Monday 28 September 2020

Rule of Thumb for Injection Moulding - " What happens in the cavity..."


"What happens in the cavity, stays in the part" - RJG Inc

"What happens in the cavity stays in the part" - this rule of thumb, coined by training engineers of company RJG Inc [1,2], I heard often from my colleagues during my time I worked in the Application Technology department of a global active material supplier. 

However, why it is such a useful advice and rule of thumb for part quality?

In general there are four polymer processing variables which impact the quality of moulded parts: temperature, viscosity, packing and holding pressure, and cooling [1]. 

Additionally, monitoring the cavity pressure helps to detect defective parts in an early stage. Cavity pressure monitoring pays off especially with parts which tend to create problems during moulding as well as high volume parts. When the pressure sensor locations are at the end of the cavity, then detection of short shots is possible. Furthermore, gate sealing detection is achieved in a similar way by adding a sensor at the gate end. In-mould sensor installation is around 20% of all injection moulds and is increasing rapidly due to automation of production using cyber-physical production systems in the past years. 

I hope you find this rule of thumb tip for injection moulding useful. 

Thanks for reading and #findoutaboutplastics 
Herwig Juster 

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