Difficulties cutting A2 tool steel with powermax45... also wondering if I should upgrade to XP

[Plasma Shootist]

I have a hyperterm powermax 45 running on a shopsabre table.
I've had the set up for a little over a year but haven't made much progress with the cut quality in A2 steel.
IMO the steel cuts more like stainless, and at that, I've still had to lower the cut rate.
Suggested cut rates for 3/16" SS on the 45 are: 70 ipm and 118V, .06 cut height
I'm cutting 3/16 A2 at: 40 ipm and 120V, .06 cut height

I know stainless likes being cut fast (I also know this isn't exactly stainless), but cutting faster leads to slag re-joining or at faster speeds, failure to penetrate/keep penetration.

What I'm seeing:
-I'm getting about a 7 degree bevel.
-extremely hard slag... some will chip off, but the remainder is so hard that the belts have a hard time with it, (to the extent I am re-annealing the steel first-- a undesirable 15 hr process)

Does anyone have any experience in this area?
I am air cutting... I'd be happy to switch to another gas that the pm45 can handle.
Would F5 gas make a difference? --- if It would greatly make a difference, I may be opt to get a powermax45xp as an alternative (It appears that hypertherm isntn't offering an upgrade duramax torch for the pm45 and I dont think I can cut with f5 without it?)

Looking forward to your experience and input
-Matt

[beefy]

Hi Matt,

I don't really have much input as I've never cut anything like that. I have done some lathework and drilling and tapping on un-annealed D2 tool steel as we call it here in Australia.

It doesn't surprise me that it cuts more like stainless because I'm guessing being a tool steel it contains chromium. The hard slag is not surprising either because it's a tool steel that is hardened with heat and quenching.

If you get no answers here, try a machining forum like Practical Machinist. If anyone will understand tool steel, they will. The do have a section on plasma cutting but not really a lot of posts on the matter. Even better may be a laser cutting forum (if they exist, no idea), as they may do more commercial work and may come across this material too.

Regarding the bevel, my Hypertherm cuts at only 0.25mm Maybe the tool steel, being more like stainless, also requires a very low cut height. Perhaps experiment and see if that improves the bevel.

And as Jim Colt always teaches us, for best quality, use the smallest consumables that can cut that thickness metal.

Air cutting causes hardening in mild steel because of the 80% nitrogen in the air causing "nitriding" of the cut surface. I think with tool steel though your hard slag may be simply due to the fact you are cutting a heat hardening tool steel. Again, maybe a machining or laser cutting forum may also be able to give some advise in this area.

Keith

[Plasma Shootist]

Keith,
Thanks... I've thought about posting on practical machinist, and also cnc zone. Both have a section for plasma but this is a pretty specific issue for plasma tables. I figured this would have been a better spot. I'll be giving them a shot.

I'm certain your right that the hardness of the slag is a result of hardening from a molten state. This after all is AIR hardening tool steel.

When you say that your cutting at .25mm (roughly .01") are you talking about cutting height? The book for my hypertherm 45 lists .06" (roughtly 1.5mm) for all material thicknesses. I've never tried cutting that low.

The bevel is very important especially for some smaller inner cuts that I make. With the outside, after re-annealing it (as much as I don't want to) at least I can grind it perpendicular and just increase the kerf to compensate. With the inside cuts, however, I'm filing by hand (or with a die filer), and even with re-annealing, it's a lot of sweat.

One thing I have noticed is that an ending overlap provides very clean, nearly straight edge. This makes me wonder if anyone has ever tried "double cutting?"

