Nov_Dec_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 1 7 2 4 5. To assess flammability, follow the UL 94 test standard, which classifies plastics based on how they burn in various orientations and thicknesses. For extreme cases, it may be nec- essary to engage a third party, an SGS or TÜV for example, that offers mate- rials testing and certification services. Another option, especially for recurring issues, would be to expand your in- house testing capabilities. We recently did that, acquiring a PolyMax plastics analyzer for our quality control de- partment. The PolyMax is a handheld spectrometer that uses laser-induced Raman scattering to confirm the chem- ical composition of plastics. The oper- ating principle is named after Chandra Raman who discovered that, under the right conditions, molecules in chemi- cal compounds vibrate at a unique fre- quency and energy, which serves as a sort of fingerprint when measured. whether it’s metals or plastics. We weeded out the truly outrageous sup- pliers, but that said, many of our best suppliers do not own inspection equip- ment, so they often have no idea what they are shipping to us. This shouldn’t scare companies away from working with manufacturers based in China as long as they have the proper testing and inspection equipment and know how to use it. AM&P: How do you ensure the quality of plastics for injection molding, CNC machining, and vacuum casting? GS: Excellent question because this is a major challenge for everyone. It’s important to thoroughly vet and establish a relationship with every sup- plier. For vacuum casting, we use one supplier, Axson, and we buy directly from them. Most problems with vacu- um casting resins are revealed during casting and include excessive bubbling, streaking, under-curing, and discol- oration. However, these are the least of our concerns. The real issue is with plastic bar and plate for CNC machining and injection-molding resins. For this, we have found the following tests to be most helpful: 1. Do a visual inspection to make sure the plate or bar looks like the specified material and check for cavities and inclusions. Also make sure that labels and bags are genuine. If in doubt, take a picture of the bag and send it to the original material manufacturer for confirmation. 2. Conduct a melt flow index test. The melt flow rate or index of a plastic depends on its additives, molecular weight, and other factors, all of which can be determined by the test. 3. Use a durometer Shore A/D test, if appropriate, to measure hardness. 4. Run a burn-off test to measure glass content. When burned, most plastics emit characteristic odors, flame colors, and melt patterns that help to identify them. test by which materials, such as met- als, fabrics, plastics, and ceramics, are exposed to low level, short-wave x-rays, alsoknownas gamma radiation. Thanks to the well-defined order of matter, each element reflects the radiation at a characteristic wavelength that tells a specially calibrated spectrometer what elements are present in the test sample and in what relative concentrations. XRF analyzers can also detect materials banned under the Restriction of Haz- ardous Substances (RoHS) legislation. The test takes less than 30 seconds. AM&P: What is the most unique material you’ve used in a prototype or product? GS: It would have to be Luvocom 50/CF/10/GF/10/TF/10/BK. It’s a poly- carbonate—10% carbon filled, 10% glass filled, and 10% PTFE lubricant— used for plastic injection molding. This particular grade of Luvocomwas select- ed because the end product had a vari- ety of conflicting needs. It had to be low friction, resistant to high and repeated impacts by metal objects, and flow easi- ly into an extremely complex geometry. It’s truly a bizarre material. Typical ap- plications are sporting goods, medical products, office goods, and industrial parts. We used the material to make components for a coin sorting machine. Flying coins are extremely aggressive, yet machine builders don’t want to use metals or ceramics due to potential damage to the coins. ~AM&P Formore information: Gordon Styles is president of Star Rapid Manufacturing Ltd., Unit 04, 11/F, Tern Plaza, 5 Camer- on Road, Tsim Sha Tsui, Kowloon, Hong Kong 999077, gordon.styles@starrapid. com, www.starrapid.com. AM&P: What about metals? How do you test them? GS: One way we test metals is with an optical emission spectrometer (OES), an instrument that uses a cur- rent to electrically charge test samples. The additional energy is released in the form of a plasma, the spectral com- ponents of which are unique to each element contained in the sample. By reading the various wavelengths in the plasma, an optical spectrometer can determine the composition of the met- al. This is considered a very detailed and accurate test. Another measurement technology we use on metals is x-ray fluorescence (XRF) analysis. This is a nondestructive The PolyMax plastics analyzer is used to verify chemical composition.