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Basic Mould Construction 1

Chapter 1

BASIC MOULDCONSTRUCTION

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Basic Mould Construction 2

INTRODUCTION

tooling. to form plastic material to the desired

product. producing large numbers of plastic parts.

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Basic Mould Construction 4

INTRODUCTION

MOVINGHALF

MOULDED

FIXED HALF

Multi impressions

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Basic Mould Construction 5

Fixed half & Moving half

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Injection Molding Chee 490 26.8

The Injection Molding MachineThe injection molding machine is comprised of:

The plasticating and injection unit: The major tasks of the plasticatingunit are to melt the polymer, to accumulate the melt in the screwchamber, to inject the melt into the cavity and to maintain the holdingpressure during cooling.

The clamping unit: Its role is to open and close the mold, and hold themold tightly to avoid flash during the filling and holding. Clamping canbe mechanical and hydraulic

The mold cavity: The mold is the central point in an injection moldingmachine. Each mold can contain multiple cavities. It distributespolymer melt into and throughout the the cavities, shapes the part,cools the melt and ejects the finished product.

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Injection Molding Chee 490 26.9

The Injection Molding Machine

Injection molding machines are classified by an international convention:Manufacturer T/P

where T is the clamping force in metric tons, and P is defined as:

Where max is the maximum injection volume (cm 3) and p max is themaximum injection pressure (bar).

1000 p

P maxmax

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Injection Molding Chee 490 26.10

The Injection Molding MachineThere are quite a few things to consider when developing an injection

molding process: A. Machine parameters

Shot size (cm 3)Injection pressure and temperatureClamping pressure

Mold temperatureHold time

B. Polymer compound propertiesViscosity - temperature and shear rate

Thermal diffusivity and heat of fusion (if semi-crystalline)Density versus temperature profile

C. Mold designCavity, gate and runner dimensions and layouts

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Injection Molding Chee 490 26.11

The Plasticating UnitThe plasticating unit is designed to melt the polymer pellets,

accumulate the melt in the screw chamber, inject the melt into the cavity, and maintain the holding pressure during cooling.

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Injection Molding Chee 490 26.12

The Clamping UnitThe clamping unit is designed to open and close the mold,

generate enough pressure to prevent flash during mold filling andholding.

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Injection Molding Chee 490 26.13

The mold is designed to

Distribute the polymer melt into and throughout the cavities Shape the part Solidify the part by cooling / reaction Eject the finished product

The Injection Mold

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