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Old 10-07-2009, 09:08 AM
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Default Plasma cut quality

I usuall pay little to no attention to this when cutting...but I had a learning experience on this yesterday. Although it was on a cnc table the same thing applies to a hand held torch.

I set up the Finecut parts in my torch and started smokin 10 guage iron.
The slag for some reason was real ugly, needed a cold chisel instead of the usual wire brush. I tried varying speeds and varying amps and it just got worse. And the edges began to bevel....
Then as I was cutting and at a way low speed, I noticed that the torch was intermittently not cutting all the way through the plate.
I took out the perfectly good tip(it is a high miler)and replaced new swirl ring, electrode, and tip. STILL lousy.

It was a newbie mistake, I had been cutting 1/2 plate and never reduced the air pressure for the Finecut tips. I reduced the air pressure to 60psi and cranked the speed to 90, and now no dross, and sharp square edges.

I recall Jim Colt of Hypertherm talking about excessive pressure weakening the plasma stream and destroying the beam, as well as causing shorter life of the tip. I guess I never took it serious til now. I'm not even sure what pressure is good but 60 psi works well.
The manufacturer recommended amps and air pressure is the result of alot of testing, and I guess it's worth listening to.

For what it costs for a Hyper 1250 G3, you would think a digital readout pressure guage would be the cat's patootie...instead of that grim little bar graph thingy they use.
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  #2  
Old 10-07-2009, 09:36 AM
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Gerry , I will file that away in , for future use , I have had trouble cutting 1/8" plate by hand with my 2050 at the lower amp settings on it . I can cut 3/4" plate real nice , but 1/8" looks like hell .
The only problem is the 2050 will shutdown if the air pressure is too low , but I don't know where that limit is right now , will check and see next time I need the plasma cutter .
Thanks .
Dan
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Old 10-07-2009, 10:03 AM
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Gerry,

I'm wondering, do you vary the pressure based on thickness, because its CNC or fine cut consumables, or is this something you always have done?? I have the 1250 G3, and never vary the air pressure at all, thick or thin same air pressure. The cut quality for me has always been very acceptable.

jack
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Old 10-07-2009, 11:52 AM
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Thanks for the tip. I never thought of reducing the air pressure for thinner material. I have always run my ESAB set at 80 psi. Seems reasonable now that I think about it. I usually dial back the amperage to the minimal necessary to cut the material.
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Old 10-07-2009, 01:44 PM
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I had a very similar experience a couple months ago with a Max100. Bad taper on cut edges, very poor tip life, had to cut at a greatly reduced speed in order to get slag to exit other side. After replacing everything and still poor results, I noticed that the expanded metal switch on, I turned it back off. Now good cuts again.
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Old 10-08-2009, 11:15 PM
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Quote:
Originally Posted by platypus20 View Post
Gerry,

I'm wondering, do you vary the pressure based on thickness, because its CNC or fine cut consumables, or is this something you always have done?? I have the 1250 G3, and never vary the air pressure at all, thick or thin same air pressure. The cut quality for me has always been very acceptable.

jack
Well, I was tending to get careless. There is a pressure setting for each tip you use. It has nothing to do with how thick the steel is. It has to do with the swirl chamber being able to shape the spinning air into a plasma beam. At the correct air pressure the flow and spin based on the nozzle size is perfect conditions for a hot straight beam. There must be a wide range, not one magic number, I think. But within this range is the area of getting to know your machine, and the setting it purrs at. Every welder or cutter has it's "feel" after a while.

In my case I aim for as little slag cleanup as possible on an ornamental piece. Because a difficult cleanup on a large amount of pieces is a PITA. And I want a smooth clean cut.
That means tweaking cutting speed and air, seldom if ever go off of the max amps for the tip. I found yesterday that there was noticeable better cut at 84 inches per min. instead of 86 where I had run at.

I think a handheld torch would not be the same, you will always get slag, but the clean and smooth cut would be aided here as well, with air and amps at the best settings.
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Old 10-12-2009, 07:53 PM
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Quote:
Originally Posted by Ironman View Post
I usuall pay little to no attention to this when cutting...but I had a learning experience on this yesterday. Although it was on a cnc table the same thing applies to a hand held torch.

