ROSEMONT, ILL. — While it may seem like injection molding is the only way to produce caps and closures, it turns out to be far from the truth.
Compression molding is offering many companies another viable option to get into the caps game.
Marco Andrea Ferri, key account and area sales manager for the closures and containers division of Sacmi Imola S.C., discussed compression molding innovation during a session Sept. 12 at Plastics Caps & Closures 2014, in Rosemont.
“In compression molding, the plastic does not have to be liquefied, so you can work at lower temperatures,” Ferri said.
Ferri noted that the process can produce more intricate parts without weld lines. Tooling costs also are lower with the process.
It does have its limitations. The process cannot be used to manufacture sport caps or closures with a hole in the middle.
The process, Ferri explained, has several advantages, including energy savings, higher consistency, faster cycle times and less complexity.
Sacmi produces an 80-cavity continuous compression molding machine. The maximum rate is 1,400 caps per minute. The optimal cycle time is a little more than 2 seconds.
In the rotary process, a large turret revolves continuously. Each of the cavities receives a small drop of resin, usually polyethylene, and is raised to clamp with the forming upper punch. The station opens and ejects the cap after a complete 360 degree turn of the turret.
The company also has developed Cool+, its new cooling concept.
“This is a modified coolant liquid circulation system inside the mold which ensures that all parts in contact with the plastic are cooled,” Ferri said. “This includes the inner and outer punch.”
The process enables the closure to be cooled much faster, which Ferri noted results in higher quality parts.
“The improvement of the cycle time is huge,” he said. “We have realized a reduction from 2.1 seconds down to 1.5 seconds for a 29 millimeter closure.”
Cool+ underwent an internal validation trial in 2011 and extensive field tests were completed in 2012.
“The test included a total of 133 days at the client's site,” Ferri said. “We were able to produce 144 million caps during this time, all values were within the standard.”
Sacmi also has developed its Colora Cap digital printing, which enables the use of high-definition digital images and imports them into the printing system in minutes, staring a new production batch without any format changeover costs. It allows images to be printed directly on the production line.
The product offers a range of decorating options and speed for these packaging components. Advantages include reduced format changeover costs, optimized logistics and reduced format changeover time.
Colora Cap also eliminates the need for personalized parts and matrix for each design or closure. It increases flexibility and produces images with a higher resolution. It also offers real-time changeover.
The machine can produce 600 22 mm caps a minute.