Setting up a plasma cutter and looking for some help.

I used the Torchmate AVHC for Zaxis control for years and as Rod says it will not work correctly with the PlasmaC branch without serious hacking. Further more depending on the actual firmware version you have the cornerlock feature may or may not work even though the input is there. If you still really want to use the TM lifter assembly (Z axis mechanics and drive) the very expensive Smartmotor on it can be programmed to work as a simple step and direction drive like your Clearpath servos. The TM lifter is a POS really so build or buy a better one.

Just spend the money and buy a Mesa 7i76E and THCAD boards, you've already splurged on good servo motors. In the end you will be much happier with the results, actually no comparison really. Did I say the TM AVHC system is a true POS compared to the PlasmaC standard?

John

So I think where the steppers will restrict you is on the maximum speed. Looks like your servos can get up around 2800 rpm (vs 750 rpm I work on for my steppers). You want to be able to get up around 800 inches per min but if your motors can go faster, try and use the max velocity and acceleration you can without the machine shaking apart.

I thought I saw someone say parports were going to max out at step pulses at about 50 kHz and the Mesas are good for 10 mHz (subject to other constraints re pulse timings). So I suspect using a parport is going to significantly limit both the top speed and the number of pulses per rev.

Do some tests and see how fast you can get it going and compare with what the Clearpaths are capable of. Then make the case to your boss about the hardware becasue with plasma velocity and acceleration are king! The faster you can accelerate into and out of corners the better your cuts will be.

Use the parallel port, make it work, later you can upgrade to Mesa. Same for the speeds and velocities, make it work, see if you can live with it, make a decision later, after you get tired of waiting from one cut to another !
But, take Icelanders advice very seriously, although i have never used that exact lifter, i had my fair share of "industrial" stuff on plasma machines that now i do not bother to think about them, throw them, make new simple ones and move on. If you need ideas, there are some on this forum, check the build logs, we have made plenty of them.

You say that you have two axis moving now. What type and thickness of material do you want to cut? What speed and acceleration can you get now? If you don't have a working LCNC configuration how are you testing you axis servos? Did you have the Teknic's sales engineer size your servos for you? If not you most likely didn't get the correct size for your table, it is much harder to correctly size servo motors for good performance than steppers. They may work now but the overall performance will never reach a servo driven systems potential.

John

islander261 wrote: You say that you have two axis moving now. What type and thickness of material do you want to cut? What speed and acceleration can you get now? If you don't have a working LCNC configuration how are you testing you axis servos? Did you have the Teknic's sales engineer size your servos for you? If not you most likely didn't get the correct size for your table, it is much harder to correctly size servo motors for good performance than steppers. They may work now but the overall performance will never reach a servo driven systems potential.

John

The motors are oversized torque wise as compared to the original ones allen bradly had on it. It has been a while so I don't recall the exact specs of the old motors.

Long story short we started this project back mid 2018 when we got the motors. Due to several reasons the motors got physically installed but the project got abandoned until I got back on it about a week and a half ago.

A bit of history on the machine. At one point it was a water cutter with an Allen Bradley control.(Bubble memory anybody?) At some point prior to my joining the company in 09 it got converted to a plasma cutter. It was using a Delta Tau PMAC ISA board connected to the original DC servo drives. This worked but was always cludgy. Well the drives started dieing and I could not get them back working. Cost wise it seemed better to just get new motors and start over. I could not make heads or tails out of the pmac board and decided to go with something like linuxcnc or mach3 or the like.

Thickness? Not sure but the plasma side of things worked fine for our purposes when it used to run. And unless something has broke in the ~5 years it has sat it should be fine.

As for speed it is currently doing way more than we will need. Don't see why accell is not as well but can't guarantee that.

I have a working configuration so much as running the step config tool as an xy machine and getting the step/inch dialed in. Linux cnc will move the machine just fine. Still have to get limit switches wired and the plasma side of things wired to LCNC but that should be it.

One note. The clearpath servos have an auto tuner that you run once they are installed. As I understand from other threads around here this is fine but using the rest of the software side of the motors kinda goes against LCNC's purpose so I am just using them in S/D mode. Still better than steppers for both torque and position as assuming the steps make it to the motor it won't loose them.

Sorry for the rambling. I keep re-reading your post to see if I missed a question and have answered them all out of order.

islander261 wrote: I used the Torchmate AVHC for Zaxis control for years and as Rod says it will not work correctly with the PlasmaC branch without serious hacking. Further more depending on the actual firmware version you have the cornerlock feature may or may not work even though the input is there. If you still really want to use the TM lifter assembly (Z axis mechanics and drive) the very expensive Smartmotor on it can be programmed to work as a simple step and direction drive like your Clearpath servos. The TM lifter is a POS really so build or buy a better one.

Just spend the money and buy a Mesa 7i76E and THCAD boards, you've already splurged on good servo motors. In the end you will be much happier with the results, actually no comparison really. Did I say the TM AVHC system is a true POS compared to the PlasmaC standard?

John

I am definitely going to look into getting a motor for the lifter/repurposing the current one. Everything I find + what you are saying leads me to believe it is not the greatest.

The mesa thcad board looks real tempting. Not sure if I have to get the i/o board. Maybe. I likely have the stuff to add a second parallel port for the extra I/O if I need it.

One random thought and a quick search later.
Ok so it looks like the Torchmate AVHC actually sells for a fair bit on ebay. Selling it and going the mesa route sounds better and better. Now to figure out a good lifter and motor here.