Plastic Pipes and Tubes from the Multifunctional Blow Molding Machine
As customers become more choosy and the times more uncertain, flexibility is trumps in production. In blow molding, such freedom is created by a 3D suction blow molding machine which can also be used for conventional (2D) blow molding. An ideal place to develop such a machine is an organization that is also experienced in training plastics technologists, especially when, thanks to contract research, it keeps a finger on the pulse of the times.
The teaching plant at the Dr. Reinold Hagen Foundation in Bonn, Germany, teaches up to 100 trainees daily. In addi- tion, the organization offers special blow molding courses for plastics companies from Germany and the Benelux countries. “Conveying the practical and process-engineering fundamentals of blow molding is an integral part of the basic courses,” explains Martin Rosorius, Head of Administration and Communication at the Foundation. Advanced seminars enable the participants to optimize processes independently.
A Variety of Deployment Scenarios
However, the blow molding machine used at the Foundation no longer meets growing energy efficiency demands, and there were increasingly situations in which the employees had to improvise. Our existing suction blow molding device has been in use since 1998, and no longer met modern requirements,” explains Karl-Friedrich Linder, Managing Director of the Dr. Reinold Hagen Foundation. The company therefore now employs a new suction blow molding machine from ST BlowMoulding. Previously, the Bonn-based company had no business relationships with the Swiss supplier. In a personal exchange, however, it quickly emerged that not only the technical characteristics and the price-perform- ance ratio were satisfactory, but also that both sides were looking for a cooperation based on partnership.
Besides education and training, the new machine also serves for working out practically relevant solutions in collabor ation with companies and universities. “Of course, the subject of resource conservation is highly topical, with high economic and environmental importance in plastics production,”says Linder. In first line, it is important to make packaging and other products more lightweight, and so reduce plastics consumption in order to gain material and cost savings.
The research department of the Dr. Reinold Hagen Foundation has long been involved in the development of simulation techniques for plastic parts, in particular of blow-molded plastic hollow articles. In the process simulation, the process of manufacturing blow molded parts is reproduced, that is to say the formation of the parison and inflation in the mold. In the product simulation, the behavior of the part is investigated under different loadings.
Hagen Engineering GmbH, a 100% subsidiary of the Foundation, which is also located here, as a development partner, supplies its expertise to companies. The portfolio extends from automotive engineering, consumer and industrial goods, through to mechanical engineering and mold making.
Hagen Engineering GmbH performs all the manufacturing steps in the devel opment of new products, from the implementation of the idea in a design appro priate to the production process, through to the production of prototypes, molds and apparatus. “It’s shared use of the technical center of the Dr. Reinold Hagen Foun dation, and therefore also of the new ST suction blow molding machine, further allows Hagen Engineering GmbH to offer material sampling and small series, in particular in the field of blow molding technology,” according to Rosorius.
Focus on 3D Parts Production
A special feature of the ASPI technology of ST BlowMoulding, which takes its name ASPI from the Italian word “aspirare” (suction), is the production of plastic hol- low articles by the 3D suction blow mold- ing process (see Box p.46). The same ma- chine, however, is also capable of manu- facturing plastics hollow articles by con- ventional (2D) blow molding. The necessary optionally available blow-molding group includes a blow pin, spreaders and parison clamps and can be very easily in- serted into the clamping unit. With the development to the ASPI 200 model, this technology due to digitization reached a new level, since this machine has, for the first time, been equipped with an IO-Link cable, which considerably simplifies maintenance and troubleshooting. The new software version of the ST control program additionally offers extended possibilities for real-time monitoring of the process, machine state and energy consumption. In additional, it is equipped with an interactive operator manual, which is part of the control system and directly links the individual chapters to the respective control pages.
The suction blow molding machine, like all models of the ASPI series, is de- signed for processing polyolefins and technopolymers, also containing glass fibers, and has an accumulator head of 2.5 l, which is generously dimensioned for conventional suction blow molding ap- plications and also permits greater flexi- bility in the 2D range. The plasticated material accumulates in the accumulator head and is extruded cyclically through the mold die as a tube, which is then sucked into the mold. Both the accumu- lator head and the extruder, in this case with 70 mm screw diameter and a throughput of approx. 130kg/h PA6, are components developed by ST Moulding. “With the new production line, we can instruct the trainees using the most mod- ern materials and under realistic competi- tive conditions,” Linder is pleased to say. “And for research and development, it also makes sense to be state of the art, and in- tegrate the latest findings.” Another major advantage is the uncomplicated handling. The machine is predominantly used for suction blow molding of 3D parts, since a second machine is available for conven- tional blow molding, which can readily manufacture smaller articles.
