In Pursuit Of The Perfect Injection Moulded Part 7 – Jetting


Jetting refers to a kind of deformation in a moulded component that can occur when there’s an initial ‘jet’ of molten material injected into the mould cavity that starts to solidify before the cavity is filled. Jetting often appears as a squiggly line in the surface of the finished component, typically leading from the initial gate of injection. This visible flow pattern can result in part weakness.

Causes and remedies of jetting in moulded parts

In Pursuit Of The Perfect Injection Moulded Part - Jetting

The chief cause for jetting is excessive injection pressure.  When molten polymer or other material is injected through a small gate at high pressure it often squirts rapidly through the gate, rather than filling the mould cavity gradually. As this initial line of material cools against the mould walls and starts to harden, the remaining mould material pushes it, leaving impressions in the surface of the finished part. Avoid jetting in moulded parts by:

  • Reducing injection pressure to prevent rapid squirting of the material into the mould cavity
  • Increasing material and mould temperature to keep the initial jet of material from solidifying early
  • Designing the mould with the injection gate located such that the material is directed across the mould, rather than lengthwise

Defects typically related to material use or storage

Injection moulding defects can often originate from the material itself or how the manufacturer stores and handles the material prior to the production process. These defects can range from minor aesthetic issues to compromised strength of the finished component. Serious safety concerns may also result, depending on the intended application of the product affected.

Patterson & Rothwell are a Plastic Injection Moulding Company based in the North West of England, UK producing goods for many business sectors. Our ethos is to offer our customers a professional yet flexible approach and of course provide attention to detail at every stage. Please contact us if you wish to discuss any Plastic Injection Moulding Project.