Kistler's joining systems give medical device manufacturer complete control

Mikron Switzerland has designed a complex assembly line for autoinjectors that involves two different assembly cells — and no less than 18 NCFT electromechanical joining modules from Kistler. Together with integrated maXYmos process monitoring systems, the modules support automated assembly, including force-displacement control and real-time data transmission and process transparency. 

Jean François Bauer, head of marketing & business development at Mikron Automation explains recent years have seen the automation sector developing at a dynamic pace: "Our assembly solutions focus on small products — you can hold them in your hand — and often involve complex processes and more and more data management." 

Pharma and medtech have gained enormous momentum in the last 10–15 years. That’s where we generate the lion’s share of our sales. As well as high-volume solutions with throughput rates of several hundred parts per minute, we also supply scalable systems for very low or medium production output. This is because clinical studies and assembly tests have to be done in various stages before a medical device is launched on the market and mass production can really get going."

To ensure maximum flexibility and efficiency, Mikron Automation opts for a modular platform approach, following the example of the automotive industry: standardised base machines are designed and specified to suit each customer’s requirements and every application.

High-precision assembly, including process documentation

In a project currently in progress for a major pharmaceutical company, Mikron is using electromechanical joining systems from Kistler integrated into two manufacturing cells. Jörg Besold has been a project manager at Mikron Switzerland AG, Boudry for almost 5 years. Together with a core team of about 10 people, he is responsible for all the steps in the design and development process — from project kick-off through to final acceptance at the customer's site.

This is how he describes the requirements: "To assemble an autoinjector, several plastic parts and a

syringe have to be assembled together in a process that must be accurate and controlled. We’re using 12 servo presses from Kistler for one cell, and six more for the other cell. That allows us to triple the steps needed so we can achieve the desired volume of more than 100 parts per minute."

The NCFT joining module from Kistler (Table I) is an electromechanical servo press that was specifically

designed for small forces in a wide measuring range from 0.05 to 1.5 kN. It can be combined with the

maXYmos NC process monitoring system to achieve complete control of all movements and forces, including detailed process documentation based on piezoelectric force measurement.

"We already had some previous experience of using force-displacement sensor technology from Kistler combined with the maXYmos system," Besold recalls. "But in view of the demanding requirements for this project, we opted for the high-end solution. It provides control of forces and positions at every point in time, as well as comprehensive process data for every product. Because the modules are integrated directly into the automation environment via OPC UA, we're able to manufacture two product variants simultaneously. The machine control sends the different parameter sets to the maXYmos NC units that control the joining modules." 

All the production data and quality parameters are stored in a database, and a matrix code engraved into every product guarantees 100% traceability for the end customer. Mikron has also integrated quality testing for each individual step into both assembly cells — an additional feature that ensures a very high standard of quality, for the benefit of the patients who will use the device.

Customised design meets challenging requirements

"We’re highly satisfied not only with the solutions from Kistler, but also with the valuable support they give us. With project lead times of 9–12 months or more, we need a reliable, professional partner who can support us throughout the various phases," Besold points out. As this was the first time that Mikron had used the NC joining systems, a joint workshop was staged at Kistler’s headquarters in Winterthur.

Besold continues: "Even though the maXYmos systems are simple to integrate, it was especially useful for our software engineers to learn how the entire joining process is synchronised with the machine and optimised."

Given that the solution is intended for use in medical environments, additional adaptations were implemented to meet the relevant requirements. André Signer, Sales Engineer at Kistler, explains: "First, we integrated a functionality to track and back up all user changes to the system — this is what’s known as an audit trail, and it’s essential for medtech applications. Then we prepared our NCFT system for production in class 7 cleanrooms. And finally, we had to replace the lubricants in all the modules to ensure compliance with the requirements."

Following a successful assembly test and release by the end customer, the automation solutions from Mikron are being handed over and mass production can start. Jörg Besold sums up: "It’s not by chance that Kistler has a reputation for high precision: these joining systems provide excellent process control for our complex assembly operations, and that’s why we’ll certainly continue using them in the future. And it was also thanks to the systems from Kistler that we achieved very high levels of quality assurance and traceability in this project."

Located in Boudry, a small town on the shore of Lake Neuchâtel in Switzerland’s French-speaking region, Mikron Switzerland, Boudry is the headquarters of the Mikron Automation division. The company is a specialist in the design of assembly solutions integrating complex manufacturing processes, with more than 700 employees at sites in Denver (USA), Kaunas (Lithuania), Singapore and Shanghai. Every day, Mikron assembly solutions are used to manufacture around 150 million products, ranging from pen and auto-injectors, inhalers, safety syringes and point of care testing to airbag parts, relays and connectors.