Yeah… it feels funny converting the input voltage to a frequency, only to be converted back to voltage at the controller. Though I figured this has to do with safely isolating the plasma from the electronics. Would frequency readings be more accurate over a length of wire than voltage readings due to voltage drop, emi, etc?
Lots of extra bucks. A “real” THC would be at least 3x the cost, though I have no idea what shipping would be like going to China. But, with the Mesa cards in hand, these things are the real deal! I’m used to handling cheapo imported boards and this ain’t that. I just wouldn’t want anyone to have the impression that we’re cheaping out on quality.
Integrating THC into an Arduino controller would be a very cool setup. It would really lower a few barriers to entry.
Yes. Anything that depends on the edges of a digital signal would be more resistant to emi. Even duty cycles, measuring the time delta between a rising and falling edge will be affected by emi, triggering a little early or late. CAN bus uses a differential signal for high noise environments (cars and trucks), and the signal is digitally encoded.
I’m not sure if Marlin can read that signal fast enough. 1MHz is fast enough to be trouble. I’m not great with embedded software, but I am guessing it would at least be a sacrifice of an interrupt, which are often hard to come by and pretty hardware specific.
You could put a slave arduino to read the frequency, and send it to the marlin one, and put them both in a metal box. That’s the simplest solution I can think of ATM.
At the maker faire this year lightburn is now controlling there nozzle height with an some sort of range finder. I know plasma has a lot of sparks and smoke, but so does laser, well fire. Maybe have a look at there page and see how they are doing it. The setup seemed to work really well. Maybe a full time induction probe, laser range finder?
I would assume a proper shielding of the cables and enclosures could be enough to get readable values, with a little filtering. I don’t think you need insane accuracy here, the cutter will work fine between a couple of millimeters. It will impact cut quality a bit but as long as it cuts you can still massage the part a little with a grinder to get proper finish later.
Well here in China you can find THCs for around 100-120 bucks. No idea if they are any good but it’s not that much more. Plus you’d need some kind of interface to convert the signal from a frequency to a voltage, so that’s another Arduino (not very expensive, but still) and some more complications/cause of failures harder to diagnose.
I’d rather prefer going for an easier DIY solution, if possible. I’m pretty sure it is doable with a few basic components for a fraction of the cost, but I’m not good enough with electronics unfortunately. This guy seem to have made it, but I’m not clear enough on his circuitry. I tried to reproduce his circuit on Falstad but it doesn’t seem to work fine, so either Falstad doesn’t work well (which is sometimes the case), or I did something wrong, or either his circuit doesn’t work… I don’t really want to find that the hard way…
Anyway, that’s not for a soon future, I’ll have to move out of the place I rented those past years so that will be a big stop to all my projects for a while…
The length of my z tubes gives me about 4 3/8". I know the 611 plate and depth of the torch will reduce that. I’m just trying to decide if I want to rig up z homing switches and if so how much travel I can afford to sacrifice for it.
My Z axis tubes are 14" long. The bottom of the water pan sits 1.5" below the lowest point of the 611 plate (was designed to have 2 3/4" pieces of mdf for a spoilboard bring it back up to the zero plane. My pan is 3" tall, and I clear it by maybe 2"? It’s plenty of Z travel, I wasn’t worried about losing any rigidity with extra Z because I wouldn’t be cutting at that height anyway. I have induction sensors mounted to one of the Z tubes and it homes to max Z. It senses off of one of the bearings.
I’ll see if I can grab a picture in case I haven’t already.
Hey, just fyi, make sure the water pan is dry before throwing the MDF on top. I just threw away a little cutting board because it was sitting in the sinc over the disposal for a week. Shaneh was out of town, and I don’t cook too much when she’s gone, so I didn’t notice it sitting in there. The moisture in the disposal started the cutting board to mold on the bottom. ?
So I was getting around to looking at your ini file, I see you had the max velocity set at between 1 and 20 ipm depending on the axis. I thought that would prevent any speeds as fast as 300 ipm. How does that work with linuxcnc?
Those settings are inches per second. Under [Traj] I have MAX_LINEAR_VELOCITY = 5 which would be 300 ipm. Not sure why I used the values I did for the individual axes, I never really fine tuned them. I was happy with how it was working
@uthayne Dear Bryan. I found your great Plasma cutter while searching through the forum and must say I am impressed by the quality it delivers. You really did a great job building it. I fear to start building a LowRider2, because of not being expert in terms of programming etc., but hope you can guide me to achieve the same quality.
Thanks, Bastian. It’s been a lot of work along the way but I’m happy with the quality coming off of the table. Tons more to finish, but that’s part of the fun (if I even cut a few parts along the way, even better!).
If you follow along with the setup I’ve chosen (Mesa hardware with LinuxCNC), there’s really no programming at all needed. At most you’d be editing a few configuration files, but it’s getting even easier by the day to get into plasma cnc. I’d say go for it, but only if you’re ok with tinkering along the way. I’d be happy to help if you use this setup. I don’t have any experience with Marlin/GRBL for plasma applications, nor would I recommend it.