in Vol. 3 - May Issue - Year 2002
Complete Process Control for Shot Peening
Computer Station for Process Visualization an Control
2 sleve units enclosed with sound panels to insure noise emission of less than 70dBA
Baiker AG, Switzerland is a manufacturer of Dry & Wet Peening and Blasting Equipment. It mainly works with the Aviation and Automotive Industry. It was founded in 1935.
The demands from the industries in terms of process control are higher than ever. In particular the aviation as well as the automotive industries are setting the standards.
On an aircraft the failure of a critical part can be fatal, therefore it is obvious why great caution is exercised during manufacturing of the parts. While in the automotive industries a faulty part on a vehicle is not necessarily a safety issue it can cost a car manufacturer huge sums of money to rectify the problem. Especially if a series of delivered cars have to be called back to the manufacturer. So it is understandable that both industries have the highest requirements in terms of process control of their equipment.
Process Control for Shot Peening
One of the problems of shot peening is that to date there are no practical and affordable means available to quantify the effect of a treated part. The Almen strip test to verify the peening intensity is certainly a useful tool but it does not give any information of what is happening on the surface of the work piece. This since the Almen test is done on a metal strip but not on the actual work piece. Furthermore the system to check the coverage using a magnifying glass or a fluorescent tracer may be usable to identify that the surface is covered with media, but once the surface is covered by 100% no further conclusions can be made. So if there are limited means to check the treated part, it becomes more important to have a process control system to make sure that the machine is working within parameters.
Machine Parameters to be Supervised
Especially for the aviation industries there are a number of standard peening specifications to be fulfilled. Not just specification designed for a particular work piece, but general specifications to be fulfilled if peening is done for the aviation. Two well known specifications are the AMS (Aerospace Material Specification) 2432 and AMS MIL-S-13165 specifying the shot peening process. The AMS 2432 is a very strict specification. It requires that the peening system shall retain in memory and print out any abort details for parameters such as media flow rate, air pressure, nozzle movement, revolution or indexing of turn table, peening time, etc.
Baiker AG in Switzerland which delivers most of its CNC controlled equipment to either the automotive or aviation industries is used to such requirements. Almost all the equipment delivered by the Swiss manufacturer can fulfil these requirements. So a standard machine which can have anything between 4-9 CNC controlled nozzle axis does not only come with a computer supported process documentation and visualization system, it also includes on request off-line supporting software to help the operator to determine the process parameters or to create Almen curves. In addition all data collected from the machine can be prepared in an optional statistical process control system. So on request diagrams of parameters over a period of time can be displayed or machine failures can be analyzed. Naturally such peening equipment is in all regards top of the line. The nozzle can move with an accuracy of a few hundredths of a millimeter, it has noise emissions of less than 70 dBA and can change the media from one size to the other fully automated.