Check out my new business website:
This is the most amazing tool. Check out this demo video I made: YouTube PlasmaCAM demo 021109
This is a demo of the quality you can get out of my CNC PlasmaCAM table. And
yes the fat guy is me..:-)
I design in SolidWorks, and import .dxf's into the proprietary PlasmaCAM software. I am getting pretty good at it. It is amazing how
fast and near laser quality it cuts parts out. It will do a 0.040" SS flame-tube (turbine engine part) nearly this quick;
Imagine blowing 150 perfectly sized and laid out holes that quick!
I had some questions, so let me answer them..
1. What is the minimum diameter hole that can be cut?
2. Does the minimum diameter hole size depend on the thickness of the material?
3. How fast (inches per second) do you set the machine when cutting? When moving between cuts?
4. What was the cost of the PlasmaCAM table?
5. What was the cost of the Miller Plasma Cutter?
1) The minimum diameter you can cut is a 1/8" hole but
it will be jagged. When initiating a cut, the plasma arc must 'pierce' the
metal. The pierce process is the torch initiating an arc near the surface of the metal internal, to the torch head. There is a flow of
compressed air exiting the orifice in a laminar column which drives the arc along the column for several inches(I work in imperial). The
intensely hot arc melts the surface of the metal and 'craters' the surface blowing the molten metal back out until the leading edge
(depth) of the 'pit' penetrates entirely through the metal. Then the molten metal exits the back of the material and 'cutting' occurs as
the edge of the plasma column erodes the edge of the slot. The plasma column is very laminar and defined, so once material is removed, very
little more taken, unless moving slowly, then there is much heat transfer. I tell you all this to say that the initial pierce,
especially on thicker material is messy and imprecise. There is also a 'lead-in', where the pierce is made, say 0.15" to one side from the
profile, then the cutting column is brought near to the profile, turns and parallels the profile.
The torch cuts a kerf on the centerline of the path; The path is offset from the part outline by an offset of 1/2 the kerf width of about 0.025". So
you wind up with a messy pierce area and short straight section and taking into account the offset, the minimum 'nice' hole you can make
is about 0.25". 0.25" are 'passing' but quality starts at about 0.375" diameter and up.
2) The minimum diameter that can be cut >with quality< does depend on
the material thickness; generally, thinner materials give better minimum diameter cuts, as does faster cutting speeds. The thickness
of the material governs the cutting speed. Aluminum absorbs a lot of heat so you can cut only 1/3 the thickness that you can on steel. The
above discussion applies the thickness of the material. You must dwell longer to accomplish a complete pierce on thicker material.
0.120" 4130 is nearly instant, but 0.25" steel takes about 1 sec. The longer the dwell, the more heat is generated in the material, which
creates a 'heat affected zone' (the bluing next to the cut (HAZ)) which 'disturbs' the material. The minimum diameter hole in thicker
material has a greater HAZ. The sidewalls of the cut are nearly perpendicular to the surface until the material is 0.5" thick, then
it has a bit of a slope (narrow at surface, wider at bottom) because the plasma column diverges a bit. So it depends on your quality
requirement. I would say in up to 0.375" steel a 1/4" hole comes out 'ok', but a 3/8" hole comes out good. And a 1/8" hole is not very
good; and because of the HAZ and the raggedness, the metal is a bit hardened and it is difficult to 'ream' with a drill bit, so you are
better off to drill 1/4" and below with a drill into virgin metal. 0.5" diameter makes pretty holes. 0.25" makes passing holes. 0.125" makes 'holes' ;-)
I have a concrete floor. When cutting aluminum sparks barely make it to the floor and there is A LOT of powdered aluminum everywhere,
which is a concern for nearby electronics. You can build a base shroud with ventilation intake to capture the burning slag and fumes,
which I intend to do. I already have the fan, and am waiting for the time. Steel slag burns/glows for a longer time and
leaves larger spatter-pellets all over similar to an oxy torch slag or stick welding and cools the same.
3)cutting speeds vary from a baseline 50ipm(0.8ips) to 500ipm(very thin steel) to 15ipm(0.25"-0.5"steel) and rapid travel at 1000ipm
(17ips)-basically really fast-Think red hot knife vs. Styrofoam.
4) My PlasmaCAM was about $11,000USD from the mfr. including $400 shipping. (see http://www.plasmacam.com/indexfla.php
(watch the Pixar video on the homepage about making machine gun props) I HIGHLY recommend getting the FREE demo DVD video
-If not just for dream-building, it will expand your imagination of what is
possible. I purchased a second PlasmaCAM off eBay for about $7500 which I have since resold. This does not include a compressor, a computer,
air processing system, metal handling equipment, and electrical modifications to support industrial amperages.
5) I think I paid ~$1600 for the Miller plasma cutter I got on a deal
at EAA Airventure-I chose the inverter model over the standard transformer driven 375 for compactness and portability. It is easily
removable for off-table use. I used it on a water heater to cut an access door and precision exhaust holes (similar to a CC inlet port)
for my Waste Oil Heater project-The kerf through the 0.125" steel was as wide as a hacksaw blade without the teeth. Recently, I was able to
upgrade the Miller torch to a Hypertherm PowerMax 65 amp plasma torch, with the ability to cut upwards of 3/4" metal.
6) OK I am not planetary, but I do like my bacon for breaky.. ;-)