Perfect Balance for High-speed Automated Lines: Meet Our New Easy-Stamping, High-Yield Bottom End Series

On visits from customers in previous years we have noticed one thing: paint factory filling lines are now being increasingly automated.​ In earlier times a filling line took five or six operators. Now one person is required to tend several machines. Seamer speeds too have risen, from 30 or 40 cans a minute to 70 or 100 a minute. That loads new and extra requirements on the bottom end. If the dimensions are not consistent, if stamping is not proper, high-speed line bottlenecks appear. Jams, skips, incomplete seals, any of these can put the production line down. We lose not only production time, but in finished goods and delivery schedule too.

We, a Chinese factory of Foshan, near Canton, PRC, have been producing Tin Can Components for thirty years, bottom ends in particular for paint and coating use. Our new Easy-Stamping, High-Yield Bottom End Series meets these challenges and demands faced in an automated line.

To deal with these problems as they affect a working line, we have focused on three areas in this new series: stamping, dimensional finish, compatibility with the seamer.

The production of a bottom end is basically stamping a circular tinplate disc through forming dies. If the material is not ductile enough, or if the die is not properly configured, the disc will crack or wrinkle or springback during stamping. On a slow moving line this condition may not be detected; on a high speed press running continuously and stamping at greater than 90% yield, even a small defect is cumulative.

We chose ductile materials , so as to be more easily formed and to cause less wear on a die. The clearance between die and punch is closer in this new series than usual, the more sharp angle on the die face having also been increased to reduce stress at the points where the steel enters the die. Result: on our customers' fast presses, our bottom ends yield above a 99½% satisfactory pick-up on each die, and die life is extended to upwards of 20% more.

Nothing upsets a line more than the simple drifting out of specification of a dimension. Outer diameter too small or too large; height in wrong proportion; curl diameter not suited to that of the can; all these defects cause a final bottoming failure on the seamer because of hang up or imperfect closure. Back in the old days of our previous series of bottoms we had what the terrific speed of the line converted was a fairly good tolerance, usually ±.20 mm on outer diameter. Now, we aim at, and frequently get, ±.080 mm. We have reduced height tolerance from ±.15 mm to ±.050 mm. Curl diameter we control within ±.1. All this may read like small-time chasing, but we are dealing with the speed-seaming machine here, a machine on which its users can make money or lose it by every pick-up and every seal. To assure that every size series of each of our nooks meets such strict specifications, we have actual inline gaging on our production lines. As stamped out, each bottom passes through a gage for checking automatically the critical dimensions. Out-size bottoms are counted out and thrown off the line; none pass to packing stage.

Various machines like the Morrison Seamer differ in size of curl end they pick up and in other ways, besides the pitch of the knurled roll runners which affects all but the most astonishingly skilled operators. We picked metals with increased ductility, to produce bottoms on which forming is easier, and so that dies will not be so quickly worn away. Die clearance and angles have also been so devised as to allow a better distribution of the stresses during stamping. Results: on our customers' high-speed presses our bottoms constantly yield more than 99.5% good, while life of dies will be of the order of 20% greater than that of the dies replaced.

In designing this new series, we incorporated some tolerance for the expected variation into our thinking. Ultimately the curl profile was developed to suit both the standard seamers as well as older or poorly maintained equipment. The hardness of the sealing compound was likewise softened to seal the bottom, while lowering the degree of pressure needed for seaming, lessening the dependence of the bottom end on the state of the machine.

We provide a separate table of seamer parameters in enough detail to allow customers to quickly set their seamers upon receipt of our bottoms. Dialling in seamer parameters used to take half a day for these customers. Now it takes an hour or so of data comparison.

Several customers have done field testing of the bottoms at their plants with positive results. A wood coatings customer operates three lines that fill cans of the product; the lines are fully automated and seam at 65 cans a minute, in three-minute cycles. A competitor's bottom ends were previously used. The plant had experienced three or four stoppages a shift caused by jamming during seaming, and they ran at least one seamer regularly per shift.

"After the bottoms are in programme and, as a rule, using out of the box parameters," data obtained after the switch indicated that the three lines were halted a total of two times in three days. Both times were due to body problems, not the bottom ends. The plant manager told us: "With your bottom ends, I really don't have to stand there beside the line anymore."

Another customer reported a dramatic die wear reduction. Previously, a die set lasted three months before being put in the scrap barrel. With our bottom ends, the same die set would last four and a half months and was still going strong. Annual savings in die costs were significant.

A good tin can components supplier, in our opinion, needs to know more than their own products; they must have a working knowledge of the equipment and processes of their customers. Along with the new series introduction, we increased the size of our technical support group. If you run into trouble in the field, we can send a technician to your plant and help — or talk you through the issues by videos from afar!

Our experience in the field also led us to build a database of common problems and their resolution. When you have a seaming issue, all you have to do is call us for an online link-up — many of our customers now do it from their own desktops without waiting for our team to arrive.

Automation is the name of the game in manufacturing circles, and paint packaging is part of the scene. The bottom end of the tin can is a very small part of the entire finished package. However, if the bottom end can't keep up with the automated lines, the line slows down too.

With this new series that's our hope: to make the bottom end the last thing you need to worry about on your line. New or old, fast or moderate, our bottom end will keep up with you reliably and keep your line running smoother and more efficiently.

If jamming is your concern on automated lines, or if you'd like a more reliable bottom end supplier, give us a call to try our samples — we're sure after trying them, you'll have to wonder when bottom ends were ever a problem.