Sense Part Temperature To Minimize Cooling Time

Improve part quality and productivity by means of a new in-mold sensor that signals the press to open the mold when the part has cooled to a predetermined ejection temperature.

Improve part quality and productivity by means of a new in-mold sensor that signals the press to open the mold when the part has cooled to a predetermined ejection temperature. The new 6190 sensor from Kistler Instrument Corp., Amherst, N.Y., combines cavity-pressure and part-temperature sensing in one probe. During set-up, the user enters the desired ejection temperature and the nominal wall thickness of the part. The sensor starts measuring cooling after the end of cavity filling, determined by cavity pressure. The system calculates the average plastic temperature throughout the wall thickness.


The sensor reportedly simplifies set-up because it is not necessary to determine a fixed cooling time. Part quality is improved, says Kistler, because of consistent demolding temperature (too-hot parts are occasionally marred by ejector pins, for example). And productivity is reportedly improved because cooling time is always kept to the minimum necessary. Kistler says a study by the University of Southern Westphalia in Germany found that 70% of molding cycles are set too long by anywhere from 5% to 20%.


Software for automatic cooling-time calculation is built into the SmartAmp charge amplifier. The unit can be accessed with a handheld PDA for set-up. Also, this module has been integrated into press controls by Engel and Demag.


More news from Kistler includes what is said to be the smallest cavity-pressure sensor on the market—1 mm diam. It uses new single-wire technology, which is said to be easier to repair in the field. Also new is Kistler’s smallest combined pressure/temperature sensor, Kombisensor model 6189A, with 2.5-mm diam. This unusual design mounts the thermocouple inside the quartz piezoelectric pressure sensor, rather than beside it. Other new entries are two special cavity pressure sensors for low-pressure molding techniques such as injection-compression. Models 6177AE (4 mm diam.) and 6178AE (2.5 mm) boast resolution four times higher than standard sensors, single-wire technology, and a measuring range from 0 to 200 bar (2900 psi).