Performance art through injection moulding
Medical technology applications place high demands on injection moulding machines and the production line. Top performance can only be achieved with sophisticated technology and detailed process know-how, says Netstal
An internationally active manufacturer of diagnostics aids was using several Netstal machines. Still, the new order was a first: "The customer made the leap from buying machines to purchasing a system," said Patrick Blessing, manager of the medical technology business unit, in describing the order. "Previously, they only purchased the machine, added the peripheral equipment and combined everything into a production line. However, the realisation has set in that purchasing the entire system from a specialist is less expensive in many regards."
In order to manage everything on a do-it-yourself basis, the user has to keep their own expensive specialists on staff and also make sure that software and hardware are always up to date. They have to cobble together interfaces and often compromise in ways that result in their system constellations operating far below their potential. And even a minimal degree of standardisation (which this customer aimed for) is very difficult to achieve based on these premises. And it all costs money.
"Nowadays we mainly sell complete solutions based on customer specifications. The customer no longer has to worry about the interaction between machine and peripheral devices and can instead task us with performing the configuration and fine-tuning," Blessing emphasises. "But that doesn't mean at all that they don't have a say in designing the system. Each system is built in close and continuous cooperation with the user."
For this reason, Netstal's ‘one team per customer’ rule applies. From the first meeting until the system is approved, the customer will always deal with the same two or three competent employees, regardless of whether they are in Europe, the US or elsewhere in the world. They know the project and understand the goals of the user. The expertise for the details of the definitive solution is always at the ready at Netstal's headquarters in the Swiss town of Näfels.
"We provide a broad knowledge base and a wealth of experience there," Blessing explains. "That goes well beyond mechanical engineering. Our core competence of developing and building high-performance injection moulding machines has long been joined by another: the integration of a wide variety of components, which were not built by Netstal, into an optimised overall system. In that way, we are providing our customers with real added value."
When looking for an injection moulding system supplier that could provide an ‘all-in-one’ system, the customer found Netstal. The Swiss company was awarded the contract for building a complete system for the production of stoppers for blood collection tubes. Such tubes, made from PET (polyethylene terephthalate), are used in doctors' offices, hospitals and laboratories in order to be able to get quick diagnostic results.
They generally contain chemical additives and a defined vacuum that ensures the correct mixing ratio between the blood that was collected and the chemicals. They are sealed with plastic stoppers. The stoppers, made from colored PP (polypropylene), are the final closures and shield these ‘miniature laboratories’ from external influences. Their colours are used to safely distinguish samples.
The new system for stopper production was supposed to consist of an injection moulding machine and multiple components from other manufacturers: a quality control gate, a conveyor system and a carousel packaging station. Two important additional requirements had to be adhered to during the design phase. Firstly, no stoppers were allowed to be dropped to the floor during the process. Secondly, the limited space in the production area had to be considered. In addition, the Mouldflo units provided by the customer (for the flow and temperature control of the injection mold cooling) had to be installed and integrated into the process.
The goal of producing 96 stoppers per injection mould and injection process with cycle times of less than five seconds was particularly ambitious. To get straight to the point: "With 3.8 seconds, we beat that target by nearly a quarter even in the internal Netstal final acceptance test," Blessing said. "That cycle time might even be reduced further once the customer runs the system in regular operation. Such performance values can only be achieved with an optimal integration of all components."
An ELION 4200-2000 high-performance injection moulding machine with a 62 LP screw is the heart of the system. In order to control it – and all other elements of the production line – Netstal counts on a pioneering system: the aXos machine controller, which is a perfect integration tool. It has a firm grip on all processes in the blood collection tube system – from material feeding to the actual injection moulding process and its cooling, the quality control gate and the air delivery system including the reject gate all the way to packaging on the carousel.
As opposed to most other controllers, aXos not only controls and monitors the machine but it also allows programming while in operation. When it was developed, Netstal's engineers wanted to provide programmers with maximum flexibility when drafting complex processes without requiring them to have extensive programming knowledge. The result is a programmable controller that provides operators with maximum flexibility – as long as their commands do not damage the machine.
"While the controller on its own provides many options, only a detailed process and component know-how stretching across all production steps allows for the true fine-tuning of the entire system," Blessing said. "And we can reach the kind of cycle times and therefore the performance as in this case, as well as many others, when we get close to reaching the optimum during the integration process." The customer seemed to agree – and placed additional turnkey orders.