Acceleration Adjustment

[Justin Wiebe]

Have any of you adjusted your acceleration for 3d carving? I want to see if I can possibly speed it up a bit. I do a LOT of 3d carving. It's where I make my money, so even a moderate increase in speed is worth some effort on my part. Here is what my Z axis currently is set at:

[*** Z Axis ***]
axisspec=p3 r4062.976 o0 a400 f150 e1 t3
axisvel=r400 f350 s20 m50 h200 c7
axishi=p3 b1 o0
altaxislo=p3 b2 o1

I'm wondering if I should be increasing the "f" parameter in the top line, and I'm also wondering if there is any advice for an increase to the "a" parameter?

[Charlie_L]

Not enough acceleration experience here to answer your questions.

I assume you are already cutting your designs with feed rates for x, y and z all set the same. Like 300 inches per minute. If not, start there too.

[DVE2000]

It's really unlikely he'd be getting 300ipm with the conservative/low acceleration that CAMaster sets. Acceleration is inches per minute per second, so if it's equal to the feed rate - say 300 ipm and an axisspec of f300, it would take a full second to get to 300ipm. That's just too slow. You could set it to 600 ipm/s (f600) and then it would take half a second to get to 300ipm. The problem is that you can easily lose steps with steppers over servos. If you're making money off your machine, it's worth doing some experimenting. Set the accelerations all to double the xyz feedrate for all axes and do a carving. I think the chances are that your machine will become more inaccurate as the carving proceeds. But you won't know until you play with them. Speed may be more important than accuracy to you, with what you want. Just park and home between jobs. You probably want to shoot for 190 ipm for 3D carving.

With the acceleration of f150, it would take two seconds to get to 300ipm.

I experimented with rapids on my upgraded machine, and I could get it to 800ipm in about a quarter of a second for rapids. I lowered it, because it's harder on the machine and I don't want to start snapping belts and stuff.

[Justin Wiebe]

Thank you for that info. I do have servos and I am doing carvings that end up getting glazed to look as if they are old so it really doesn't need to be super accurate in this case. Do you know if I need to adjust the axisvel line? Or just the axisspec? And do you know how high you went in your experimenting? I was thinking of changing the axisspec to f400 and then setting all the axis speeds to 200ipm and see how it works.

[DVE2000]

I haven't cut any hardwood since I've upgraded my machine. That should change this weekend, so I'll get to see effects. But if you have servos, I'd think those numbers are way too conservative. axisvel specifies the maximum IPM you can specify. You really should read the WinCNC manual. Everything is pretty much there, even if it's not always easy to understand.

The math can start getting a bit involved to convert from max motor RPM to IPM. I also don't know the model of the servos you have (and they're probably ClearPath) so I don't know their max RPM. I also don't know the diameters of your pinion gears or the ratios of your belt pulleys. FWIW, I currently have f350 for my max ipm on XY and acceleration of 700 ipm/s. I have 210/420 for Z feeds. You can start off with acceleration being twice the ipm. I'm a lot more aggressive on the acceleration for rapids, and the theoretical max speed of my XY (with the motors I have) is 830ipm. I've set it to 800. Don't need to max out the motors. My z rapid feed is 270ipm. It's around 95% or 98% of the max motor speed. Can't remember. But again, these are for MY motors. They're among the slower 342x motors, but they have the most torque. (I can rapid xy across my table and hit esc. Machine stops immediately on the abort without loss of position. Tested many times.)

[james mcgrew]

Make sure you back up your entire wincnc folder in a safe location !

[Justin Wiebe]

Ok thanks, it does help just to see some other numbers for reference. I have been digging into the Wincnc manual, and yes I do have a second copy of it all backed up to dropbox.