Mitsui Seiki USA has announced that several of its customers are cutting 10-14 class ring gears in low- to mid-volume applications on its CNC vertical and horizontal machining centres.
Traditionally, manual gear hobbers or CNC gear cutting machines are employed.
However, benefits are surfacing in certain applications, such as for aerospace and power generation, using highly precise machining centres.
In particular, Mitsui Seiki's Vertex machine is suitable for ring gears up to 16in (41cm) and a special gear-making model incorporates a rotary trunnion table for the finish turning operations.
Mark Speier, sales engineer at Mitsui Seiki, said: 'This machine can turn the gear faces, the final profile of the internal bore and generate the gear teeth.' On one of its largest precision five-axis machining centres, the HU80A-5X, users are producing spiral bevel gears up to 35in.
Speier added: 'One of the benefits of producing gears on that machine is that the relative gearboxes or gear cases, and even reduction gear boxes, can also be processed on this one machine.
'The gear housing is a critically precise piece.
'The accuracy of both parts has a direct correlation to the transmission performance over the life of the motor.
'The end product reliability is a positive factor, too.
'Further, the gear is mounted flat and then turned up 90 degrees - or another angle - so that the end mills can cut at the optimum attitude to the gear profile.
'This results in excellent roughing efficiencies.
'For finishing, ball nose end mills generate the final profile before heat treating,' he said.
Mitsui Seiki's initial foray into gear cutting involved cutting the gear teeth and roughing and semi-finishing operations prior to heat treating.
Now, by adding turning operations to the Vertex machine, accuracies have improved through the single setup for all operations, according to the company.
Mitsui Seiki anticipates that turning functionality will be available on the HU80A-5X in about six months.
Speier continued: 'The traditional gear-cutting machines may run faster; however, [as a result of] the tooling economics, improved accuracy through one-setup machining and improved process control, the overall cost may be advantageous, especially in low-volume runs.
'Plus, this application may enable our current gear-making customers to get more use out of their Mitsui Seiki five-axis machining centres,' he said.
One of the key aspects to successful gear cutting on a Mitsui Seiki machining centre is software.
CNC Software, the developer of Mastercam, has generated the optimum toolpaths for spiral bevel gear cutting.