Quality
Waterjet Newsletter ¨C 09/12/2006
Cost Analysis of AWJ Cutting Cost analysis of abrasive water
jet (AWJ) cutting is an important but complicated task. Several attempts have
been made. The latest attempt was from Andersson and Holmqvist(*). The results
of their analysis are highlighted here. Their cost analysis is part of a
joint effort from a group of 12 members including equipment developers and
users, aimed to promote competitive use of waterjet technology. The primary
goal is to provide practical guides for optimizing the process. A database
containing 500 different combinations of process parameters are being built.
The optimum setting is then determined. As an example, the following
charts (Left ¨C total cost; Right ¨C running cost) shows the cost distributions
based on these assumptions: investment 272,000 €, abrasive 0.43 €/kg,
operator 32.6 €/h, working hours per year 3750 h, pump power 37 kW, max pump
pressure 410 MPa, utilization 70%, orifice/focusing tube 0.35/1.1 mm,
abrasive feeding 625 g/min, 1 cutting head, cutting speed 88 mm/min (cutting
18 mm stainless steel).
Cost distribution charts (in the
paper) for 2 cutting heads as well as 4 cutting heads with smaller nozzles
(0.25/0.76 mm) clearly indicate the advantage of multiple heads in reducing
the percentage of fixed costs (from about 2/3 to about half of total costs)
and thus the cost per unit length. But that comes with more programming and
setup time, more scrap material, and reduced flexibility. Abrasive cost is the biggest part
of the running cost. Increasing abrasive feeding will increase cutting speed
up to a certain point, beyond that the trend will be flatten and even
reversed, called saturation curve. The saturation curve depends on a specific
machine setup. Higher pressure will increase the cutting speed, but will also
increase downtime and maintenance cost. As an example, pressure increase from
350 to 410 MPa will increase cutting speed by 27%, but will triple the cost
of spare parts. * Andersson,
U. and Holmqvist, G. (2005) Strategies for cost ¨C and time-effective use of
abrasive waterjet cutting, in Mohamed Hashish (Ed.), Proceedings of the 2005
WJTA American Waterjet Conference, Houston, Texas, USA, August 21-23, Paper
7B-2. Beyond High
Pressure Fredrick Equipment, a
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Call toll-free at 1-888-928-3758. |
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