Decoupled Injection Moulding Setup Principles for Technical Parts
Decoupled injection moulding decouples volumetric filling velocity from packing pressure to achieve tight tolerances and repeatable technical part production.
Hold Pressure Profile
Meaning
A multi-step pressure stage applied after cavity filling forces additional melt into the mould to compensate for volumetric thermal contraction. Injection moulding machine controllers execute a hold pressure profile to control sink mark formation and dimensional warpage. Amorphous resins like ABS require different pressure step-downs compared to semi-crystalline polymers like polypropylene.
Setting hydraulic pressure levels too high causes flash at parting lines or tool binding during part ejection.
Shrinkage Compensation
Volumetric contraction during resin solidification requires sustained pressure to push material into shrinking core regions. Programming a stepped hold pressure profile reduces internal residual stress by gradually lowering hydraulic force as gate areas freeze. High holding pressure maintained until gate seal prevents backflow into the runner system.
Proper profile tuning balances part weight against molded-in stress, preventing delayed environmental stress cracking in service.
Gate Freezing
Gate thickness determines the maximum duration over which packing pressure remains effective inside the mould cavity. Profiling a hold pressure profile beyond the gate freeze time wastes electrical energy and increases machine cycle times without altering part density.
Pressure Transition
Smooth transition from peak injection pressure to packing pressure prevents pressure spikes that overload delicate core pins. Optimized hold pressure profile parameters ensure uniform density distribution across complex geometric parts.