Hey All!
I know ! I know ! Look at previous postings for answers on plasma
cutters ! And I have read many, many of these postings. But things
seem to change so fast in the plasma cutter world. I saw one
advertised in Machinist's Workshop or Home Shop Machinist that was
surprisingly inexpensive. I spoke to the guy selling it and he was
very helpful and informative. He gave me a reference to a fellow using
it in a light industrial setting as I would be. It turns out that it
would not work for me, but would be great for a hobbiest. So for me it
boils down to either Hypertherm or Thermal dynamics. It seems that
these machines are priced closely, use consumables at approximately
the same rate, and parts are easily available. So it comes down to
trying each one and seeing which one feels better. But where I need
help is deciding what capacity is best for my situation. Currently the
thickest mild steel plate I cut is 3/4". The thickest stainless plate
is 5/8" I use the oxy-acetylene torch for the mild steel and saw for
stainless. All the cuts are then machined to size. Not too much
welding is done in my shop but I do turn away welding business from
time to time because it is such a small part of my work and I like
machining better. But this will probably be changing this year. I'm
looking to hire a welder with some machining experience who wants to
learn machining. So a plasma cutter will hopefully be getting more
work. And that work will be welded assemblies. So the cuts will
preferably be final and many will be welded to other parts.
Just how bad is the cut when it is "severed"?
Is machining this "severed" surface hard on cutters the way a torch
cut surface would be?
Can the cut be improved by pre-heating the plate?
How much grinding is required to make a "severed" cut close to the
same quality as a proper cut?
Is there a point where it is better to use a torch because of
thickness?
Is 3/4" near this point?
Will a higher amperage machine make better cuts on thinner material?
If so, can a machine that will cut 1" be used economically to cut 16
gauge?
Does the cut have less bevel when using higher amperage?
Can I tig weld to a plasma cut surface without any prep or with
minimal prep?

I think that's it.
Thank You,
Eric R Snow,
E T Precision Machine

I purchased a Hypetherm. I was lead to beleive that the consumables
would be less exspensive and they would last longer than the
competetion machines. This proved not to be true. The consumables are
very exspensive and they have a short life span. It is cheaper to use
oxy- acetelyne. I would buy one only if I needed it for cutting non
ferrous materials.

Charlie

Bogone wrote:

I purchased a Hypetherm. I was lead to beleive that the consumables
would be less exspensive and they would last longer than the
competetion machines. This proved not to be true. The consumables are
very exspensive and they have a short life span. It is cheaper to use
oxy- acetelyne. I would buy one only if I needed it for cutting non
ferrous materials.

Charlie

What are the prices based upon ? - Oxy vs. Hypertherm ? No contest in some places.
Some places Hypertherm wins easy due to the restrictions.

The numbers are plasma vs. plasma by different companies.

Martin

--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

On 20 Jan 2005 21:47:49 -0800, "Bogone" wrote:

I purchased a Hypetherm. I was lead to beleive that the consumables
would be less exspensive and they would last longer than the
competetion machines. This proved not to be true. The consumables are
very exspensive and they have a short life span. It is cheaper to use
oxy- acetelyne. I would buy one only if I needed it for cutting non
ferrous materials.

Charlie
How dry is your air? Or do you use nitrogen? I don't like torch
cutting because of the surface it leaves. Plasma is so much cleaner
and so requires much less time cleaning it up. I have had some pieces
plasma cut for me and the cut edges were beautiful. Not so for torch
cut parts. Especially if I'm the one doing the cutting!
ERS

Eric R Snow wrote:
On 20 Jan 2005 21:47:49 -0800, "Bogone" wrote:


I purchased a Hypetherm. I was lead to beleive that the consumables
would be less exspensive and they would last longer than the
competetion machines. This proved not to be true. The consumables are
very exspensive and they have a short life span. It is cheaper to use
oxy- acetelyne. I would buy one only if I needed it for cutting non
ferrous materials.

