Ever drive a screw that
you thought was short enough, only to have the tip of it break through the other side of your workpiece?
The screw that
had lower levels of tension was the dual core--double thread and the higher in the dual core--single thread.
Do not allow the tip of the screwdriver to turn plum purple or red or the temper will be lost and the screwdriver tip will deform when you are attempting to remove a screw that
is dug in tight.
Also introducing Posi-Melt injection screw that
delivers higher output and better mixing at lower melt temperature.
Here [([Delta]P/L).sub.backward] represents the pressure gradient of the backward pumping screw that
is needed to determine the backward pumping screw characteristic curves.
The Doublemelt is a double-flighted screw that
is said to provide more uniform plastication and prevent melt-cushion fluctuations in small screws of 18 to 30 mm diam.
You may have to experiment with a few different lengths to find a screw that
you can drive fully and that holds securely.
Or, you could be using the wrong screw and/or barrel, a screw that
's too short, adapters and flow channels that are too wide, inappropriate die design, or incorrect heater or thermocouple locations.
The initial compression zone of the kneader is also redesigned with a tapered screw that
allows five times higher free volume.
* Micromolding demands a small screw that
is proportioned to the shot size, but there is a limit to how small.
The next step in this investigation will be to build and evaluate a proposed optimum screw that
combines a short barrier section in the transition zone (for higher output) with a single Union Carbide mixer in the screw's midsection (for good color dispersion and temperature control).
Macro Engineering will show its new Macroplast extruder with a screw that
can be removed from the rear, also without removing downstream equipment or the die.
Like the Buss Kneader, B&P's new CK and CKS machines have a single reciprocating screw that
interacts with stationary pins on the barrel wall.
Compex has a new patented mixing element on the screw that
moves material backward, lessening pressure, shear stress, and temperature, Berstorff says.
Low-intensity vertical mixers for compounding and pellet mixing have a central vertical screw that
transports product from the lower portion of the mixer cone up through the product mass and discharges at the top.