December 2008 Edition

waterjet

A New Approach

With quick processing as a goal, a shop tried using a waterjet instead of a CNC mill for a job and it did so with success

Creative thinking and the ability to look at things from a different angle are characteristics that set East End Welding, Tallmadge, OH, apart from its competitors. When faced with the need to have a slot in each end of a stainless steel shaft, it looked beyond the obvious choice of CNC milling and sought a different approach – a waterjet.

With traditional CNC milling, the shaft would be mounted vertically in a fixture and clamped into position. A vertical mill would then take several passes until the slot depth of about 1" would be cut. The tools used would also have to be shaped to ensure that the bottom of the slot was flat with a minimal radius in the corners.

Once the slot was completed, the shaft would be rotated 180° and the same procedure repeated; straightforward and not too difficult for a shop with machining experience. But, instead of turning the piece 180°, East End Welding rotated its viewpoint.

"We wanted to be able to get these parts processed as quickly as possible," John Susong, owner of the company said. So he decided to try something else.

The company operates a dual-head, high-definition, 5-axis plasma; a 30'×13' four-head waterjet cutting system; a dual-head 5-axis oxy-fuel cutting system; a 6-axis 4,000W laser, and a variety of CNC machinery including a 30'×15'×5' vertical mill.

Few companies have such a range of manufacturing equipment under one roof. So it is always a challenge, according to Susong, to see which process is best for each project and to see if a traditional method can be replaced by a more efficient, non-traditional process.

In the case of cutting the slot, CNC machining, on the surface, was the obvious choice, but after some consideration of alternatives, the shop selected the waterjet. It offered several advantages:

• With a four-head waterjet, four parts could be cut simultaneously. The parts could be cut laid into a fixture so each shaft centered itself.
• The slot at each end could be cut in one program, the waterjet cutting the slot at one end, then moving to the other end, cutting the other slot.
• The fixture required minimal holding force of the shaft, a single clamp could hold the part during cutting.
• The fixture could accommodate eight shafts – four shafts would be cut while another four were loaded. The waterjet could alternate between each set of four parts, with no dead time between cutting. Production would be driven by the cycle time of the machine rather than the speed of the operator.
• Cuts would be clean and meet specifications.
• The fixture could be made from a flat sheet of steel, fabricated easily, cut with the four-head waterjet, and would not need to be saved.
• Programming would be easy since no special skills or software were needed.
• The cost of making the parts would be less than milling with the CNC.
• Using the waterjet would free the CNC to do work that only it could do.
• No special operator training is needed to cut the parts. The waterjet operator would handle the job in the same manner as a flat sheet of material is cut.

The Three R’s

East End Welding operates a waterjet cutting system from WARDJet, Tallmadge, OH. The cutting system has two 100 hp pumps, with 50 hp allocated to each of the four cutting heads. A 0.014" orifice combined with a 0.04" nozzle, running at 60,000 psi with 1.3 lb of 50 mesh garnet abrasive generates the cutting stream. All abrasive is recycled through the abrasive recycling system.

With abrasive as the largest cost of operating a waterjet, abrasive recycling can cut operating costs. It is possible to reuse up to 80 percent of the abrasive, reducing the cost of abrasive to 20 percent of what it costs new. If abrasive is up to 50 percent of the total cost, recycling could reduce operating cost by as much as 40 percent.

The Right Decision

A multitude of shafts have been processed since the first set were completed using the waterjet. The decision to use waterjet to cut slots proved to be easy, cost-effective, and successful.

With eight parts loaded, and four parts being changed while the other four are cutting, production times and operating cost are predictable and quantifiable.

"There is no doubt using the waterjet to process and cut these shafts is the right way to go," Susong said.

"The focus of building our waterjets is to be true to our motto, Not Just a Waterjet" Richard Ward, president of WARDJet, said. The company’s mission is to offer the advantages of waterjet cutting to users so it can be viewed as a CNC platform with which many processes can be automated. WARDJet, Inc.

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What do you think?
Will the information in this article increase efficiency or save time, money, or effort? Let us know by e-mail from our website at www.ModernApplicationsNews.com or e-mail the editor at pnofel@nelsonpub.com.