Novel Back-Facing Operation on Hanging-Spindle Lathe Halves Capital Investment

When a UK automotive subcontractor won the contract to supply fuel injection pump adapters for a new diesel engine, the company decided that a dedicated cell was needed to machine the high-pressure aluminium die castings on both ends within a 76-second TAKT time. The obvious choices were to install four 3-axis horizontal-spindle lathes and employ two operators, or to invest in two opposed-spindle turning centres. However, Geo Kingsbury Machine Tools came up with an alternative that was around half the capital cost, based on a turnkey cell with a single Index V160C hanging-spindle lathe. Key to achieving the cost-effective solution was the ability to machine the a dapter in one clamping, rather than two, using a bespoke two-jaw chuck that allows sufficient clearance at the back for the component to be turned on the reverse end using a special tool that accesses the back face through the bore. Not only is one machine sufficient, but the 54-second cycle is well within the TAKT time of the line, which includes assembling an O-ring onto the adapter and pressure testing prior to just-in-time delivery to the car manufacturer.

The Index V160C works around the clock, the operator loading castings onto a built-in conveyor with fail-safe location pots. From here, after completing a machining cycle, the vertical spindle picks up the next part and transfers it to the machining area. The OD of the casting is turned to 62.97 - 62.94 mm (datum C), followed by turning of the main face, including the lugs, to ± 0.25 mm on depth (datum D). The bores are opened out, the front section to 53 ± 0.1 mm, the lead bore to 52 ± 0.15 mm and the oil seal bore to 50.039 - 50.000 mm (datum A). To achieve this latter tolerance, particular attention has been paid to the clamping pressure of the jaws. The special cutter, which uses polycrystalline diamond inserts (as do all the other tools), then turns the back face (datum B) to 30 microns perpendicularity to datum A. Finally, using the spindle's C-axis and live tooling in the turret, the holes through the four lugs are opened out, two to 10.5 - 10.7 mm and the others to 9.0 - 9.2 mm.

According to the subcontractor, this is a highly capable production cell that turns out components within tolerance from a cold start, although 24-hour operation means that the machine is only switched off during shutdown periods.

Moreover no insert changes, or even tool offsets, were needed during the time that the first 4,000-off parts were machined, indicating a very stable process.