I'm thinking there are three possibilities to explore:
1) Cutting the material once and having a second pass, on the same path, for the whole cut. (This might only work for inside cuts)
2) Cutting first with a wider kerf and second with a reduced kerf.
3) Just cutting so slow that you get similar results (I'm thinking of cutting the speed in half... 20ipm)

The worry I have in the back of my head is about the HAZ. I know that proper cutting has a relatively small HAZ and it has never worried me. I even dug up a college term paper on it... all evidence leads me to believe that plasma cutting, with post grinding, leaves the metal in a ready for service state. However, slowing the cutting down this much, is not something I can find any documentation on. I suspect you'd have no or relatively small metallurgical changes as gravity and electromagnetic forces here are relatively weak, on top of that the metal is only molten and able to transform for a short period of time (I'm not talking about transition states, those would occur and can be remedied by re-annealing, rather I mean the separation of additives to the extent that they are no longer uniformly distributed and re-annealing wouldn't correct the change) But that's only my suspicion.

I've included a couple of pictures. They were both taken after the majority of the slag had been knocked off and post annealing (hence the steel color). You can see the overlapping exit in both picutres. I tried to get it as clear as possible, I'm sorry it's not better.

I'd be happy to entertain any ideas, but I'm trying to reduce the amount of trial and error as a 10"x36" piece of A2 is about $200.

I was kinda hoping Jim might pop up with the answer... he pretty much has them all.

Also is anyone cutting stainless with something other than air on their PM45?
or alternatively
Has anyone upgraded to the PM45xp and seen a substantial improvement on the bevel for thick stainless cuts?

[beefy]

Matt,

yeah the quarter millimetre I mentioned (0.254 mm) for cut height is for Finecut consumables on a Powermax 1250. For later model machines using the Duramax torch it double to a massive 0.5mm (a little sarcasm there ). I believe all the other nozzles are 1.5mm cut height.

I'm absolutely gobsmacked about something you just thought of (going over the cut a 2nd time). I've just been emailing someone 5 mins ago about hole cutting and suggested this very thing as an experiment to cut away hole taper. Thought because the slug will have dropped out (hopefully otherwise collision disaster if it only tips) and by going around the hole a 2nd time, the "flame" will be hunting for metal and may burn away some of the taper. May be able to achieve this by setting the "overburn" in Sheetcam long enough so it runs the circle completely a 2nd time.

The "ending overlap" you mentioned is actually a well known thing and is available in Sheetcam. It gets called "overburn" by many, and is typically used to get rid of divots in holes. Also it gets combined with turning the torch off during motion so that when the torch actually stops movement the flame is already extinguish and you don't get a divot burned in the metal caused by the exothermic reaction (metal continues burning for a short time due to heat and the oxygen in the air, similar to oxy/fuel cutting where it's primarily heat and pure oxygen doing the cutting). Search on this forum for threads on hole cutting and you should be able to get some good knowledge.

I don't really know what to suggest with this problem. Would it not be worth it to put it out to a 3rd party laser cutter, or will that simply kill your profit.

Keith.

[jimcolt]

I would suggest using the Stainless Steel F5 shielded cut chart for the Powermax45 XP with your Powermax45. The 45 amp shielded consumables internal designs are very similar between the two systems and will produce the same results....and should improve the cut quality on grades of tool steel that have higher levels of chromium as compared to mild steel. Attached is a cut chart that you can use with the shielded 45 amp consumables on a Powermax45.

Note: do not use the consumable part numbers listed on this chart with the original Powermax45 (this is the chart from the 45 XP operators manual) as they will not fit in the torch. Use the correct consumables for 45 amp shielded air cutting for your 45, however use the cut specs from this chart with compressed F5 gas....regulated and delivered to the plasma cutter air inlet at between 90 and 120 psi.

F5 45 amp chart.docx

(83.71 KiB) Downloaded 73 times

F5 45 amp chart.docx

(83.71 KiB) Downloaded 73 times

[Plasma Shootist]

Keith

Thanks, I didn't know it was called "overburn." I'll look for that specifically. Getting rid of the divot was exactly what I had been trying to do. But, as you can see by the picture, it kept the divot and then I have a small burn-out hole from pausing .25 seconds at the end (correctable). I worry too about the collision danger, but as I'd not be using that technique much, I could just stand over the E stop, and watch as it finishes the first pass. I'm curious if you try it!

