Molding - Manufacturing and Industrial Engineering Interview Questions

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Top Mechanical Interview questions and answers on Molding with explanation for Manufacturing and Industrial interview, competitive exams and entrance test.

1. What  is the  important characteristics of plastics?         

It can be molded into finished product by application of heat and pressure. 

2. What are the advantages of plastics over metals?
  • Low weight 
  • Corrosion resistance 
  • Insulation properties
  • Electrical properties
  • Cheaper 
  • Easy to handle 
  • Surface properties 
  • Reusable
 3. Explain the disadvantages of plastics? 
  • Low strength 
  • Low heat resistance
  • Poor mechanical properties
  • Difficulty to repair
4. How to classify the plastics?
  • Natural : milk of rubber tree, cellulose
  • Semi synthetic
  • Synthetic
5. Types of plastics based on chemical behavior?
  • Thermo plastics 
  • Thermosetting plastics
6. Difference between thermo set and thermo plastics?
 Thermoplastics:
  • Can be re softened and reused
  • No chemical changes during heating.
  • In granular form
  • Needle structure 
  • Hard but not brittle
Thermo set plastics:
  • Cannot be re softened and reused
  • Chemical changes during heating etc.
  • In powder form
  • Cross linked structure 
  • Hard and brittle 
7. Give Example of thermoplastics

ABS, PP, CA, PMMA, PS, PC, POM etc.

8. Perspex is the trade name of ---- ?

 CA

10. Perspex is the trade name of ---- ?

CA

11. Nylon is the trade name of ---- ?

 PA

12. Delrin is the trade name of ---- ?

POM

13. Teflone is the trade name of ……….?

PTFE

14. What  is MFI?

Flow capacity of different grades of thermoplastics are inversely proportional to molecular weight.

15. About ABS? 

Shrinkage 0.5%. It is heat resistant, provides good insulation and exhibit electrical properties. Examples are general purpose safety helmets, pipe fittings, television, radio etc.

16. About  CA ?

Shrinkage 0.3-0.8%. Its main properties are transparency and surface texture. Examples are Tool handle, goggles, TV screens.

17. About HDPE?

Shrinkage 3-4%. Main features of HDFE are high density, rigidity, strength, hardness and chemical resistance. Examples are milk bottle crates, fish boxes etc.

18. About LDPE?

Shrinkage 0.8-1.5%. It is crystalline and not available in transparent form. Examples are shopping baskets, waste baskets etc.

19. About PA?

 Shrinkage 0.7-1.5%. It is tough and high rigid. Examples are light duty gears, sprockets, bearings etc.

20.About PC?

Shrinkage 0.5-0.7%. It is known optical transparency, rigidity and toughness. Examples are goggles, lenses, safety helmets etc.

21.About PP?

Shrinkage 1-3%. It is flammable and degradable in sun light and stable. Examples are air cleaner, garden furniture etc.

22.About PS?

Shrinkage 0.2-0.8%. It is clear, brittle and it can be easily molded. Examples are toys, house hold appliances, electronic housings etc.

23.About PVC?

Shrinkage (FLEXI 1.5-3%,RIGID 0.2-0.4%). It is rigid and not very tough and very low cost. Example - Pipes fittings.

24. Examples for thermosetting materials ?

Alkyds, epoxies, pf, mf, urea, polyester

25. What  is fillers and additives?

Adding of small molecules to plastics to get some characteristics (color, flexibility etc.). Fillers are commonly used with thermosetting plastics. Additives are of two types,

  • Physical means such as plasticizer
  • Chemical means--- stabilizer.                      

26. What  are the mold release agents?

  1. External with mold surface e.g. Polyvinyl alcohol 
  2. Internal with resins eg. Silicon oil 

27. What  are the types of injection molding machines?

  • Plunger injection cylinder 
  • Two stage plunger injection cylinder 
  • Pre plasticizer two stage screw injection cylinder 
  • Reciprocating screw injection cylinder

28. What  are the divided sections of screw of injection molding machines ?

  • Feed zone 
  • Compression zone 
  • Melting zone  

29. What  do you meant by nozzle ?

Nozzle connected to the end of the barrel through which soften materials inserted in the mold. 

 30. What  are the types of nozzle ?

  • Reverse taper (melt valve)- for PA, ABS etc.
  • Removable tip
  • Standard of general purpose 

30. What are the types of nozzle ?

  • Reverse taper (melt valve) - for PA,ABS etc.
  • Removable tip
  • Standard of general purpose
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