Thermoplastic oil filter housing warpage prediction due to injection moulding

For such applications of heavily loaded structural components reinforced thermoplastic materials are predominantly used, mostly filled with glass fiber.

This yields in high stiffness which is why the products must be manufactured with good precision as they must not be forced into position while assembling. Additional problems are caused due to warpage after moulding as a result of orthotropic material properties and different shrinkage factors in the fiber orientation directions and perpendicular to it.

Problem definition

  • movement of assembly holes out of tolerance fields
  • uneven sealing surface
  • cilindricity on the mounting spot for oil filter cap



Based on our know-how and experience we used injection moulding simulations and analysed several possible runner systems, process parameters and cooling set-ups. In the end we achieved the following results:

  • cilindricity within tolerances with optimisation of runner system and process parameters
  • optimised process parameters in terms of ease of material flow and injection pressure curves
  • predicted the exact position of mounting holes
  • predicted the shape of sealing surface

Based on these results the client successfully compensated the warpage in tool cavities - CAD model of cavity was corrected in a way that the holes were moved in the opposite position to the predicted one and analogous procedure was made on the sealing surface.



  • elimination of risks in the industrialisation phase
  • less tool trials - shorter time-to-market and lower industrialisation costs
  • focusing on product's functionality by outsourcing the technological problem solving to an experienced partner
  • optimal process - longer tool life and shorter production cycles


CAD-model izdelka

3D model of product


Prikaz odstopkov tesnilnega dela

Warpage of the sealing surface


Meritve odstopkov cilindričnega dela

Measurement of cilindricity and holes on the simulation results


Prikaz orientacije vlaken

Display of fiber orientation - different shrinkage in the fiber orientation direction
and perpendicular to it are the main cause for residual stress
and large and often unpredictable warpage of such products after injection moulding


Prikaz skrčkov in deformacij po ohlajanju izdelka

Display of shrinkage and warpage after cooling

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