PETpla.net Insider 11 / 2018

BOTTLE MAKING 15 PET planet Insider Vol. 19 No. 11/18 www.petpla.net whereas at 1,500b/cph it is already up to 0.72s or an almost 50% increase, although small in real numbers. Most linear machines use a higher percentage of overall time for unproduc- tive time as it takes longer to shuttle the preforms and bottles in and out of the mould, and open and close of the mould. However, there is no change in this whether the machine runs at maxi- mum speed or not; these movements always take the same amount of time. Potential buyers should always ask what the process time is for a given output and then judge from their range of applications which type of machine fits best. 4.5 Rotary machines comparison While there are many suppliers of linear machines, the rotary machine market is dominated by four suppliers:  KHS Corpoplast, Germany (Blowmax series IV)  Krones, Germany (Conti- form Generation 3)  Sidel, France (Matrix)  Sipa, Italy Since this market pro- duces the vast percentage of all PET bottles, it is worth to compare the different machine characteristics so the reader can better under- stand what is different about them. I will examine the latest offerings in Table 4.4. One should note that only bottles with stretched-out bases, such as lightweight water bottles, can be moulded at these speeds. Thicker bases require longer cooling time to avoid the creeping out of the base center, which can lead to an additional “leg” causing the bottle to rock (the so-called rocker bottom). In carbonated soft drinks (CSD) bottle production, this is espe- cially important as the center disk is stressed significantly and must stay rather thick. This in turn is required by the pressure cycles inside the bottle that may reach up to 5bar (70psi) when the bottle contents are agitated as happens during a bumpy truck ride. One of the param- eters that quality control has to monitor is the so called base clearance to make sure this does not happen. All machines show decreased output as the number of cavities increases. This is because the centrifu- gal forces become rather large with the larger blow wheel diameters. A COLOUR IDENT I TY LIQUID COLOURS AND ADDITIVES FOR PACKAGING repi.com The trend in blow moulding machines has been to eliminate the turning of preforms and/or mandrels, which reduces handling and wear issues that have plagued some of the systems. Only Sidel turns the preforms after the oven section up, whereas Sipa uses what is referred to as a “cat- erpillar” oven where preforms travel upward and downward on their man- drels but there is no actual turning.