Today's KNOWLEDGE Share
π‘ Why the Melt Cushion Matters More Than You Think in Injection Moulding
In injection moulding, everyone talks about cycle time, clamping force, or cooling efficiency — but very few talk about the melt cushion.
Yet this small, often overlooked parameter plays a critical role in ensuring process stability, consistent part quality, and machine repeatability.
The melt cushion (or cushion size) is the small volume of molten plastic left in front of the screw after the holding phase. It acts like a pressure buffer, ensuring that the material can still be packed properly as the part cools and the gate starts to freeze off.
If your cushion is too small — or worse, inconsistent — you’re basically losing control of your process.
π Pressure transfer becomes unstable.
π Part weights start to drift.
π Dimensional tolerances suffer.
π And your cycle-to-cycle repeatability disappears.
Maintaining a stable and adequate melt cushion is not just about machine setup — it’s about process discipline.
It reflects how well we understand our injection profile, screw recovery, material viscosity, and even back pressure.
The problem? Many technicians focus only on speed or pressure settings, not realizing that the melt cushion is the silent indicator of whether the process is truly under control.
So next time you’re optimising a moulding process —
check your melt cushion consistency.
It’s often the difference between “it runs” and “it runs well.”
source : Tivadar HamzΓ³k
#InjectionMoulding #ProcessStability #meltcushion
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