Design-mold basics of flow

Injection molding Basically the cause can be with the material, the machine, the operator, the operating conditions, the mold or the part design. To check on the material, try material from another supplier to check the machine, use same material, conditions, mold on another machine if the trouble is random, then it is probably the machine try a different operator on the machine trouble appears same location in the product, then flow conditions and look for problems from the front of the piston to the gate. The symptom-cause information is presented as issues related to appearance (color, surface finish and transparency), strength and shape defects and operation and symptoms. 

The basic point of the preceding illustration is that there is a great amount of repetitive information flow in the design process. As a result, what is perceived to be an extremely creative process is actually very repetitive in nature. The types of analytical problems that are encountered in the mold/die design process generally fall into the sciences of fluid mechanics and heat-transfer theory. 

When the melt is forced into the mold, the plunger action could cause the melt to flow back into the screw flights. Generally, with heat-sensitive resins such as PVC and thermosets, a plain or smearhead screw tip is used. For other resins this is not adequate, and a number of different check valves are used. These devices work in the same manner as a check valve in a hydraulic system, allowing fluid to pass only in one direction. These check valves, which are basically a sliding ring or ball check design (Fig. 2-10) are supplied by many manufacturers. Here are some comparisons (100) ... 

The Brabender plasti-corder flow test is used with screw injection molding of TS resins to graphically and accurately measure the flow as it relates to IM. Concern about whether a compound would have a sufficient flow life during its residence time in the barrel led to the use of this test. It is basically a torque rheometer designed to measure and record torque (in meter-grams) vs. the mixing time. It produces a flow curve that is a measure of the compound s processability. 

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