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be used as a guide to self-deception. If the tolerance limits are freely invented, and the desired machine capability is not reached, it is tempting simply to reinvent the limits. Judging the advisability of this method is left to the reader. ASSISTANCE SYSTEMS FOR PROCESS CONTROL Anyone who is aware of the above-described pitfalls can sidestep them where possible and thereby obtain a value for the repeat- ability that is actually convincing—at least for the moment. As mentioned above, it is not foreseeable how disturbances will change in future and how they will conse- quently influence the quality of the parts and the repeatability of the process. A solution to this problem is offered by new intelligent assistance systems for process quality. One example is "iQ weight control" from Engel. The software module forms an automatic control loop that is superimposed on the familiar injection and holding-pressure controllers. When the disturbances change, it adapts the injec- tion, changeover, and holding-pressure parameters in real time—during the same cycle—so that the shot weight remains largely constant. This software package is part of the "inject 4.0" program, with which Engel is paving the way to the smart factory for its customers. FIG 4 Many modern machine controls can generate a quick graph from the process data log at any time. 5 15 25 35 45 55 65 Check out our product video (707) 838-6272 sales@microvu.com www.microvu.com EXCEL 501 Automated Machine 500x400x160mm $48,200 VERTEX 251 Automated Machine 250x160x160mm $35,275 SOL 161 Manual Machine 160x160x160mm $14,775 Prices include InSpec Metrology Software. Other models with sizes up to 2500x1600mm. AUTOMATE Measuring PLASTIC Parts? MICRO - VU'S FAMILY of MEASURING MACHINES is a FAST , ACCURATE , and EASY solution. Shots Temperature Zone 5 Zone 5 Temp., C 224 223 222 221 220 219 218 Tolerance limits for process variables are not found in the part drawing. Where you set those limits will determine the statistical repeatability of your process—but not the actual performance of your machine. 52 SEPTEMBER 2017 Plastics Technology PTonline.com INJEC TION MOLDING