模具介绍27474.pptVIP

Tooling Considerations模具設計考量 Injection Molding Tooling 圓形 流動效能 最佳 Hot runner Tooling 熱膠道系統 Injection Molding Tooling Injection Molding Tooling Injection Molding Design Moldability Holes Injection Molding Design Moldability Holes Injection Molding Tooling Injection Molding Tooling Ejecting the Part Draft Angle WILL Change with Pressure WILL Change with Temperature WILL Vary with Tool Age WILL Vary Tool to Tool WILL Vary Molder to Molder EJECTOR DISCUSSION. ALL THESE FACTORS MUST BE CONSIDERED WHEN BUILDING THE TOOL. OBVIOUS RULES OF THUMB. LARGE DIAMETER PINS REDUCE THE PRESSURE AGAINST THE PLASTIC PART. YOU MUST HAVE DRAFT. SHRINKAGE ON SIDEWALLS OF THE PART CREATE LARGE FORCES WHICH KEEP THE PART FROM EJECTING. HAVING DRAFT MOVES THE MATERIAL AWAY FROM THE STEEL AS SOON AS EJECTION BEGINS.. SELF EXPLANATORY IF A SIDEWALL IS TEXTURED, THE DRAFT ANGLE MUST BE INCREASED BY 1 DEGREE FOR EVERY .001” IN TEXTURE DEPTH TO AVOID WIPING OFF THE TEXTURE DURING EJECTION. AS PROCESS CONDITIONS, TOOL AGE, THE MOLDER, AND OTHER CONDITIONS CHANGE, THE APPEARANCEOF THE TEXTURE MAY VARY. THIS REQUIRES CAREFUL CONSIDERATION WHEN MOLDING MATING PARTS AT DIFFERENT LOCATIONS. THESE ARE SOME DATA SHEET MATERIAL SHRINKAGES. NOTICE THE DIFFERENCE BETWEEN SHRINKAGE IN UNFILLED AMORPHOUS MATERIALS AND CRYSTALINES. TAKE SPECIAL NOTE OF THE FACT THAT THESE ARE DATA SHEET VALUES AND ARE NOT NECESSARILY TRUE IN THE REAL WORLD! THE REASON WHY THIS IS SO IS ON THE NEXT SLIDE. SHRINKAGE IS A MATERIAL PROPERTY IN ITS’ NATURAL STATE, BUT NOT ON A MOLDED PART. AN UNFILLED LEXAN PURGING WILL SHRINK .006 INCH PER INCH (THE DATA SHEET VALUE) BECAUSE IT IS BEING ALLOWED TO COOL AT ITS’ OWN RATE AND IS NOT RESTRAINED IN ANY WAY. HOWEVER SHRINKAGE IN A MOLDED PART IS CONSTRAINED BY PRESSURE, GATE LOCATION, FLOW LENGTH, COOLING RATE ETC. AND SO MAY NOT BE THE SAME. THIS MAKES SHRINKAGE IN A MOLDED PART A SYSTEM FUNCTION, NOT A DATA SHEET PROPERTY. THE BOOK ANSWER TO THIS QUESTION IS “A”. BUT