PET: Top in form

Automation in stretch blow-molding


The design makes the difference: The emergence of the compact and high-performance L42X stretch-blow molding machine from Amsler Equipment clearly illustrates how medium-sized machine manufacturers can benefit from the engineering support of an automation partner that can act not only as a system supplier but also as an i4.0 enabler.


100% designed, built and maintained in North America: The Canadian company Amsler Equipment Inc. is the only North American manufacturer of fully electric linear PET stretch-blow molding systems. In a sophisticated process, these systems manufacture a wide variety of different PET bottles from so-called preforms. Like many medium-sized machine manufacturers, Amsler is confronted with the challenge of simultaneously concentrating on its core competencies while also keeping pace with digitalization. For the new stretch-blow molding machine L42X, the company was therefore looking not only for intelligent drive and control technology, but also for rock-solid engineering support.


New engineering partnership

Background for the redesign of the stretch-blow molding machine: The previous machine concept ran up against its own technical limitations, which stood in the way of the desired precision and output quantity. The further development of the mold closure and the linear transport concept have overcome these limitations. At the same time, the new machine also had to be made fit for i4.0. After long market research and in-depth discussions, the decision was made to intensify cooperation with Bosch Rexroth, which had already proven itself since the time when it was first founded. In addition to a local presence, other factors in favor of cooperation were precise market knowledge and the resulting ability to play a supporting role in the conceptual development and design of a total of twelve axes for the new machine.

The preforms shortly before transfer to the transport carrier (Image: Canadian Packaging).]


Fully automatic manufacturing process

The new fully automatic Amsler L42X stretch-blow molding machine is aimed at bottlers of food and non-food products. With four workstations, it can manufacture up to 6,000 high-quality PET bottles per hour in challenging designs. The preforms are first taken from containers via a conveyor belt system and separated, aligned and transferred to transport carriers. In a second work step, they are routed linearly through four heating ovens and heated to temperatures of approx. 90 to 120°C under regulated conditions. A specially designed conveyor system positions the heated preforms precisely in the blow mold, which consists of two halves. A new slider crank mechanism has been specifically developed for reliable uptake between the two molding plates. In the actual stretch-blow molding process, a rod coming from below lengthens the perform mechanically while it is simultaneously blown into shape using compressed air. Depending on the volume capacity of the finished products, two or four units can be manufactured per machine cycle. In the fourth and last work step, the plastic bottles are removed from the blow mold, aligned for further transport with the base facing down, and transferred on a conveyor belt for further processing.


Key area – the closing mechanism

A characteristic element that differentiates the LX42 from previous stretch-blow molding machines is the special closing mechanism of the blow mold. To be able to manufacture PET bottles at a rate of up to 2.2 seconds each, a special slider crank mechanism has been developed that closes both plates extremely rapidly and accurately. With the help Bosch Rexroth’s engineering knowledge, IndraSize dimensioning software and MS C Adams simulation software, Bosch Rexroth has been able to find a technically and commercially optimal drive solution, which has made it possible for the L42X to achieve market readiness very quickly.

The Amsler L42 stretch-blow molding machine in action (source: Amsler Equipment Inc.)


Less pneumatics, more control

Another special feature of the L42X is its consistent use of electromechanical servo-axes, which has made it possible to significantly reduce the number pneumatic axes that is typical for stretch-blow molding machines. The effect of this action: lower operating costs, shorter cycle times and more control over the manufacturing process. Including the closing mechanism of the blow mold described above, nine of twelve axes are moved by the IndraDrive Mi decentralized drive technology. The gradual pushing of the preforms through the oven by means of an electromechanical cylinder (EMC), which Rexroth has also delivered from a single source.

Maximum precision with control cabinet drive technology and high-performance control: The preforms move through the oven in a perfectly synchronized rhythm. (Image: Canadian Packaging)


Twelve axes, precisely synchronized

An essential requirement of the drive concept was to synchronize the movements of the twelve axes perfectly, for example unloading after molding, and the transfer and setting down on the outgoing conveyor. Amsler solved the latter task with the help of two CKR compact modules that are provided installation ready, including tooth belt drive and control. The Rexroth motion-logic system IndraMotion MLC75 takes over the higher-level synchronization and monitoring of all machine movements.

With two CKR compact modules from Rexroth’s linear motion technology portfolio delivered installation ready, the finished bottles are placed on the conveyor belts with perfect synchronization. (Image: Canadian Packaging)


i4.0 ready

The new remote diagnostics function is an important selling point for Amsler’s worldwide customer base. This allows the Canadian manufacturer to query the machine state remotely in consultation with the customer, and if necessary to act immediately. Thanks to the Open Core Interface open technology interface, the selected Rexroth MLC also offers many more comprehensive options for meaningfully connecting the automation level with the IT level. This means, for example, that Amsler is able to network its new generation of machines with IoT applications very easily.

Enjoy improved customer service thanks to i4.0: Rexroth Project Manager Paul Thiele with Werner, Jason and Heidi Amsler (from left to right). (Image: Canadian Packaging).


Smaller control cabinets, fewer cables

In addition to maximum availability and optimal service, Amsler has always stood for elegant and compact design. One of the ways the manufacturer underscores this claim is via drive technology without control cabinets. The slim design with intelligent, decentralized IndraDrive Mi drives in addition to appropriate standard and compact converters from the IndraDrive C and Cs series have made it possible to reduce the control cabinet size so much that Amsler has been able integrate it into the machine for the first time. This simplifies not only shipping, but also unloading, setup and installation at the target site. Reduced wiring costs result in further cost savings. Instead of up to 18 cables in a conventional design, the nine IndraDrive Mi of the L42X are supplied and controlled via a single hybrid cable.

The inner life of the integrated control cabinet with Motion Logic Control from Bosch Rexroth, which monitors and synchronizes all axis movements (Image: Canadian Packaging).


Live at Pack Expo 2017

With the help of the well-founded engineering skills of its engineering partner and its intelligent solutions from the fields of automation, drives and linear motion technology, Amsler has succeeded in bringing a groundbreaking stretch-blow molding machine to market within a short period of time, setting new standards in terms of design, performance and connectivity. At Pack Expo in Las Vegas exhibition visitors can see first hand that Amsler not only has its fingers on the pulse of the times, but also hits the mark for its target group.



About the Author:

Is a Senior Application Engineer for Plastic Machines at Bosch Rexroth AG in Lohr a.M., Germany. He studied Mechanical Engineering -Dipl.-Ing. (BA)- with a focus on design engineering at the DHBW Mosbach. He gained his first experience in engineering while working in the automotive industry as designer of an internal gear pump for CVT-Gearboxes. Since 1999 he has been working at Bosch Rexroth AG. starting in the development department of pumps for industrial applications. Supported on his experience of mass production and automotive quality standards, in 2005 he was in charge of the Quality Management for industrial pumps in Lohr. Since September 2010, he is responsible for major global customers and defined country responsibilities in the plastic machine branch. In addition, he has a global responsibility for Foam and Shape Molding Machines.

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