11/02/2011

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Rampf Tooling expands its rapid prototyping product range

[image_0]Rapid prototyping is a particularly quick process to produce prototype and functional parts. The latter are used for initial samples, pilot series, small series, functionality and performance testing as well as for simulation of series materials. The rapid prototyping technology saves the user time and money as it helps to shorten development times, to prevent potentially costly development and engineering mistakes, helps to simplify design changes and to improve products at an early design stage. Contrary to conventional modeling materials the Raku-Tool polyurethane products from Rampf Tooling GmbH & Co. KG based in Grafenberg, Germany, allow for an easy and fast imitation of thermoplastics like polyethylene, polypropylene as well as acrylonitrile butadiene styrene. Also in comparison to thermoplastic systems the Raku-Tool prototyping systems can already be used to produce a small number of parts. Thermoplastic systems are processed using an injection molding process which is normally only economically viable when large quantities are produced since the investment for the tools is very high. A further advantage of the rapid prototyping systems is that their use is not limited to the production of small parts but also large parts like whole car bumpers can be made. The company's product range of rapid prototyping systems comprises nine systems. The latest systems to have been introduced into the market which simulate PP and ABS thermoplastics are PR-3608 / PR-3652 / PR-3654 in connection with PH-3905 or PH-3908 based on polyurethane. All of these systems have a high temperature resistance (HDT between 100 - 130 °C) and are therefore specially suited for areas with thermal exposure or impact like parts in the under-bonnet area or headlamp housings. The new systems, that can be processed at room temperature (18 - 23 °C), offer the user good mechanical properties and other advantages. They can be demolded within minutes and do not exhibit any brittle phase which is important during demolding of the parts. PR-3608/PH-3908 does not show any brittleness with aging. This is important with parts that are assembled using ears or clips. If the material is brittle, the ears/clips break and the part will be unusable. All materials are also available in small, handy 25 liter containers that can be used to process smaller quantities.[image_1_right] Two of the systems (PR-3652 and PR-3654) are filled with glass fibers and exhibit a high flexural strength (flexural modulus 1,500 - 1,800 respectively 2,000 - 2,400 MPa). Even with temperatures up to 130 °C the rigidity is retained and they can therefore be used for engine covers. To process the Raku-Tool Rapid Prototyping materials it is recommended to use a two component low pressure casting machine with a static dynamic mixer. For this, the company Tartler, Michelstadt, offers the MDM 6 mix and metering machine which can be supplied with various pump types, e. g. a precision pump for the processing of materials with a low viscosity (under 400 MPa) or a wear resistant type for abrasive materials. A further advantage of the Tartler MDM 6 machine is that the mix ratio can be set precisely and continuously variable with the A and B component. When needed, tanks as well as tube and loader can be heated up to approximately 80 °C. This however is not necessary for the Rampf prototyping systems as the material can be processed at room temperature, between 18 - 23 °C. In addition, the company Tartler offers a customized adjustment of the machine to meet the customer's specific requirements. To produce the molds, the established build-up methods like milling, lay-up or shell construction techniques can be used. Rampf Tooling is offering a choice of materials which are optimally suited for the different techniques: For machined molds: working board WB-1404 or Close Contour Casting CC-6507
Advantages:  easy to machine, polishable, good impact strength and low thermal expansion For laminated molds using the lay-up technique
- Modeling board MB-0600, to mill the master model
- Gelcoat EG-2105, can be polished and is temperature resistant
- Coupling layer EL-2209, universally applicable, excellent interlayer adhesion
- Laminating resin EL-2203, glass fiber (GFR) or carbon fiber reinforced (CFR) fabrics
- Laminating paste EL-2207-2, necessary layer thickness can be applied in one step For cast molds
Epoxy casting resin EC-2404, temperature resistant
Polyurethane casting resin PC-3415, low shrinkage, high layer thickness
Polyurethane casting resin PC-3403, low shrinkage, high layer thickness All these materials have an important advantage which is that the molds do not need to be heated. Only if the wall thickness of the part to be produced is more than 4 mm they need to be heated to compensate sink marks. When producing the molds, mold surfaces need to be completely sealed, i. e. depending on the materials used they might have to be sealed as even finest air bubbles can lead to flaws in the final part. Metal cast surfaces are unsuitable as they are microporous. Furthermore, the molds need to be suitably reinforced to withstand the injection pressure. Processing information
Before the material can be put into the machine, the polyol component first has to be well stirred or shaken to disperse individual raw materials. When processing the rapid prototyping materials a constant temperature of 18 - 23 °C has to be observed. This should also be the processing temperature for the mix and metering machine. The material has to be injected into the mold during the indicated pot life time but as slowly as possible to avoid any air entrapment in the cavity. The mechanical properties, especially the temperature resistance can be improved through the appropriate post cure. This is necessary for systems with a higher temperature resistance to obtain the temperature resistance of 130°C (HDT) in the final part. During this process it is important to observe a post cure in steps as well as slow cooling of the post cured parts.

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