260A Operating Costs?

[jgramlich]

I wandered over an interesting article on thefabricator.com today. It's called "Estimating your cutting costs":

http://www.thefabricator.com/PlasmaC...cle.cfm?ID=146


Right about the same time our accounting department is telling me a job that I did a week or so ago came out to be over double the price of our competition and that we shouldn't be doing such jobs but subbing them out. I don't care much for subbing out. :-)


So, I need to fix their formula, not my cutting process, and I could use a hand with estimating these costs.

The unit is an HPR 260, manual gas. I cut mostly between 1/4" and 3/4" but occasionally...well, lets call it about 10% of the cutting is between 1" and 1 1/2" (yes, yes, yes, the '260 is only rated for 1-1/4", blah blah blah...I don't cut *that* much 1.5 on it, and yes it does eat the dickens out of my consumables when I do...).

We usually run 6' x 10' sheets and my anecdotal consumable usage gets me:

1 sheet of 1" at 260 amps per electrode.
2 sheets of 3/4" at 260 amps per electrode.
3 sheets of 1/2 at 130 amps...
4 sheets of 1/4...

Of course it's all relative. I've done 12 parts on one sheet with no holes and 150 parts on one sheet with a thousand holes.

Btw, Jim, I caught your excellent article on consumable life:

http://www.thefabricator.com/PlasmaC...le.cfm?ID=2009

Good stuff...gonna wash my hands more often now ;-)


So anyways...electricity usage? Any ideas? I can gauge my oxygen use pretty easily, I'm getting about 2 months out of a LiqOx bottle. Labor is fairly easy to estimate, but what I'm really looking for is how much electricity am I using. Anyone out there have a chart with amperage vs hours of cutting in kWh?

As to other costs...how big a factor is consumable usage in total cost? 5%? 20%? It seems to me that consumable cost, as long as you're nice to your torch and use proper settings that they'll last long enough to make their cost negligible, but I could be wrong.

[PlasmaGuru]

Using 260 amp consumables, 500 pierces per set, and approx 60 seconds per cut. If you only consider consumables, gasses, and electricity your approximate costs per foot of cut for mild steel would be

1/4" = $0.008
1/2" = $0.013
3/4" = $0.021
1" = $0.03

As you can see these are very low which is why the HPR series of industrial high definition plasma systems from Hypertherm are the choice of most plate cutting houses looking for the lowest possible operational costs.

The only way to come up with a cost per hour is to take into consideration the "human factor" i.e. material handling etc.

The real expense is operator labour. Increase "arc-on" % per shift and your operational costs drop like a stone. Typically this is achieved by loading and off-loading your machine more efficiently and miminizing the time require changing consumables.

Best regards,

[jgramlich]

Interesting. That is very low. Lower that I figured. Do you know how those numbers were generated or is that from a study someone did once-upon-a-time?

[PlasmaGuru]

Those numbers are a combination of Hypertherms research data and ongoing real world experience.

Typically the consumable portion of the operating cost is 1.5-2% of the overall cost to run the machine.

To take it one setup further lets say you are cutting 1" MS at 260A and achieve approx 35% "arc-on" time in an 8 hour shift. The rest of the time is wasted in material handling, coffee breaks, lunch and misc stuff. If your operator is getting paid $20/hr your overall cost to run the machine per hour would be $24 not including the cost of the material itself or the capital repayment of the machine.

We have found these numbers to be quite accurate all things being equal assuming your machine is running properly i.e. 1"MS @260A with approx 4.5 hrs per consumable set running for 4.5 hrs straight. Cutting at 65 ipm you cut approx 1462.5 feet @ $0.03/ft which would cost approx $44 in gas, elec, and consumables

[jgramlich]

Thanks! That's some great data. I'm going to have to see if I can't replicate that with my own setup.

[jimcolt]

jrgramlich,

If you want I can email a spreadsheet that you can plug some of your numbers into...that will help you calculate your operating costs with a Hypertherm system. There are a lot of variables....as you know, that affect your cost per part! Plasma Guru's numbers are pretty close.....however consumable cost as a percentage of total operating cost is in the 6% to 9% range with a system with long consumable life technology such as your HPR260.....can be as high as 20% with lesser plasma systems. Still....material handling.....getting plate on the table and parts and scrap off are the easiest ways to improve plasma operating costs.

Many people think that a low cost cutting machine and a low cost air plasma with low cost consumables are the key to making metal parts inexpensively......and it may be in low volume, low duty cycle applications. In high duty cycle and high production applications....high definition plasma cuts dramatically faster, with better cut quality and at lower operating cost...

Send me a reminder email with your direct email address....and I'll forward the cost calculation spreadsheet for Hypertherm plasma.

Jim Colt