I set up the Finecut parts in my torch and started smokin 10 guage iron.
The slag for some reason was real ugly, needed a cold chisel instead of the usual wire brush. I tried varying speeds and varying amps and it just got worse. And the edges began to bevel....
Then as I was cutting and at a way low speed, I noticed that the torch was intermittently not cutting all the way through the plate.
I took out the perfectly good tip(it is a high miler)and replaced new swirl ring, electrode, and tip. STILL lousy.

It was a newbie mistake, I had been cutting 1/2 plate and never reduced the air pressure for the Finecut tips. I reduced the air pressure to 60psi and cranked the speed to 90, and now no dross, and sharp square edges.

I recall Jim Colt of Hypertherm talking about excessive pressure weakening the plasma stream and destroying the beam, as well as causing shorter life of the tip. I guess I never took it serious til now. I'm not even sure what pressure is good but 60 psi works well.
The manufacturer recommended amps and air pressure is the result of alot of testing, and I guess it's worth listening to.

For what it costs for a Hyper 1250 G3, you would think a digital readout pressure guage would be the cat's patootie...instead of that grim little bar graph thingy they use.
Hey. I like my bar graph. the green lights are pretty too.
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Old 10-13-2009, 11:18 AM
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Default Bar Graph

Quote:
Originally Posted by lars66 View Post
Hey. I like my bar graph. the green lights are pretty too.
Well at least you got a bar graph. My only indication of the air pressure is the gauge on the air regulator/filter on the back of the unit. Mfgr recommends 60 PSI but if I put it up over "40" it blows out the plasma. Under "40" the safety switch shuts the unit off. Of course it's not 40 PSI but just where the Chinese made dial happens to fall. I guess I should replace it with a nice digital regulator/filter and re-plumb the thing so I can actually see and adjust the pressure from the front. Another project for 'someday'.


DrBob
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  #9  
Old 11-26-2009, 11:45 AM
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Default More info on cutting pressures.

As I am not as clear and eloquent in my posts sometimes, I thought I would post this email from Jim Colt at Hypertherm, re the pressures for cutting. Now this is for FineCut tips, and will differ for the regular ones. Obviously my settings for the regular 40 amp tips do not apply to a Finecut.

Quote:
-----Original Message-----
From: Gerry Hess [mailto:ghess@netkaster.ca]
Sent: Thursday, November 26, 2009 12:16 AM
To: Colt, Jim
Subject: Finecuts

Hi Jim, mailing you off forum for this.
I have a DHC2 and 1250 Hyper.
Today and recently I noticed a loss of performance from the torch.
Running at 40 amps on the 1250 G3 and about 50-60 psi. with new tip and
electrode.
Cutting 10ga CR at 86 ipm, with a beautiful square edge and completely
dross free.
This project was 198 pierces and 1825 inches. After about 75% done I
could hear the tip starting to "whistle", and tried to make it, but with
50 inches to go it started gouging and not cutting through.
I cleaned the tip(which looked perfect) restarted and dug another
trench. So I upped the air pressure to 70 psi on the panel, and the
whistle went away and good cutting resumed for the rest of that path.
I suspect the tip is baked, but am I running too low a pressure for the
finecut tip?.

The FineCut consumables should be operated at about 70 to 75 psi dynamic
(air flowing). Turn the amperage knob all the way
counterclockwise....air will flow through the torch...then set the
regulator to operate in this range.

Of course these parts will cut at lower pressure...as you have been
doing....however normal wear on the nozzle (tip) orifice causes the
orifice to become larger, which drops the internal pressure even more.
When the orifice gets larger and the pressure drops...the arc loses
energy density. By running a little higher air pressure you actually are
boosting the energy density (measured as Amps per square
inch)....providing more velocity and more energy to penetrate the steel.

If you go too high with the pressure...the cooling effects (that are
created by gas swirl inside the torch) are minimized....which can causes
shorter nozzle life.

Consumable life and cut quality are closely related to gas (air) purity,
flowrate and pressure....its a delicate balancing act. Our high
definition industrial plasmas have an extremely accurate gas flow
control system that contiously monitors gas pressures and flow and
adjusts automatically as the consumables wear....just the gas panel for
these systems cost more than 2 Powermax1250's!

The FineCut parts do not last as long as the standard shielded
parts.....that is a trade off for the higher energy density, square
edges. It sounds to me like you are getting fairly normal life out of
them.

Good luck....have a good thanksgiving. Jim

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  #10  
Old 11-26-2009, 01:23 PM
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Hey Gerry, thanks for that.
Gonna try to see that this gets filed for future reference.
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