Car brake discs are safety components that must be produced reliably and with extreme precision while minimizing costs. To run disc production batches quickly, machine tool maker EMAG has enhanced its pick-up turning centers, the VSC and VL series, to work in coordination with TrackMotion automation.

Disc brakes advance

The quality of cast blanks has increased in recent years, while compound brake discs – multi-material designs such as gray cast iron friction rings with steel or aluminum bowls – are reducing vehicle weight as engineers increase their use. Those changes in net-shape accuracy and materials are creating new machining challenges.

Users are looking for flexible machining units that can be retooled for new workpieces without long downtimes. At the same time, original equipment manufacturers (OEMs) are increasing unit volumes in brake disc production to meet platform strategies.

The TrackMotion automation system allows users to swap out a machine from the process if not all steps of the operation are required for the workpiece.

“Having an extremely flexible machine and automation concept available” will allow suppliers to respond to rising demand, says Peter Loetzner, president & CEO of EMAG LLC. “Our main focus of attention is the VSC and VL machine series with vertical pick-up spindles. Their modular technology can be configured to custom-fit requirements and can be combined in a production line. Customers end up with a flexible overall solution they can retool for new parts in a short time, greatly decreasing downtimes. For brake discs in particular, this is a decisive factor since the actual machining times cannot be improved much due to the physical limits of the clamping devices, in spite of higher performance potentials of the cutting materials.”

Workpiece transport

Inside-ventilated front-axle brake discs are usually machined in four clamping operations – performed by four spindles. EMAG’s TrackMotion automation system links the spindles (or separate machines) using a track-mounted gripper unit that moves linearly. It transports the workpiece from the blank infeed via the individual machines and process steps to the finished-part outfeed. Users can modify the overall system at any time by switching out a machine from the process if not all the steps of operation are required for a workpiece. This might be necessary for different brake disc types due to changes in the clamping sequence, minimizing retooling for different clamping devices.

TrackMotion can integrate several machines into the chain to perform the same operation in parallel. The system can distribute workpieces to machines with available spindles, keeping production going while employees service or retool other machining centers.

Fine machining of friction ring faces is done by parallel processing both surfaces with a straddle tool.

Finish machining

Individual VL and VSC machines can be combined in different sizes to support various component features, allowing users to process gray cast iron friction rings and aluminum bowls on the same production line. Quick loading of the pick-up working spindle shortens cycle times, as do high linear feed rates and short turret indexing times.

Fine machining of friction ring faces is generally done by parallel processing both surfaces with a straddle tool. Stably integrating the tool into the process prevents vibrations which would reduce quality.

“In addition to the classical mounting of the straddle tool on the tool turret, EMAG offers the alternative option of placing it on a special console inside the machining area,” Loetzner says. “This results in perfect damping, and consequently, high surface qualities and minimized thickness variations.”

A statistical process control (SPC) station is standard on EMAG VL machines, allowing users to check part quality while the production line continues running.

Accompanying processes – marking, balancing, measuring – can also be integrated into the line design. In addition to TrackMotion, other automation options are available, including pick/flip and place units or line gantries.

A modular brake disc machining line features several EMAG VL series machining centers and an automated loading system.

Industry 4.0

EMAG Fingerprint software can detect wear on axis drives early, allowing advanced maintenance planning. Lifetool-Analytics allows users to monitor machine performance and health via a smartphone app.

“These machines are extremely robust. Some have been in operation for decades,” Loetzner says. “Our customers know and appreciate that. We have a worldwide service network and when needed, are quickly on site with our own service engineers. We want to continue to target these benefits to the market in the years to come.”