SYNOPSIS OF A HEAT PIPE
THE HEAT PIPE IS BASICALLY A SEALED COPPER-ALLOY TUBE FILLED WITH A THERMALLY CONDUCTIVE GAS MIXTURE. THE DEVICE IS DESIGNED SO THAT WHEN ONE END OF THE HEAT PIPE IS AT A HIGHER TEMPERATURE THAN THE OTHER END, HEAT IS TRANSFERRED RAPIDLY AND CONTINUOUSLY FROM THE HOTTER END TO THE COOLER END. HEAT PIPES ARE INHERENTLY MORE THERMALLY CONDUCTIVE THAN COPPER.
FREQUENTLY ASKED QUESTIONS
CAN THEY BE MACHINED?
NO: HEAT PIPE HEAT CONDUCTORS ARE DESIGNED TO BE INSTALLED INTO OTHER STRUCTURAL COMPONENTS OF THE MOLD, AS IS, AND CANNOT BE MACHINED. THEY CONTAIN A SMALL AMOUNT OF GAS AND IF PUNCTURED, THE HEAT TRANSFER GAS WILL BE VENTED AND THE DEVICE WILL STOP FUNCTIONING.
HOW ARE THEY INSTALLED?
THE DEVICE CAN BE INSTALLED WITH ONE OF THE INSTALLATION HEAT TRANSFER COMPOUNDS. THE SILVER COMPOUND IS 8 TIMES MORE THERMAL EFFICIENT THAN THE COPPER COMPOUND.
WILL THE DEVICE WORK IN A HORIZONTAL POSITION?
YES, THE HEAT PIPE HEAT CONDUCTORS HAVE BEEN SPECIFICALLY DESIGNED FOR MOLD COOLING WHERE THE MOLDS ARE USUALLY IN A HORIZONTAL POSITION. THE DEVICE WILL ALSO FUNCTION VERY WELL IN THE VERTICAL POSITION WITH THE HEAT INPUT AT THE BOTTOM, BUT THE UNITS LOSE EFFICIENCY AS THE HEAT IS CAUSED TO MOVE DOWNWARD.
WILL THEY HEAT?
YES, HEAT PIPE HEAT CONDUCTORS WILL HEAT OR COOL WITHIN THEIR TEMPERATURE RANGES AND ARE AVAILABLE WITH MAXIMUM OPERATING TEMPERATURES TO 600 DEGREES FAHRENHEIT.
WHY IS THERE MORE THAN ONE TEMPERATURE RANGE?
THE LOWER THE MAXIMUM TEMPERATURE, THE MORE EFFICIENT THEY ARE WITHIN THEIR TEMPERATURE RANGE.
DO THEY COOL DIFFERENTLY THAN WATER?
YES. HEAT PIPE HEAT CONDUCTORS ARE SO EFFICIENT THAT THEY CAN REMOVE HEAT FROM PLASTIC AT HIGHER WATER TEMPERATURES. THIS IS DUE TO THE FACT THAT THE SURFACE OF THE HEAT PIPE IS ALMOST THE SAME TEMPERATURE OF THE WATER. CHILLED WATER IS NOT RECOMMENDED AND CONSEQUENTLY, AS A SIDE BENEFIT, ELIMINATES SWEATING AND SHORT THERMAL SHOCKS. HEAT PIPES ALSO HAVE A HIGH THERMAL MASS, WHICH COOLS THE PLASTIC IN A DIFFERENT MANNER THAN WATER COOLING. THIS PROVIDES A PART THAT IS MORE STRESS-FREE THAN A WATER COOLED PART.
NOTE THAT FOR THE "TPL" SERIES HEAT PIPE, TOWER WATER THAT IS USUALLY 60-80 DEGREES FAHRENHEIT IS RECOMMENDED. THE "TPH" SERIES SHOULD BE UTILIZED WITH A WATER TEMPERATURE OF 90-110 DEGREES FAHRENHEIT, TYPICALLY FROM A THERMOLATOR.
