Tuesday, February 15, 2011

Waterjet Cutting Gasket vs. Diecutting

Written By Mark Batson Baril

Waterjet Cutting Gaskets may be a better answer than die cutting.

"Given A Diecuttable Product In Production Quantities - No Other Cutting Method Can Beat Diecutting For Processing Speed."

Here's a quick one from a friend in NJ. He recently called seeking out a little relief from the mighty jamb he had gotten himself into with a good customer. It would seem that the drawing that was first sent on over to be looked at and quoted upon had been blown up to about four times its' actual size so the engineer could see all those fine nooks and crannies. Well, when the actual order came in for the 100,000 gaskets, the dimensioning was full and complete and revealed that the looming Christmas season may be a little more stressful than usual this year. Here's how it all went down.

The Question:
Please check out the attached drawing of a gasket product we just realized is perhaps too tough for a steel rule die. Can you suggest another type of tool or punch, or anything that will get the job done for us? "We're in a pinch and could use some relief" (I believe those were the exact words used.)

The Answers:
Some of the details of the fax that followed showed us a smallish gasket about 1.000" x 2.000" (25.4mm x 50.8mm) with a few small ovals, a few round cutouts, and four incredibly tight dog bone style cut outs that just about filled the image with clutter. The dog bone shape had a narrow slot to it that curved and the width of that slot was a mere .050" (1.27mm) wide. The kicker was this - the material is a specialty, ground to thickness, material in about a 65 durometer (pretty non-squishy stuff) in a finished thickness of .065"(1.65mm). Bingo! Very quickly the thinking started to shift. Steel rule dies and specialty punches were immediately ruled out. Cutting would be tough, and ejection would be even harder. They'd blow up a few thousand dollars worth of these tools and we would get taken off this guys Christmas list real fast. Male/Female tooling with a progressive design may accomplish the task but it was still risky since the other thing that wasn't on the original print or on the fax sent to us was the tolerancing. Yep... ±.005"(.127mm) on the finished part for all dimensioning! This is a really tough part to cut!

We started to explore the waterjet end of our industry for the short haul while at the same time our stressed-out inquirer explored specialty molding for the long haul. Sample cuts were made on the waterjet and the results were fantastic. Tolerances could be held and perfect nesting eliminated the amount of waste that would have typically been produced during a normal punch and feed. So now the trick was to get the pricing close to where the job had been quoted originally. Maybe to save face the diecutter would loose a bit of money or perhaps if the customer were understanding, there could be some room for upward movement in the price. I didn't think the diecutting price could be matched with waterjet cutting and once again the basic rule was proved. The rule of thumb on pricing diecutting vs. other cutting methods is this: Given a diecuttable product in production quantities - no other cutting method can beat diecutting for processing speed.

We did have several things working in our "Save Face for the Customer" favor, however.
  • The parts were going to be close to impossible to produce well on any type of cutting die. This was going to be a tough one for any diecutter to handle.
  • The Waterjet process will use less material to produce the same number of parts and that's great on this particular job because this material is pricey.
  • Partial deliveries were due on this job and partials could be produced without tooling, almost immediately.

So to make a long drawn-out process seem a bit shorter - A manufacturer was found that waterjet cuts using a four head machine. Processing speed got better by four times compared to the prototype run and although the price was higher than diecutting, and unfortunately higher than the base quote, the job dropped back into the producible realm. This dropped the stress level back into a manageable level and kept a few purchasing agents happy for a while. The larger batch of yearly parts will more than likely go to some type of a molding process to save money, but in the short run the problem was solved. This fix will also afford a bit of time to explore male/female tooling that has what we feel is a remote possibility of being the best method.

7 comments:

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