Environmental and cost factors have a knock-on effect on quality control and how this is achieved by vehicle manufacturers.
The trend to increase the number of valves per cylinder drives the demand for faster, more accurate measurement methods.
Measurement and inspection equipment maker Brown & Sharpe has developed a fully automatic valve inspection machine for the components division of a French manufacturer of car engines.
The computer-controlled machine inspects and sorts engine valves coming off a fully automated grinding machine line at the rate of 1,200 parts every hour. No human could handle that throughput.
Valves that pass inspection carry on to the packing line as finished product.
Those that fail are picked by robot and placed in one of 12 locations, to be reworked or to be scrapped.
The machine is unique for this application in that it combines contact and non-contact measurement techniques.
It is very fast, gauging one valve every three seconds. But it is also extremely accurate, measuring key dimensions repeatable to within 5 m.
The valves are shaped like mushrooms with elongated stalks; a face angle ground on the underside circumference of the ‘mushroom’ mates with a seat, which is also ground, at the cylinder inlet and exhaust ports.
A close fit prevents gas under pressure leaking from the cylinder before combustion.
The machine measures the accuracy of the ground face angle and other parameters.
It is capable of taking measurements for up to 26 inspection areas.
There are eight measurement stations on the ‘walking beam’ type machine which takes 0.2secs to make a 120mm controlled transfer between stations. Sensors measure diameters, lengths and other values.
A P80 optical non-contact system checks the depth on a collet groove.
Because it measures more points in a given time, it produces even more accurate results.
On a modern engine the cost of replacing a faulty valve is put at £1,500. Ensuring a valve is not faulty is a prime objective.