Düsseldorf, Germany – German injection blow moulding machinery maker, Ossberger, has exhibited its Pressblower SB2-260 to the public for the first time at K-2022, the international plastics and rubber trade fair. The machine is designed for making flexible, protective TPU bellows and gaiters for the automotive industry.
The demonstration machine, at the Weissenburg-based manufacturer’s stand, has been producing automotive air suspension bellows from Huntsman’s Irogran A 92 TPU, a material which is claimed to be oil- and weather-resistant, flexible in cold temperatures, and to exhibit ‘very good’ mechanical properties. The machine has been optimised for the material peculiarities of TPU, and features twin injection heads, allowing for side-by-side manufacturing of pieces, in two automated stations, within one cell.
Ossberger began business in the 1960s making machinery for cosmetics packaging. It started to penetrate the automotive industry in the 1980s but, by the 1990s, when the globalised cosmetics industry began to require mass-produced packaging, automotive became the company’s primary focus.
Klaus Haub, sales manager of Ossberger, explained: 'As the cosmetic industry got more global, with much more mass production than before, our process was not efficient enough to cover [the volume needed by] the cosmetics industry.'
Since the 1990s, the company has specialised in machinery for the production of boots and bellows for the automotive industry. While the Pressblower machine is classified as an ‘injection blow moulding machine’, Haub believes this is a misleading nomenclature: 'It’s not classical injection blow moulding. We call it "pressblow injection blow moulding", or you could use the shorter term, "pressblower". "Injection blow moulding" means you are injection moulding a preform which is blown up. This is not what we're doing.'
Likewise, Haub said, it is unlike extrusion blow moulding, where there is a continuous parison. The first step in the pressblower process, he explained, is the injection moulding of a ring, which is then used to create individual parisons.
Haub said: 'The second step is that the injection [moulded ring] is moving upwards and, at the same time, the injection piston is pressing material out of the accumulator, through the nozzle, upwards. So, we have these three synchronous movements which are necessary to create a parison which has a defined wall thickness.'
Ossberger’s previous Pressblower machines were focussed on TPE. They were aimed at producers of gaiters for CV joint boots, and shock absorber boots, which have relatively small diameters compared with the suspension air bellows, and steering bellows, for which the Pressblower SB2-260 is designed.
The market for suspension air bellows is increasing, Haub said, because 'there are more and more heavier cars – the SUVs, the battery electric vehicles'.
Haub said: 'We had the idea to enter this market by offering a machine which is running with two stations (to accommodate mass production); which allows bigger diameters than before; and which is able to process TPU.'
Ossberger had to modify the technology of its existing Pressblower DSE 250 and DSE 260 machinery to meet the demands of working with TPU, and the highly-conformant wall thicknesses the material choice necessitates. The DSE machines were unsuitable because their plasticising screws couldn’t process TPU. Haub said: 'For running TPU you need a bigger diameter, and longer length, for the plasticising screw. And you need a slower screw speed – otherwise you shear the material too much and produce a material that is too liquid, not elastomeric enough, to create a parison.'
After the formation of the parison, the moulds for the gaiters move into place, and a blowing unit expands the parison from within to accommodate the mould. The company says the blowing unit has ‘high clamping forces’ and is suitable for the production of articles up to 200mm in diameter.
The last step of the process is the simultaneous cutting of the head and base from the moulded parts, to reveal a hollow, cylindrical, concertinaed bellow.
Currently, Haub said, only one-in-three air suspension gaiters are made from TPU. But, with ever-growing demand for heavier vehicles, this one-third share will represent a very significant market.
K-2022 continues until 26 October.