plastic injection moulding

Keeping your cool: create quality plastic injection moulded parts

The outbreak of the human coronavirus (COVID-19) pandemic has strained the supply chains for injection moulded parts significantly. As a result, the need for exceptional standards of quality control has never been greater; the key to the consistent production of high-quality plastic injection moulded parts is the way in which the polymer is cooled after it has filled the mould cavity.  

High injection moulding reject rates 

The uneven cooling of injection moulded parts can create a range of issues. These include distortion which affects: 

  • Tolerances 
  • Poor crystallisation of polymer, which affects its mechanical properties.  

The more complex and convoluted the design of the tool, the more difficult it becomes to ensure that parts cool uniformly. These issues can lead to high reject rates and increase production costs.   

Legacy methods of injection mould tool cooling 

How then can plastic injection moulders ensure that the parts they manufacture are cooled properly 

Conventionally, channels through which cooling water can flow are drilled into the tool, but this approach can limit the geometries of the parts to be moulded. Drilled cooling channels must be straight. It can be difficult to position them close to complex, curved or spiral mould shapes for cooling to be consistent across the plastic injection mould tool. This can be especially challenging if cooling channels have to compete for space in the tool with other features, such as ejector pins or moving inserts. 

The obvious solution to these problems is to create cooling channels that have curves and bends in them, enabling them to follow the contours of the mould cavity precisely and to be routed around ejector pins and inserts.  

Conformal cooling can be a challenge 

Producing tools with conformal cooling channels, however, is no easy feat. Using conventional subtractive machining, channels can be created on the surface of inserts, which are then stacked on top of one another to create a finished tool. This process is expensive and time-consuming.  

Similarly, additive manufacturing (AM) processes such as laser sintering are relatively slow, and yield tool inserts with poor surface finishes that must then be machined.  

Our hybrid approach 

We have solved these problems with a process, called ConformL Coolthat exploits the benefits of AM and conventional CNC machining. Using our specially developed machine, the first of its kind to be installed in the UK, we can build steel mould tools or inserts layerbylayer using laser sintering. After each layer is added, however, automated secondary machining processes rapidly remove any excess material. The high dimensional accuracy and fine surface finish that results enables complex tools with conformal cooling channels to be manufactured automatically in one operation; this can significantly reduce costs and production times, by comparison with conventional subtractive and additive manufacturing techniques.  

As this is our expertise, we’ve created a breakdown in our latest conformal cooling white paper. It outlines our innovative approach to producing plastic injection mould tools efficiently and quickly. Check it out here:

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