Types Of Injection Molds

Plastic Injection Molds can be classified in different categories based on:

  1. Feeding system
  2. Number of parts
  3. Mold Opening
  4. Type of component

Based on Feeding System molds can be classified in two categories:

1. Cold Runner injection Mold

In Cold runners injection moulds, runner system is a unheated physical channel that are used to direct molten plastic into injection mould tool cavity after it passes through the nozzle.

In cold runner injection mold, the runner is cooled and ejected with the part. After the complete cycle runner need to be removed from injection moulded part.

2. Hot Runner injection Mold

In hot runners injection moulds, runner system is a heated physical channel that is used to direct molten plastic into a injection mold tool cavity after it leaves the nozzle.

In a hot runner injection mould, runner is part of injection mold and kept at a temperature above the melting point of the plastic.

Injection molds are also classified based on number of parts produced per injection mould cycle.

1. Single Cavity Injection Mold

Single cavity mould produces single part per cycle. Initial investment is lower but unit part cost will be higher for single cavity tool. It is  used for low production rates.

Instead of multi cavity, single cavity tool is used  to ensure production is always running even if there is a breakdown in one mold.

Single cavity mold will have flexibility in controlling injection molding process.

2. Multi Cavity Injection Mould

Multi cavity injection mould produces more than one part per cycle. Initial investment cost is higher but unit part cost is low for multi cavity injection tool.

Multi cavity mold are used to increase production rate.

Cost of multi cavity injection mold is higher as compared to single cavity mould.

Higher tonnage machine is required to run a multi-cavity mould as compared to single cavity mould.

3. Family Injection Mould

Family mould produces two or more different parts per cycle. With Family mould overall tool cost is reduced as two different parts are manufactured with single mold.

Injection moulded parts in family mould shall be of same material and color.

Injection molds also classified based on how mould is opening. In another words how core separates with cavity.

1. Two Plate Injection Mould

Two plate injection mould has one parting plane and the mold splits into two halves at parting plane. The runner system must be located on this parting plane.

Two Plate injection moulds are used for parts that are typically gated on or around their edge, with the runner in the same mold plate as the cavity.

2. Three Plate Injection Mould

Three plate injection moulds have two parting planes, Mould splits into three sections every time the part is ejected. Because of two parting planes, the runner system can be located on one parting plane and the part on the other.

Three plate injection moulds are used because of their flexibility in gating location. A part can be gated anywhere along its surface.

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