PETpla.net Insider 10 / 2016

CAPPING / CLOSURES 43 PET planet Insider Vol. 17 The lower forming pressures used also create less residual stress in the finished cap. Cycle times as low as 3.2s are possible. A CM machine may also be equipped to form a liner made from a different material as a second step. This makes them ideal for clo- sures for hot-fill bottles. 4.6.3 Comparison of IM–CM The main differences between the two methods stem from the fact that in IM the entire tool has to move for each cycle whereas in CM individual cavaties move. This and other differences make CM more energy efficient:  Less mass is moving for the production of each cap  Material temperatures are lower  A continuously run- ning turret requires less energy than the discon- tinuous operation of an IM machine  Compression pressure is lower than injection pressure CM also does not need sophisticated systems to center two mould halves, but instead relies on rela- tively simple guide bush- ings. Because it does not need the plates and complex hot runner sys- tems used in IM moulds, CM tools are generally less expensive, especially when the capital cost is com- pared with the output per year. Another advantage is that the lack of hot runner channels speeds up colour changes. CM is somewhat limited in tool complex- ity and is mainly used for standard beverage and hot-fill caps. CM tools do not allow slitting the caps right inside the mould, and these slits must therefore be added in a secondary operation. Many proces- sors try to minimise these, and therefore a case can be made for either pro- Figure 4.37 Compression machines like this Sacmi CCM011 are an attractive alternative to IM. (picture courtesy of Sacmi) cess. An ample supply of spare parts and knowledgeable techni- cians that can come at short notice may be the deciding factors when machinery buyers have trouble making a deci- sion between the two processes. PET Line #GermanBlingBling #PETLine We do more. CHINA BREW CHINA BEVERAGE 2016 Shanghai New Intern. Expo Center 11 – 14 October, Hall B, Booth 2200