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Twin-screw, co-rotating compounders made by Coperion Werner & Pfleiderer are the world’s most popular compounders used in the production of engineering plastics. Engineering plastics are polymers which are used as structural materials in a wide range of end products. In-line compounding and production of long fiber reinforced parts in a single-stage process taps into a significant economisation potential without any associated loss of quality. Parts made of long fiber reinforced plastics have an excellent stiffness to weight ratio, a good modulus of elasticity and very good impact resistance and tensile strength.
The technique of reinforcing plastics with glass or natural fibers up to 100 mm in length is now in a dynamic growth phase. Production of long fiber reinforced compounds has more than tripled in the last 10 years. This trend continues unabated due to the cost-effectiveness and high flexibility of long fiber technology. The most important market for these products is the automotive and transportation industry, which accounts for about 95% of all applications.
The D-LFT process has become an es-tablished method of producing long fiber reinforced thermoplastics in recent years. D-LFT is a direct process which eliminates the semi-finished product stage and instead produces parts directly using fiber glass, polymers and additives.
LFT parts combine the design freedom of extruded parts with excellent mechanical properties.
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Applications in car production.
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| The D-LFT process embedded in the part production process |  |  |
Advantages:
| - | | Low material costs due to elimination of production of semi-finished products |
| - | | Highly flexible part production |
| - | | A high degree of automation can be achieved (only one operator is needed for monitoring and maintenance) |
| - | | Very short cycle times translate into high productivity |
| - | | High system on stream factor |
| - | | Low reject rate |
| - | | 100% reusability of punch scrap and reject parts |
| - | | Minimal space requirements |
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| 1 |
Polymer and Additives |
| 2 |
Rovings |
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Twin-screw compounders ZSK |
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Degassing |
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| 5 |
Cutter |
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Separating unit |
| 7 |
Robot |
| 8 |
Press |
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| The core element in the D-LFT process – the Twin-screw compounderZSK | | |
The ZSK used in the compounding process features a modular design and contains the following main subassemblies:
| - | | Drive motor |
| - | | Gearbox with axial bearings and oil circulation lubrication |
| - | | Process section |
| - | | Discharge unit |
The process section is composed from individual barrel units, that when fully assembled contain the co-rotating screws. Engineers have a choice of several barrel configurations and various conveying, kneading and mixing elements which are mounted on spline shafts. The barrels and screw elements can be combined to produce the optimal configuration for a particular application.
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