Processing PEEK precisely in injection moulding
PEEK processing begins before the first shot
Many of the decisions that shape PEEK processing are taken long before the first mould trials. Manufacturer data and material data sheets provide important guidance, but they do not replace a technical assessment of the specific part. What counts is how geometry, mould design and process control interact under real conditions.
That is why we assess PEEK projects early with subsequent production in mind: where do thick sections occur? How long are the flow paths? Which contours are function-critical? Where does holding pressure have to remain effective? This assessment is the basis for a process that supports not only individual trial parts but robust production.
Assessing geometry and shrinkage realistically
Wall thicknesses, wall transitions, flow path lengths and tight tolerance requirements determine how mould filling, shrinkage and dimensional accuracy behave in production. With thick-walled PEEK parts in particular, it is not enough to resolve deviations afterwards through holding pressure or corrections to the process.
The actual processing shrinkage has to be considered in the mould design at an early stage. Only when mould filling, thermal balance and the dimensional concept are aligned can the geometry remain under control in production.
Typical PEEK parts from practice
Thick-walled housing parts show immediately whether thermal balance, holding pressure and surface quality are under control. Sleeve bearings with tight tolerances reveal the effects of shrinkage, tooling corrections and temperature control. Gear parts require function-critical contours to be reproduced reliably. Parts like these show whether a PEEK process has merely been trialled – or whether it is understood.
Controlling mould temperature, not just setting it
For a stable PEEK process, what counts is not the set point on the temperature control unit but the actual temperature at the mould surface. Sluggish heating, hotspots or poorly managed zones can quickly narrow the process window.
Mould construction, steel selection, insulation and mould temperature control must therefore be designed so that the cavity surfaces are maintained uniformly at a stable temperature. A high mould temperature alone does not make a stable PEEK process.
Designing gating and holding pressure to be effective
With PEEK, the gate plays a major part in whether holding pressure can remain effective for long enough. Gates that are too small shorten the effective holding pressure phase, encourage sink marks or voids and make the process more sensitive to variation.
For single-cavity moulds, direct gating can be a robust solution. Multi-cavity moulds can be implemented effectively with hot-runner systems, provided that nozzle design, temperature control and the manifold concept are kept under control.
Venting as a process prerequisite
Venting is not a side issue with PEEK. Air that cannot escape reliably from the cavity quickly leads to surface defects, burn marks or incomplete mould filling. Conventional venting via the parting line and moving mould components is not sufficient in every geometry.
For demanding parts, actively evacuating the cavity can be worthwhile. Air is then not merely displaced but removed deliberately before filling – helping to achieve stable surfaces and reproducible mould filling.
Managing drying and material condition
Drying PEEK is a process step in its own right. What matters is not only the drying operation itself, but a reproducible material condition. Residual moisture, drying time, material handling and dryer technology all interact.
In practice, controlled drying conditions and clean material handling are therefore important. Dew point monitoring, defined procedures and controlled handling of material from opened containers help to keep variation from becoming visible in the part.
Maintaining equipment condition and material purity
At the high processing temperatures used for PEEK, foreign material, carry-over or thermally degraded material quickly becomes a risk. It can impair the surface and mechanical properties and, in unfavourable cases, also place additional load on the hot runner or plasticising unit.
Stable PEEK processing therefore requires consistent control of cleaning, material changes and equipment condition. Cleanliness here is not an organisational extra but part of process capability.
What this means for injection moulding projects
Processing PEEK precisely in injection moulding means managing the entire process technically: from the material condition through mould and temperature to gating, venting and inspection. That is where the real challenge lies – and the difference between a successful mould trial and stable production.
BERGER therefore does not assess PEEK as a high-performance polymer in isolation, but in conjunction with geometry, tooling concept, process control and production requirements in precision injection moulding.