HOW CAN I TELL IF A HEAT PIPE IS FUNCTIONING?
SIMPLY STIR THE HEAT PIPE HEAT CONDUCTOR OR THE MOLDING PORTION OF THE CORE IN A CUP OF WATER. THE HEAT PIPE SHOULD COOL UNIFORMLY ALONG ITS ENTIRE LENGTH.
WHAT ABOUT SMALL DIAMETER HOLES OR WHERE HIGH WATER CORROSION OR SCALING EXIST?
HEAT PIPES IN GENERAL, REDUCE CYCLE TIME. SINCE HEAT PIPES DO NOT SCALE OR CORRODE, THEY PERFORM CONSISTENTLY AND UNIFORMLY OVER THE LIFE OF THE MOLD, RESULTING IN LESS MAINTENANCE AND NO CHANGE IN COOLING RATE OVER TIME.
WHAT ABOUT PERFORMANCE OF VERY LARGE DIAMETER AND LONG HEAT PIPES?
THESE APPLICATIONS NEED TO BE REVIEWED. IF THE HEATED LENGTH IS OVER FOUR TIMES AS LONG AS THE COOLING LENGTH, THE APPLICATION IS NOT RECOMMENDED. IN MANY CASES, THE HEAT IS REMOVED VIA THE MOLD BASE AS WELL AS THE WATER COOLING ON THE END OF THE HEAT PIPE. THIS MOLD LENGTH MUST ALSO BE TAKEN INTO CONSIDERATION WHEN DETERMINING THE RATIO OF ONE TO FOUR.
WILL ADDING HEAT PIPES TO OTHER PARTS OF THE MOLD REDUCE CYCLE TIME?
YES. HEAT PIPES CAN BE USED ANYWHERE THERE IS A HARD PORTION OF THE MOLD THAT IS IN CONTACT WITH THE PLASTIC. TAKE THAT HEAT AND MOVE IT BACK TO THE "COLD" BASE. SIMPLY DRILLING HOLES AND INSTALLING THEM INTO THAT SECTION OF THE MOLD WILL REDUCE CYCLE TIME AND TUNE UP THE MOLD AND MAKE BETTER QUALITY PARTS. MANY PEOPLE HAVE TUNED UP THEIR MOLD BY ADDING MANY LAYERS OF HEAT PIPES AND HAVE OBTAINED GREATLY REDUCED CYCLE TIMES.
DO YOU NEED WATER COOLING ON THE HEAT PIPES?
IN MANY CASES, SUCH AS SLIDES, REMOTE SECTIONS OF THE MOLD AND OTHER MOVING PARTS, WATER IS NOT FEASIBLE NOR NECESSARY. THE HEAT WILL DUMP INTO THE COLDER AREAS OF THE MOLD BASE. HOWEVER, WATER IS PREFERRED AS THE COOLING MEDIUM TO THE HEAT PIPE.
HOW DO I KNOW WHERE TO INSTALL HEAT PIPES WITHIN THE MOLD BASE?
SIMPLY CHECK THE MOLD AN HOUR AFTER IT HAS REACHED OPERATING TEMPERATURE. THIS WILL TELL WHERE THE HOT SPOTS ARE AND WHERE THE NEXT COOLING NEEDS TO BE ACCOMPLISHED.
ASK FOR THE D-M-E HEAT PIPE HEAT CONDUCTORS BROCHURE.
FOR FURTHER INFORMATION ON THE D-M-E HEAT PIPE HEAT CONDUCTORS REFER TO THE INSTALLATION INSTRUCTIONS THAT ARE PACKAGED WITH EACH UNIT. IF YOU HAVE FURTHER CONCERNS, PLEASE DO NOT HESITATE TO CONTACT D-M-E APPLICATION ENGINEERING.
HEATPIPE.doc
04-01-04