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Pressed parts

 

 


 PRODUCTS | presses parts

    Plastic pressed parts made of PTFE

    Handling a high-quality material – Progress due to professionalism

    Due to its high melt viscosity, PTFE – unlike most thermoplastics –cannot be processed by casting, injection moulding or transfer moulding into semi-finished or finished products. Due to its high molecular mass of approx. 10 million g/mol, PTFE forms extremely long molecular chains, which mean that the material remains a solid even when the melting temperature of approximately 327°C is reached. For this reason, different methods are necessary here than for other thermoplastics.

    Manufacturers supply the raw material in the form of fine or free-flowing powder. The bulk density for fine powder is about 300 – 500 g/l and about 700 – 950 g/l for free-flowing powder. Homogeneous PTFE material is achieved by compression to around 2,100 g/l. Depending on the type of powder, this corresponds to a compression ratio of 2.2:1 to 7:1. Compression must be carried out very slowly so that the air contained between the powder particles can completely escape. This is achieved with high pressures of 12-130 MPa. Special tools are required to withstand these enormous pressures.

    These tool moulds are usually made of high-quality steel. Even a relatively small expansion of the mould during the pressing process can lead to shearing and cracks in the material. Often the result is a partial or total loss of the part. At Beichler + Grünenwald, such failures are minimised to the greatest possible extent by means of the special geometry and design of the tool moulds.

    Pressing process

    In static pressing, PTFE granulate is compressed into press moulds under hydraulic pressure to form simple moulded parts. These blanks are sintered in the furnace with precisely defined sintering curves. The blanks are also sintered in the same way during isostatic pressing. Beforehand, however, the PTFE granulate is placed in custom-cut tools – very close to the finished part contour - and pressurised on all sides. This is the most efficient way to process PTFE for finished parts with dimensions that vary greatly.

     

    Your Contact

    Martina Wölky
    Order Consulting
    T +49.7143.9609-132 
    F +49.7143.9609-100
    martina.woelky@b-u-g.de

    Nicky Schnelle
    AL Pressing Plant + Extruder
    +49.7143.9609-154
    +49.7143.9609-100
    n.schnelle@b-u-g.de

    Uwe Friedland
    AL Isostasy + Development
    T
    +49.7143.9609-153
    +49.7143.9609-100
    u.friedland@b-u-g.de

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    Complex manufacturing processes for pressed semi-finished products and finished products made of PTFE

    PTFE powders are usually compacted with hydraulic presses which are specially adapted to the compression requirements of the material. After the compressing into various shapes such as plates, cylinders or hollow rods, the blanks are still very fragile. It is only in the subsequent sintering process in specialised sintering furnaces that the moulded material acquires the typical PTFE properties.

    The blanks are usually sintered at a temperature of about 375°C. To prevent heat-related stresses from causing cracks or cavities in the fragile blank, special programmes regulate the heating, temperature stability and cooling of the blank. Depending on the component, this process can take 12 to 90 hours.

    After sintering, the blanks generally undergo further processing by turning or milling. The resulting component is given the required dimensions and tolerances. Since the volume of the blanks reduces during the sintering process – depending on the type of powder – between 2.5% and 5% and the resulting tolerances are too coarse for most requirements, this post-processing is nearly always essential.

    The processes described also apply equally to PTFE with fillers. The fillers ensure that the component is properly equipped and reinforced. Beichler + Grünenwald provides you with experience and know-how in the process of choosing the ideal mixture of raw materials, manufactures moulds according to your requirements and accompanies your product through until it is completely finished.

     

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    Static and isostatic pressing processes

    PTFE semi-finished products are manufactured by either static or isostatic pressing. The difference between the two processes lies in the pressing direction used to make the blanks. The blanks made from both pressing processes are sintered in special furnaces. In static pressing, PTFE is compressed into press moulds with hydraulic pressure in axial direction to form simple moulded parts, whereas in isostatic pressing, the material is pressed from all sides with uniform pressure using specially cut tools. The isostatic pressing process optimises the already excellent properties of PTFE due to the exceptionally homogeneous structure of the material. A further advantage is that even housings with complicated contours can be lined with PTFE. In this respect, there are limits to the process of static pressing.

    Beichler + Grünenwald designs and engineers tools for customer-specific component production that enable efficient material savings of up to 90%. In addition, we use special processes to prepare the surfaces to be coated in such a way that an absolute, vacuum-tight bond is achieved.

     

    FIND OUT MORE!

    Would you like to find out more about PTFE? This applies to all industries: With this high-performance plastic, the most diverse technical requirements can be implemented constructively at the highest level. We would be happy to provide you with a personal consultation. Do not hesitate to contact us and request a quote.

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