college project : plasma cutter vs water cutter

[ross1993]

Im in the final year of my hnc and ive decided to do reducing costs in structural manufacture. The main part of my project is comparing the use of a water cutter to that of a plasma that my company bought recently.

does anybody have any experience of water cutters good or bad
does anybody have any reasons why they dislike plasma cutters
even information of decent websites or books or anything

so far ive mentioned the haz the poor finish and the fume created from the plasma and have talked about the capabilities of the water cutter in regards to cutting all sorts of materials and various thickness.

any help would be greatly appreciated ,

Cheers ,

Ross

 

[Rrunnach]

How about capital cost and, running cost for each type, to include training costs, too.

 

[ross1993]

ive covered capital cost and running cost and things , never thought about training at all though haha , thanks

 

[Dormeister]

Water cutters tend to be very expensive to repair, and require regular maintence.
For a company that does structural steel I would lean towards a plasma cutter. Two reasons, quicker production times and cheaper consumables.

The only positives for a waterjet machine are the fact that they can cut virtually anything at any thickness.

I used to work for a company that had a waterjet machine, and it would amaze me what it would cut - 75mm Hardox400 sheet was definately up there. Slow mind . . . . . .

 

[Maker]

I've got all this from Google so I don't know how much of it is true (But it all sounds about right to me).

Waterjets are far more expensive to buy, they need loads of maintenance (=lots of downtime), there are more consumables to replace, there is an abrasive garnet which needs replacing every so often, the cut is very slow, the pump draws loads of current, the kerf is more tapered and they make a mess with the spray. The upside is no HAZ, more accurate and a wider range of thickness and material.

Plasma is cheaper to buy, needs less maintenance, has less consumables to replace, has a higher cutting speed, draws a lower current and cuts with a squarer edge. The downside is the HAZ, they can only cut metal and they're less accurate.

I think it's clear which is both cheaper and the better choice for a structural workshop.

 

[ross1993]

we have a python x plasma cutter at work and although it is quick quite a lot of the cuts have to be tidied up with a grinder adding more time to the job , by the time you add this time on the water cutter is finished with a better cut. in response to the cost , the majority of water cutters are less than the python x system we have purchased.Only reason I decided to think about water cutters was down to the versatility of the machine, being able to use rotary axis for circular sections being able to cut all sorts of material.Cheers for the help , looks like im going to have to do a bit more reading

 

[Rrunnach]

Have you looked at laser?

 

[ross1993]

yeah we have one at work , dont get me wrong its great for flat plate , but its limits are 15mm stainless plate and 25mm carbon steel

 

[Maker]

we have a python x plasma cutter at work and although it is quick quite a lot of the cuts have to be tidied up with a grinder adding more time to the job , by the time you add this time on the water cutter is finished with a better cut. in response to the cost , the majority of water cutters are less than the python x system we have purchased.Only reason I decided to think about water cutters was down to the versatility of the machine, being able to use rotary axis for circular sections being able to cut all sorts of material.Cheers for the help , looks like im going to ahve to do a bit more reading

Oh, it's for structural sections, I was picturing a 3 axis one for sheet/plate. In that case, the initial cost is probably fairly similar but what I said about the increased maintenance and running costs still stands true. Could a different cutting head leave a better finish with the plasma you all ready have?

 

[ross1993]

not to sure , think ill have to ask the maintenance lads tomorrow , might be worth looking into that

 

[Maker]

I know Hypertherm make High definition plasma cutters which run on oxygen instead of air, That might be worth looking into if you aren't all ready using that.

 

[Wedg1e]

We used a water-jet cutting company to cut us a range of thicknesses of mild and stainless steel to be turned into calibration blocks used by UT techies: compared to roughing-out by any other method, at the thicknesses we needed, waterjet won hands down and at a fraction of the cost, plus less distortion of the pieces.
Complex shapes cut to within a gnat's chuff of finished size meant less time on the mill/ surface grinder, less wastage for the machine shop and so on.
We could get the thinner pieces laser-cut but when the quality control process includes materials traceability it makes more sense to get the whole batch done in one place.

 

[MrFluffy]

What about the draft angles of the two processes. Ie tolerance, how accurate/square/surface finish are you wanting, what range of sections, what industry, are there any contamination issues at a very small level affecting post cut machining or welding etc, what about the material property changes near the cut.
One up for the waterjet is it can cut non conductive materials. Ie gasket materials, cork, wood etc, whereas the plasma is only able to cut conductive material.
Downside for the waterjet is portability, waterjets are large and bulky usually.
Second downside, the electricity consumption, have you got enough power to the building to support the electrical demands for the high pressure pumps needed, its all part of the upfront cost.
Ongoing you have the materials cost + potentially disposal charges for the abrasives with the waterjet but the same deal with the sludge out your plasma box periodically, both processes have wear parts to factor in.
Also worth looking at service intervals on the kit and comparitive costs too.

 

[ross1993]

cheers everybody , wasnt expecting this much of a response , i appreciate it , currently we have http://www.pythonx.com/ and this is the water cutter i am looking at http://jetedge.com/products/waterjet-motion-systems/edge-x-5-5-axis-waterjet-system believe it or not its cheaper to run the water cutter and cheaper to buy , not too sure on productivity of each yet though.