Ask: The Search Engineer

Dear Search Engineer: I have a cutting machine for plastics and a flatbed laser for manufacturing. Currently, D-2 tool steel is the standard for the cutters, hardened to 55-60 Rc, but costs could be greatly reduced if a laser cuttable steel could be substituted. (We have not been successful in cutting D-2 with the laser.) These machine cutters need severe abrasion resistance plus hardness for glass-reinforced plastics we are using. Any suggestions?-A.C. in D.C.

Dear A.C.: D-2 is darn tough stuff and few machine shops want to fool with it. Have you considered Industrial Hard Chrome Plating the cutters made out of a 4140 material? The hard chrome plating is very lubrous and has a hardness of about 60-65 Rockwell. You can also try a steel that is suitable for nitriding or a boron-treated AR steel. They are low alloy and are likely amenable to nitriding.

Search Engineer: I am looking for electrically controlled fiber optic devices, components, etc., that allow several fiber optic inputs (up to 12) to a single output fiber. The input photon signals (very low level) need to be electronically selected via TTL control. Both multiplexer and demultiplexer devices are needed. -D.O., Albany, NY.

Hi D.O.: Both Lucent and TI make micro mirror arrays that are digitally controlled. Weed Instrument has a fiber optic MUX as well.

Dear readers: Part of my astute answer was cut off in the 4/21/03 issue. As a result, we had several letters and even more comments. I've included the entire answer and added a few reader comments as well.

Dear Search Engineer: I have an application requiring a highly "springy" material. The particular property of importance is the dissipative loss or hysteresis, which I require to be a minimum. In other words, I would ideally wish the material to "ring" indefinitely when struck/plucked. -J.A. from Huntsville, AL.

Hey there J.A.: Cobalt-nickel alloy, Egiloy, is a very good spring material. It has high strength, ductitility, excellent fatique life, non-magnetic, and suitable to high temperature application. Hope this rings true with you!

T.G in Toronto pointed out that titanium alloys also make excellent springs due to the material's combination of modulus of elasticity and strength. Stack heights are also lower and have a more progressive "feel."

And R.F., Ph.D. from Lexington, MA writes, "Years ago I ran tests to find the metal with the lowest internal damping for making a "tuned" gyro. We made cantilever beam samples and vibrated them with a capacitance pickoff in a vacuum chamber. After shutting off the forcing function, we measured the decay time. The winner was...aluminum!"

Keep those cards and emails comin' in folks!