Machining Plastic Parts – and the Parts for Molding Them

April 29, 2021
Wittmann Battenfeld recently added a new mill/turn machine to produce plastic rotating machine components.

The countryside south of Vienna is famous for vineyards and thermal springs, and it’s where Wittmann Battenfeld produces plastic injection-molded components for industrial, medical, and numerous consumer products.  The Wittmann Group employs over 450 people at Kottingbrunn and supplies injection molding machines, robots, and peripheral equipment for plastics processing industry.

Wittmann Battenfeld operates a range of servo hydraulic or electric injection-molding machines – horizontal or vertical depending on the customer's needs. Complete machining of components has long been a part of its production strategy, much of it supplied by WFL Millturn Technologies.

"We introduced the principle of complete machining into the company way back in 1993, beginning with the purchase of a M70 Millturn,” recalled Martin Gorzolla, head of production at Wittman Battenfeld. “In 1995, we added a M50 Millturn. Before this, we had a multi-step production process, i.e., turning and milling on several machines."

Even then, all turning, drilling, and milling operations had been combined in a single machine. “Complete machining” makes production more efficient, reduces wait times, and ensures flexibility. "Above all, excellent accuracy was one of the most important requirements for the machine," Gorzolla explained.

An M60, an M65, and an M40 Millturn were added in subsequent years. The two older M70 (1993) and M50 (1995) models were replaced with the new M30 Millturn in 2020. In addition to maintaining the high level of accuracy, the key criteria behind the purchase were value for money and machine reliability, both of which were fulfilled by the new WFL machine.

"One of the other deciding factors was the proximity of WFL," Gorzolla said. "The Service department is very quick; the WFL team can be here in just two hours.

“Also, the WFL service team have always been excellent in terms of speed and reliability,” he added.

The Millturn range. The Millturn machines can fully machine the range of parts, from screw tips, the plasticizing unit, captive C-washers, and hollow shafts to struts and many other workpieces. "We use these machines for anything that needs to be ultra-precise. We usually only need one of each component that we produce for our injection molding machines,” according to Christian Grafl, head of maintenance. “Our products are highly customized, so we don't have any big batch sizes. Everything must be ready just-in-time."

Not only are Production and Assembly set up to handle this, but programming is highly customized too. The programming team use the EXAPT Plus programming system to apply the CAD data, and to create and simulate the program quickly and reliably. Thanks to the perfectly optimized post-processor, the programs are converted fully automatically into machine-readable programs and sent to a PC directly next to the machine in question via the internal network.

The machine operator calls up the jobs, loads the program into the machine's NC controller and – if they are not already in the magazine – orders the required tools from the warehouse via the internal tool management system.

Workpieces with diameters of 85 mm and lengths of 4200 mm are currently being produced on the different Millturn machines. "This has allowed us to reduce machining times by around 20%. A real advantage when it comes to highly efficient production," Gorzolla said.

The new team member. In 2020, the M30 Millturn was acquired to replace the M50 and M70 machines. With a milling power of 20 kW, it efficiently machines workpieces up to a maximum diameter of 520 mm and a maximum machining length of up to 2000 mm.

Currently, the extremely different workpieces are mainly being manufactured individually on the Millturn. The machine model’s extreme stability, reliability, and precision offer peak performance for all machining tasks, with 4000 or 9000 revolutions per minute on the main drive and turning-boring-milling unit.

The turning-boring-milling unit, with a strong gear spindle with backlash-free B-axis, allows Wittman Battenfeld to use of large drills and milling cutters and therefore high feed-rates with a large cutting depth.

Stability is essential – and it’s achieved thanks to the solid slant bed of grey cast iron, and WFL's typical axis arrangement, which directs the main cutting forces vertically into the bed. Particularly wide guide spacing, large guides and minimal distances between the machining point and the guides all help ensure stable behavior during difficult cuts as well as thermal stability for high-precision machining.

Optimal chip flow is ensured by the fixed, completely smooth guide plate on the lower slide. The tightest of tolerances in all angles can be achieved thanks to the high-precision, stable B-axis with direct measuring system, and additional mechanical indexing through a Hirth coupling. Wittmann Battenfeld generally uses machines with a tailstock. A stable, steady-rest slide with an automatic self-centering steady rest also is fitted. This configuration offers flexibility and enables a wide range of workpieces to be machined with little changeover work.

A 40-position disc magazine provides a sufficient tool stock at the machine. Wittmann Battenfeld opted for a Capto C6 tool system for the M30 Millturn. It features a selection of boring bars with C6 coupling as well as excellent stability and precision. Tools up to 450 mm long can be used in the machine. The magazine capacity and tool length could be greater, if required. 

An 80-bar coolant pump is used, especially for a wide range of internal machining operations. The standard milling spindle design not only permits high pressure (up to 150 bar), but also an extremely high coolant flow through the spindle. This leads to a noticeable improvement in chip breakage, chip removal, and the process reliability for all drilling operations.

WFL has a reliable coolant interface for the tool as well as matching hardware components, such as high-pressure coolant pumps, microfilters, and additional cooling devices.

The increasing use of high-strength materials requires technologies that can reliably machine these 'super' materials. Along with the time savings, there is an improvement in process reliability and surface quality,  as well as controlled chip removal. Unwanted heating of the workpiece is reduced to a minimum.

Eyes set on the future. Wittmann Battenfeld aims to increase its global market share for standard machines. "The most important thing is maintaining manufacturing and production expertise for critical parts in-house and extending the necessary production know-how to increase efficiency and optimization," according to Marc Zachmann, head of production. 

"We've already connected operational technology to our ERP system and will continue on this path. "The main reason for connecting this technology is to increase production efficiency, for example with automatic generation of technical parts lists during autonomous processing of orders in fully automatic welding systems, as well as production responses from production units to our ERP system," Zachmann explained.

Wittmann Battenfeld offers a proprietary Industry 4.0 solution for the products; complete injection molding work cells, consisting of an injection molding machine, automation and peripheral devices. This makes it possible for production units to be formed of several intelligently connected components operating in a work cell. This allows the individual components to talk to each other via OPC UA, share settings and statuses, and even carry out self-optimization.