Zero CNC Experience DIY Plasma table THC guidance needed

[shaolincrane]

So I've decided to add an Ohmic lead before I button everything up. TD mentioned I would need some special kind of filter called a *spopick?* that he couldn't spell for me. Anyone have an idea of what it's called? I plan on tapping into the line inside the machine to keep from having an exposed external wire.

[shaolincrane]

This got put on the back burner with some other shop BS and then my belated honeymoon. I also added a laser.to the shop which has divided my attention but when the laser runs I tinker with the plasma


It was good to see it cut some parts, then melt some consumables. I really need to brush up on the causes of things. It cuts well enough but I get a lot of slag.

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[adbuch]

That looks like a pretty good cut on that thick material, and I agree that it might be time to replace that shield.

David

[shaolincrane]

Is that much dross normal on only 1/4"? I use to cut it by hand all the time and never had much at all.

[acourtjester]

For the dross you may speed things up a little, do some test cuts bumping up the speed until the dross is less. Attached image may show some slop in the drive assembly. Might want to attach a sharpie to the torch for test marking in place of cutting metal to find where the problem is.

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[shaolincrane]

It passed a marker test pretty well. Only that circle cut like that. I made a few attempts since i had various failures and restarted the cut. I couldn't find any slop in the assembly but I did get a little whip at times. I'm going to pack the bearings and see if it helps any.

[shaolincrane]

So I ran another circle cut, smaller this time and it got that same wonky edge. The assembly is very tight, no slop. Any other ideas of what could have caused it? Maybe a generic file issue?

[weldguy]

I think for your slag you can eliminate at lot more of it making sure your cutting at the correct height and dialing your speed in, a little faster may really help with the dross.

As for the edge I doubt it is a file issue or you would have seen that with the marker test unless the marker was super dull.

Does your setup have and auto torch height controller?

Sometimes those can cause vibration and/or oscillation that will create an edge like that if not set up ideally.

[shaolincrane]

Yes, I have auto THC. When I ran it with a pencil, I didn't see anything like it. I tried running it faster but it failed to cut and left a lot of splatter on the top plate. I'll try smaller increments to see if it helps. Sometimes though I get slag in the first half of a piece, but not the second, or vise versa but never the whole piece. I'm starting to lean towards the THC more than anything.

[weldguy]

OK, I suspect your THC is causing the rough edge. With 1/4" it won't really warp so you can try cutting the circle without THC and see if edge quality is improved.

Running with a pencil your THC won't be doing anything because there is no arc voltage and in most cases when a controller sees no arc voltage it shuts the THC off automatically.

If your using Hypertherm plasma be sure your cut height is correct by pausing the machine mid cut and measuring torch to material distance with a feeler gauge and be sure your .065" off the material. If height is not correct adjust it and cut a few more inches and measure again until you get it right.

With the height correct you can now try bumping up your cut speed 5 ipm at a time and find the ideal speed dross is minimal but your still cutting through with ease.

Do all this with THC off until you get things dialed in and then we can turn it on.

[shaolincrane]

I am aware a pencil won't show THC issues, which is why I'm certain there's no slop anywhere. When running with a pencil, everything was sharp.

I'm running a 60a Thermal Dynamics with their machine torch. I was using their recommended settings and it was not even close, they want something like 1300ipm at 45a and it just scorched the surface

[acourtjester]

Whoa slow way down 1300 ipm maybe cut paper, cannot say about TD but Hypertherm cutting 1/4" steel at 45 amps is about 48 IPM.

[shaolincrane]

Woops, I typed IPM but meant MPM. Which is pretty close to the raring for Hypertherm but anything beyond 700 millimeters per minute is very sloppy. Splatter everywhere

[acourtjester]

Another thing you may look at is the torch mount and the cable drape. If the cable drape is to tight it could pull the torch slightly, moving the plasma flow direction. If you can wiggle the torch at all could also effect things like that notch. With a machine torch I liked to have 2 mount clamps for a stable torch, see attached image.

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[weldguy]

I am aware a pencil won't show THC issues, which is why I'm certain there's no slop anywhere. When running with a pencil, everything was sharp.

I'm running a 60a Thermal Dynamics with their machine torch. I was using their recommended settings and it was not even close, they want something like 1300ipm at 45a and it just scorched the surface

Well that's great that you have ruled out slop in the machine. I would still try what I suggested above to determine if it is the THC causing your rough edge. Curious what you find out.

[shaolincrane]

Another thing you may look at is the torch mount and the cable drape. If the cable drape is to tight it could pull the torch slightly, moving the plasma flow direction. If you can wiggle the torch at all could also effect things like that notch. With a machine torch I liked to have 2 mount clamps for a stable torch, see attached image.
4X8 table for sale (4).JPG

The mount is not the best but it's set up like a break away, it won't wiggle, the torch head will just fall. I am planning in changing it at some point but for now I have to deal with it.

[shaolincrane]

I am aware a pencil won't show THC issues, which is why I'm certain there's no slop anywhere. When running with a pencil, everything was sharp.

I'm running a 60a Thermal Dynamics with their machine torch. I was using their recommended settings and it was not even close, they want something like 1300ipm at 45a and it just scorched the surface

Well that's great that you have ruled out slop in the machine. I would still try what I suggested above to determine if it is the THC causing your rough edge. Curious what you find out.

I definitely will, I can generally only run the machine on weekend but I'm definitely going to test it first chance I get. I appreciate everyone's help