Hi folks, I'm new here. I've been through the forums a lot and feel that I already know you guys
As a beginner as well as not being the sharpest cutter in the shop, I was trying to research as much as possible before posting obnoxious questions all over the place. But now I think it's time to bother the cnc wizards a little with my broken English. I posted this at the acorn forum, but since there is a lot of experts on this forum, I thought I'd try here as well. There are threads for this kind of stuff, but it's old or for other hardware.
To the point:
I'm trying to set up a freshly arrived Taig mill and a taig lathe (ballscrews).
I went for acorns, dyn2 drivers and dmm 57n-dht motors (was this a good choice?)
I've searched all over and watched the precious Martyscncgarage videos and got to the conclusion that I should use the 2000/8000 pulse settings for Gear_num and pulse count on the Acorn.
Then I came across this bit of text somewhere on a forum (forgot where, sorry):
So from that I thought I would calculate the best settings for my ballscrew taig, dmm 57n and acorn. And I came up with this:
My taig has 2.5mm pitch diameter ball screw, I want to target a rapid speed of 100 ipm on the Taigs.
2.5mm = 0.0984252 inch pitch = 10.16 rpi (rotation per inch)
rpi x steps = spi (steps per inch on driver)/4= steps per inch on acorn
What ipm max speed can dmm 57n motor take (rated at 3000rpm)?
3000 rpm / 10.16 rpi = 295 ipm (motors rated at 3000 rpm)
I need 100 ipm
100 ipm x 10.16 rpi = 1016 rpm (lots of head room to 295 ipm)
So the motors can take 100 ipm (our target) easy = 1016 rpm (torque is consistent up to 3000rpm)
What maximum steps per seconds can Acorn controller do?
MAX frequency is 400 kHz (you have to set this in the wizard, default is 200khz) so that means 400000 steps per seconds
(the pmw can’t be shorter than 0.8us on dyn2 driver, and from what I understand acorn will give us just a bit over 1us pmw at 400khz)
What steps per seconds do I need at 100ipm (1016rpm)?
1016 rpm = 16.93 rps (rotation per seconds)
16.93 rps x steps = sps (steps per second)
controller 400’000 sps (capable) / 16.93 rps = 23626 steps per rotation are available
motor max steps per rotation is 65’536 (16 bits encoder) but we are allowed only 23’626 from acorn at a speed of 100ipm.
the motor has 2.73 times more res than acorn is capable of.
That's why I can't use the full 65'536 the motor encoder could take.
To be safe, I'll set my encoder settings (pulse per rotation) in acorn at 20480 steps per rotation
on the dmm dyn2 driver (GEAR_NUM x 4) it will be /4 = 5120
and our rpi is 10.16
For more headroom but less precision I could go 4096 and 16384
Does this look correct? or do you see obvious mistakes?
I'm gonna try this and see how it goes, but I'd be happy to see what you guys think about this to help me troubleshoot.
I've read somewhere that when people go over 2000/8000 they get problems even though it should work.
Thanks and Cheers.