Here at work we have an old, 1996, plasma and torch combo. We bought another plasma table around 2004 and quit using this one, only using the torch on occasional jobs over 1 inch mild steel.
For the past 4 or 5 years we only used this machine as an “auto” aluminum annealer so you dont have to stand there with a torch.
About a year ago the controller went up in smoke, well I want to make this hunk of metal move again.
I dont need any plasma or torch control, I just need to be able to move the torch head around.
Im not sure if the servo motors on this thing are any good and I dont want to use them.
Even as dirty as this thing is right now, with the rack and pinion disengaged it rolls really easy and smooth.
I dont need it to move very fast, 20mm/s is plenty and it wont have any extra load being put on it.
So Im wondering if a Nema 17 or if need be a 23 would move this thing. Pushing it feels like no more force needed than to push my lowrider.
Would the 33.9:1 reducer work?
If the reducer is fine then it will be just a matter of mounting the stepper where the servo is now and making the pulley on it fit on the stepper.
Firmware is something I have no idea about, Ive flashed it, Ive ran PID tunes and entered them and stuff but Im not sure where to start with this.
Looks to me like you are on the right track, but you really need to understand what amount of load you’re going to put on the steppers. Try this, get hold of a fish scale and pull the machine through it’s movement range. That should give you some idea of what force is needed. The bigger Nema 17 motors can handle 75 oz-in or so of torque, you need to be able to accelerate the weight to speed and decelerate from speed. If you can’t find a Nema 17 that’ll do it swap to Nema 23s and put standalone drivers in place instead of using the RAMPS.
The reducer adds some complexity. It has a 50rpm limit and reduces it 33, that seems really slow, you will have to figure out the rest of the gearing as well. Nema 17s love the slower RPM ranges (60 and under) so that is a plus, I have not looked into the 23’s though.
That looks like our big Lockformers we have at work… If its similar to those, theres no way those little NEMA 17’s are going to move that thing around. The servo motors on ours are pretty big… The gantry itself is pretty heavy. Seems smooth because it rides on bearings or something but its actually pretty heavy (I know this because sometimes it goes nuts and falls off the track and tries to cut itself in half and we have to lift it back up)
So I decided to go with a 269 oz Nema 23 with a super simple arduino nano and tb6560 driver setup. I only bought one for now to test and it is a success. The reducer has it going slow but it is fast enough for my needs. It goes a little bit faster than in the video, I jumped up the rpms after taking it. Put it on the Y side and it worked too, still has pretty good strength too, takes a good bit of force to make it skip steps.
About to order the rest of the stuff, Z axis is going to be neat, I’ll take a picture of it when I get a chance. Its like something Ryan would come up with.
Oh yeah, does anyone know a raspberry pi based grbl controller? Or something of the sorts to control this thing? Right now Im using estlcam from a windows tablet.
I use the prontoneer piCNC board, which is basically an Arduino nano with grbl and breakouts for motors on a pi hat. IIRC, he also sells little expansion boards for connecting to external drivers via the drv ports. I’ve had good luck with it, and the image he has also set up bcnc and CNC.js. ready to go.
Do not use reducers, they will introduce backlash.
You can, either:
-Use bigger motors, apparently you bought a NEMA 23, seems ok, but next time if you are not sure about power, then go for the longer versions. The longer they are, the more torque.
-Find a way to use two motors instead of one, using some kind of pulley system or anything more suitable.
I would do anything to avoid using a gearbox if I were you, unless this is a very nice and fancy one especially designed with backlash compensation in mind.
I dont need this machine to be super accurate, I pretty much just need it to move. The only reason I am using the gearbox is because with it mounted with the pinion for the rack it takes just making a simple motor bracket to mount the stepper and move, otherwise I would be making a lot more brackets to get this thing to move.
So I got the Raspberry Pi board in and got the motors moving with bcnc, I like it.
I gutted the machine of all the old wires and stuff and cleaned it up a little, she hasnt rolled this good in many many years.
This weekend Im taking home the old control box and 3d printing brackets and mounting all the new electronics in it. I need to keep the 24v power supply seperate right?
Ill hopefully have some more pictures and videos next week.
95% of the way done. The Nema 17 for the Z is just barely not strong enough to hold the head up always, it slips every once in a while, so I got a Nema 23 coming for it.
Im getting 200 inches per minute on the x and 150 for the y, not bad at all. Had a video of it rapiding around but dont know what happened to it.
This video is what we will mostly be using it for, except I line up and 5 of these parts and it goes back and forward to aneal them.