And yes, looking to keep things in house so that I keep the costs down. Waterjet would actually be best for me, as no hardening would occur, but in my oven (less wear and tear expenses) its about $6 to re-anneal the blanks... one or a dozen.

Jim
First, thanks for taking the time to respond. You and your frequent posts around all the sites is THE hands down reason I bought a Hypertherm (and to day its coming in handy... personally).

I have a few questions based on your response if you have a moment...
Regarding the gas pressure;
1) is the electrical/LED pressure light on the pm45 just a dummy gauge set to the range for mild steel?
2) Will supplying gas at 90-120 cause any problems with the internals or alternatively shorten lifespans of consumables?
3) Could I also try increasing the pressure of plain old regular compressed air to the pm45 in that range as an alternative?

Regarding the new gas;
4) I noticed you emphasized shielded consumables (I will definitely heed that), but is that what Hypertherm's F5 page meant when they said "Do not use this process with the Powermax45 and T45m"? I've previously been afraid to try it because of that page.

Thanks again.
I'll get some gas next week and see what I can post back with.
-Matt

[jimcolt]

1. The LED indicators on the front panel of the Powermax45 are a real gauge (not sure what a "dummy" gauge is!). We design our consumables to operate best in the range where this electronic feedback pressure is supposed to be set. This is the cut pressure that goes to the torch, which is different than the inlet pressure.
2. The Powermax 45 is designed to operate with a pressure range of 90 to 120 psi. Below 90 psi at the inlet and the system will shut down (internal safety pressure switch) due to low inlet pressure. Above 120 psi at the inlet and you could damage internal components. The F5 process uses the exact same inlet and cut pressure specs as for using either air or nitrogen.
3. Increasing the cut pressure (which you set by activating flow at the torch (amp knob fully CCW) and turning the onboard regulator knob until the front panel LED's are satisfied.) will cause short consumable life and torch misfiring with any inlet gas, air, N2, F5.
4. I (40 years at Hypertherm) am suggesting you can use F5 with the Powermax45 if you follow the specs for inlet pressure, cut gas pressure as listed here, and use the shielded consumables (which are the only ones we recommend for F5) and follow speed and cut specs from the Powermax45 XP operators manual for F5. When the manual was written we had not tested this process, so we suggested against using it.

New development....we have just announced that you can upgrade the original Powermax45 with the same Duramax torches as used on the newer Powermax units. More details on that soon! Jim Colt Hypertherm

[Plasma Shootist]

Jim
I meant no disrespect by "dummy gauge" (I was just referencing lights on dashboards rather than old school gauges... oil press, engine temp etc.).
I have never experimented with inlet pressure before. I had always used the recommended psi for cutting, and was under the impression that you'd only vary the incoming pressure for different operations (gouging). So this gives me a whole new level to experiment with : )

Jim Thank you so much for your detailed responses! If you're ever in Castaic, beer's on me!

Also looking forward to the possibility of the duramax torch.

And for everyone's benefit, hopefully I'll be back with good pictures in a day or so... I ordered the gas, regulator and adapters yesterday : )

[jimcolt]

I call them idiot lights, just never heard the term dummy gauge! You should always keep the incoming pressure between 90 and 120 psi (Powermax45 and older Hypertherm systems) and between 90 and 135 on the newer systems. The internal regulator is for adjusting the cut pressure which is set differently for gouging and cutting needs. On the newer systems (45XP, 65, 85, 105 and 125) the cut air pressure is auto set using the electronic feedback regulator that compensates for torch lead length, different consumable sets, consumable wear, and auto sets for gouging and marking (45XP only). Takes the guesswork out of it.

