The tool shop of the motion plastics specialist igus uses innovative cooling lubrication concept in automated production cell

The tool shop of the motion plastics specialist igus uses innovative cooling lubrication concept in automated production cell

With an innovative cooling lubrication concept in three 5-axis precision milling machines, the igus tool shop not only mills better surface qualities. The Mediumverteiler on the Röders milling machines also makes it easier to clean the workpieces. And the automated process is more sustainable, partly due to the substantial energy savings. In May 2024, Röders and Dymato will present this technology at a knowledges session organized by and held at Mikrocentrum.

The motion plastics from the German family business igus can be found in numerous machines and installations. From energy chains to guides and self-lubricating plastic bearings. igus makes the world move with innovative plastic products. The pace of development is high. Around 1,000 new injection moulded parts are produced every year. The focus in the business model is on short delivery times and tailor-made solutions for customers. "That's why it was decided a few years ago to invest heavily into the tool shop in-house," says Thilo Schultes, CEO dry-tech New Businesses & iform Mold Making at igus. "That gives us the opportunity to perfect concepts and create individual geometries for customers."

Technical heart of igus

Thilo Schultes, who did his PhD at RWTH Aachen with a focus on Production Management, leads the mould making department. Here, a team of a hundred craftsmen work on the moulds and other production tools. The technical heart of iform is the automated production cell for the mould inserts. It consists of three 5-axis machining centers from Röders (1 x RXP601DS and 2 x RXP601DSH, with a larger table diameter and longer Z-axis), supplemented by sinking EDM machines, a washing plant and a measuring machine. In this cell, mould inserts are hard-milled and sparked 24/7.

The graphite electrodes for sinking EDM are also milled in the cell. Everything is done unmanned as much as possible. Accuracy is everything to Thilo Schultes' team. "We only process technical plastics into motion plastics. The plastics we develop are self-lubricating and replace oil and grease in moving structures. To properly injection mould these parts, we need very precise tools." That's why igus uses sinking EDM machines in addition to hard milling for the production of the tools.

Medium distributor

Graphite electrodes for die-sinking EDM machines are usually milled dry. Two years ago, when expanding the cell with two new Röders machining centers, igus decided to equip all three machines with a Mediumverteiler that Röders offers as an option. This system, developed in Germany, is an alternative to wet milling and MQL (Minimal Quantity Lubrication). It can be used for dry machining and as system with air oil mist. When producing graphite electrodes it is used with compressed air only for dry machining. When working in hardened steel it is used with air oil mist for better lubrication. As with an MQL system, lubrication is done during milling with a mix of oil droplets and compressed air.

The big difference is that with the Mediumverteiler, the nozzle holder is mounted in a fixed position on the spindle housing. Attached to this holder are the connection points for oil and compressed air. The 16 nozzles in the Mediumverteiler create an up to 6 bar strong ring of air oil mist blown downwards around the tool. Regardless of the position of the spindle and the speed at which it rotates, the air oil mist ring remains in a constant position relative to the cutting edges and tool because the Mediumverteiler does not rotate with it. This has the effect of pulling the mist towards the cutting edge. "As a result, the mist (oil and air) is directed exactly to the cutting edge and the lubrication goes exactly where it is needed," explains Thilo Schultes. With rotating MQL systems, there is always a risk that air and oil particles will be separated.

Multiple benefits

This innovative cooling lubrication concept for CNC machines offers several advantages for high-speed milling of hardened steel and graphite electrodes. One of these is better surface quality with both materials. "This is important for the injection molding quality and the stability of the injection molding process," says Schultes. Since no water is used in the process, as is the case with wet milling, cleaning after machining is easier. No coolant remains on the hardened steel.

With the graphite electrodes, no residual contamination remains on the electrodes. Graphite is normally always dry machined, as the coolant can clump during wet machining. However, when graphite is dry machined, tiny particles of graphite may remain behind, which can lead to an erroneous measurement result when measured automatically in the production cell. Thilo Schultes: "You can't clean an electrode with compressed air. By using the Mediumverteiler for the cutting process, no residual particles remain on the surface; they're blown away with it."

The 6 bar strong airflow also provides better chip control. The chips are broken and blown away. An additional advantage of this coolant concept is that it has a positive effect on the thermal stability of the precision machining centers. When wet hardened steel milling, part of the coolant - the water - evaporates and cools down the inside of the CNC machine. This decreases the temperature inside the machine with the risk of thermal drift. When milling with the Mediumverteiler, the oil-air mixture dissolves completely and therefore cannot affect the thermal stability of the machine. 

More sustainable machining

As far as costs are concerned, Thilo Schultes thinks that the Mediumverteiler provides a small advantage at the end of the day. The higher accuracy, better surface quality and no cleaning of the electrodes are more important advantages. In addition, the Mediumverteiler contributes to making production more sustainable, which igus attaches great importance to. "Sustainability is important to us. With the Mediumverteiler we use less coolant and the energy consumption of the CNC machine is lower," says Thilo Schultes about the sustainability aspect.

The latter is due to the fact that in wet machining, the CNC machining centers must be equipped with large pumps to pump the coolant. This easily accounts for up to 30% of the machine's energy consumption. With a Mediumverteiler, only a relatively low amount of compressed air is sufficient, which consumes much less power.

Cooling lubricant concept for precision machining during Manufacturing Technology Conference

Röders will present this cooling lubricant concept for precision machining during Manufacturing Technology Conference, April 16^th in Veldhoven. Click for more about MTC 2024

Together with Dymato, the Dutch partner of Röders and the machine tool dealer for the Röders brand in the Benelux, ASML and Mikrocentrum will organise a special knowledge session for suppliers in de supply chain of ASML. This knowledge session is about new Minimum Quantity Lubrication for an optimal milling process, energy and cost savings and a more sustainable optimal machining process. This session will be held in Veldhoven at May 23^th 2024. Click here for more information.