New grinding machines and grinding concepts increase variability

By: Ulf Hensler, M.Sc., Institute of Machining Technology, Dortmund University of Technology

As in many industrial sectors, the effects of current crises and structural challenges are also becoming apparent in the grinding industry. Against the backdrop of cost pressure and a shortage of skilled workers, approaches to resource optimisation were presented by manufacturers of equipment, such as cylindrical and non-cylindrical grinding machines, tool grinding machines for cutting and machining tools, surface grinding machines, grinding, polishing, and hollowing media, as well as clamping technology, filter technology, and grinding oils. The focus was on reducing energy and raw material requirements, as well as mitigating the shortage of skilled workers through automation and digitalisation. Some of the solutions and technological highlights showcased at GrindingHub are presented below.

Erwin Junker Maschinenfabrik GmbH from Nordrach presented grinding machines based on the newly developed Platform 3 for the first time at GrindingHub. These are grinding machines that can be flexibly adapted to their application using various configurations. A modular construction kit allows implementation of grinding machines and processes designed for various applications on a uniform basis and using as many identical parts as possible. Examples include high-speed grinding machines for machining with CBN and diamond tools or grinding machines for conventional corundum grinding processes. This not only increases cost-effectiveness, but also reduces throughput and delivery times. In addition, the increased number of identical parts increases spare parts availability. The basis is a machine bed produced as a mineral casting. Based on this, various table assemblies, guides, workpiece spindles and tailstocks that are matched to the respective application can be mounted. Up to three grinding spindles can be used. The machines are equipped with an in-process measuring system that measures the workpiece dimensions in the process and calculates correction data on this basis in order to compensate for process influences such as tool wear and temperature fluctuations. A special feature in this class is the use of an absolute measuring system for internal machine dressing. In addition, Platform 3 grinding machines come with an integrated automation concept. This includes approaches for manual loading, as well as loading by industrial robots or loading by internal and external gantry loaders.

In the field of external cylindrical grinding, the NSH Group, Chemnitz, exhibited its latest Wotan S3A model at GrindingHub. This is a compact external cylindrical grinding machine for processing small to medium-sized workpieces up to a maximum of 600 kg and a selectable center width of between 600 and 2,000 mm, depending on the version. In addition to a granite machine bed, the machine has two CNC-controlled linear axes with hydrostatic bearings in the z and x directions. In conjunction with a linear drive, they exhibit reduced wear compared to ball screw drives or recirculating roller units. Depending on accuracy requirements, the machine can be equipped with a belt-driven, direct-driven, or hydrostatic spindle. Further adaptation options relate to the integrated dressing technology, measurement technology and configuration of the grinding unit.

Rollomatic SA from Switzerland presented its new GrindSmart 630 RS machine. This is a 6-axis tool grinding machine for the production of tools up to a total length of 500 mm in a diameter range from 0.1 to 20.0 mm and a maximum groove length of 140 mm. These tools are, for example, used in medical technology in the form of bone drills operated with surgical robots. Tool handling within the machine is robot-controlled. Various configurations with and without grinding wheel changer can be implemented on the spindle side. The axes are driven by linear motors.

In order to reduce pollutant and particulate emissions, the Euro7 standard sets an upper limit for particulate emissions from braking systems. This is therefore a focus of current development and research projects. One approach to implementation is hard-coated brake rotors. These offer the potential to reduce abrasion by up to 90 percent. However, the hard material coating poses challenges during machining due to the relatively soft matrix with embedded carbides and the different machining behavior of the two materials. Among others, the process chain for manufacturing hard-coated brake rotors includes turning, laser coating, and grinding. These process steps result in further influencing factors that must be taken into account in the process control of the grinding process. This requires a holistic view and coordination of the process steps.

At GrindingHub, the Emag Group from Salach presented parts of the machining chain for hard-coated brake rotors, such as the VLC 450 DG, a special machine for the high-precision grinding of hard-coated brake rotors. Double-sided grinding is used here. Due to its high productivity thanks to simultaneous machining of both friction ring surfaces, high throughput, and short cycle times, the process is mainly used in brake rotor production. The cross-ground structures created perpendicular to the axis of rotation improve the tribological running-in behavior of the brake rotors compared to structures in the circumferential direction. The vertical spindle arrangement facilitates the removal of the hard material particles, while at the same time enabling good accessibility for set-up and maintenance work. The grinding tool is designed as an interchangeable ring which, thanks to its low weight of less than five kg, enables relatively easy handling when changing tools. The machine features automated loading and unloading via a feed shuttle and a workpiece lift. This allows integration into the production line.

Many smaller manufacturers also presented their products at GrindingHub. Examples include Avyac Machines from Veauche (France) and the Swiss start-up G-Elements GmbH.

Avyac showcased their 5-axis NC18 CNC drill grinding machine. This is a fully automated, compact machine concept for the production of HSS and solid carbide drills in the diameter range from 1 to 8 mm, which can optionally be extended to 14.5 mm. The maximum tool length is 320 mm. A circular loader allows up to 90 tools to be used, which are loaded and unloaded using gravity thanks to a special design. Diamond or CBN grinding wheels with a diameter of 100 mm are used. The integrated measuring sensor enables the cutting edges to be scanned, which in turn allows the cutting position to be determined for tool regrinding processes.