QUESTIONS 1. Why are injection molding machines not as effective for mixing addi
ID: 2087519 • Letter: Q
Question
QUESTIONS 1. Why are injection molding machines not as effective for mixing additives or other resins as are traditional extrusion machines? 2. Where is the normal separation point between the material that is removed with each cycle and the material that is in the machine and used in the next cycle? 3. What feature in a mold will allow a hollow, cylindrical part to be made? . What two measures are used in rating the size of an injection molding machine? 5. What is packing the mold, and why is it important in obtaining good injection molded 6. What is a vent in the mold, what problems are prevented by the presence of a vent, and what parameters controi its size? 7. How does high crystallinity in a resin affect the way the resin is injection molded, in- cluding any postmolding operations that might be done? 8. Explain the purpose of a preplasticizing unit. 9. Why is it important to have the sections of the molded part as uniform in thickness as possibie? 10. If nonmelted resin particles are noted in the molded part, what corrections might be made? 1I. Assume that you are assigned to determine the minimum clamping force for a part to be molded out of polystyrene. The part cross-sectional area is 10 x 14 inches. What is the clamping force required if, as a general rule, 2.5 tons of force are needed for each square inch of cross-sectional area? 12. Why is good weldability desirable in a mold cavity material? 13. Why is low specific heat capacity desired in a mold cavity material for some applica- 15. Identify four advantages and two disadvantages of using aluminum rather than tool 16. Identify one major advantage or use of the foilowing gate types: submarine, edge, and ring. 18. Identify three ways to ensure that an injection-molded part stays on the B side of the tions and a high specific heat capacity desired in others? 14. Why are ejector pins made of hard yet shock-resistant materials? steel to make cavities for injection molds. 17. What is the purpose of cold-well extensions? mold when the mold opens. 19. Identify two advantages of using inserts in injection molds.Explanation / Answer
1. Ans - In traditional extrusion machines the barrel is equipped with a screw which blends the mixing additives and other resins and due to the heat generated by mechanical action of screws the blending is more effective than Injection moulding machines.
2.Ans -The separation point lies in the mold.
3.Ans -Cores can be used in the mold to make hollow cylindrical parts.
4.Ans -The two measures are ,Capacity of the mold and the clamping force on the dies.
5.Ans -Packing of mold is a process which takes place when the pressure in the mold is continuously incresed to compact the melt to compensate for plastic shrinkage.It is important because it helps in producing high density products.