by Michael Riehn
featuring Dan Michki, Controls Engineer
Check out the latest installment of the How to Series videos by Beckwood Press Company. See the basic functionality of the LabVIEW HMI control system, A PC Based Control System for Hydraulic Press Control.
VFD (Variable Frequency Drive) is an innovative press feature that significantly increases energy efficiency over traditional hydraulic & mechanical presses motors. By controlling the frequency of electrical power supplied to the motor, the VFD drastically cuts down on unwarranted energy expenditures while maintaining full functionality.
Energy cost studies predict a payback of less than two years on many applications. Other benefits of the VFD include the ability to program pressing speeds without the expense of proportional valves, and reduced noise & heat levels during idle periods.
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.