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A variable-drive pump motor adjusts the motor speed to compensate for the demands of the process. These systems typically consume only 70% of the energy consumed by a traditional fixed volume pump. In this system the pump still provides more hydraulic flow than is necessary to mold the actual part and the excess flow which is diverted back to the hydraulic tank. This excess fluid results in an energy loss.

A servo-drive pump motor uses a precisely-controlled servo-motor to drive the hydraulic pump. Rather than maintaining a line pressure, diverting excessive flow, and adjusting servo valves, the flow from the pump is directly sent to the rotary or linear actuator performing the machine function. Since the pump is precisely controlled, the speeds of actions such as injection and screw rotation are controlled directly by the servo-motor. Pressure limits are easily controlled by limiting the torque of the motor. Since the no un-necessary flow is generated, the efficiency of such machines are about as high as a hydraulic machine can be. In many cases, these machines consume only 30% of the energy consumed by fixed drive pump motors.

-Andy

Although I have not seen any studies, I have used these myself with no problems and I know many colleagues who believe they help with screw recovery.

Although these tips intuitively make sense, I would like to see a side-by-side study comparing conventional screw tips with spiral tips to quantify the actual benefits.

-Andy

Generally speaking, amorphous polymers require a long transition zone to properly soften and melt the polymer. This provides a more consistent and homogeneous melt.

When processing semi-crystalline polymers, the polymer softens quickly once the polymer reaches it’s melting temperature. For this reason the transition zone is typically 5-7 times the diameter for semi-crystalline polymers.

Although the transition zone length is small, it is critical to ensure that a long fee zone is being used for semi-crystalline polymers. This allows the material to heat up using more energy from the heater bands to help melt the polymer with less shear. When processing these materials, it is very common to have a feed zone which is nearly half the overall length of the screw. 

-Andy

Although there is no true standard of nomenclature for blended polymers, TPO typically stands for a category of polymers known as Thermoplastic Polyolefins. Polyolefins are a group of polymers comprised of mainly hydrogen and carbon, mainly polyethylene and polypropylene. TPO’s are typically a blend of polyolefins with other additives designed to create a polymer which has a very specific processing and performance characteristic.

In many cases the TPO blend has less semi-crystallinity, less strength, more ductility, higher toughness, more flexibility, and more shrinkage than the base polypropylene and polyethylene constituents.

-Andy