Molding - Manufacturing and Industrial Engineering Interview Questions

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61. What  is runner?

Connecting member between gate and sprue bush.
62. What  is gate?

Connecting member between impression and runner.

63. How can we calculate the cycle time of mold?
Cycle time Tc=m*3600/P
 Where ,Tc =minimum cycle time obtainable 
 M=mass of the shot 

P=plasticizing capacity of the machine with the particular polymer being molded (kg/h)

64. What  is parting surface?

The surface where top and bottom half closed together and prevents the loss of plastic material from the impression.

65. What  are the types of parting surface?

 Flat and non flat

66. Name the types of non flat parting surfaces?

 Straight, stepped and angular.

67. What  do you meant flash ?

 If the parting surfaces are not properly matched, the molding material from the impression will escape through the gap. This escaped melt is called the flash.

68. Why do we provide vent in mold?

Vents are provided in the mold to allow such air to escape freely. The vent is a shallow slot not more than 0.05 mm deep and 3mm wide. If the depth is more, the plastic material can pass through the slot and leave a flash mark.

69. What  are the types of runner ?

  • Fully round
  • Rectangular
  • Hexagonal
  • Trapezoidal
  • Modified trapezoidal 

70. Explain briefly about sprue gate ?

When the molding is directly fed from a sprue or secondary sprue, the feed section is term as sprue gate.The main disadvantage with this type of gate is that it leaves a large gate mark on the molding. This sprue gate is used only for single impression molds.

71. What  is rectangular gate?

This is the general purpose gate and it is a rectangular channel machined in on mold plate to connect the runner to the impression.

72. Write a short note about fan gate?

Fan gate can be considered as the other type of edge gate but it does not have a constant width and depth. The fan shape spreads the flow of the melt as it enters the impression and a more uniform filling is obtained with less flow marks and surface finish.

73. What  is tab gate?

This is particular gating technique for feeding solid block types moldings. This is mainly used to avoid undesirable jetting on the molded part.

74. What  is overlap gate ?

 It can be considered as a variation of basic rectangular edge gate and is used to feed certain type of molding. In this type of gate we have a better control over the flow rate. Main disadvantage is that it leaves big remnant mark after degiating.

75. What  is diaphragm gate ?

This gate is used for single impression tubular shaped moldings on two plate molds.

76. What  is ring gate?

The function of this gate is identical to that of a diaphragm gate. This type of gate is used for tabular type moldings when more than one impression is required in a simple two mold.

77. What  is film gate?

This is a long rectangular type edge gate and it is used for large thin walled components to assist in the production of warpage free products.

78. What  is pin gate?

Used for 3 plate mold and under feed mold. Small degating mark will be there.

79. What  is round edge gate?

This gate is formed by machining a matching semi circular channel in both mold plates between the runner and impression.

80. What is submerged gate?

Automated degating with less mark also called as sub surface gate or submarine gate.

81. What  is winkle gate?

This is a curved variation of the subsurface gate and for that reason it is sometimes called a “curved subsurface gate” or “curved tunnel gate”.

82.What  are the types of injection techniques ?

  1. Pin injection 
  2. Sleeve injection
  3. Stripper bar injection
  4. Blade injection
  5. Valve injection
  6. Air injection
  7. Stripper ring injection
  8. Stripper plate injection

83. What  is Pin injection ?

This is the most common and simple type of injection. The molding is ejected by the application of a force by ejector pins.

84. What  do you meant by sleeve injection ?

In this method, the molding is ejected by means of a hallow ejector pin which is called sleeve.

85. What  is stripper bar injection?

This method of injection is suitable for thin wall box type moldings because of the effective injection area obtainable are greater.

86. What  is blade injection ?

The main purpose of blade ejector is for the injection of very slender parts such as ribs and other projections which cannot be satisfactorily ejected by the standard type of ejector pin.

87. What  is valve injection ?

A valve ejector is basically a large diameter ejector pin. It is used for the injection of large components.

88. What  is air injection ?

This is the simplest to install. It is easy to connect to the fixed or moving half. The medium of actuation is compressed air.

89. Explain briefly stripper ring injection?

The stripper ring is a local stripper plate and it is used on molds with one or two impression only. The stripper ring is made to seat in the mold plate.

90. What  is stripper plate injection?

This injection technique is used mainly for the injection of circular box type moldings and for moldings with thin wall sections.

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