Running Cost Spreadsheet Help 1

[Ryian]

Hi guys,

My new Trumpf Laser 1030 has arrived today and Im looking for some advice on running costs. I would like to make a spreadsheet so I can cost parts up for quotations. We have Radan software so it gives me the cutting time to complete the job but I need more info for example.

I know the cost of my gas per litre but I have a formula from Trumpf how to work the amount you use, They say its 2x the nozzel did x 0.555 x gas pressure. this gives me how much gas is being used. Then for electric its so much pence per hour. But I really want to know if anyone has a spreadsheet i could use pls.

 

[Foostrap]

I don't have a spreadsheet, but you will have to add those items if you want to be accurate:
First you have your fixed charges (things to pay even if you don't run the machine)
-Depreciation (amount paid for machine / number of years to pay machine back). Then convert to $/hour.
-Interest paid. Based on interest %, calculate interest paid/year, then convert to $/hour
-Space cost (area used * $/ft2. Calculated $ paid per year and convert to $/hour)
-Maintenance. Get quotes for all the PM required in the next 6 years (for example). --> calculate $/hour

Then you have all your variable charges (things to pay based on cutting time):
-Energy. Take machine max kW (including laser, chiller, exhaust, compressor,...). Multiply by your average kWh --> get $/hour of cutting.
-Consumables (price of lenses, nozzles,...). Estimate how many hours you get out of each item (3000 hours on lens, could be less depening on power and gas pressure).
-Laser gas consumption (get flow rate, cost of bottle, volume of bottle and calculate $/hour)
-Assist gas. This depends on material to be cut (get flow rate for a couple of materials, get price/volume unit, calculate $/hour)

-Operator cost

 

[Ryian]

Foostrap ur information has been well received thankyou. The other parts I need to get my head around is the consumables. We cut a part for example say 2mm mild steel with oxygen it's a 50mm sq with four hold 10mm in dia. I know how long it would take from the software and I know the machine will be running at 1500kw to cut it but how do I work out how much gas and electricity do I use.

 

[Foostrap]

Based on the material to cut, you know the nozzle size and the gas pressure. With that you can calculate the assist gas flow. Multiply by how long it will take to cut the part, and you will get the volume of gas needed. Then multiply by your gas cost per volume and you can calculate the gas cost.
For the electricity, this is harder to know how many kW your machine uses based on the power commanded. I would use the kW based on the machine max power. Unless, you can get some type of chart from the machine manufacturer showing kW used per commanded laser W.

 

[Ryian]

Do you have an example pls. For instance. If the nozzle is 1.5mm and the part needs 1 bar of pressure and it takes 60 sec to cut the part. What would I use. We pay .55p per litre for liquid oxygen it's a big vessel. Thanks

 

[Foostrap]

With 1 bar and a nozzle of 1.5mm, oxygen flow is about 85 ft3/h or 2407 l/h, or about 40 l/min. So if it takes 1 min to cut the part, you would use about 40 l of gas oxygen. 1 liter of liquid oxygen will expand to about 800 liters of gas oxygen. So your cost would be about 0.55p/800 * 40 = 0.03p
Problem with liquid oxygen is that the pressure keeps on building inside the tank. This means that when not cutting, you will eventually lose oxygen through safety valve (if not cutting overnight for example).

 

[Ryian]

Footstrap your a star. Thank you do much. How did you work out the litres needed?

 

[Foostrap]

volume = flow * time.
Knowing your gas flow is 40l per minute, and that your part takes 60 seconds to cut (which is 1 minute), volume = 40 * 1 = 40 litres.

 

[Ryian]

Ok Mate.

Let me see if Ive got this right.

Gas..

Nozzel dia sq x gas pressure x .555 = CM3 (cubic meters sq per hour)
Example:- 1.5mm dia nozzel SQ = 1.23 x 5 bar pressure x .555 = 3.41 CM3 hour.

My tank holds 240L Liquid oxygen which expands to 201,600L converted to cubic meters would be 201cm3. Air porducts believe you lose 2 per cent a day thats 5L Liquied oxygen.
from this i can work out what im using if its right???

Electic...

the 1030 uses 52 KW full wack so if im paying .10p a KW hr then thats £5.20 an hr to run it??

 

[Foostrap]

Hi Ryian,
Not sure if the formula Trumph gave you is correct. For a 1.5mm nozzle and 5 bar gas pressure, I'm calculating a flow of about 270 ft3/h (about 7.6 cubic meter per hour). For the 2% oxygen loss, that means you'll lose less when the tank gets empty, but that gets too complicated. Assuming 5 l loss per day should be safe.
For the electrical, yes, that seems correct.

 

[Ryian]

Ok. How do you work out the cm3 per hr?

 

[Foostrap]

Attached is a little program that will calculate the flow for you. Kind of wrote it quickly, so let me know if there are any problems.