There has always been the tension of choosing between fixed and flexible automation. Fixed automation is ideal for high-volume work, chunking out thousands to millions of something. The problem with fixed automation is, well, it’s fixed. Changeovers to new products are expensive. Often, this is because the dimensions of the product it was built for are cast in the fixtures and transfer mechanisms. So too are any tools for drilling, milling or threading parts.
This has led to the rise of flexible automation, especially one-armed robots. These programmable devices are easy to repurpose when it is time to make a new product. And, low-volume production runs are becoming the norm in modern manufacturing, making any kind of flexible automation an obvious choice.
Which leads to the question: Is there still a place for automation that isn’t built from one-armed robots? Yes, in many cases. The special case of the rotary transfer machine is an example.
When considering their utility, rotary transfer machines are often compared to traditional production methods. Traditional shops have a fixed number of machines that can perform many operations. Parts move from machine to machine with multiple setups. In such a traditional shop, a part may start on a lathe, then move to a milling machine and perhaps finish with a drill. Rotary transfer machines consist of many tools in a single machine. A central round table, where the components to be machined are fixed, transfers the pieces from one station to another for sequential processing. A raw piece is fixtured once and unfixtured when complete.
“The Mikron Multistar CX-24, for instance, has 24 stations with machining units that work simultaneously from above, below, and from the side. In total, this machine supports up to 44 simultaneous work units,” said Axel Warth, head of marketing and business development for the Mikron Machining Division. “Rotary transfer machines are commonly used for mass production of metal parts that are complex, yet numerous.” This includes mass-production of metal parts.
Mikron’s machining systems and solutions support industrial production companies in a variety of sectors–such as automotive, medtech, consumer goods, writing instruments and watchmaking–by reducing unit costs, space requirements and staffing costs, and by increasing manufacturing quality. Mikron’s ultimate goal is to enable its customers to improve their production processes, product quality and profitability. The parts can range from simple to complex, depending on the layout of the machining tool.
Warth further explained the advantages of a rotary transfer machine. “We think about lowering the costs per part, up to 10-20 times versus a traditional production solution,” he said. Why is this? He listed advantages that include less floor space, fewer employees, and fewer machines when compared to traditional production methods. A key point is that since there is a single clamping of the part during its production, higher quality goes with reducing cost through a single setup.
Warth cited a case of replacing a traditional solution for making air spring valves for ventless molds. The challenge was to make 30 million parts, including both male and female components. To make them required turning, drilling and milling operations to tolerances of ±10 μm. Overall production costs were reduced 45 percent, while reducing floor space by two-thirds and using more than six times fewer labor hours.
While rotary transfer machines are often custom-designed for manufacturing of a single part or family of parts, Mikron recognizes that in today’s world, flexibility and quick changeovers are important. For more flexibility in rotary transfer machines, Mikron offers its MultiX, first presented at EMO 2019 in Hannover, Germany. “It is very easy to convert and offers unique possibilities with machining solutions for the production of 50 up to 5 million parts,” he explained. The new platform includes “simple reconfiguration for new applications: once the application for which the system was initially configured is no longer needed … the system can be easily and quickly reconfigured with a patented concept” for switching out tooling stations.
The company offers a case study for flexible operation in an application job shop, using the C-8 configuration of its MultiX line. Each station could be programmed for different operations, depending on the part presented. Warth noted it can machine from bar (turning or milling), with three machining units working simultaneously at each station. Additional multispindle-lathe and transfer machine capabilities are also available in this one machine. “Customers have a complete set of machining units at their disposal. The machining units differ in size, number of axes, size of compatible spindles, strokes, stiffness, and can be exchanged within the platform and re-used in various different configurations,” he said.
To make it easy to work with, Mikron made the machine modular. “The modular software package and the Mikron HMI interface are designed for ease of use and quick adaptability to any machine configuration,” he said. “This enables a simple and efficient operation, configuration and reconfiguration of the desired machining solution.” Further flexibility is provided by scalability: customers can start producing with a single-cycle Mikron MultiX configuration and add supplementary cycles according to volume growth.
Will the future move to only flexible rotary transfer machines, as some might predict? Not necessarily. “We think we will see both,” said Warth. “There will be highly productive transfer machines for dedicated single applications where no flexibility and modularity is needed—a perfect example is the Mikron Multistar LX-24 for highest volume applications, like writing tips.” The Mikron LX-24 produces up to 600 parts/minute, and 95 percent of all ballpoint pen tips worldwide are produced on Mikron LX-24 machines, he stated. On the other hand, Mikron developed its MultiX as a modular concept, as described above.
Without giving up the old, companies like Mikron are looking to the new—ever more flexible and modular automation.
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