Next-gen gearbox design challenges the limits

Online Editor

Ralf Matke discusses the benefits of increasing the efficiency of industrial gearboxes.

In various grinding processes in the mining industry, it is no longer just about the reliability and availability of the drives. For instance, engineers use high-pressure grinding rolls (HPGRs) where the energy-efficient size reduction of hard rocks, minerals and ore is required. Fluctuating loads, extreme peaks, continuous and non-stop operation for maximum throughput, high axial and radial stress on the bearings and structural components, heat, and dusty conditions have all placed extreme demands on the drive system. Couple that with the OEMs continually increasing performance with innovations that have doubled the service life and output of the HPGRs in the last couple of decades.


“With an eye on the market’s continuous request for higher performances and output, we invest continuously in the development and improvement of our Redulus4F gearbox series,” says Dr Nico van de Sandt, global head of engineering Industrial Drives at ZF. “The focus, or rather the strength, of the next generation of successful Redulus gearboxes continues to be on the entire range of highly stressed industrial applications. We aim to support the current technical developments and challenges within these applications with the best products.”

The new Redulus4F gearbox series still stands for a flexible design to fit most applications and has a compact design to reduce cost and handling efforts. The latest series guarantees advanced serviceability to minimise downtime, and ZF has maximised the load capacity to increase lifetime and performance.

ZF says it develops gearboxes at the highest technical level in terms of torque density, service life and robustness. The new series has 20 gearbox sizes with a torque range of 127kNm up to 7,200kNm (nominal) which is approximately 50 to 80% higher than previous models. The torque densities of Redulus4F are currently leading the market.


How is such a significant increase in power density possible? The ZF engineers have utilised the newest development tools, designing and evaluating all components in the gearbox according to the latest findings in transmission technology.

This applies, in particular, to the geometry and qualities of the individual gears, the choice of materials, improved technological properties and the revision of the structural components for maximum torque and power transmission. Adapting the required bearing concepts to the increased service life or suitable sealing and lubrication systems also plays a part.


OEMs have two choices with Redulus4F. One is to maintain the existing size but increase the torque rating compared with the previous generation of these gearboxes. This results in a considerably higher output capacity of the HPGR and improved gearbox service life.

The other option for the OEM is to select a gearbox that can be up to two sizes smaller. The advantages are clear: lower weight, improved handling, saving on installation space with the option of smaller roller distances, better maintenance access around the rollers, and reduced investments.

ZF says it can meet the high requirements for development and delivery times for the respective application-specific solutions with its optimised configuration concept.


The maintenance-friendly design for assembly/disassembly, borescope inspections of the Redulus4F gearboxes, and the proven condition monitoring system ZF ProVID considered during development, also enable quick intervention in an emergency to avoid lengthy downtimes.

Markus Christen, project manager for Redulus4F, adds: “The developments and innovations ultimately have one goal: maintaining the competitiveness of our customers when using our drives.”

ZF states it has mastered this challenge excellently with the Redulus4F series but cannot and will not rest on its laurels. As the saying goes: ‘after optimisation is before optimisation’. These are the requirements for the next generation of the company’s industrial gearboxes.

Ralf Matke is with ZF.

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