Originally Posted by
jimcolt
High Definition plasma or laser or abrasive water jet. Three different processes, all of which can cut metals, yet each has its strong points , weak points and best quality/productivity niche. I have been in many modern shops that have all three processes at their disposal, and use each for what they do best.
Here are some rules of thumb for each process....and for plasma I am talking a igh definition plasma on an industrial quality precision cnc machine. A whole different animal as compared to an air plasma on a low cost machine.
Process comparisons:
Plasma....can cut any conductive materials. Cut quality and accuracy can be very good on gauge to 1/4", medium cut speeds in this thickness range. On materials thicker than 1/4", plasma cut quality gets better, and speeds, as compared to the other processes are by far the fastest. Plasma will pierce and cut to 2"
Laser.... can cut a lot of materials, do not have to be conductive like plasma, but different material reflectivities will affect the ability to cut. Laser is the fastest, most accurate of the 3 processes on materials thinner than 1/4", especially steel and stainless. Most lasers have limitations with higher grades of aluminum due to reflectivity. On material thicknesses above 1/4", laser speed drops off dramatically, and quality gets similar to high definition plasma. A 4kW C02 laser can pierce and cut to 3/4".
Abrasive water jet....can cut just about anything. Speeds are very slow as compared to the other two processes. On thin gauge materials defelection of the material durring cutting can be an issue that affects accuracy. Water jets are typically limited to about 6" thick materials.
Capital equipment costs, operating costs:
Plasma. A high quality 6 x 12 precision cnc machine with a Hypertherm HPR400xd high definition plasma will typically cost about $150,000 installed with fume control equipment. Operating cost is by far the lowest of the three processes...oxygen and other gases are used in relatively low quantity, plasma consumables typically will last up to 3 shifts of cutting, and total cost per foot of cut is much lower than the other processes primarily due to faster speeds on most materials. Can hold cut part tolerances typically of .015" to .020"
Laser. A 4kW C02 laser on a 6 x 12 laser cnc machine will typically be priced in the $450,000 range, installed with fume controls. Operating cost components are primarily assist ga useage...at relatively high pressure and flow (oxygen and nitrogen usually). Laser is far less efficient in regards to electricity....less of the wall power is converted into real cutting power due to inneficient conversion of power to light energy. Operating cost per foot of cut with laser are typically 1.5 to 4 times plasma cutting costs, accuracy of parts is ususally better than plasma on materials up to about 1/4". Can hold cut part tolerances of typically less than .015"
Abrasive water jet. A 50 HP abrasive water jet on a 6 x 12 cnc cutting machine will cost close to $300,000. Operating cost is largely related to the use of garnet abrasives as well as nozzles for the cutting head. Cut speeds are slower than the other processes, and operating costs as compared to the plasma can be 3 to 6 times higher. Can hole cut part tolerances typically of less than .010"
A few notes about each:
Plasma....the latest High Definition plasma systems are by far the easiest systems to learn to operate and cut with great accuracy. Simply load in your part drawing to the CAM software, choose how many, and push the start button. There are no settings to tweak, and since the control is windows based, learning curve is very short.
Laser.... best cut quality and productivity on thinner materials. Accuracy is also very good, learning curve is high, and operator needs some experince to get the most out of his machine. After 5 to 6 years expect to have to rebuild the laser resonator....$50k to $75k typically.
Water Jet....excellent cut quality, non heat affected materials. Unfortunately it is a rather slow process. Abrasive slurry is messy, often these machines are kept in a room by themselves.
Hope this gives a little insight and comparative info.
Jim Colt