Following a brief mention by Jazz in a different thread, I had a look at the CS-Labs website where they say that the CSMIO/IP-M now has slave axis functionality. They also say that it does not include full gantry geometry correction (which the CSMIO/IP-S does do, at about 2.5x the price!). I have mailed them to see if there is any more information available, but this looks like an important enough development that it deserves a thread of its own.
My new machine has reached the point where I am thinking about an external motion control card, as well as alternating on a more-or-less daily basis about whether to go single motor/twin belts or two motors for X. Even if I go single-motor now, I don't want to get a motion controller that stops me going 2-motor at a later date if I feel it necessary. If I were happy with single motor then the IP-M would be my choice, but if it is single-motor only, I might look at alternatives (ESS maybe? Does that do slave axis homing properly now? Pure Logic PLCM-something?). This new development might solve the problem - IP-M can do both, has 24V operation for good noise immunity, decent opto-isolation and other nice features including spindle speed control on the same board. I'm guessing that there are others out there in a similar position, or at least thinking about upgrading to an external motion controller.
I've had a look at the IP-S manual to try to second-guess what the lack of gantry geometry correction might mean. As I understand it, the IP-S can do a calibration run where it homes both axes, measures the offset between home switches, and builds this into the configuration parameters. The user can then tweak the offset value to fine-tune for squareness, etc. Maybe the IP-M will lack this calibration capability, which means manual adjustment of home switches? Don't know - but would like to! It looks as if the IP-M manual available online hasn't been updated with this new functionality yet.
I shall post any more information received from CS directly, but would like to hear any other comments or information or especially experience of playing with it in this mode!
The Following User Says Thank You to Neale For This Useful Post:
28-11-2014 #2Spelling mistakes are not intentional, I only seem to see them some time after I've posted
Eddy - how do you cope with the possibility that the steppers lose position when you switch off, so that possibly the gantry goes slightly out of square each time you switch on? Or do you square it manually somehow from time to time? I thought that that was the advantage of two homing switches. Or does practice trump theory, as is often found?
I think you need two homing switches. I use the Pure Logic PLCM-something from Zapp and it home very well with the two switches but I have to set it up by adjusting one of the switches to get the gantry squaring correct, after that it sorts its self out at every home position. ..Clive
I would agree that programming an Arduino (just because I know that one) would be pretty easy if all I wanted to do was measure offset between a couple of not-quite-accurate home switches. I haven't thought through the details, but I suspect that that is only simplifying what is not a particularly difficult task anyway. Measuring gantry squareness seems like the biggest issue rather than tweaking switch positions and that's common to all setups. However, I'm not sure that I could use those values in any of the usual solutions, so the straight hardware-based "tweak switch until dual-homing leaves the gantry square" solution seems inevitable.
I currently use LinuxCNC and I've had a look at that from the point of view of dual-motor homing and operation. It seems somewhat incredible that with all its users, there still seems to be no official solution to this particular problem. From what I see and read, it seems to be bound up in the internal representation of a machine which makes a generalised solution very difficult, although I did wonder if a custom job for my particular machine geometry might not be possible. Still, at the time, the latency of my garage/CNC PC was such that an external motion controller looked like a good option for my Mk2 router, despite needing a move to Mach3. Then the motherboard went pop a week or so back, and the cheap replacement is performing much better, so I'm just confused.
Stay with LinuxCNC? That forces me to single-motor/twin belts, but I probably now have sufficiently low latency figures that I can get reasonable performance. Dual-motor? That means Mach3 (or one of the dedicated hardware/software combinations like PlanetCNC). What I don't want to do is invest in kit that limits later options, at least not unreasonably, and the CS Labs boxes seem to have a decent reputation from the point of view of reliability, etc. Hence the interest in this new IP-M development.
So Neale what you do normally when you start your machine? Bump the gantry to some gantry hard stops as a dedicated Linux user?
Its seems incredible, but its the same with Mach3. I am sure half of the motion control plugins are not capable of it or are very obscure. Mostly cause people who write them have mills and dont have a way to try it or think that all people in the world use servos with absolute encoders.
The way i see it it is a must for steppers.
No, my current machine doesn't even have home switches, so I'm not exactly pushing the limits of LinuxCNC!
I know that LinuxCNC does not support master/slave motors; thinking about it, I've never looked at whether or not Mach3 supports this natively (via parallel port, no motion controller). Is this a capability that comes from a motion controller, not Mach3?
So what you need is someone with a IP-M to test this for you.!!. . . . . Ermmm
Well It just so happens I know a guy, who knows a guy, who's got a friend who knows a Gal, who's brothers got a couple sitting around doing nothing. .
Ok I'll try and test how it works for you. Not got a dual axis machine in a build state to test just at minute but I'm sure I can Rig up something to test how the motors sync and home on the bench.!. . . . Leave it with me a few days(weeks,months,years!!)
I've Nagged CSlabs brains out for this option since I started using these and it was mentioned that it couldn't be done due to hardware restrictions so I'm intrigued my self.?
I suspect it will work just like any other mach3 motion controller in that each motor just hits the switch and backs off. The IP-S works the same with steppers, thou it can HOME using the Index signal of servo encoders or if shaft encoders are fitted, where the IP-M can't do this I believe.
The IP-S also has an option to measure the trip error between switches and correct. This works very well because I tested it the other week using dial gauges and setting a large error. It brought it back perfectly to within 1000's/mm.
It also the option to measure and Not correct the error just display error in the plugin.
Know to me the this is useful but not like your probably thinking.? It's useful to me for setting the switches accurately as it works out the error between them so I could set the gantry square without twisting the gantry to make square, Which you don't want or need too ! . . Now I'm sure Golden Balls could easily do all this with the Pic up is arse.!! . . But I'm into using machines which means I want a quick way to set the machine accurately and forget not thrashing the few remaining bits of gray matter or pulling my Togger over capabilty's of Pic.!
I'll most a Vid if I get time.
Last edited by JAZZCNC; 29-11-2014 at 10:51 AM.
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