The Duramax torch is definitely a better torch in terms of cut quality, allows Finecut consumables, has longer expected reliability (because of the spring electrode and different manufacturing materials), and consumable life is a bit better than the original 45 torch. Jim Colt Hypertherm

Jim
I meant no disrespect by "dummy gauge" (I was just referencing lights on dashboards rather than old school gauges... oil press, engine temp etc.).
I have never experimented with inlet pressure before. I had always used the recommended psi for cutting, and was under the impression that you'd only vary the incoming pressure for different operations (gouging). So this gives me a whole new level to experiment with : )

Jim Thank you so much for your detailed responses! If you're ever in Castaic, beer's on me!

Also looking forward to the possibility of the duramax torch.

And for everyone's benefit, hopefully I'll be back with good pictures in a day or so... I ordered the gas, regulator and adapters yesterday : )

[Plasma Shootist]

Does the spring electrode also mean that it will be able to do submerged cutting?

[beefy]

Matt,

no doubt Jim will correct anything I say that's wrong, but I don't think your standard Hypertherm torches can do submerged cutting. However, I've often wondered if you could frig the system to allow it.

My guess is that if no air is flowing, the nozzle may flood and you can't initiate the arc. However, what if the gcode could issue a very momentary Torch On signal to get the 10 second air flow happening, THEN the torch touches off and fires while the air is flowing and keeping water out of the nozzle ??????????????

Jim, tell me how bad my idea is LOL.

Keith

[Plasma Shootist]

For sure the current mechanical (or manual) torch on the 45 cant or isn't supposed to cut submersed. I've heard of people doing it "under" 1/8" but I don't think its recommended. It's my understanding that the electrode is held in place by gravity at the beginning, allowing the arc to start, but the air pressure makes it blow back after it starts. I think this design is the major reason why it cant do submersed cutting (other reasons include small switches which aren't waterproof). When he said that the new torch has a spring electrode... it got me wondering if it would be possible. Of course, my understanding could be completely wrong... I've been wrong before, just ask my wife.

In other news. The gas came in. But the regulator that came in was not the one I wanted.

I will try varying the inlet pressure and re-adjusting the on-board regulator this weekend to see the differences (on MS).
I'll also try the double pass on some hole cuts (also on MS).

Sorry it's taking so long for the results... if only this were my day job. :p

[steel 35]

Matt,

no doubt Jim will correct anything I say that's wrong, but I don't think your standard Hypertherm torches can do submerged cutting. However, I've often wondered if you could frig the system to allow it.

My guess is that if no air is flowing, the nozzle may flood and you can't initiate the arc. However, what if the gcode could issue a very momentary Torch On signal to get the 10 second air flow happening, THEN the torch touches off and fires while the air is flowing and keeping water out of the nozzle ??????????????

Jim, tell me how bad my idea is LOL.

Keith

I have seen this happen on my machine, My regulator for the fill doesn't close all the way, thanks for reminding me! I still need to check or replace.
It did exactly what you're describing, I already started the cut but it slowly went above the plate and it was pretty cool to watch

[steel 35]

Not trying to get into the A2 VS D2 thing but I Have very good results cutting D2 with book settings finish is very smooth, The pieces drop but as you pictures show the tiny little pieces of Dross are very hard. Glad I don't grind them.
Looking forward to seeing results from your determination.

[jimcolt]

You can cut with the Powermax units submerged about 1/2 of the height of the retaining cap. They are not recommended for deeper underwater cutting. Our industrial and high definition class plasma's can be completely submerged....the deepest underwater I have cut is about 30 feet, and that was cutting a 4" thick stainless steel heat shield out of a nuclear reactor cooling unit, amperage at about 1200 Amps!

[beefy]

You can cut with the Powermax units submerged about 1/2 of the height of the retaining cap.

Very interesting Jim, never expected to hear that. I may try it sometime and see it it cuts down on the noise during a cut.

I'm guessing though it won't make much difference because the air flow will just blow the immediate water away around the nozzle.

Keith.

[jimcolt]

Underwater cutting with Plasma systems to 800 amps is often done just for noise and UV issues. Cut quality on steel will suffer (more dross, rougher cut edge) but on stainless often improves. Use a Powermax with N2 instead of air with the torch submerged....nice cuts.

