In Europe, Kautex is regarded as the inventor of blow molding technology. The first machine for the production of plastic bottles was developed back in 1949.
In blow molding technology, continuous extrusion is the basic process for the production of blow molded articles from a parison. In this manufacturing process that is still used today, the extrusion speed depends on the screw r.p.m.
Characteristics for continuous extrusion:
Materials with high viscosity
High melt stiffness
Short, light parisons
Coextrusion, especially with thin layers
As early as the 1960s, blow molded articles were starting to exceed the critical limit of between 80 and 100 liters and were therefore too large for the continuous extrusion process that had been used up to then.
So Kautex developed this process in order to maximize the output rate for the production of larger products.
In contrast to continuous extrusion, in this process the melt is transported into a storage chamber and, after the previous part has been released from the mold, it is ejected all at once at high speed. This means that the extrusion speed is much higher and is no longer dependent on the screw r.p.m. The storage chamber can be refilled again during the cooling and mold release stages.
Discontinuous extrusion necessitates the use of accumulator heads.
Characteristics for discontinuous extrusion:
Materials with low viscosity
Low melt stiffness
Long, heavy parisons
e.g. barrels, IBC (Intermediate Bulk Containers), fuel tanks (Mono, Selar)
High rate of output
Low draw-down of the parison
Less cooling of the parison lower end
High temperature extrusion
Towards the end of the 1990s, plastics manufacturers developed new materials for different requirements, such as fiberglass-reinforced polyamides capable of being blow molded. Some polymers have to be processed at melt temperatures of up to 360 °C, so Kautex developed a high temperature extrusion process in the early 2000s.
This specialist sector needs supplementary parts that have been specially developed by Kautex Maschinenbau. These include:
- Extruder and head made of special steels that are resistant to high temperatures
- Specially designed electrical components
- Heat separation for feed zone, transmission, mold/clamping plate
- Special die heating
- Special screws developed for this use
- Special oil temperature control for feed zone and mold
- High-quality head insulation
- Facility for support air and preblowing air with heating
- Automatic lowering of the extruder temperature after extended downtime
Kautex Maschinenbau had developed 3-D design processes as early as the mid-1990s in order to reduce the otherwise considerable ”flash” of up to 80 percent down to almost 10 percent (see figure).
For this process, the extruded parison, with a diameter smaller than the molding diameter, is brought directly into the mold cavity and possibly previously shaped and manipulated so that the remaining compression seam length is reduced to a minimum. The 3-D process also includes so-called suction blowing, where the parison is drawn by vacuum through the blow mold.
With suction blowing machines (K3D-SB), horizontal machines with vertical opening movement (K3D-HP), and hybrid machines with insertion robots and moving mold parts that do not use a clamping unit, Kautex Maschinenbau offers a wide range of 3-D blow molding technology to meet every requirement.
The RWDS process for controlling wall thickness was developed by Kautex Maschinenbau in the mid-1990s in connection with the new requirements of 3-D technology, as in the conventional extrusion process, strongly curved blow molded parts would lead to excessive differences in wall thickness in the interior and exterior radii of the curves.
The "radial wall thickness control" (RWDS) was developed in order to equalize these differences in wall thickness and compensate for premature tool contact. It also permits the wall thickness of the parison to be adjusted according to circumference.
RWDS units are optionally available at Kautex Maschinenbau for all extrusion heads (Mono, SeCo, CoEx 6/7).
The exterior nozzle ring can be adjusted as required to regulate the wall thickness, so that the otherwise uniform die gap can be changed. The wall thickness can be influenced at every point of the manufacturing process so that the transfer of forces can be directed bi-axially over 90°.
The coextrusion process has been offered by Kautex Maschinenbau since the early 1980s. It was developed to meet new requirements in agricultural chemicals packaging.
The term "coextrusion" stands for the simultaneous processing of diverse materials that are bonded in the extrusion head into a multi-layer parison by means of an adhesive promoter. For particularly challenging applications, Kautex Maschinenbau offers equipment for the production of up to seven layers.
Low requirements for master batches in the outer decorative layer reduce the costs of Deco/Reco produced parts and additionally allows regrind or recycled material to be embedded into the middle layer. This process, with the inclusion of a suitable barrier layer, can be used toprotect food products from environmental influences and prevent chemicals from being discharged into the environment.
Sequential Coextrusion (SeCo)
In the mid-1990s, Kautex Maschinenbau was the first company to develop a sequential coextrusion process.
This technology permits the extrusion of both hard and soft plastics in one procedure, with a smooth transition between the materials. In this way, parts with different component stiffness characteristics can be produced without having to use additional labour and materials to assemble them after manufacturing.
The figure below shows the savings that can be made in terms of component and manufacturing costs.
Sequential Coextrusion (SeCo) is primarily employed to manufacture 3-D products. Two extruders feed a SeCo parison head.
With this process the sequence (e.g. hard-soft-hard or vice versa) can be freely selected, for instance for products with soft ends and a hard center section or integrated soft bellow areas.
Integrated Slosh Wall Insert
With the patented C3LS® process, Kautex Maschinenbau has developed a new technology that reduces emissions by inserting system components into the tank interior of plastic fuel tanks. The Integrated Slosh Wall Insert process is based on the same principle.
In direct comparison, however, the Integrated Slosh Wall Insert is not designed to minimize the emission of hydrocarbons, but to suppress undesirable noise. Due to the automatic start/stop devices often installed in new vehicles today, regulatory requirements have been imposed concerning the slosh noise. To meet these requirements, plastic walls (baffles or slosh walls) are inserted in the parison and welded in place during the blowing process.
After further development of the production processes, changing market requirements have necessitated the manufacture of CoEx-6 plastic fuel tanks. A range of technologies are now employed to manufacture these kinds of automotive fuel tanks and have resulted in a major reduction in hydrocarbon emissions from plastic fuel tanks.
These processes primarily involve the placement of vehicle fuel system components in inside the plastic fuel tank in order to save subsequent drilling and fastening onto the tank external surface. This not only brings cost savings but reduces the risk of leakage because the number of openings in the plastic body are reduced.
Kautex Maschinenbau has already helped many customers to perfect processes such as IST, TSBM and TAPT.
With the Kautex developed C3LS® process, a completely independent manufacturing method was developed in order to satisfy existing market requirements.
In 2009, the patented C3LS® process was developed by Kautex Maschinenbau as an optimized alternative for manufacturing LEV3 and PZEV-capable plastic fuel containers.
C3LS® has the following characteristics:
C3 > C for C-shaped extruded parison
> C for the functional parison gripper
> C for Center Preform Module
L > L for Loading
S > S for "System" (insertion and welding automation on the tank inner surface)
The concept also especially permits the conversion of existing large blowing equipment to C3LS® technology. This process can be applied without changing the footprint or the height of the machine.