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PRACTICAL TIP 1: Has the Process Settled Down? In most cases, it is difficult to assess whether a process has settled down. To make an assessment of this kind, it is necessary to mon- itor multiple parameters shot by shot over a relatively long period. Some modern controls, like the latest CC300 machine control system from Engel, offer the possibility of graphically displaying process parameters. This allows changes in the process or the state of the process to be assessed at a glance—in up to six graphs on one screen page, in the case of the CC300. Searching for changes in apparently infinite columns of figures is thus a thing of the past. Machine-specific parameters or process-specific parameters give an indication of whether a process has settled down or not. On start-up of the machine, it can be seen (Fig. 3) that the process- specific parameters of injection volume (3a), viscosity change (3b), and plasticating time (3c) are stable after just a few cycles. Given the temperature differences between the inlet and return in the mold-cooling circuit (3e and 3f ), it should be observed that the two cooling circuits have not settled down at the same point in time. In this case, the difference can be explained by the fact that the two temperature circuits supply different regions of the mold. If the mass to be cooled is larger, it takes longer for a stable temperature difference to be established. In the case of toggle machines, the clamping-force peak value (3d) changes as the mold is brought up to its service temperature because of thermal expansion. This parameter is particularly suit- able for assessing whether the mold is already heated throughout. For the case in which six graphs are not enough, or where it is desired to investigate the profile of any other arbitrary parameter in the process data log and display it graphically, the CC300 allows the operator to simply tap into the column of the particular data value. For example, the quick graph generated in this way can show that at least 25 cycles are necessary before the temperature of a cylinder zone has settled down (Fig. 4). Process Control