A US manufacturer of aerosol cans needs to ensure that, for each can, only one bottom is inserted into the press that applies and crimps the bottom to the can body. This checking must be accomplished without physical contact while the product is moving.
The application involves a conveyor with a stainless steel glide plate backed by a permanent magnet to ensure that can bottoms travel perfectly flat on the belt transporting them to the assembly stage. If double-bottoms are fed into the assembly stage, the result can be machine jams, tool breakage and downtime.
Checking needs to be accomplished without physical contact and while the bottoms are attached magnetically to the fast-moving belt. The gage of steel used to produce the can bottoms (~ 0.33 mm in thickness) is, however, too small for the detection range of the customer’s normal automatic double-sheet detector.
The special properties of Full Inox family sensors (series 700) provide a simple, cost effective solution. They operate on the basis of Condet® technology, which enables these sensors to detect the mass of a target (by inducing a voltage in it) rather than simply its surface.
A Full Inox sensor (DW-Ax-70X-M12) is mounted approximately 4 – 5 mm above the intended target: the dome of a can bottom. On its own, the 0.33 mm thick target presents insufficient mass to switch the sensor at this distance. However, the presence of a second bottom piece increases target mass sufficiently to switch the sensor. This triggers rejection of the double-bottom further downstream, where the part is blown free.