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Automated drive for heavyweight loading

08 August 2023

When Hermle needed a heavy-duty version of its HS flex handling system, it created an automated drive that integrated a rack and pinion drive, planetary gear unit and servo motor from STOBER

HERMLE'S PALLET handling systems make it easy to automate the processing of different component types and sizes without robots and their machining centres provide an economical entry point into automation for operating companies.

During operation, blanks and components are loaded onto pallets and held in a storage module before the handling system then loads and unloads the components to the machining unit automatically. This enables the manufacturing operation to work continuously, even overnight and at weekends. This reduces non-productive times and increases production capacity.

While the standard version transports different pallets weighing up to 450kg (including components) between the setup station, storage modules and the working area of the machining centre, the new HS flex heavy can handle double this weight.

A tower, which moves the workpieces inside the cell, can perform rotary, lifting and travel movements, which according to Johannes Berg, head of the South-West Sales Center at STOBER, must be “Fast, dynamic and precise”.

Berg continues: “In the standard version of the HS flex, STOBER supplied ZV series helical-geared rack and pinion drives for all three movements. These are based on case-hardened, ground pinions with high gearing quality and precisely matched gear racks.”

In the new HS heavy flex centre, STOBER combined the rack and pinion drives with its new generation of planetary servo geared motors and, in doing so, has significantly reduced the overall lengths of the gear units. For high flexibility, all STOBER motors, such as EZ synchronous servo motors, can be directly attached in any desired size without adapters.

Compact and lightweight

The result is extremely space-saving, lightweight and has a high-power density. The elimination of an adapter means that the overall solution is even more compact. In addition, there is no need for separate assembly of the motor and gear unit as the completed drive unit is ready for use.

Owing to the design of the space-saving 3rd generation planetary gear units from STOBER, everything is now more open and accessible for the operator and eliminating the adapter has an extremely positive effect on the mass moment of inertia. As a result, the full dynamics of the drive can be used, resulting in real added value that is reflected in shorter cycle times and improved energy efficiency, especially for small and medium sizes.

Reinforced lift drive

As the HS heavy flex can pick up components weighing up to 1200kg, STOBER had to design a stronger lift drive, which led to the specification of the ZTR series of rack and pinion drives. This design, with a bolt on pinion onto the flanged output of the planetary gear unit, offers high linear rigidity at high feed forces. Also, STOBER can also use variable motor adapters to combine their planetary gear units with all third-party motors in any size.

Trouble-free operation and safety during maintenance were prime requirements of the design. For example, the HS flex makes it safe for people to remain in the workspace during setup as the drive axes can be put into a safe state.

As heavy loads are suspended from vertical axes, these are secured by brakes, which prevent loads from falling. Safety must also be reliably maintained in the event of a power failure, so STOBER’s attention was focussed on the supply of high-performance brakes with a narrow tolerance field for this purpose. The safety functions of the HEIDENHAIN controller take care of regular brake monitoring and any necessary adjustments to calibration.