Polyurethane moulding

Our 3 Processes at Rimplas

Posted on in News

We offer 3 different processes at Rimplas and we often have potential customers, design houses and engineers ask about the differences between the three processes we offer and which is most suitable for their application.  More often than not, the deciding factor is annual production volume or the expected life of the product itself. The higher the annual volume, the more quickly the tooling investment is paid back.  However, it’s not just about cost.  Another important consideration is the material properties required for their product. For example, do you need low or high density, high impact resistance, or an FR/V0 rating?

Below is breakdown of PU-RIM moulding VS Engineered Structural Foam moulding (ESF) VS Injection moulding — focusing on how they work, materials, strengths, and when to use each.

PU-RIM Moulding (Polyurethane Reaction Injection Moulding)

Process type & how it works: Chemical Reaction inside the closed mould tool.  The two liquid components (Polyol & Isocyanate) are mixed and injected into a closed mould.  They chemically react and expand, forming Polyurethane.

Key Characteristics

  • Low injection pressure which means Aluminium tools can be used which reduces tooling costs.
  • Can create thick, large components
  • Excellent surface finish (paintable)
  • Good impact resistance

Common Uses

  • Automotive bumpers and body panels inc Speaker cabinets
  • Medical & Scientific equipment housings
  • Large enclosures
  • Panels and covers

Advantages

  • Large parts with low tooling cost
  • Good structural strength to weight ratio
  • Raw moulding has a smooth surface finish
  • Two material options with Densities of 0.60 & 1.10

Disadvantages

  • Slower cycle times
  • Not ideal for very high-volume small parts
  • Parts often need painting due to base material not aesthetically pleasing

Engineered Structural Foam Moulding (ESF)

Process type & how it works: Gas-assisted injection moulding. Plastic resin (for example ABS/HIPS/PP) is mixed with a chemical blowing agent.  When injected, the material expands inside the mould, creating Solid outer skin & Foamed cellular core.

Key Characteristics

  • Low internal stress
  • Thick walls without sink marks
  • Lighter than solid plastic
  • Most Thermoplastics can be foamed inc ABS, HIPS & PP

Common Uses

  • Medical & Scientific Equipment
  • Industrial housings
  • Furniture bases
  • Equipment frames & chassis

Advantages

  • Very strong-to-weight ratio
  • Reduced material usage
  • Lower warping
  • Ideal for large structural parts Inc metal replacement parts
  • Materials can be recycled

Disadvantages

  • Surface finish has a marble affect due to the Blowing Agent used and sometimes require painting depending on application.

Injection Moulding

Process type & how it works: High-pressure thermoplastic forming.  Plastic pellets are melted and injected under high pressure into a mould.  Material cools and solidifies into final shape.

Key Characteristics

  • Solid plastic part
  • High precision
  • Fast cycle times
  • Best for mass production

Common Uses

  • Consumer products
  • Small precision components
  • Medical disposables
  • Electronic housings

Advantages

  • Excellent dimensional accuracy
  • Smooth surface finish
  • Very high production volumes
  • Wide range of materials

Disadvantages

  • High tooling cost
  • Thick parts can warp or sink
  • Heavier than foam alternatives

If you need any more information please get in contact with us at [email protected].