Plated CBN on high rigidity Edgetek machines

Citation

(2007), "Plated CBN on high rigidity Edgetek machines", Aircraft Engineering and Aerospace Technology, Vol. 79 No. 3. https://doi.org/10.1108/aeat.2007.12779cab.003

Plated CBN on high rigidity Edgetek machines

Plated CBN on high rigidity Edgetek machines

Enterprises that are willing to pay up to ten times more for CBN grinding wheels expect a large payback in terms of faster material removal, or more parts per wheel, or better form consistency, and usually all three. However, although it might seem easy to add a high speed spindle to an existing machine to take a CBN wheel, the user might then find that his parts have surface finish problems caused by the machine vibrations and chatter, which can occur at these high speeds.

This is not usually a problem with the abrasives; rather it is with the machines onto which the CBN wheels are applied. Fitting new high technology wheels onto old or existing machines is almost certain to result in the wheels not achieving their production potential, leading to disappointment for the user.

The most obvious reason why higher production rates cannot be achieved on conventional machine tools is that the spindles simply do not go that fast; but there is also another reason: the machine must be designed for fast set- ups and with the accuracy and stiffness that anticipates such elevated process speeds.

The same problems do not apply to machines designed specifically to employ the latest plated CRB wheels. Holroyd's Edgetek range is said to be a good example: the machines are produced with high power/high speed spindles that optimise the use of plated CBN wheels at surface speeds of up to 9,000m/min.

This reportedly enables them to achieve high depths of cut and optimised metal removal rates far exceeding those of more conventional machines, such as CMC lathes, milling and machining centres and grinders. In addition, the Holroyd Edgetek machines are manufactured with a polymer granite base, which has been shown to have strong damping properties. These are said to have been proven in dynamic response tests carried out by AMTRI.

Developed to satisfy the need for extreme rigidity and enhanced vibration damping, the polymer base typically weighs 3ton and has no resonant frequency. As a result, it enables higher precision machining to be achieved.

Combining this stiffness and damping capability with the Edgetek's ultra high speed machining capabilities and plated CBN wheels, is reported to be drastically reducing cycle times in many crucial industry sectors. In one example, the cycle times for producing automotive parts manufactured from sintered metals were reduced from 1min 10s per component to just 22s. At the same time, the Edgetek's plated CBN technology is cutting consumable parts costs, achieving a reduction from $1 US to just 3.3 cents per component. This is the result of the Edgetek machine producing a much larger number of components between tool changes: 15,000 as opposed to the 50 achieved with conventional milling and turning machines.

It is reported that in another UK application, a single 5-axis Edgetek machine is slashing process times with single lift and set-up. The Edgetek is replacing seven conventional milling and grinding machines, providing a reduction in the throughput time for a complex finished part from 8h to just 12min. This application epitomises Lean Manufacturing technology, said Holroyd sales Director, Neil English. “It provides the opportunity to begin with a hardened blank, and then produce a part complete in a single set-up, using plated CBN wheels.”

“It is not the cost that is driving the trend toward plated CBN but the productivity,” said Neil English. “Smaller production runs and more set-ups, means that many companies no longer have the luxury to amortize the cost of bonded wheels, and the long non-productive set-up times associated with them, over extended production runs. Plated technology fills the need for high metal removal rates with short set-up times and eliminates the need for dressing.”

“The plated CBN form wheels we use on our Edgetek machines have several advantages over bonded conventional or superabrasive wheels: they have higher material removal rate capabilities, and are freer cutting, which reduces thermal metallurgical damage to the work's surface. Equipped with steel cores they are also safer, providing safety at high operating speeds in excess of 20,000sfm.”

“In addition, plated wheels offer the highest levels of consistency: they grind virtually the same profile, from the first cut to the last, across hundreds or thousands of workpieces. As a result, the times associated with set ups, wheel changing, and wheel dressing are significantly reduced or eliminated. Also greatly reduced is the average wheel cost. This is because the wheels can be stripped of worn CBN and re- plated several times.”

The flexibility of the Holroyd Edgetek design, and the huge variety of machine types and multi-axis configurations available, enables the machines to provide levels of precision and productivity in the manufacture of almost any type of parts – airframe actuation components, gears and sprockets, rotors and impellers, medical instruments, hand tools, air foils and nozzle guides, ducting supports, mechanical seals- and many, many, more. The machines serve a broad spectrum of industry types, including aerospace, power generation, automotive, medicals, tools and general engineering.

Figure 2 Plated CBN on high rigidity Edgetek machines delivers reduced process times with single lift and set-up

They can be tailored to suit specific applications and supplied as complete turnkey solutions as part of a manufacturing cell. A world-wide service network provides support for the machines, and they also benefit from manufacturer-developed preventative maintenance plans.

Details available from: Holroyd Precision Ltd, Tel: +44 (0) 1706 526590, Fax: +44 (0) 1706 353350, E-mail: Neil.English@renold.com (Figure 2)