Router Build number 2

[Neale]

how is the CSMIO/IP-M now with dual motors? I know there was talk about it a few years ago

I was one of the people asking about it, because I was trying to decide whether to go one big motor/long belt or two motors, one per ballscrew. In the end, I went the two-motor route with an IP/M. There are probably two issues - initial homing and keeping sync when running. Second point first - I have had no problems with the two motors staying in sync when all is running well. I set up the IP/M as per the manual and it does what it says on the tin. I use EM806 digital drivers with stall detect and they trip if one motors stalls (which has generally been when I've been pushing the machine a bit). Fault signal goes to safety relay which signals IP/M and everything stops with no damage.

Now - homing. I spent some time initially squaring the gantry, using the "four pins in a square and measure diagonals" method. I have inductive proximity switches as home switches on both ends of gantry; one is wired to the IP/M and the other is not. Well, it is really but not configured in Mach3. When machine is first switched on, I home all axes as usual (configured so X and Y home simultaneously to save time). I then hit estop which cuts power to motors. I tweak the slave axis pulley by hand, simulating the Mach3 homing process and watching the led indicator on the switch. That is, I wind the screw until the light goes out, then slowly wind it the other way until it relights. Reset estop, re-home just to make sure (only takes a second or two) and I'm set to go for the rest of that session. Unless estop is triggered for some reason I never go through the manual process again for the rest of that session; on the odd occasion when I've checked it's been bang on. Generally it's close enough even after shutting down and restarting later. Because of the motor cogging effect, I'm probably no better than the nearest full step doing this. So, that's to within 0.025mm at the end of a 1000mm gantry. Probably good enough for a machine used primarily for wood.

I've thought about adding a little bit of complexity which would do a proper master/slave homing job. With a lesser motion controller with the usual 5V single-ended signalling this would be easy but the IP/M lets me use differential connections to the drivers and 24V signalling which complicates putting an extra bit of electronics between the two. On balance, I would rather keep differential signalling and the manual homing. And yes, I know it's not that difficult to put the electronics together, but it's more effort than just sticking an Arduino board in there. Or I could have spent nearly three times as much for an IP/S...