Plastics: Gas Shows New Side

Injection molding machines represent an established, reliable, effective means of making plastic parts, but use of the process becomes more challenging as the size of the part increases. The larger the part, the more tonnage required to clamp the part. In addition, common internal plastic part features such as reinforcing ribs, fastener bosses, component mounting placements, all become more problematic with larger parts because these features can create visible sink marks on the exterior side where aesthetics matter most. But now, an emerging technique is attracting attention because it can create a large plastic part that is ribbed for strength, yet is thin-walled and absent of sink marks, ejection pin marks, warping and other part distortions.

The technique, called external gas molding, uses pressurized nitrogen gas that is injected into the mold cavity that has been nearly filled with plastic resins. The gas forms a micro-thin layer between the plastic and the adjacent mold surface and uniformly presses the plastic against the opposite mold surface, smoothing out sink marks that could form as the plastic cools and begins to solidify and shrink.  Find out more.

The Meller Sapphire and Ruby Balls are available for use as check valve elements, bearings, spacers and other applications requiring a spherical, wear-resistant, and chemically inert ball. The miniature balls are offered in 42 different inch and metric sizes from 0.1 mm to 1/2-in. diameter and feature 0.000025 in. (AFBMA Grade 25 tolerance) per ball sphericity. They exhibit Moh 9 hardness, and are impervious to common acids, alkalis, solvents, and bodily fluids, and are fracture-resistant. They have finishes of 20 to 10 scratch-dig or better and can be precision ground and polished into plano-convex lenses if required. Find out more.

Insul-Tacks permanently fasten insulation to prepainted metal surfaces without marking the finished side of the metal. Zinc-plated and heat treated, they do not degrade in extreme temperatures or corrosive environments. Insul-Tacks are manufactured with a precisely formed conical point that is driven through the insulation and into the sheet metal with controlled impact. The point penetrates no more than 0.015 in. and grips into the surface of the sheet metal. Insulation is held in place with a 1-in. retaining cap. Each fastener holds about 40 lbs. and they are applied with automatic equipment and no adhesive overspray and no need for fume hoods or for special adhesive-fume ventilation. Want to learn more?

PEM R’ANGLE self-clinching fasteners create right-angle attachment points in metal sheets as thin as .04 in. The aluminum fasteners come in self-tapping or steel threaded versions. They eliminate tab cutouts for better EMI/RFI shielding and time-consuming welding operations, material and assembly cost savings due to reduced hardware, and more attractive unmarred assemblies. Type RAA aluminum self-tapping fasteners for thin aluminum sheets accept thread-forming screws in sizes #4-40, #6-32, #8-32, and M3 and M4. Type RAS steel threaded fasteners for thin aluminum or steel sheets are available in thread sizes #4-40, #6-32, #8-32, and M3 and M4. Depending on type, maximum side loads for the fasteners upon installation can range up to 21 lbs. Find out more.