All photos courtesy of Leister Technologies
Coatings on automotive components can be cured with infrared heat.
Manufacturing applications are constantly being modified to improve efficiency and quality. As process improvements are redefined, so is the equipment that is used. For example, one of the more commonly used tools in manufacturing is the electric air heater. Hot air has benefitted many of the commercial products used in our daily lives and covers various materials. Products produced with composites, plastics and nonwoven materials take advantage of electric air heaters to improve final quality and aesthetics.
Electric air heating efficiency is critical for a number of reasons. It can have an impact on the following:
With an inefficient equipment configuration, operators could potentially see dwell time and temperature increases that can cause a decrease in production output. In addition to manufacturing issues, operators also could notice issues related to quality such as surface imperfections, stretching or tearing of materials, and flaws affecting structural integrity.
The question arises: What do you do if your process is missing the mark on application efficiencies?
In order to achieve a higher quality operation, having efficiency standards in place is just as critical as choosing the right type of electric air heater, the amount of airflow and the accessories used.
Products such as spices can be dried with hot air and a rotating tumbler.
Whether a hot air blower or infrared heater is called for, the path to achieving quality throughput takes a similar approach. It starts with understanding the application and material standards. Setting benchmarks for your application can mean the difference between process acceptance or failure. In order to review certain aspects of efficiency, let us review a common manufacturing method as an example: a drying application.
Drying applications have been used in a multitude of manufacturing processes. Whether it is based on part/product quality or removal of moisture content, drying can be a beneficial component of manufacturing — and it can be designed to suit manufacturing needs. Drying can occur via a continuous stream of air in an enclosure, or it can occur in an open environment with temperatures varying from one application or zone to the next. It also may be used to expedite the curing time of a component or to remove process contaminants.
While the introduction of heated (hot air) airflow can expedite the process, this does not necessarily mean that it has been applied properly. To make the drying process more efficient, the introduction of an electric air heater can be used to improve component or product quality or manufacturing throughput. Before you can optimize the drying method, however, different improvement aspects of the application must be identified.
One aspect of the drying process is reviewing the existing methods and equipment, which can provide insight into application hurdles. By identifying potential pain points and bottlenecks and then making the necessary adjustments, you can improve quality and throughput. One pain point manufacturers often encounter is residual or excess heat from the drying procedure. As the heat is being introduced, the resulting residual heat is considered wasted energy. One opportunity to overcome this obstacle is through the exploration of energy-recovery methods.
Heat recirculation is an energy-recovery method that takes residual energy that was previously introduced in the process and redirects it back via ductwork through the blower to be reused in the application. This allows the system to begin the process with a higher temperature, causing less stress on the heating equipment. In order to achieve an efficient heat-recirculation system, proper ducting and insulation must be a part of the design. This helps minimize heat inefficiencies and energy loss through atmospheric dissipation. The design should include products that are rated for higher return-air temperatures along with insulation to ensure heat recapture and return. This will prevent the recovered heat from simply being radiated from the duct work.
Besides reviewing existing methods and equipment, special consideration needs to be given to the part or material itself. While one drying process maybe similar to another, each scenario has its own unique characteristics. Before you can identify an appropriate electric air heater for the drying process, you must know the type of parts you are working with and the desired outcome you intend to achieve. Specifications related to part size or surface drying on one side versus multiple sides will influence the electric heater design selected for the application. If the part is small and requires a minimal amount of heat, a smaller heater with minimal airflow may be the more suitable option. Having too much energy in the process would yield residual heat that can cause stress on the part itself, excessive power cycling by the heater and increased utility costs.
For process efficiency, the system must utilize a repeatable design. Another avenue to explore is the control system, which can be done in either an open loop or a closed loop. Both can be beneficial in many applications; however, knowing which one is best suited for the process will depend on the manufacturing standards that are in place.
In an open-loop design, the system takes an easier approach by offering a simplistic control scheme with no system feedback, in comparison to a higher-level remote controller such as a PLC. With open loop, end users can make manual adjustments to the process, which allows for ease of operation and maintenance. Keep in mind, however, that when operators have the ability to make manual adjustments, the potential risk of inaccuracies is increased. These changes can have a direct impact on the process efficiency. If the main goal is to produce a repeatable application, end users may want to explore a different control system.
An electric heater and an air source are used to heat a chamber for drying and warming various parts.
A closed-loop system allows end users to gain repeatability and efficiencies from their process. By taking advantage of the external feedback provided from a thermocouple into a separate control system, a closed-loop system can provide automatic temperature regulation based on application parameters. This approach ensures repeatability, which permits end users to gain system accuracy, process efficiency and, by extension, output quality.
Another aspect that should not be ignored is the placement of the system’s thermocouple to ensure that the process is being optimized. The thermocouple provides necessary feedback at defined locations along the application. This information is fed to a temperature controller or high-end control system that can make any necessary adjustments. If the process is calling for precision control of the heater, the thermocouple should be placed closer to the discharge of the heat source to help achieve a tighter heater discharge tolerance and response time. If the thermocouple were to be placed further away from the discharge of the heater, the feedback would tend to run at a lower discharge temperature. In this situation, there is potential to affect the process setpoint and possibly cause nuisance temperature overshoot. This would force the heater to work harder than necessary.
In conclusion, whether it is the drying of various coatings and nonwoven materials for automobiles or preheating casting molds for aluminum extrusions for structural components, processors can reap the benefits of hot air through an assortment of products. Electric air heaters are a powerful tool for various manufacturing applications. As the applications become more complex, the requirement to have standard manufacturing practices in place becomes more critical.
Having such standards in place can aid in the identification of the appropriate equipment, as can defining manufacturing metrics, which can help further define the process. By understanding part characteristics, control schemes and the mechanical aspects of existing equipment, end users can better classify the areas of manufacturing that need to be addressed in order to improve efficiencies. If end users still feel overwhelmed by the various aspects of a process, it is recommended that they consult with an engineer or OEM manufacturer with experience with their specific application for further guidance. Taking the necessary steps to address these items can lead to increased throughput, improved part or material quality, and reduced manufacturing costs.
Jason Sanders is the manager of industrial heat in the United States for Leister Technologies. The Itasca, Ill.-based company can be reached at 855-534-7837 or visit leister.com.