Molding Interview Questions & Answers

Question 1. What Is The Important Characteristics Of Plastics?

Answer :

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

Question 2. What Are The Advantages Of Plastics Over Metals?

Answer :

• Low weight 
• Corrosion resistance 
• Insulation properties
• Electrical properties
• Cheaper 
• Easy to handle 
• Surface properties 
• Reusable

Question 3. Explain The Disadvantages Of Plastics?

Answer :

• Low strength 
• Low heat resistance
• Poor mechanical properties
• Difficulty to repair

Question 4. How To Classify The Plastics?

Answer :

• Natural : milk of rubber tree, cellulose
• Semi synthetic
• Synthetic

Question 5. Types Of Plastics Based On Chemical Behavior?

Answer :

• Thermo plastics 
• Thermosetting plastics

Question 6. Difference Between Thermo Set And Thermo Plastics?

Answer :

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 

Question 7. Give Example Of Thermoplastics?

Answer :

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

Question 8. Perspex Is The Trade Name Of ---- ?

Answer :

CA

Question 9. Nylon Is The Trade Name Of ---- ?

Answer :

PA

Question 10. Delrin Is The Trade Name Of ---- ?

Answer :

POM

Question 11. Teflone Is The Trade Name Of ……….?

Answer :

PTFE

Question 12. What Is Mfi?

Answer :

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

Question 13. About Abs?

Answer :

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.

Question 14. About Ca ?

Answer :

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

Question 15. About Hdpe?

Answer :

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

Question 16. About Ldpe?

Answer :

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

Question 17. About Pa?

Answer :

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

Question 18. About Pc?

Answer :

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

Question 19. About Pp?

Answer :

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

Question 20. About Ps?

Answer :

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

Question 21. About Pvc?

Answer :

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

Question 22. Examples For Thermosetting Materials ?

Answer :

Alkyds, epoxies, pf, mf, urea, polyester.

Question 23. What Is Fillers And Additives?

Answer :

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. 

Question 24. What Are The Mold Release Agents?

Answer :

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

Question 25. What Are The Types Of Injection Molding Machines?

Answer :

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

Question 26. What Are The Divided Sections Of Screw Of Injection Molding Machines ?

Answer :

• Feed zone 
• Compression zone 
• Melting zone  

Question 27. What Do You Meant By Nozzle ?

Answer :

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

Question 28. What Are The Types Of Nozzle ?

Answer :

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

Question 29. Define Drooling ?

Answer :

Leakage of plastic material through the nozzle in between shots.

Question 30. What Is Injection Capacity Or Short Capacity?

Answer :

Maximum volume material injected by the screw during one cycle of operation.

Question 31. What Is Plasticizing Capacity ?

Answer :

It is the amount of material that can be processed by the machine per hour. It is expressed in kg/h.

Question 32. What Is Injection Pressure?

Answer :

It is the maximum pressure by which the material is injected through the nozzle. It is given in kg/cm2.

Question 33. What Is Injection Rate Or Injection Velocity ?

Answer :

It is the maximum rate at which the screw can inject or shoot materials from the barrel during one shot.

Question 34. What Do You Meant By Clamping Force?

Answer :

It is the maximum force that the clamping system can exert on the mold or it is the maximum force by which the mold halves can be closed together. It is given in ton or kilo Newton.

Question 35. What Is Maximum Daylight?

Answer :

It is the maximum distance that the machine platen can be separated from each other and it can be obtained by adding the maximum mold thickness to the maximum opening stroke.

Question 36. What Is A Mold ?

Answer :

It is a custom build tool in which we converts plastic raw material into finished product.

Question 37. What Are The Main Elements Of Mold ?

Answer :

The main parts of molds are core and cavity.

Question 38. What Are The General Types Of Mold ?

Answer :

Injection molds, compression molds, transfer molds.

Question 39. What Are The Types Of Injection Mold ?

Answer :

• Two plate mold 
• Three plate mold 
• Hot runner mold 
• Insulated runner mold 
• Hot manifold mold 
• Stacked mold 

Question 40. What Is Two Plate Mold ?

Answer :

Mold which consists of core and cavity situated in plates. It is logical type tool where component require large gate. For simple type components there is only one daylight.

Question 41. What Is 3 Plate Mold?

Answer :

It consists feed plates with core and cavity.

Question 42. What Is Hot Runner Mold?

Answer :

In this, runner kept hot to keep the molten metal into fluid state also called runner less mold. In this, runner contained in a plate of its own runner section of the mold is not opened during molding cycle.

Question 43. Note Down The Advantages Of Runner Mold ?

Answer :

• No molded side products 
• No separating of gate
• Cycle time can be reduced

Question 44. What Is Insulated Runner Mold ?

Answer :

It is a variation of hot runner mold in this type of molding. The outer surface of the material in the runner acts as a insulator.

Question 45. What Is Hot Manifold Mold ?

Answer :

This is a variation of the heated hot runner and not the runner plate. This is done using electric cartridge.

Question 46. What Do You Meant By Stacked Mold?

Answer :

A stacked mold is a multiple two plate mold with mold placed one over the other. A stacked mold construction doubles the output from a single molding machine and requires the same clamping force.

Question 47. Explain About Injection Molding?

Answer :

In this process, the plastic material is injected in to the mold through a sprue bush by means of a screw plunger. This process can be used for both thermosetting and thermoplastic materials.

Question 48. What Is Compression Molding?

Answer :

In this process, the plastic material is placed in the cavity and use a force for compressing the compound as the mold closes, these molds are generally used for thermosetting materials. 

Question 49. What Is Transfer Mold?

Answer :

In this process, the plastic materials is transferred from a transfer pot and then forced in to the cavity by means of plunger. This method is used for molding thermosetting materials only.

Question 50. Write A Short Note About Blow Molding ?

Answer :

Blow molding is very much like compression molding because the blow mold generally closes on a hollow shape that has been deposited in between the halves of the mold. Air or gas pressure is introduced at the center. This internal pressure causes a flow of the heated material in to intimate contact with the relatively cold mold sections. Here the plastic material solidifies and is subsequently ejected.

Question 51. Explain Vacuum Molding?

Answer :

The mold used for this process is similar that of the female half of the compression or blow mold auxiliary equipment on the machine heats the material and drags it over the cavity as indicated by the precise technique chosen.

Question 52. Elaborate About Rotational Molding?

Answer :

The machine provides the means of holding the mold and rotating it about two axis at the same time. This rotation causes the powdered material that was loaded in to the mold before it was clamped in to the machine to solidify and cling to the wall of the mold.

Question 53. What Is Impression ?

Answer :

Gap between core and cavity is called impression. Impression provides the shape of the component.

Question 54. What Do You Meant Cavity?

Answer :

Female portion of the mold and it gives external form.

Question 55. What Is Core ?

Answer :

Male portion of the mold and it gives internal form.

Question 56. What Is Sprue Bush?

Answer :

Connecting member between register ring and runner.

Question 57. What Is Register Ring ?

Answer :

It is used to align the mold with machine platen.

Question 58. What Is Runner?

Answer :

Connecting member between gate and sprue bush.

Question 59. What Is Gate?

Answer :

Connecting member between impression and runner.