The resulting savings in floor-to-floor times of between one-half and two-thirds are due to increased metal removal rates during cutter engagement, significantly reduced non-cutting times through faster axis movements, fewer operations due to better fixturing methods and faster component changeover through off-line set-up on the second pallet.
Furthermore, with the twin-pallet configuration, if there is an issue during machining of a component it can be brought out of the working area for inspection, allowing production of the next part to commence. Such troubleshooting would have resulted in a lot of unproductive time on the previous machine.
Renold's gearboxes are large prismatic components that can measure more than two metres in height and weigh up to three tonnes. Around 20% of products are standard, the remainder being customer-specific designs that are manufactured in quantities of between one-off and 30-off per month. Fast, flexible machine tools are needed to produce such relatively low batch sizes cost-effectively and allow the manufacturer to compete in world markets.
When the company's CEO was appointed in 2013, he instigated modernisation initiatives that started with the factory infrastructure. A programme followed of drive and control retrofits and mechanical upgrades to what are fairly specialised machine tools, such as worm screw and wheel production centres.
Three years later, the production staff was asked which machine on the shop floor they would most like to replace and the large HMC was almost unanimously chosen. Its unreliability by then was resulting in sometimes having to subcontract out machining to meet production deadlines. After several twin-pallet HMC options had been considered, a BW MCX1400 with a 3,200 x 2,200 x 2,000 mm working volume and B-axis NC table was purchased.
Key elements of the machine specification that deliver such high productivity are acceleration at up to 5 m/s² to rapid traverse speeds of 60 m/min and a 60kW / 3,500 Nm / 5,000 rpm spindle with HSK‐A100 interface.