Rochdale-based Renold Gears has installed two Japanese-built machine tools with automatic component load / unload, a Takamaz X-15 Hi-Server lathe and a Kira KN30VE twin-pallet machining centre, to form part of a line for producing gears for the 1100 Series engines which power small excavators and mini diggers assembled by Perkins Shibaura Engines Ltd (PSEL) in Peterborough. One of the largest manufacturers in the UK of worm reduction and helical gearboxes ranging from 30 mm to 710 mm between centres, Renold Gears secured in 1997 a 10 year contract from PSEL to supply three families of crank, cam and idler gears. In addition to these nine parts, a gear component for a Volvo engine was included in the agreement.

As is so often the case with automotive subcontract work, margins were tight.

Renold Gears decided that to make the business pay they needed an automated production line dedicated to this work and set about researching the market for suitable equipment.

The intention was to progress from raw steel forgings to finished components with minimal manual intervention.

The final configuration, in addition to the Takamaz and Kira machines sourced through Yuasa Warwick Machinery, comprised a Murata twin-spindle lathe, a Mitsubishi gear hobber, a Cardinal broach, a F„ssler gear hobber (the only non-automated machine) and two special purpose assembly rigs.

Automatic gauging stations were included between the machines to check sizing and quality of gear teeth, the latter being finished to JIS4.

Said Neil Felton, then Head of production engineering at the Rochdale factory, 'During machine evaluation we were looking for a twin-pallet, light-duty, vertical machining centre or a turret drill to engrave a timing mark and complete all drilling operations.

'It was difficult to find a machine small enough for such a simple requirement, let alone one with automatic component load / unload as standard.

'We were fully expecting to have to over-spec the machine and retrofit the automation, with all the attendant disadvantages which that brings in terms of interfacing problems and split responsibility for servicing.' However, a visit to Yuasa's showroom in Warwick revealed the existence of the 10-station, turret-type Kira with twin pallets as standard, which Mr Felton considered to be of good build quality and which fitted the requirement exactly.

Furthermore, there was an auto-load version of the machine in the catalogue on short delivery and it was even possible to choose from three variations of robot loading.

So the order was placed for a pallet change machine with gantry loader.

A hydraulic fixture package was supplied with the machine.

Drilling and countersinking are performed in the first operation while Op 2 involves deburring and engraving the timing mark, all in a very fast cycle time of two minutes.

There is a tight angular tolerance between the timing mark and the gear teeth but acceptance trials were no problem whatsoever.

While in the Yuasa showroom Mr Felton saw a small lathe, the Takamaz X-15 Hi-Server, which also had automation equipment factory-fitted as standard.

Again, it was very unusual to find a machine of that specification in a catalogue, certainly in 1997.

Renold Gears was looking at hard turning the gear components instead of grinding them and trials were carried out on the Takamaz to check the feasibility of this.

At the time, Renold Gears had proved hard turning to be a viable process but were not using it in a mass production environment, although this would soon change.

The idler gear required hard turning of the bore, spigot OD and gear faces, one of which is machined using a back-facing tool.

There are holes drilled through the spigot so both the boring and OD turning operations involve intermittent cutting.

The crank and cam gears have an external keyway and also present an intermittent cutting challenge as well as requiring hard boring.

The steel forgings are pre-hardened to Rc 58 - 62 and all cutting was performed dry using CBN tooling.

The trials were remarkably successful and all results were checked independently by PSEL.

A surface finish of Rz 2.5 was achieved, twice as good as specified on the drawings.

Dimensional tolerances on bore and OD were 20 microns.

Additionally, cycle times were in the region of 30 seconds, around eight times faster than grinding.

The order for a gantry loaded Takamaz was placed immediately after completion of the evaluation exercise.

Capability trials were carried out for all machines in the line, initially at the supplier, then on delivery and finally three months after commencement of production runs.

Cm = 1.67 was required and both Yuasa machines 'sailed through', according to Mr Felton.

An up-time guarantee of 96 per cent over a 15 month period was written into the contract and a creditable 98 - 99 per cent has been achieved in practice for both machines during the first two years of two shift operation.