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Ask the Search Engineer

Ask the Search Engineer

Dear Search Engineer: I have a 120-cavity mold that produces small parts, each with a dome with a 0.5-mm radius in the bottom of a tapered recess. I need to check all 120 parts from one shot to verify the radius and height of the dome relative to other surfaces on the part. This measurement exercise needs to be repeated every time maintenance is done on the mold. I could try to grind each part down exactly to the center line of the dome and measure under a microscope, but this would be very laborious. Is there a service available that can take these parts and then run through some sort of precision profile measuring machine to check them? -T.M. in Cork, Ireland

Top o' the day to ye: A roundabout way to solve this problem-rather than directly measuring dimensions-is to ask: "Is the mold wearing?" Measuring the change in volume might be the easy way to do this. Simply fill the mold with a fluid and measure how much will fit. Or have a "go/no-go" gauge fabricated, which would basically be a thin piece of hardened metal with the centerline (or other critical aspect) cross section profile(s) of your part ground away, allowing for such tolerances as you define. This gauge can then be used at your site to test each shot group, or as an ongoing quality check, testing parts selected from the production output. The part is placed on a flat, true surface, then the gauge is placed on the part to test for fit into the gauge profile.

Dear Search Engineer: I'm looking for inexpensive ways to attach stainless steel sheet metal (approximately 18 gauge) together without using sheetmetal scews. The product is portable and has a working temperature range of 500F. - B.E. in Ontario, CA

Greetings B.E: We've got several suggestions:

  • Lord 400 Series Acrylic Structural Adhesive works well in bonding stainless to stainless as well as stainless to aluminum. This is a two-part adhesive available in cartridges, making appilcation easy. Product handles temps to 600F.

  • BTM Corporation offers a sheet metal joining system called Tug-L-Loc that requires no fasteners.

  • VHB tapes from 3M work well in this type of application.

  • Other options include spot-welding, riveting, crimping, and clamps.

Dear Search Engineer: I'm looking for a formula to determine the forces needed to crimp the end of a short, hollow cylinder. Do equations exist to calculate the force, knowing the material of the tube, its thickness, and the amount of deformation? -S.C. in PA

Dear S.C.: The action described sounds similar to the crimping of a copper terminal lug. The following manufacturers provide crimping tools and dies for their terminal lugs, so they may be able to provide you with some data:

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