Backward Pumping Kneading Block

Backward-pumping elements give a good distributive mixin, as the name implles they transport the product upstream instead of downstream. They are used for performing a more longltudunal homogenization.

The backward pumping kneading block plays a role of adjusting the fullness of the material and extending the residence time of the material in the barrel during the material mixing. Its blocking force is weaker than the reverse feed screw sleeve, but slightly stronger than the 90 ° kneading block. Which area should choose the backward pumping kneading block? How to use it with the reverse screw sleeve in the full length? How many reverse elements should be selected for the full length of the screw? All of these questions are testing the experience and skill of the modification engineer, which has a considerable impact on the quality of the modified special material or masterbatch. For example, in the case of nylon (PA66) flame retardant enhanced modification, the first kneading zone must be stringed by four kneading blocks (such as 30 ° + 45 ° + 45 ° ++ 45 ° L), and must be finished by 45 ° L blocks Stuffing, the whole machine can stably plasticize and stably extrude the PA66, a strong crystalline plastic.

The materials for selection and the heat treatment

△ The nitrided steel, 72h ( two-stage gas nitriding);
△ The high-speed tool steel, W6Mo5Cr4V2 (vacuum quenching);
△ The die steel, D2(1.2379, SKD11,K110)  (quenching + tempering);
△ The bimetal composite rods (inside tough, outside hard or corrosion resistant), supplied by SAAR company from German or HTM company from Swiss;
△ Other special materials such as Hastelloy, W-C, nickel-based alloy, etc.

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