Help With 375 Plasma Cutter

[mingy]

Hello and thanks in advance.

I got a Spectrum 375 Plasma Cutter and am trying to learn how to use it. The manual is pretty useless: I know warnings are important, but there is maybe 2 pages on using the darn thing and they really don't tell you much.

Anyhow I set up at 240 volts and tried to cut a piece of 3/16" Aluminium Rather than a nice clean slot like cut, I end up with a dirty, splattery cut that doesn't reall separate the pieces. It looks like the material sort of freezes back in place and the underside is real messy.

I have to be doing something wrong, but the manual is pretty silent on technique. For example, they say

"For maximum cutting speed and tip life in non-shielded applications,
use a standoff distance of 1/8 in (3.2 mm). Dragging tip will reduce
tip life for non-shielded applications.
For maximum cutting speed and tip life in shielded applications,
place the drag shield directly on the workpiece."

But they don't explain what the heck a "shielded application" is.

Also, there is a current knob, but they don't explain how to adjust it, they just provide a table that shows cutting speed with various thicknesses of mild steel at two settings of the knob.

By the way, I am using the non drag cup because a drag shield did not come with the unit.

Any suggestions?

[jjsjeff]

Did you try cutting at different speeds?

[fun4now]

i'm just guessing here but it sounds like you need more air, or slower cut speeds. if you have proper current for the cut, speed can make a huge difference. try a changing speed. some times a little slower will get you a better cut, at the same time too slow will allow the slag to reseal the cut. your air flow should also be sufficient to clear the slag as you go.
what psi is your air set at and what kind of air supply do you have? clean air is important, if you have an auto oiler in the system or in the hoses you need to start over with new hoses and no oiler.
can you give us a pic of the cut's ??

[mingy]

Thanks

I set my air to about 120 psi but the hoses are old and maybe too long. I have a little sort of water absorber thing which may be limiting flow (I don't know for sure).

I tried to use different speeds but I wasn't moving all that fast. What changes is I go from dirty cut to not cutting through.

I also tried at various current settings.

I have a 4 day weekend , so I'll try and post pix of the set up, and the result cuts.

Thanks for the ideas

[fun4now]

almost sounds like the air is too high. i would try dropping it a bit. try around 80-90 psi and bump up the amps, then just try some different speeds. i know speed plays a big part in my cut quality.

[jjsjeff]

I tried to use different speeds but I wasn't moving all that fast. What changes is I go from dirty cut to not cutting through.

I'd turn the amps up all the way and see what happens when you cut. You can't hurt anything.

[pthunberg]

I have the same machine. Check your ground, if it is not good it will cut like you describe. Also the air has to be really dry and clean. Look at underside as you cut the sparks should be coming out just slightly behind the cut if your travel speed is good. I set the heat control at the lowest setting when following a pattern on thin material and higher on thicker material. You will just have to play with it to get the speed and heat you like. The little green air light will go out if you do not have enough air flow to the machine. My compressor is set at about 100psi. I just set the regulator on the cutter to the middle of the green on the gauge and have at it. If you turn the heat all the way down you can pull the trigger and just get air to make the adjustment. I have not had to change the air setting much. I have around 3 hours on the machine and am really just now getting consistently good clean cuts. The learning curve was steeper than I thought it would be. That said I wish I had purchased this cutter a long time ago I would have saved hundreds of hours of work. Miller makes a great product.

Paul

[SavageSunJeep]

I have the same machine. Check your ground, if it is not good it will cut like you describe. Also the air has to be really dry and clean. Look at underside as you cut the sparks should be coming out just slightly behind the cut if your travel speed is good. I set the heat control at the lowest setting when following a pattern on thin material and higher on thicker material. You will just have to play with it to get the speed and heat you like. The little green air light will go out if you do not have enough air flow to the machine. My compressor is set at about 100psi. I just set the regulator on the cutter to the middle of the green on the gauge and have at it. If you turn the heat all the way down you can pull the trigger and just get air to make the adjustment. I have not had to change the air setting much. I have around 3 hours on the machine and am really just now getting consistently good clean cuts. The learning curve was steeper than I thought it would be. That said I wish I had purchased this cutter a long time ago I would have saved hundreds of hours of work. Miller makes a great product.

Paul

It sounds like you are not getting solid ground and the air pressure might be too high at 120.

I think the Miller is made by Hypertherm for Miller and it is the same unit as the Hyper Powermax 30.

The cutter will cut without a ground but you will lose the arc after about 15 secs or so (ask me how I know ).

[Miller RicJames]

A few things to consider:

- 120 psi into the machine is fine as long as the regulator on the machine is set at 60 psi WITH THE AIR FLOWING. If the air pressure is set without air flowing it will be less when the air starts moving.

- Aluminum does not leave a smooth finish when cut. Because of aluminum's physical properties, it disipates heat much faster that steel which causes the heat from the arc to be drawn away from the cut. That is why the edges of the cut are rough instead of smooth. That is also why aluminum has less of a rating when it comes to cutting capacity.

- The amperage knob can be adjusted for different thickenesses or cutting speeds. Most times it is left at 27 amps and the speed is adjusted to the thickness of the material.

- HT DOES NOT MAKE ANY MILLER PLASMA CUTTERS!!! It was the other way around for two of their machines.

- "Shielded" applications use drag consumables, "non-shielded" applications use regular consumables.

- Do not over tighten the retaining cup. The number one complaint that I get is that the machine does not cut very well and the arc goes out in a few seconds. If the retaining cup is too tight it will cause that. For that machine, if you can wiggle the tip as it sticks through the retaining cup, it is just right. It should not be sloppy, but if you can't wiggle it a bit, the cup is over tight and may cause problems.

- Make sure your air is clean and dry. Any moisture in the air will derate the ability to cut. It will also reduce consumable life. Verify also that the air lines are of proper size to allow good air volume. Volume of air is another characteristic that is easily overlooked.

Ric

[mingy]

Thanks for the tips

Da boss gave me 5 days work to do over my 4 day weekend.

I didn't even get out to the shop. It sounds like a root problem may be with the air. It maybe the little 'air dryer' gizmo I bought restricts airflow.

I will investigate (boss willing)