Rods "Spaceship" Scratch built Plasma Cutter build

Rod

I think your neighbors machine uses HV/HF start like most industrial machines so yes he should have the local ground rod for the table. You may not need one depending on the amount of moisture in your slab and how well the rebar was bonded when it was poured. I don't need one because the rebar in my slab is welded together for good bonding and then has it's own stranded #4AWG copper wire connection to the buildings ground rods.

John

Well, I didn't get as much time today as I had hoped but I did get the Meanwell isolated 24 volt power supply (with the blue light) fitted so that mains power to it is dropped when estop is pushed.



The blue solid state relay is just sitting there for now but it is triggered when the torch shield touches the work piece. I've got two of these relays (for the Aussies, I sourced them and the power supplies from Ocean Controls).

I rigged this up on the table in a temporary way and hooked a 9 volt battery across the relay load terminals and was able to confirm everything worked as expected.

I figured that I need a couple of IN4007 1000 volt diodes to prevent the torch voltage being introduced into or circuit so I found a couple of terminal strips and soldered them on to a scrap of vero board. Then I remembered i had a current sensing board at home with a DIN rail mount so before I cut the vero board down, I decided to see if I could mount it in the DIN rail mount. five minutes later, I had it all fitted up nice.



The relays don't have any LED indicators on them, so I think I might add a bit more circuitry to this board for some diagnostics.

This looks so neat, I gotta do the same with the other dodgy circuit board that drives my LED power indicator lights. At the beginning of my build, a friend told me to add these for each power supply in the system for error checking and they saved a lot of time today. I inadvertently disconnected mains power the 48 volt power supply driving the steppers. I couldn't work out why I had problems until I check my power diagnostics LEDs and I instantly knew what I had stuffed up!

Hopefully, I'll have most stuff mounted up and working tomorrow.

Well I nearly have this done. Its taken a while which might be why I've been putting it off for ages.

So I've now got the power supply and the relays mounted up


I had a few issues and had some strange voltages floating around the table frame until I consulted my friend Chris who knows about these things so we just earthed the negative power rail of the isolated ohmic power supply to one of the copper posts inside the control panel and relied on contact between the table frame and the control panel where its bolted on.

Then I realised that the solid state relays I purchased were designed to switch AC only so when they triggered, they latched on as there was no zero crossing to turn them off. Grrr. I ordered some more but the company was out of stock so fell back to good old fashioned mechanical relays I had lying around!



So the left hand relay is connected to an output and it switches power from the isolated power supply to the ohmic sensor. When the torch touches the plate, it will trigger the right hand relay which will switch field power to an input for ohmic sensing.

So in practice, we enable an output to say we are probing which enables the ohmic sensing circuit. Then when the torch touches the plate, the signal will reach the ohmic input.

So with a bit of tidying up of the wiring, plasmac here we come!

But before we do, can someone educate me about flyback diodes/? I've heard I should use them to protect the Mesa inputs and outputs but not quite sure what I need to do.

Thanks Tommy. I just had dinner and remembered I left a soldering iron on up at the shop so no red wine for me tonight. I better go and turn it off!

so i think i need to replace regulary the cable
the tables 4 Plasmas in shop are running almost the whole workday
so it is a matter of time to get them broken

Well it too a while but I've finally added ohmic sensing and the plasmac config to my tale and I'm really excited how well plasmac works. It really is quite simple to install if you already have a working config as I described in this thread. forum.linuxcnc.org/plasma-laser/36410-in...her-plasma-component

I was doing it hand in hand with wiring in an ohmic sensing circuit which took a lot more effort than the new config.



So with plasmac all you need is a M3 S1 command and all of the touch off, torch voltage sampling ant THC just happens automatically. Anyway here is a video

Sorry mate for getting the geography wrong. I was just checking you were watching it!

Funny that one of my best customers called to see me today on his way past which was nice. Dare I say it but he's from Canberra too!

Time is non existent for me. It took 2 months to finish the upgrades and I bought everything and made the drag chain support back then too! I really wanted the ohmic sensing working. I'll order some steel now and set up to cut 200 or so small parts similar to what I ws cutting which will save me a fairly expensive laser cutting job.