CNC plasma in scotland

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I am looking at various cheap and cheerful CNC plasma options before i commit to building a full sized machine.

I already have a water table for hand cutting with a plasma which is 5 foot wide and 2 foot long. Yes its an odd size but it is actually an extension for my welding table.

I have many questions most of which i haven’t thought of yet but here is a few.

Is 5 foot too wide for this design? I am thinking it is pushing it but seeing i will be hanging a plasma cutting torch from it which is lighter than a router with zero cutting loads it will probably do okay.

Will the electronics survive being sat next to a plasma?

Do you need a computer near the machine to run it?

Is there any really good idiot guides for the electronics as my knowledge of electronics is roughly. NIL
Heavy electrics i am perfectly happy with but the idea of getting all the electronics together is somewhat daunting.

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You can easily build a machine with a mini rambo from Ryan, series wiring harness and a kit. That will definitely move like a cnc. The lcd Ryan sells has an sd card for printing without a computer. All of that is pretty standard and will go together “easily”.

Attaching a plasma torch to it will require some kind of mount. I don’t do plasma cutting but I guess you want to do some judo while cutting like be at a higher distance to pierce and then bring it down to cut. So there will be some tricks when setting up your toolpaths in CAM for that kind of stuff.

The torch is pretty light and there is no load, but you’ll want the cables to have no resistance when the machine is pulling them. A 5x2’ would probably work. If you’d like to cut wood sometimes, you might instead consider a 2’ wide low rider instead, which would be very rigid. You lose about a foot in each direction to the machine. So if your table is two feet wide, it will end up only one foot wide workspace. There are online calculators for both machines.

The plasma addition is not very common (there are 5-10 posts about it) and not completely explored. Dui’s machine had a ton of emi problems, including smoking a few arduinos. He did manage to get it working with enough shielding on the electronics. I haven’t seen that again. It might be that his plasma torch is especially noisy and others are not. The emi, the mount for the torch, and the cable management are what I would suspect are the biggest risks. But you’ll have to decide if you want to go exploring it.

@Crash85 has just been building one. Maybe he has more input:

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I’m not sure on the width issue. I would think it wouldn’t be a big deal if you are only using for plasma cutting. You’ll have an overhead suspension point with to hold up the plasma lead and the z axis wiring most likely, which will keep weight off the gantry. You can incorporate a spring if needed to lift even more load off the gantry.

I run my machine with just the LCD and SD card. In my best Scottish voice “When I was just a young lad,” I ran a CNC plasma and had a lot of issues having a computer connected and near the machine. So when I started planning out my MPCNC I decided not to run it with a computer hooked up.

For protecting the electronics, I went a little overkill and double shielded everything. Really what you are going to want is a metal box to house the board and power supply, shielded electrical connectors, and shielded wiring. I was able to find some cheap 6 pin metal connectors on amazon, along with shielded 8 conductor braided cable.

Box
Cable
Connectors

The shielding gets clipped back and not connected to anything on the motor/endstop ends. But on the end where the cable is soldered to the connector, you’ll make sure the shielding wire contacts the metal case of the connector. That allows any emi generated by the plasma to travel down the shield wire, through the connector, into the metal enclosure (which you will ground to a grounding rod or through the electrical supply. (I use an Estop to kill power to the entire machine, so I bonded the ground to the case at that point.)

Estop

You can use a relay to trigger the torch, and some gcode to ensure all the timing is correct when it comes to light off, pierce, cut, and cut completion. (That’s currently what I am working on, but it’s not difficult.)

Relay - Not available currently, but there are a bunch of other suppliers for the same thing

As for plasma machines and machine torches, I went just about as cheap as you can (which generates the most EMI) and got a CUT50P off of Amazon along with a machine torch that took about 6 weeks to get from China. (If you order a machine torch, go ahead and order a package of consumables as well so you have them on hand instead of waiting an additional 6 weeks!) The pilot arc is a must have in my opinion, because you don’t have to scratch start.

Plasma Cutter
Hand Torch Consumables
Machine Torch
Machine Torch Consumables

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For a plasma cutter i already have a hypertherm powermax 30 which is excellent

But you can’t fit a machine torch to it without some butchery

So the plan is to use that for a while before eventually upgrading to a powermax 45 with a machine torch and a hand torch

As a plasma cutter is great for making awkward bolts go away

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