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Mazda Develops Plastic Molding Technology Which Reduces Consumption of Plastic Resins by 30%

Mazda1
Elements of Mazda’s injection molding process. Click to enlarge.

As part of its efforts to reduce vehicle weight, Mazda Motor Corporation has developed a new plastic molding technology that enables a substantial reduction in the weight of plastic parts used in vehicles. This plastic molding manufacturing technique cuts the consumption of plastic resins that are used as raw material by approximately 20 to 30%, with associated reductions in vehicle weight.

The most common manufacturing method for producing automobile plastic parts is injection molding. Mazda’s improved injection molding process involves mixing supercritical fluid (SCF), made from common inert gases such as nitrogen or carbon dioxide, with the plastic resin raw material.

A supercritical fluid is any substance at a temperature and pressure above its thermodynamic critical point. It can diffuse through solids like a gas, and dissolve materials like a liquid. Compared to their natural gaseous forms, nitrogen and carbon dioxide, as supercritical fluids, increase the solubility of plastic resin and enable it to form foam with a standardized micro-cell structure.

The Mazda process utilizes a particular characteristic of SCF to mix readily with other substances at the molecular level to raise the fluidity of the liquid plastic resin and cause it to expand rapidly when injected into a mold. As a result, smaller amounts of the raw material resin are needed to fill molds.

Furthermore, by using a core back expansion molding process—which enables thicker parts to be manufactured using less plastic raw material—Mazda has successfully developed plastic with a multi-layer structure.

Core back expansion molding is a form of injection molding. Once the foamed resin has filled up the mold, the volume of the mold is increased, causing the foam to expand. This means larger plastic parts, with low density and good rigidity, can be made from the same volume of plastic resin.

The bubbles in the outer layer of the plastic are kept microscopic to ensure each part has the necessary strength and rigidity, while the size of the bubbles in the core layer can be freely adjusted to reduce its density as desired.

With this proprietary technology, substantially less material is needed to manufacture plastic parts that are lighter and have equal or greater strength and rigidity characteristics compared to conventional, non-foamed parts.

This plastic foam molding technology can potentially be applied to nearly all plastic parts used in vehicles. Because the core back molding process enables control of the foam’s structure, it is possible to add extra value by enhancing the heat insulation and acoustic characteristics of plastic parts.

Conventional plastic foaming methods use a gas formed through the thermal decomposition of organic and inorganic compounds. However, through the use of SCFs, Mazda’s foamed resin molding technology does not result in adverse effects from residual chemical compounds, has a smaller impact on the environment, and produces parts that can be easily recycled.

Comments

Ben

Wait, I thought polymer chemical engineers have been doing this for years?

garth

This would have negligible effect on the over all weight of a typical passenger vehicle.

100 to 150 pounds of plastic interior pieces reduced down by 20-30% may be negligible in a 3000+ pound vehicle but it is still worthwhile if it reduces costs (through less use of the raw materials without an increase cost of the processing).

justinvp

Significant reductions in mass will be realized through many small, incremental improvements, such as this.

I am in the bicycle industry, and when you want a light bike you do it just like this - find cost effective ways to reduce mass in dozens of little parts. Soon, you've gotten yourself a really light bike. Cars are no different.

This is indeed an important step towards making vehicles lighter and more efficient. The prospects of better tuning plastics for accoustic and insulating properties is also exciting.

@justinvp:

I fully agree with you. Car manufacturers should redesign every component of their much too heavy vehicles to reduce the weight of an average car below one ton.

Major
fuel consumption and GHG

Reality Czech
This would have negligible effect on the over all weight of a typical passenger vehicle.
Cutting 45 lb from the interior can cut more weight from the suspension and drivetrain, resulting in lower cost and greater efficiency. Being able to mold an interior panel in one step with superior thermal and acoustic properties would slash costs.

If this reduces the cost and weight of plastic panels for exteriors, there may be cascade effects. Plastic can be made into shapes that metal cannot, and one molded piece may replace several welded ones. This cuts more cost.

Reality Czech may want to inject a little more reality...welded metal parts are used in places that need strength (because they may be mounting points for the plastic pieces!!!). This process does nothing to improve strength - it gives more finite control of the properties of the produced piece but does not create structural members especially when the density is decreased.

GreenPlease

@Reality Czech

Exactly. This is the sort of thing that could set off a virtuous cycle. Lighter interior panels + lighter exterior panels (assuming they move to all plastic) = less weight and lower cost. Less weight from those two components mean that the engine doesn't have to push as much and can be smaller. Reduced weight from that means that the suspension doesn't have to be as robust making the car lighter still.

Just as justin said, the improvements will be incremental. Lighter materials used inside the car. Lighter materials used for body panels. Light li-ion batteries instead of heavy lead acid. Ceramic coatings inside the cylinder head, on the piston, and in the exhaust mains would lead to increased heat rejection and would reduce the load placed on the cooling loop which would allow it to be smaller.

Reality Czech
welded metal parts are used in places that need strength (because they may be mounting points for the plastic pieces!!!). This process does nothing to improve strength
A piece with a foam core and solid skins is much stiffer, and has greater buckling strength, than the same weight of solid material. If the piece can be bonded along an entire surface instead of just at spot welds, the strength of its connection goes up also.

Aluminum has less tensile strength per weight than many steels, but it is used for aircraft because its lower density gives it greater buckling strength in standard forms for skins and spars.

Patrick Plastics Corp

Patrick Plastics Corporation is supplier for Plastic Machining, Plastic Screw Machining, CNC Plastic Machining, Tight tolerance Machining, Plastic Injection Molding based in Illinois,USA.

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