Jim Colt Hypertherm

[hsolve]

Good day gents.
I have cut S/S with N2, no water table and the edge was a blueish finish, smooth, next to no dross, but the top edge was slightly rounded. Just connected up my PM125 to a N2 bottle with a high flow regulator and set the pressure to the max recommended for the plasma. Samples were 3mm to 12mm, so overall worked OK

[Plasma Shootist]

Not trying to get into the A2 VS D2 thing but I Have very good results cutting D2 with book settings finish is very smooth, The pieces drop but as you pictures show the tiny little pieces of Dross are very hard. Glad I don't grind them.
Looking forward to seeing results from your determination.

By book settings, do you mean for MS or book settings for SS?
As for the dross, have you tried taking pliers to them?
I'm also curious about what angle you see at the edges...

[Plasma Shootist]

I'm back with results.
Apologies for the delay, but life happens while you're trying to have fun in the garage.
This was a rather long path to get to a simple result... the short of it is the F5 gas works great!
The long of it is as follows over the next few posts,
(not all of it is on the original topic, but in response to above ideas)

So I've always been running at 80 psi and I needed to test what Jim said about running between 90 and 120psi.
I did 4 test pieces on 3/8 MS, all running 32ipm and book cut height, with psi's of 80, 90, 100, and 110.
I can't do a 120 psi test because my compressor tops out at 120, and it wouldn't maintain that pressure for a complete cut.
The pressure was measured at the machine with a gauge accurate to within 1%, with the air flowing.
The internal regulator was adjusted at each pressure as instructed.

I noticed no appreciable difference between the four trial cuts.
But for good measure, I'll be keeping the pressure at 90 psi for MS from now on (since my compressor kicks in at that pressure).
Again thanks to Jim!

[Plasma Shootist]

The topic of double cutting the holes also came up as a possible solution to poor inside cuts.
I tried this on the .375 MS also, because I figured it would show the greatest angle difference.

Using the same test piece cut outs as before, I tested 1/2 hole path overlap and also just over 2 full hole path overlaps.
The 1/2 path overlap only passed the initial entrance point once, the 2x path overlap passed the entrance point twice.

On the front there was very little difference, on the back the 2nd pass did made a noticeable difference in reducing the entry bump.

I additionally tried making the holes with the double pass at different feed rates-30, 25, 20 and 15.
(The picture shows 25 twice, it's correct-- I forgot to change the speed).

Regardless of the speed, the cut was not so substantially improved that I'd call any of them great.
In addition, the second (and third) passes melted the upper lip and blew the melt down on the inside of the hole.
I would not recommend cutting a hole twice or three times as a result.

(Of course I didn't test changing pressure or speeds between passes... some variation of which might get good results)
I feel a slower end passing the entrance once, or possibly a back step would work best, but my controller doesn't have these options.

[Plasma Shootist]

So,
I got the gas... industrial grade 95 nitrogen 5 hydrogen mix.
It was around 80 before fees and rental and taxes and some more taxes they called fees.
It would have been three times as much to get the actual "F5" gas. I figure industrial grade is fine.

I ordered a regulator and an adapter to go to the hydrogen mix tank (reverse threaded).
The regulator turned out to be the wrong one, which added to my delayed response.
Then after getting a new regulator, my local store didn't have an adapter to go into a regular NPT air line.
Another wait for a second adapter....
And a week later I had everything I needed.

(Side note, my local gas supplier had never heard of F5 or using it for plasma cuts, and they referred me to their distribution center...
Their distribution center had never heard of using F5 mix for plasma cuts and said, "hydrogen...!!!! that's flammable, I wouldn't use that for plasma..." --I honestly think they wouldn't have sold it to me had their computer not listed that this gas is "non-flammable". Outside of that the guys were very helpful.)

Because A2 is so darn expensive, I did some test runs on SS first.

First with Air, for comparison, then with the F5 (I tried the double hole thing again on SS just to be sure-- nothing usable).

