Wheelabrator manufactures machines that clean and surface-treat parts. The machine throws fine steel hot at the parts using a wheel. It literally slings the shot into the surface and abrades the surface, cleaning it or preparing it for further surface finishing, including painting. The company builds these machines to order and to stock. The machines that are built to order are custom designed to shot blast a particular part or group of parts. The machines that are built to stock are called Tumblast, Spinner Hanger, or Table machines. The Tumblast is typically used for cleaning and deflashing diecasting, scale and rust removal, shot peening and similar kinds of operations. The parts are placed on a rubber or steel belt inside the machine and are given a tumbling action. The centrifugal blast wheel propels shot into the parts with a controlled pattern, performing a chemical free surface cleaning/preparation process. The spinner machines have hangers for the parts and the parts are rotated through the blast. In table machines, the parts sit on large rotating tables for blasting. These machines are often modified to meet special customer needs. Machines built to order are custom designed and built to meet specific part requirements or production rate/volume requirements.
The typical Wheelabrator machine (one of the many models is shown below) is comprised of 5 basic elements; the blast wheel or wheels, the cabinet which contains the process, a material handling system for manipulating the part or parts under the shot blast, a shot recovery and recirculation system, and a dust collection system to remove dust and abrasive fines. The machines are essentially large metal boxes (the box is called the cabinet or the blast chamber) which are normally fabricated (welded) inhouse. The box must be designed to accommodate the conveyor inside the blast chamber used to tumble the parts under the shot blast. Machines with large rotary tables on which parts are set and rotated under the blast require huge cabinets compared to the machines with hangers suspended inside the blast chamber and parts are hung inside the chamber and rotated while blasting. Regardless of the cabinet design, the blast is very abrasive and erodes lines, plates, and seals inside the blast chamber and these must be periodically replaced along with wheels that sling the shot into the parts. The plates are made from very strong magnesium steel which is very wear resistant but also very hard to machine.
For the custom machines, the design of the box and the number of blast wheels is dictated by the customers requirements, mainly the shape of the parts and the production rates required for the machines.
As shown in Figures 2 through 4, machines are built for pipe and plate and structural members as well as individual cast or forged parts. The cabinets are shaped and sized according to the parts to be blasted inside the cabinet. The shot used in the process must be collected and recirculated to the blast wheels. In the roll conveyor application, the collection system at the bottom of the machine delivers used shot to an elevator which carries the shot above the machine for gravity delivery back to the four blast wheels. As shown in these figures the machines are relatively large and require a high bay facilityfor fabrication and assembly.
Parts of this page were excerpted from: Dr. M.V. Uzumeri and Dr. J.T. Black, Wheelabrator: A Case Study of Variation in Manufacturing Management, A Report for the Thomas Walter Center for Technology Management at Auburn University, January, 1995. For more information about this case study, contact:
Dr. Mustafa V. Uzumeri, Department of Management, College of Business, Auburn University, AL 36849, (334) 844-6531, uzumeri@business.auburn.edu
or
Dr. J. T. Black, Department of Industrial Engineering, College of Engineering, Auburn University, AL 36849, (334) 844-1375
This project is made possible by the openness of the Wheelabrator Corporation and has received financial support from the Thomas Walter Center for Technology Management at Auburn University.
DISCLAIMER: Dr. M.V. Uzumeri bears total editorial responsibility for the contents of this document. No other party, specifically including the Wheelabrator Corporation, Auburn University, the Thomas Walter Center for Technology Management and any of their employees, is in any way liable for its contents.