Aerosol Can End-Making (Ends and Bottoms)
Aerosol ends and bottoms may be the most challenging to make and to measure. The aerosol cans have to stand up to high pressures. The material is thicker and thus more difficult to form. The parameters are difficult to measure, as illustrated in Figure 1.
Manual measurements are not very reliable, suffer from poor repeatability and are labor intensive. The solution is an automatic gauge, as shown in Figure 2. In this particular gauge, ends and bottoms can be measured automatically, without tooling change.
Aerosol Can End-Making from ETP or TFS
The material used to make aerosol can ends can be the same as that used for the can body. The coating is mostly the same as that of the can body, as it has to stand up to the same requirements of the content. Coatings can be tested for thickness, but are mostly subjected to a porosity test, already referred to as Enamel Rating.
Machinery used for end making ranges from single die presses making ends from strips of ETP to multiple die presses, stamping ends from a coil. A popular modern press uses a single die (for larger ends) or a row of dies. To effect the most efficient material usage, the sheet (or coil) is moved in a zigzag pattern. During the end stamping process, the end curl is started. In the next operation, the curl is finished curled and last, the sealing compound is injected into the outer edge of the end.
Two dimensions on ends have traditionally been checked with "Go-No Go" fixtures, the Chuck Fit and the Pin Fit (or Curl Opening). During the double seaming process, the curl of the end and the flange of the can are rolled together in the first operation and pressed tight in the second. The exterior force is applied by seaming rolls. The interior counterforce is provided by the seaming chuck, acting as an anvil.
The chuck has to fit well into the countersink of the ends. If the fit is too tight, the end with the can seamed onto it may get stuck to the chuck. If the chuck is too loose, the end might not be seamed properly, the seaming rolls might skid. In the past, this chuck fit was measured with a set of "Go-No Go" fixtures.
The pin fit (or curl opening) is the space that the flange of the can needs in order to fit into the curl of the end. In the past, this gap was tested with a pin, which was guided along the gap of the end curl, the Curl Opening. If it did not get stuck, the end was OK. If not, the curler had to be adjusted. Today, both Chuck Fit and Pin Fit (or Curl Opening) can be measured with contact gauges like that shown in Figure 2.