Plastics Technology

APR 2017

Plastics Technology - Dedicated to improving Plastics Processing.

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WHICH ELBOW PROBLEM DO YOU NEED TO SOLVE? PROBLEM CAUSE SOLUTION Formation of streamers, angel hair and snake skins when conveying plastic pellets Plastic pellets skidding against the outside radius of conventional elbows create friction and heat, melting pellet surfaces. Smart Elbow ® replacements from HammerTek eliminate these problems by eliminating impact Unlike conventional "impact" elbows and "plugged-tee" elbows that rely on material impact to change direction, HammerTek's Smart Elbow ® design features a spherical chamber that protrudes partially beyond the desired 90º or 45º pathway, which causes a ball of pellets suspended in air to rotate, gently deflecting incoming pellets around the bend. No impact means no wear and no fines and no streamers, angel hair or snake skins. Wear and failure when conveying glass-filled, mineral-filled or other abrasive pellets Abrasive pellets hit the outside radius of conventional impact elbows at high speed, continually wearing through the elbow wall. EE-0299 Free, No-Risk Trial Offer See how Smart Elbow® deflection elbows eliminate conventional and plugged-tee impact elbow problems—at no cost or obligation. 1-610-814-2273 sales@HammerTek.com www.HammerTek.com 45° and 90° elbows available in diameters ranging from 1.25 to 18 inch measured the hardness value of one of these inserts to be 180 HB. These inserts are a nice feature. It would be nicer if they were over 300 HB. A couple of suppliers offer inexpen- sive locating rings made of plastic to prevent damage to the platen. I am not a big fan of these plastic rings for several reasons. However, I know some supervi- sors with ruthless setup men who love them. Another more expensive alterna- tive is a relatively new design that incor- porates a soft plastic bumper projecting from the front face of the ring. If you look carefully at your platen (and your tie rods), you will see the majority of the dents are straight, not curved. These dents were obviously not caused by locating rings. The edges and corners of your molds caused them. Most mold bases are made of either pre-hard AISI P-20 steel (DME #2) or pre-hard 420 stainless steel (DME # 7), both of which are over 300 HB. That's as much as three times harder than most platens. Most of the damage caused by locating rings is at or near the alignment hole of the platen. The most concerning damage occurs when setup personnel close the mold under high pressure with the ring not properly aligned or fully engaged in the hole. This typically damages both the ring and the hole. Standard and LN type locating rings do not protrude very far beyond the face of the mold and are usually partly to blame for this type of damage. The damage is typi- cally on the non-operator side and occurs when only one person sets up the mold. That's because it's relatively easy to see the locating ring's vertical position, as well as the one visible side. Everything looks fine until you hear that crunching sound. To help ensure the entire locating ring is fully Most of the damage caused by locating rings are at or near the align- ment hole of the platen. Here is platen damage caused by the edges and corners of a mold. @plastechmag 39 Plastics Technology T O O L I N G

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