M

Machine Shot Capacity: Refers to the maximum volume of thermoplastic resin which can be displaced or injected by the injection ram in a single stroke.

Mar Resistance: The resistance of glossy plastic surfaces to abrasive action. Masterbatch: A concentration of a substance (an additive, pigment, filler, etc.) in a base polymer.

Material Safety Data Sheets: Documentation regarding the toxicity or hazards associated with contact with some substances. The manufacturer of the plastic prepares these data sheets.

Mechanical Property: Properties of plastics which are classified as mechanical include abrasion resistance, creep, ductility, friction resistance, elasticity hardness, impact resistance, stiffness, and strength.

Melt Flow Rate: A measure of the molten viscosity of a polymer determined by the weight of polymer extruded through an orifice under specified conditions of pressure and temperature. Particular conditions are dependent upon the type of polymer being tested.

Melt Flow: Rate of extrusion of molten resin through a die of specified length and diameter. The conditions of the test (e.g. temperature and load) should be given. Frequently, however, the manufacturer’s data lists only the value, not the condition as well.

Melt Index: The amount of a thermoplastic resin, measured in grams, which can be forced through a specified orifice within ten minutes when subjected to a specified force. (ASTM D-1238) Continue reading “M”

L

Land (Gate Area): Gate dimension parallel to the direction of melt flow.

Land Area: The area of surfaces of a mold which contact each other when the mold is closed.

Light, UV Stabilizers & Absorbers: These additives increase the ability of the material to withstand the negative effects of light and UV exposure, thus increasing the service life of the material.

Linear Mold Shrinkage: The difference between the size of the part and the size of the mold cavity. Values given are often the average of a range.

Linear Thermal Expansion: The fractional change in length of a material for a unit change in temperature.

Liquid Injection Molding (LIM): The process that involves an integrated system for proportioning, mixing, and dispensing two-component liquid resin formulations and directly injecting the resultant mix into a mold which is clamped under pressure.

Low-Temperature Flexibility: The ability of a plastic to be bent without fracture at reduced temperatures.

Lubricant: Internal lubricants, without affecting the fusion properties of a compound, promotes resin flow. External lubricants promote release from metals which aids in the smooth flow of melt over die surfaces.

Molding Machine & Process

Parts of a Typical Molding Machine:

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 Reference: http://fimmtech.com/knowledgebase/injection-molding/

Hydraulic injection cylinder
Screwdriver motor
Hopper
Control panel
Barrel
Nozzle
Platens
Clamp mechanism

Molding Process :

  1. The plastic raw material is stored in the hopper.
  2.  The plastic falls on the rotating screw.
  3. It is conveyed forward by the flights of the screw and is gradually melted as it moves forward.
  4. When enough melted plastic has accumulated ahead of the screw, the screw stops rotating.
  5. The screw, acting as a plunger, pushes the melted plastic out of the injection barrel.
  6. The plastic goes through the nozzle, sprue, runner, gates, and on into the mold cavities.
  7. Packing occurred- a little more plastic is forced in after the cavities are full.
  8. packing continued until the gate freeze.
  9. when the plastic in the gate freezes, the pressure on the screw is released. The screw rotates back to melt and convey the next shot of plastic ahead of the screw.
  10. when the parts are cool enough to hold their shape, the mold opens, the parts are ejected, and the cycle is repeated.