Some functions of the machine, which offer significant advantages in fa- cilities producing large quantities and changing parts, only play a minor role in the Foundation’s technical center. “Be- cause production is not our main activity, but training and further education as well as R&D, a secondary role is taken by rapid screw exchanges or the system’s com- munication capability,” explains Rosorius. “For us, networking of the systems with one another does not play a major role. In the free market, however, Industry 4.0, and thus networked production, are more and more important with a view to efficiency and competitiveness.
Such Industry 4.0 functions, along with the upward and downward net- working of the machine, also include the networking of internal machine components. Maintenance measures can thus be greatly simplified and better planned, by functions such as predictive and pre- ventive maintenance, and via innovative cabling by means of I/O-Link. This topic will increasingly also be more relevant in training and further education, and as- sume greater importance in the scope of special training units, Rosorius is con- vinced. “However, we are also capable of analyzing the data recorded during the tests where required, and drawing con- clusions from this.”
Summary: Win-Win Situation
“We followed the calling of ST Blow- Moulding as a technology and market leader in the field of suction blow mold- ing, and a recommendation, and were not disappointed,” sums up Linder. “With this state-of-the-art machine, we can continue to educate our trainees and the technical staff, as well as actively pur- sue R&D.” The plant manufacturers from Switzerland also benefit from the coop- eration in the long term. Thanks to the wide range of practical deployments, the Foundation can give it qualified and exact feedback, in case it sees further need to optimize the blow molding ma- chine; and can test expansions, such as the newly developed and patented swell monitoring, for monitoring the die-swell behavior of the material in real time. This permits better process control and successive interventions in the pro- cess before defective parts are pro- duced. Both partners hope not only to benefit from the good networks, but also to be able to build up new mutual business relationships.
Comparison of 3D Suction Blow Molding and Blow Molding
3D suction blow molding allows production of tubular parts with complex three-dimen-sional shapes, which are used in diverse geometries and applications, for example in theautomotive industry and household technology. In 3D suction blow molding, a ductile parisonis extruded through a blow mold, which is only open at the two ends of a tubular contour. Inparallel, at the lower opening of the blow mold, a vacuum is generated, which, by means of acontrolled air stream, sucks the parison through the cavity of the blow mold, which may have acomplex three-dimensional shape. In 3D suction blow molding, three-dimensional blowmolded parts (usually tubes and pipes) are produced, while during conventional (2D) blowmolding, “only” two-dimensionally shaped hollow articles can generally be produced, sincehere the tube drops vertically downwards and is then clamped in the mold and inflated.
After the preform has been introduced into the cavity in this way and has positioned itself dueto the high temperature and resulting greater flexibility, the inlet and outlet openings of theblow mold are closed by means of slides. Subsequently, one or more blowing pins within theblow mold pierce the parison. As compressed air is applied, the still-ductile material conformsto the mold wall and retains its contour and dimensional stability as it cools.
While the part is still in the mold, the adhering waste – lost heads and parison waste – can be cutoff the article, which, among other benefits, significantly reduces the amount of parison waste.In conventional blow molding, the parison is first ejected and then clamped in the mold. As a re-sult, the parts usually have parison waste all round, which in turn must be removed. During suc-tion blow molding, the parison is sucked into the three-dimensional cavity while the mold isclosed. There is therefore no lateral parison waste. Consequently, considerably less melt isnecessary for each product, resulting in corresponding savings in the energy needed for theplastication.
Moreover, 3D suction blow molding often also requires using materials with a high processingtemperature. Such materials are used predominantly in the automotive industry for engineparts, which make up about 95% of the suction blow molded parts. Some of them must havehigher resistance to temperature and chemical and mechanical loads (e.g. turbocharger com-ponents). In addition, the process is used for technical parts, such as kitchen and householdappliances (“white goods”).