HOT RUNNER SYSTEM

 

INTRODUCTION

Multicavity injection molds can be built to make over 100  parts per cycle. Each part cavity is filled with melt through sprue and runners.

  • As the attached sprue and runner cools down with cooling of plastic part, the sprue and runner comes out along with the plastic product when the product is ejected from the injection mould .
  • The runners has to be seperated from the moulded plastic part which involves handling and regrinding of the sprue and runners.

HOT RUNNER SYSTEM

Unlike cold runners they are heated channels that keep the plastic molten during the entire cycle.


HEATING MECHANISM

Runners are kept hot by two ways 

a) External heating

By surrounding the melt channel with an appropriate electric heating element.

b) Internal heating

In the internal heating system their is an electric heating element which is kept inside the melt channel.


DEMERITS OF HOT RUNNER SYSTEM

  • Hot runner system is more complicate and expensive.
  • Hot runner mould is more difficult to start moulding process than cold runner system
  • Hot runner system needs more care and maintenance in comparison to the normal mould.





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