cut 2ftx4ft.  I have 18mm ballscrews on all axes, now i’m thinking that the X (gantry) screw which is about 5ft long needed to be beefier.

My plan is to upgrade to 5 axis with a new gantry once i have the kinks worked out. 

I’ll be at the machine again this weekend so i can up the acceleration then.  The Y axes can definitely handle some acceleration but the X may need some tweaking.

Thanks.