Smart Molding International 1-2022

34 peripherals & automation smart_molding international 1/2022 P lastics Engineering Company manufactures a wide range of custom-formulated moulding compounds and industrial resins. A big share of its production is dedi - cated to novolac and resol thermoset moulding compounds — also known as phenolic resins — which it sells under the PLENCO trademark. These resins are highly adaptable and used across many applications. As a result, the company tailors its products to each customer’s requirements. That could entail adjusting the molecular weight, moisture content, viscosity, pH, particle size, reactivity and other properties. Immediately prior to packaging, the resins are blended with reinforcements, minerals, fillers and/or liquid addi - tives, a task performed by two model 700-TSC-180-MS Rotary Batch Mixers which have been in service since 1983. Five-minute tumbling prevents degradation The mixers have no agitators, inter - nal shafts or related bearings or seals. Instead, a horizontally oriented ves - sel rotates on external trunnion rings located at each end. Ingredients flow into the vessel through a stationary in - let at one end and discharge through a stationary outlet at the other. With - in the vessel are mixing flights, also called baffles or lifters, which create a gentle four-way tumble-turn-cut- fold mixing action that produces on- spec blends in 3 to 5 minutes. Randy Block, a mechanical engineer at Plastics Engineering, says, “We get a good, thorough blend without degrad - ing the product.” To fill the vessels, a pneumatic con - veyor transports resins from com - pounding units to a holding hopper, which also separates out dust. When enough material accumulates in the hopper, it is discharged to one of the mixers as it slowly rotates. Continuous rotation of mixer drum during discharge prevents stratification of ingredients having disparate sizes, shapes and bulk densities, and empties the batch rapidly in a steady stream. Five minute blending of compounds going on four decades Photos source: RAPP ADVERTISING, INC.