Automatic plating barrel
Automatic plating barrel

Most often the hoist system is automated to reduce manual labor and provide uniformity of the finish on the processed parts. It also provides consistency in the repeated timing and sequence of process operations.

The automation generally comprises POL control of mechanical aspects of the hoist to immerse and transfer the loaded metal finishing barrels from one process tank station to the next. The timed sequences generally consist of programmed steps of the following processes: clean, rinse, pickle, plate, phosphate, black oxide, conversion coat, seal and, possibly, drying the work pieces. This results in treated and coated parts that are finished consistently to the required product specification standards, such as appearance, mechanical and/or service uses, and protective and environmental requirements.

However, as a result of current technological developments, there are possible enhancements to the automatic operation of a metal finishing barrel process line. Additional associated operations that may be automated include the capability to weigh and load the plating barrels at the beginning of the process line and unload the plating barrels at the end of the process cycle into waiting bins, or baskets, for further processing or shipment.

There are significant benefits that result from the automation of these additional “end operations” on a barrel plating line. First, there is a considerable reduction in manual labor hours, which, in turn, saves on labor costs. Manual weighing, loading, and unloading are eliminated as required operations for line personnel. Automating this process means it is only necessary to monitor that proper function is maintained. Line operation becomes much more convenient, possibly resulting in less required personnel.

Secondly, enhanced automation of plating barrel process operations (e.g., weighing, loading, and unloading) greatly increases the level of workplace safety because line personnel are not required to physically interact with the plating barrels or the weighing, loading, and unloading apparatus. Again, it is only necessary to monitor and observe that proper function is maintained.

Achieving automatic end operations of a plating barrel hoist line means using a plating barrel assembly that incorporates automated unlocking, opening, closing, and locking to access and handle the work load. This can be accomplished via an automatic door that remains an integral part of the barrel assembly while providing the previously mentioned labor saving and increased operational safety benefits. Manual handling and manipulation of the barrel door is eliminated.

An automatic door lock can further enhance your barrel plating system. Automatic unlocking and locking of the barrel door is performed in the load/unload station in sequence with the associated opening and closing operations.

Automatic operation of the barrel assembly/system is facilitated by powered reverse rotation/operation of the plating barrel in the superstructure assembly. This is achieved when the hoist system places the barrel assembly in a motorized load/unload station. The load/unload station is equipped with a reversing drive to facilitate opening and closing of the barrel door, rotating the barrel to empty the finished work load and positioning the door opening for subsequent loading of the next workload.

Upon positioning in the load/unload station by the hoist, the finishing barrel is first rotated in the same direction used in the process tanks until the door is aligned with an apparatus that automatically operates the locking mechanism. The door is unlocked and then the barrel is rotated in the opposite direction from that of the process tanks. This rotation opens the automatic barrel door. Rotation continues in the same direction to unload the finished workload into the output baskets or bins. The unloaded barrel continues to be rotated in this same direction until the door opening is automatically positioned in alignment with the weighing/loading apparatus/chute to receive the next workload.

After the barrel is loaded, rotation is automatically reversed, which causes the barrel door to close. Rotation continues in this direction until the closed barrel door is automatically aligned with the apparatus that automatically operates the locking mechanism. The door is then locked, and the loaded barrel assembly is then automatically picked up by the hoist to enter the process line to finish the parts. Upon completion of the finishing process for the new workload, the hoist system then automatically returns the loaded barrel assembly again to the load/unload station for subsequent operations and workloads.

It is important to mention that the valuable “up-rotation” feature provided on most automatic hoist barrel finishing lines—which minimizes “drag-out” cross-contamination of other tank solutions in the process line—is an available feature that is also included on hoist lines using automatic door barrels. Up-rotation is achieved by rotating the barrel containing the workload in the raised top position above the just-exited process tank to maximize drainage of any remaining solution on the parts and in the barrel back into the previous tank. This eliminates the vast majority of solution carryover that would otherwise contaminate the subsequent process stations. This operation is made possible by the automatic locking feature of automatic barrel assemblies.

One consideration necessary before contemplating automatic opening and closing barrels for your process is that the tank drive rotations on the processing stations must all rotate in the same direction. This is necessary to maintain the barrel doors in the closed and locked position.

Powered conveying equipment can be installed on the loading end of the process line, enabling automatic weighing and loading of the finishing barrel. The powered rotation drive on the load/unload station provides automatic unloading of the work after processing. This powered unloading of the work can be directed into drying equipment if desired.

The use of an automatic unlocking, opening, closing, and locking door barrel allows for hands-off operation. The barrel is automatically loaded and emptied without manually lifting, placing, and/or manipulating the barrel door. Manual metal finishing barrel doors are typically secured with clamps, knobs, or other retaining devices that are unnecessary with an automatic door system. Because the automatic door typically remains an integral part of the barrel assembly, these retaining devices are eliminated, further reducing costs.

Automatic loading and unloading metal finishing barrel technology can be applied on new automatic hoist systems. This technology is also adaptable to existing metal finishing barrel hoist systems. And, as an added bonus, the elimination of manual interaction by operators means a dramatic increase in worker safety.


Ray Singleton is the president and majority owner of the Singleton Corporation of Cleveland, Ohio. Singleton is a manufacturer, since 1947, of barrel-type metal finishing equipment for electroplating, phosphation, black oxidizing, metal cleaning, and related processes. Ray Singleton owns patents for both metal finishing and corrosion testing equipment and is a graduate of Baldwin-Wallace College, with a degree in mathematics. He is a member of the National Association for Surface Finishing, NASF, and the American Society for Testing and Materials, ASTM, where he is the chairman of Cabinet Corrosion Tests and the instructor for the ASTM technical professional training course on accelerated corrosion testing. Singleton is the author of the “Barrel Plating” and “Accelerated Corrosion Testing” sections of the Metal Finishing Guidebook & Directory, as well as the “Cabinet Testing” section of the American Society of Materials Handbook.