The edges were beautiful, but the F5 left material that was much tougher (read it had to be weakened several times with pliers before it could be removed) on the back side.

The test sample on the top of the last two images was actually trying different cut heights. I did several tests, I don't have pictures of all of them.
My machine cant handle .04 except in perfect conditions, but I feel that .05 works slightly better than the book recommended .06.

Other than the nice shiny edges... I was getting fairly bad angles from the F5 gas-- all sides seemed to slant to the right, so the front and back surfaces were fine, but both left and right surfaces leaned from the bottom right to the top left, with a greater angle on the right and a nearly vertical, but still negative, angle on the left.

I had just swapped the nozzle and electrode prior to beginning these test, so I assumed that was not the problem.
I remember reading that someone had a problem like this where it was caused by the o-ring, even where inspection found no flaws in the ring.

So I ordered new o-rings, and lube, and a swirl ring just in case. I also ordered new nozzles and electrodes, as I was now using my last new set.
Yet another week of waiting, sigh.

I swapped out the o-ring only and the direction changed, now the cut slanted to the left. @#$@#$)*%^*!
I swapped out the swirl ring and the direction changed again, now slanting to the front left. More @#$)(@#$)@(#)~!
I swapped out the new swirl ring for the old swirl ring and the direction changed again, now slanting to the left again, and slightly front.

I lost the picture of the side view of the first piece...

I quit for the night...

I was certain the shield and the nozzle were not the issue because they tighten to a stop in the same place every time.
Whatever was causing the issue was changing position in the torch with each reassembly.
After trying several more things I eventually gave in to replacing the new electrode and nozzle. Grrrr.
Here are some pictures of the old ones, not sure exactly what they are supposed to look like as I've not paid that close of attention before.
I'd appreciate any insight on their wear pattern.

[Plasma Shootist]

With the new nozzle and electrode, I got outstanding results, at least comparatively.
The sample cuts are on 3/16 SS plate.

These results were achieved using the recommended powermax 45xp settings on my powermax 45 using F5 gas.
The pressure was set to 110psi, measured while flowing.

[Plasma Shootist]

And finally, after squaring away everything with the machine, and getting all the necessary equipment....
The F5 test on A2 steel.... (110 psi and 0.06 cut height as recommended)

I previously had to use 40 ipm with compressed air at 80 psi and had horrible edges... both in edge quality and angle.
Further the edges were hardened to the point that belt grinding was very difficult.

I tested the F5 at 50(accidentally), 49(the recommended speed for SS with the 45xp using F5), 40 and 30ipm.
At first, when none of the pieces fell through, I was very disappointed. The back side looked worse than with air!!!

They samples were stuck in the parent piece harder than with air too.
I had to hammer them out. And with that I found that the dross would come off in chunks... So I pried away with my pliers.

This was new... This did not happen with air cutting. I was already very happy at this point. This process is going to save a lot of time!
Once I had broken away all of the dross with pliers (none of these pieces were ground), I saw crisp clean edges all the way around.
I noticed no appreciable difference between the cut speeds.

So I would recommend using the fastest cut as a 200cf bottle only gives about 40 minutes of cut time.
(Also, to be fair the front face did suffer a little at slower cut speeds with a small lip of ejecta coming out of the cut.)

Here are the angles on the fastest cut piece.

I did notice that there was a tendency for the angles to be negative here.
I also saw that this was amplified around the corners.

I think increasing the cut height here might solve this problem, maybe to .07?
I also think it's possible that a faster cut might be achievable.
However, as the material is so expensive, I will wait until I have some scrap pieces to test these ideas, and I'll be going with what works for right now.

Again, apologies for the delay.
I hope the results help...
-Matt

[Plasma Shootist]

I just realized, I didn't mention the dimensions for scale reference.
The sample pieces are 1" x 1.25", with a 5/8" center hole and like the stainless, they are 3/16" thick.

Cheers.