Working with Baumüller, Bemaco Engineering developed a highly productive plastic blow-molding machine with fully electric clamping unit
High-precision customized solutions from Bemaco Engineering ensure precise, fast and reproducible hollow articles made of plastic in all kinds of different shapes and materials. The latest development, a continuous multilayer blow molding plant with fully electric clamping unit is unique on the market and meets the requirements of the automotive industry – and it runs like clockwork.
Everyone knows them: Bobby Cars, pedal tractors, rain barrels, watering cans, canisters, barrels, bottles and flacons. Yet only real experts know that they are made with the help of plastic blow molding plants. The company Bemaco Engineering, based in the northwest German town of Langenberg, has specialized in plants for manufacturing hollow articles made of plastic. It produces coex plants and modernizes used machines. Since 2014, the company has produced high-precision plastic blow molding machines for the production of fuel tanks (KKB) or filler tubes. Its machines are used to produce different plastic fuel tanks in a reproducible and precise way – perfect for the automotive industry.
The continuous multilayer blow molding plant with a mold clamping force of 150 tonnes was specially developed for a customer who uses it to produce hollow articles for plastic tanks with a capacity of 45 liters. These are installed in cars that run on gasoline. The customer’s requirements are very high, since the products are for the automotive sector: The tanks must have a precise wall thickness, exact dimensions and high reproducibility. In addition, only a small quantity of rejects may be produced. The repeatability and the quality are thus important factors, which make this machine a very sophisticated plant. “Each tank must look exactly like every other”, emphasized CEO Jörg Johannpaschedag.
His company, Bemaco Engineering, uses a Baumüller drive concept not only for the extrusion but also for the clamping unit. This consists of high-torque DST2-200 motors and servo drives of the type b maXX 5500.
How the coex plant works
The machine operates according to the following principle: Plastic pellets are melted by an extruder within the 200 degrees Celsius range. Here, the interaction between pressure and temperature in the extruder is decisive: “High torques and precise speed control are required to melt the pellets”, explained Jörg Johannpaschedag. In the next step, the hot, viscous mass is extruded to dorm a plastic tube, which is transferred to the blow mold and is blown by compressed air and is thus shaped. This process takes place in the fully electric clamping unit.
Advantages achieved by doing without hydraulics
Eschewal of hydraulics produces numerous advantages: There are fewer wearing parts, since there is no need for the hoses, belts and the transmission. In addition, an enormous amount of energy can be saved and the noise level is also reduced. “The main advantage here is the faster build-up of clamping force and the faster traversing speeds. In addition, the electric clamping system runs like clockwork. Viewed overall, the unit handles the material more carefully and is more energy efficient”, continued Jörg Johannpaschedag.
The fully electric clamping unit closes very quickly. Yet caution is required when welding the seam. Therefore, the final centimeters run slowly so that a uniform weld is produced. The welding and pressure build-up require a high torque and enormous locking forces. This is decisive for the reproducibility and the product quality. The high-torque DST2-200 motors are ideally suited due to their precise control dynamics.
Multilayer method ensures high leaktightness
A multilayer process has been required by the market since the 1990s, in order to improve the leaktightness of the plastic tank. The coextrusion enables a hollow article with multilayer wall thickness to be produced. The pellets are therefore melted in several extruders, are merged in the blowing head and are extruded as a multilayer tube. At Bemaco, six layers are arranged on top of each other. A coupling agent layer, that is to say a kind of adhesive layer, is arranged between the substrate and diffusion barrier. The blowing and molding take place as described above.
Compact drive technology
For the development of the new coextrusion plant, Bemaco Engineering worked with Baumüller as a competent partner. Apart from space-saving, compact, water-cooled components, the decisive factors for Bemaco Engineering were also the development know-how and high torques that can be generated from the standstill condition with the Baumüller torque motors.
Baumüller has supported us since 2014. At the time the company needed a partner for extruder drives. We looked for drives with which we could do without the transmission and this is where Baumüller then came into play with its high-torque motors.
Jörg Johannpaschedag, CEO of Bemaco Engineering
Thanks to the perfect interaction of the controller and motor, the build-up of the mold clamping force was improved and the traversing speed was increased. The Baumüller b maXX 5500 servo converters, as mono units, control the machine’s drives. Together with Bemaco Engineering, Baumüller dimensioned the drives and assisted with the initial commissioning of the machine.
The continuous multilayer blow molding plant developed in partnership by Bemaco Engineering and Baumüller is energy efficient, compact and precise. It offers many special features which enable, for example, the fully electric clamping unit, the even faster mold clamping force as well as a higher traversing speed and which allow the machine to become low in emissions and even more precise. Working with Baumüller, a plant was created which completely does without hydraulic drive concepts and therefore means large reduction in machine maintenance costs and significantly increased product quality.