We have developed dedicated equipment for the producing high-quality engine covers with polyurethane.
March 19, 2020
Engine covers are commonly used in vehicles to absorb heat, noise and vibrations coming from the engine. And because it looks far nicer when exhaust headers, oil seepage, valves, and so on are hidden, it has also an aesthetic function.
The engine cover’s insulation properties are obtained by using polyurethane foam: some automakers require engine covers entirely made of PU, others opt for an injection-molded thermoplastic surface, with a polyurethane layer applied on the back that creates a sheet of expanded cellular material that increases the cover’s sound- and thermal-insulation characteristics.
This polyurethane part is generally produced separately, foamed in small self-equipped molds, which are then manually assembled behind the rigid thermoplastic cover, using starlock clips.
A newer trend is on the way: a fully automated process that allows the production of thermoplastic engine covers back-foamed with PU. Sapa, an Italian industrial group dedicated to injection molding for the automotive sector that supplies the major automakers all over the world, has developed the One-Shot® all-in-one injection method, allowing components to obtained in one operation where previously multiple steps were needed.
In particular, the One-Shot® manufacturing method combines injection moulding for the thermoplastic shield with back-foaming using polyurethane foam.
The entire process happens in the same press, with a mold performing both operations: manual steps are eliminated.
For manufacturing engine covers with a PU layer on the back, both separately produced (and assembled) and back-foamed, we are at the forefront, supplying dosing machines and mixing heads that integrate with injection molding presses.
In parallel with increasing insulation performance, OEMs require significant performance for fire resistance, in accordance with the evolution of auto industry regulation SAE J369 on the flammability for polymers used in vehicles.
Among fire retardants, expandable graphite is commonly used, added to the PU formulation.
Being a fragile material – usually in form of a powder or flakes – graphite has to be handled with care both when mixed with polyol to form the so called “slurry” and when the slurry is injected in the mixing head.
We developed dedicated high-pressure solutions for adding graphite into polyurethane formulations. Besides the dosing machine, we provide a free standing module called SoliMix to blend graphite with virgin polyol and a free standing unit called SoliStream to dose and pump the slurry into the mixing head. Processing expandable graphite requires hardened heads: our FPL AN and AX, both available in armored versions, are perfect for producing PU engine covers and other parts containing graphite.
