Oven cycle optimization

Microprocessors that control processing improve the precision of the product (Chapter 3). It optimizes the process by controlling the machine cycle based on temperature and time, rather than time alone by using an infrared thermometer to monitor the mold s outer temperature. The molding cycle data for the oven and cooling chambers can be stored for different products and recalled when needed. Cycle time, oven temperature, major and minor axis speeds, fan and water spray times are typical of functions under complete computer control. 

A postcure or additional curing step, usually done out of the mold simply by placing the part in an air-circulating oven, will complete the cure. The part will then have achieved optimal properties, and further reaction will not be probable. Thermoset compounders generally can recommend postcuring cycles where appropriate. 

Although oven temperatures between 282-357°C have been sueeessfully tried for rotomolding ECTFE, the recommended range is 288-315°C.1 1 At temperatures above 321°C, small bubbles are formed that are difficult to eliminate from the part. Cycle time has to be determined experimentally. The best approaeh is to begin with a short eyele and inerease it until the optimal cyele has been determined. Speeific gravity and tensile property measurements ean eontrol the quality of the part. Table 9.10 gives examples of cycles for a few different part designs. 

---