Reliable machining of camshaft ends is key to efficient production

KASTO News

	'The reliability of the Caorle machines has been excellent and would be our automatic choice if we needed to buy similar end-working machines'
The working area of the Caorle machine at the start of the Federal Mogul line producing the eccentric shaft that goes into BMW's 4-cylinder engine.

The two lines at Federal Mogul's Godalming factory that produce the eccentric shafts for BMW Valvetronic engines are each headed by a double end-working machine built in Italy by Caorle, whose UK sales and service agent is Kasto, Southampton. Since 2001, the lines have been working 18 hours a day, producing around 200,000 shafts per year.

Commented Graham Nicklen, Engineering Director of Federal Mogul Camshafts, "You must be able to depend on the machine at the start of a production line, otherwise all the others will be starved of parts. The reliability of the Caorle machines has been excellent and would be our automatic choice if we needed to buy similar end-working machines."

He went on to say that the supplier had engineered a very effective system for delivering forgings from a manually-fed input conveyor to a special fixture in the machine. Here the part is held temporarily in the jaws, probed on the drive gear, released and reclamped in the correct angular and lateral positions. Both are critical to ensure that the shaft ends are milled, drilled and tapped to the required accuracy.

Federal Mogul Camshafts is a long-term user of many types of end-working machine, but the Caorle CL132s on the Godalming site were the first to incorporate tapping, as the Italian company offers this as a standard function. On other potential suppliers' machines, tapping heads were an option for which a very high premium was quoted.

The patented Valvetronic engine has a conventional intake cam, but also uses this secondary eccentric shaft to steplessly vary the timing and lift of the intake valves, which is claimed to yield efficiency improvements of 10 per cent. One line at Federal Mogul manufactures the shaft for the four-cylinder engine built in Hams Hall, near Coleshill, that goes into the BMW 3-Series. The other line produces a very similar shaft for the V8 engine built in Munich for the 5- and 7-Series models.

Once the 380 mm long forging is clamped in position, it undergoes machining operations using six tools, three in-line opposing each other at either side. First is a mill that faces the ends, and in the case of the four-cylinder shaft, also mills a recess at one end only. Next, a form drill centres, drills and counterbores the ends; followed by M6x1 tapping using through-tool coolant. Total cycle time is a little over a minute. The four- and eight-cylinder eccentric shafts are very similar, so both lines are able to produce either variant.

Operations further down the line are 4-axis turning, milling, bearing and cam grinding, deburring and polishing.

	'A transfer line would be needed if production volumes were very high, but for heading up medium-volume lines, the Caorle machines are ideal as they are robust, and may be reconfigured relatively easily to produce a new component when the time comes'
An eccentric shaft for a 4-cylinder engine after endworking, showing completed machining operations including the additional milled recess.

Concluded Mr Nicklen, "A transfer line would be needed if production volumes were very high, but for heading up medium-volume lines, the Caorle machines are ideal as they are robust, and may be reconfigured relatively easily to produce a new component when the time comes."

(Since these Caorle machines were installed, the manufacturer has brought greater flexibility to endworking with the introduction of new, more compact models with an automatic toolchanger.)