Plastics make their mark in agricultural engineering

The automotive and commercial vehicles industry is continuing to move away from sheet steel in bodywork parts to the use of high performance plastics.

Alongside the familiar benefits of plastics such as their greater freedom of design and lower weight, their cost-effectiveness in production is also gaining in importance. Manufacturers are currently focusing their efforts on producing larger and larger parts in a single molding process. The success achieved in this field, coupled with the possibility of integrating additional functions and components in the mold, means they can cut both costs and manufacturing time. Another important factor is the use at the processing stage of very low-viscosity plastics materials that can find their way into even the smallest cavity in the mold to deliver reproducible results. Tailor-made polyurethane systems make it possible to produce even large moldings with complex structures such as undercuts and ribbing in a single shot with no need for post-molding treatment.

A recent example from the commercial vehicles industry involves the two side panels and tailgate of the "Jaguar Green Eye" forage harvester from Claas KGaA mbH in Harsewinkel, Germany. Each of the molded parts is manufactured by Pestel PUR-Kunststofftechnik GmbH (Pestel PUR-PLASTICS engineering GmbH) in a single shot. They are produced from the flame-retardant, microcellular polyurethane system Baydur* 110 from Bayer MaterialScience supplied by the BaySystems BUFA system house. The excellent flow characteristics and low cavity pressure impose virtually no restrictions on the geometric design of the molded parts, especially in the edge and interior areas. This enables undercuts, openings facing away from the demolding direction, and "slider-in-slider" designs. Each of the large side panels has exceptionally large dimensions of 4 x 2 meters and weighs around 40 kilograms. The tailgate has external dimensions of 1.7 x 1.6 meters and weighs around 30 kilograms. All three components feature complex structures such as undercuts, ribbing and significant changes in wall thickness. Inexpensive aluminum molds are used for production. Metal bushings and other inserts are integrated into the molding process.

Cost-effective production of complex components in a single step
Each of the two side panels and tailgate of the “Jaguar Green Eye” forage harvester from Claas (photo at right) is manufactured by Pestel PUR-PLASTICS engineering GmbH in a single shot from the flame-retardant, microcellular polyurethane system Baydur 110 from Bayer MaterialScience. The material, which is supplied by the system house BaySystems BUFA is characterized by a very low viscosity at the processing stage. It can find its way into even the smallest cavity in the mold to deliver reproducible results.

However, complex applications of this kind cannot be mastered simply by optimizing the plastics materials alone. Intensive technical collaboration is required with the customer to optimize the production workflows, for example. BaySystems*, the umbrella brand for the global polyurethane systems business of Bayer MaterialScience, offers the perfect solution. "Through the global BaySystems network we are able to provide users with a customized service. Customers can benefit from proximity to this network and from the fact that our know-how is available globally. In this case, the service portfolio also included simulation calculations for optimizing the flow behavior, which BaySystems experts performed in Leverkusen", explains Henrik Oelschläger, head of the Molded Parts segment of BaySystems BUFA. These calculations were used to ensure smooth production of the parts as early as the design phase, prior to construction of the molds.

"The benefits of polyurethanes over conventional materials such as glass fiber reinforced plastics or sheet molding compounds become particularly apparent when manufacturing large moldings with complex interior surfaces", says Ulf-Peter Pestel, Managing Director of Pestel PUR-PLASTICS engineering GmbH. The company's headquarters located at Friedrich Oskar mould road 23 - 25, D-09120 Chemnitz, Germany houses equipment that can produce polyurethane parts with shot weights of up to 90 kilograms. Pestel PUR-PLASTICS engineering GmbH, are manufacturers of predominantly wide plastic parts from PU. The foam molds this requires are produced in the company's own mold construction facility. The company also has its own paint shop capable of handling all popular coating systems. "As a professional systems supplier, we can provide our customers with support for everything from product development to ready-coated parts preassembled with add-ons if necessary", said Pestel.

* Trademarks of Bayer.

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