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Zenith 400 Helical Profile Grinder


A great deal of industry excitement has already surrounded the launch of Holroyd’s new Zenith machine, Holroyd’s first with the capability to use the three grinding technologies of aluminium oxide, Electro plated CBN (cubic boron nitride) and vitrified (dressable) CBN. The Zenith machine will have the capacity to grind some of the largest rotors in the industry at 420 mm and offer the flexibility to use tooling from customers existing grinding machines.

This is a new generation of grinding machine technology, encompassing modern innovations, coupled with an exciting new easy feel control system that incorporates both a development and production software suite to suit all potential user requirements in either research and development or mass production.

The new Zenith machine is an extremely compact machine that gives high loop stiffness, good thermal resilience and rigid work holding. The machine’s increased diameter capacity can accommodate components of up to 420 mm. in diameter. Thanks to careful orientation of axes and guide-way layout, overall length capacity could be increased with a reduction of machine footprint. Use of a single-piece iron casting using precision ground linear guideways removed traditional constraints regarding the orientation of the guide-ways. While disassembled the entire machine and coolant filtration system will easily pack into 40’ shipping containers, facilitating transportation as well as reducing the factory space required. A two-wheel arbour with wheel slide allows two non-dressable grinding wheels to be mounted simultaneously, a high speed spindle offers 6,200 RPM capability and when required, a twin-wheel dresser caters for all types of dressable wheel, a live spindle drum rotation axis offers increased angular capacity to allow the grinding of components with zero lead angle, such as spur gears, while the drum-mounted probe increases probing range for the continuous probing of ‘normal’ components with the capability to access both ends of extra long components.


The new Zenith machine is as user-friendly as it is efficient. Ease of access is significantly improved through a unique slideway design. A software ‘wizard’ guides the operator smoothly and efficiently through the CNC programming without the requirement for high levels of expertise while still offering options for personal operator control. Operator-free coolant application eliminates the possibility of human error. An inductive flute-finding probe allows rapid orientation of the part. Simultaneous probing of both journals measures the run-out of the blank before grinding. Work pieces are automatically loaded and extracted. Power-assisted doors provide easy access at the touch of a button. Fast mist extraction prevents coolant mist from escaping into the workshop when the doors are opened. Full automatic vitrified wheel balancing and Radio Frequency Identification chips and reader make the operator’s life easier still. While dresser touch detection enables the machine to locate the position and profile of the grinding wheel to ensure economic dressing.


In designing the new Zenith machine, the Holroyd development team was careful to be as sensitive to the environment as it was to the needs of its customers. In the light of this, a warm up cycle mode was incorporated to avoid leaving the machine running for long periods when not in use and to provide thermal stability. Auxiliary units such as the coolant filtration and chiller system are under central control and so can be switched off into ‘sleep mode’ when necessary. Coolant flow is controlled to avoid excessive application, reduce the heat generated from pumping the fluid and the energy used to filter it. A directly-mounted backlash-free torque motor, meanwhile, reduces cost, build time and performance degradation.

As Rod Macdonald, Managing Director of Holroyd Precision explains:
“The development of the new Zenith machine has provided an exemplary case study of the way in which we like to operate here at PTG. By taking as our starting point the concerns and considerations of our customers through a thorough and exhaustive market study, we believe that ultimately we have been able to develop an entirely new generation of helical grinding machines to satisfy the demanding needs of accuracy and versatility on the one hand and productivity and ease of use on the other. While the important and newly- emerging consideration of energy efficiency was also a very important factor in the development of what we believe to be a truly groundbreaking machine.”