by Josh Schroeder
When selecting a heat source for your heated platen press application, you should first consider your process requirements followed by the total cost of ownership. In your evaluation there are advantages and disadvantages you should consider for each method of heat transfer.
Heat Transfer (Fluid) Systems
The advantages of a Hot Oil or Heat Transfer System are that it produces the most accurate and uniform temperature control across the surface of the platens. Accuracy is typically from 1 to 5 degrees Fahrenheit depending on the platen design. Process temperature ramping can also be controlled consistently with this type of system and large heat loads are possible. The maximum operating temperature is around 700 degrees Fahrenheit.
Another advantage is that cooling of the platen can also be achieved utilizing the same circulating system. This will allow product to be removed from the press at a safe operating temperature for personnel. This can also be used to provide an end of shift cool down for equipment.
Maintenance of these systems can be considered both an advantage and disadvantage. The heat system is external to the press and therefore routine maintenance and electrical connections can be serviced without disrupting the press. The down side is that the oil is a flammable medium and can be a fire hazard if proper industrial hygiene and preventative maintenance are neglected.
These systems are very accurate and provide uniform temperatures even with large heat loads. The cost for this level of accuracy is much higher than metal sheath style heaters and maintenance of these systems can be demanding but if your process requires tight tolerances these systems are the best choice.
Metal Sheath Insert Heaters
The advantages of metal sheath insert heaters are that they can produce fast heat up and recovery times. They provide efficient energy usage with the heaters inside the platens and can achieve high temperatures up to 1,200 Fahrenheit. The initial cost is also much lower than the hot oil systems and maintenance cost would be considerably less. The risk of fire is greatly reduced as well.
The disadvantages are that temperature uniformity across platen surfaces is not as accurate. The delta range is typically from 15 to 30 degrees. Also the physical dimensions of the platen may limit the amount of KW that can be installed.
Maintenance on these systems is relatively low in comparison to hot oil however should a heater failure occur often the heater must be drilled out of the platen. This may lead to extended downtime.
Metal Sheath Insert Heaters provide efficient energy usage and fast heat up and recovery times coupled with higher temperature capabilities but they do not provide the same level of accuracy or uniformity. If you are looking for a lower cost option and your process does not demand the higher accuracy or uniformity of the hot oil systems then insert style heaters would be the best choice.
by Ryan Pendleton
As part materials continue to move from traditional substances to high-tech composites, the requests for hydraulic presses which incorporate heated platens continue to rise. From my desk, the number of heated platen hydraulic press RFQ’s has increased at least two-fold over the past three years.
Heated platen presses offer the ability to mold various parts through the controlled application of heat and pressure. The heat source can be determined by the application/customer and usually takes the form of electrically heated rods, hot oil, or steam/hot water.
Of particular interest as of late are the multi-cavity heated platen presses which allow the customer to press multiple parts for each press cycle. Depending on the part in question, these multi-cavity designs can greatly increase productivity with minimal increases in the initial machinery investment.
My personal opinion is that the apparent increase in the need for heated platen presses will continue to rise for the foreseable future as composites establish their rightful place among more traditional materials such as steel and aluminum.