Originally Posted by
jimcolt
I use a real simple formula which allows me to achieve my shop hourly rates, and seems to deliver competitively priced plasma cut parts. This is for cut metal with no secondary operations such as tapping or welding or forming. It also assumes that the customer supplied a .dxf file with the part properly and accurately drawn, I eat the time for post processing (adding kerf, lead ins, nesting, etc)....but no additional part drawing.
1. Do the math to determine your material cost per square inch. This number should include delivery cost. So if I buy a 4' x 8' piece of 3/16" steel for $130, and have to pay $20 delivery, then I take $150 and divide it by 4608 square inches, which comes out $.032 per square inch. Double that, so your selling price for 3/16" steel now is $.064 (6.4 cents ) per square inch.
2. determine how many square inches of 3/16" steel you will use in the part you are cutting, add about 1/4" to accomodate scrap and kerf, if you are cutting something not rectangular, figure rectangular area around what you are cutting to cover your inevitable scrap loss. So, if you are making a round 11.5" dia circle, figure a 12" square for material. 12" x 12" is 144 square inches, so the material cost is 144 x $.064 or $9.22 rounded off.
3. For cutting cost, use the same number generated in 1 above, but figure out you lineal inches cut. Most software can calculate the lineal inches in a part program, but on a 11.5 " dia circle there is 36.11 lineal inches of cut, round it to 37 inches, multiply by $.064, which comes to $2.37 cutting cost.
4. Add your cutting cost to your material cost, $2.37 + $9.22 = $11.59. That is what I would sell an 11.5" 3/16" circle for.
If I am nesting a bunch of parts efficiently, or using up a whole sheet of steel....I figure I am saving material handling time, and I will use my discretion discounting, but making sure that I can make my minimum hourly shop income. When my plasma machine or welder is running, I shoot for $100/hr in my one man shop. If it is just me grinding or doing other menial tasks, $60/hr.
This works for me, while I only do it as a hobby....it has paid for my cnc machine as well as a whole shop full of tools.
Jim