CNC Mill with EMC2

[slizynski]

My teacher has a Lab Volt 5600 CNC Mill and asked me to hook it up to a linux box. I installed the Ubuntu 6.10 distribution with EMC2 pre-installed and I have it connected via serial port. Upon starting the EMC2 software I was asked to choose a default configuration. I have no idea what to do, I've never worked with any sort of CNC machinery and I have some limited experience with Linux. Can anyone point me in the right direction?

[daedalus]

Do you mean serial port there, or printer port?

[slizynski]

It's a serial port. He already had it connected to the mill, so I just used that.

[acondit]

slizynski,

Generally speaking, EMC2 is really not setup to run via serial port. If you really want to convert this mill to run with EMC2, you will need to determine what signals are needed to activate its drives, bypass its on board computer and interface (through a parallel port) to its drives, switches, etc. It is probably not an overnight job.

Does it use servo drives or steppers?

Alan

[daedalus]

acondit is right, to be honest unless you want to stick with the software that comes with it you will need to do some rewiring. Worst case you may have to upgrade the drives.

If you can open the casing and take some photos of the controller / drives and post them here, we might be able to help identify whats involved.

[slizynski]

The mill has a parallel port connection so I could ask my teacher if he has a cable and hook it up to the printer port. Would that work?

Edit:
I was mistaken, the mill doesn't have a parallel port. I found a serial to parallel adapter so I connected it to the printer port on the computer. Will this work.

[acondit]

Originally Posted by slizynski The mill has a parallel port connection so I could ask my teacher if he has a cable and hook it up to the printer port. Would that work? Edit: I was mistaken, the mill doesn't have a parallel port. I found a serial to parallel adapter so I connected it to the printer port on the computer. Will this work.

The quick answer is no.

The reasons that the parallel port is required relate to the speed of actions and reactions that is required and the number of signals that must set by the computer (outputs) and monitored by the computer (inputs). For a stepper driven system the computer must flip signals for each step that a stepper takes (on, pause (very short), off or off, pause, on depending on the polarity that the driver requires. So on a three axis mill that potentially means three different signal pins being flipped up to several thousand times a second. If it is servo driven the signals can be even more complicated. Most of the guys who work on emc2 say that a serial protocol just can't handle the load (although there is an ongoing discussion about the possibility of doing down the road with ethernet).

Most serial to parallel converters won't even come close to generating the signals needed to emulate a parallel port for this use. You don't want to have a mill hit a limit switch at high speed and not have the controller respond immediately.

And, finally, if the machine expects serial input to communicate with an on board processor, you would need to know what the software interface between LabVolts software and the on board processor is like. This would basically require a serial line monitor to trap the communications stream and reverse engineer the protocol. I have done this before and believe me it is not an easy task.

Alan

[daedalus]

Acondit is right, it isn't practical to use the current serial port protocol in EMC or mach, you need to interface to the mill in a different way. This doesnt have to be an expensive change, but you will need to assemble / buy a few pcbs, and do some wiring.

The safest way to proceed would be to build a seperate controller, with 3 stepper drives and a parallel interface. That way you would just plug the stepper motors into the new controller to use emc/mach, and if you ever want to go back you can just hook the motors into the mills internal controller again.

To do this you will need:
a parallel port breakout pcb
3 stepper drives
a power supply for the steppers

Assuming you need to do this on a tight budget, and you have the ability to etch some simple pcbs, then i would look at the following places for parts.
http://www.cnc4pc.com breakout board
http://www.fromorbit.com/projects/picstep/index.php stepper drives

[acondit]

Originally Posted by daedalus Acondit is right, it isn't practical to use the current serial port protocol in EMC or mach, you need to interface to the mill in a different way. This doesnt have to be an expensive change, but you will need to assemble / buy a few pcbs, and do some wiring. The safest way to proceed would be to build a seperate controller, with 3 stepper drives and a parallel interface. That way you would just plug the stepper motors into the new controller to use emc/mach, and if you ever want to go back you can just hook the motors into the mills internal controller again. To do this you will need: a parallel port breakout pcb 3 stepper drives a power supply for the steppers Assuming you need to do this on a tight budget, and you have the ability to etch some simple pcbs, then i would look at the following places for parts. http://www.cnc4pc.com breakout board http://www.fromorbit.com/projects/picstep/index.php stepper drives

I looked at the LabVolts site. If the mill is a new mill then I would not convert it to steppers if it already has servos. You do need to find out what kind of motors and drives that it has on it before making any other decisions.

It may be an extremely easy matter to convert to EMC2 or it may take some serious work. You need to determine what kind of motors and drives it has to have a clue about what is required.

Alan

[daedalus]

Alan,
From looking at the site i was under the impression that the Lab Volt 5600 CNC Mill was stepper driven. http://www.labvolt.com/display_left....84&view=topics mentions this in the description.

If that isnt the case i did not mean to suggest changing to steppers.

[slizynski]

The mill is stepper driven, so that means I have to make a seperate controller?

[daedalus]

You might not HAVE to make a seperate controller, but it would be the easiest route to take, as you dont have to spend any time figuring out how the old one works.

If the mill has discrete stepper drives inside it, you could reuse them, but without a photo or two of the insides i have no way of telling. If the mills current controller is just a big pcb with 3 stepper drivers integrated and a microprocessor, then the only thing you will be able to salvage is the power supply (i suspect this is how it will have been built).

The other issue is that if this mill is currently working (with the old software), building a seperate controller means you dont do anything irreversable.