Charlie

How dry is your air? Or do you use nitrogen? I don't like torch
cutting because of the surface it leaves. Plasma is so much cleaner
and so requires much less time cleaning it up. I have had some pieces
plasma cut for me and the cut edges were beautiful. Not so for torch
cut parts. Especially if I'm the one doing the cutting!
ERS

I have a Cutmaster 75 (Thermal Dynamics?) and put a dessicant filter on
it right at the back of the machine. After a full year of cutting around
the farm and building an automatic firewood processor with it, I think
I've gone through two or three tips and nozzles. Use very dry air and
avoid using more amperage than you need and plasma cutting is
super-cheap. The newer machines seem to get MUCH more milage out of
consumables so don't bother with a used machine.

Jason Marshall

On Fri, 21 Jan 2005 12:24:26 -0600, Jason Marshall
wrote:

Eric R Snow wrote:
On 20 Jan 2005 21:47:49 -0800, "Bogone" wrote:


I purchased a Hypetherm. I was lead to beleive that the consumables
would be less exspensive and they would last longer than the
competetion machines. This proved not to be true. The consumables are
very exspensive and they have a short life span. It is cheaper to use
oxy- acetelyne. I would buy one only if I needed it for cutting non
ferrous materials.

Charlie

How dry is your air? Or do you use nitrogen? I don't like torch
cutting because of the surface it leaves. Plasma is so much cleaner
and so requires much less time cleaning it up. I have had some pieces
plasma cut for me and the cut edges were beautiful. Not so for torch
cut parts. Especially if I'm the one doing the cutting!
ERS

I have a Cutmaster 75 (Thermal Dynamics?) and put a dessicant filter on
it right at the back of the machine. After a full year of cutting around
the farm and building an automatic firewood processor with it, I think
I've gone through two or three tips and nozzles. Use very dry air and
avoid using more amperage than you need and plasma cutting is
super-cheap. The newer machines seem to get MUCH more milage out of
consumables so don't bother with a used machine.

Jason Marshall
Thanks Jason, that bit about new vs old is good to know. I had not
decided whether to but a used machine. I haven't been looking for a
used one but sometimes the welding supply has good used machines and
if the price was right one of 'em might have followed me home.
Eric

I think you are on the right track by buying either hypertherm or TD.
they are the hands down best machines.
I currently run a Thermal Dynamics Pakmaster 75, which is nominally
rated at 3/4". I find the ratings are a bit overly optimistic, and you
should really overbuy in terms of size. Best policy is to go to a
welding supply store, and actually cut your material with the machine
you want- then you can see how it really does on real steel. My welding
supply store will do this willingly- most will. And most good stores
carry both Hypertherm and TD.
Consumables are, well, consumable. They get used up. And they are
indeed expensive. Life of consumables is directly related to number of
pierces- this is the hardest on them. Theoretically, they would last a
lot longer if you just made one long cut, instead of lots of short
ones.
It is true that a good quality water filter will help consumable life,
and edge quality as well. I like the big black anodized "toilet paper"
style from motor guard, available at most good welding supply stores.

As far as edge quality goes- the damn torch gets hot- 45,000 degrees or
so. So even though the HAZ (heat affected zone) is very small, it does
do a number on any steel that can be hardened. Edges, and slag, get
hard. Slag is the hardest- I always try to knock it off before grinding
or machining, as it is really hard stuff. We use an air chisel to knock
it off the back side, then an aluminia zirconia mop disc on a 4 1/2"
grinder, before we machine it.
Slag production is directly related to proper cutting speeds- at
optimimum speed, slag is minimal, and it just falls off the metal, for
mild steel. At too slow of cutting speeds, slag welds itself to the
base metal, and is really hard to get off.
Most high amperage machines have a control for turning down the
amperage, so you can cut thinner material and still get a nice clean,
minimal kerf.
We tig weld to the plasma cut edge all the time- and yes, we
occasionally notice some bubbles from the edge, but it is rare. But we
do prep all edges first- slag removal and light sanding, usually.
Stainless and some bronze alloys are a lot worse in terms of slag- They
need to be cut in a neutral atmosphere for good edges. So expect more
grinding on them.
At correct speed, the edge quality is better than oxy fuel, unless the
oxy fuel is being machine cut, or run by a true expert torch man.
But plasma too gives you its best cut when machine cut. I use a
motorised cutting machine for my plasma cutting, and it works really
well.