in Vol. 7 - July Issue - Year 2006
Focus on Media
Author: Werner Laursen
Why should a company invest money and energy in the best equipment there is to secure a stable reproducible process, when the media itself does not make it possible?
Volvo Aero Norge AS (VAN) tried to find a media supplier who can fulfil the requirements of AMS 2431/1. In addition the media should be conditioned 100 times (VAN requirement). All suppliers contacted, deliver media with a certificate verifying that testing and the result of testing complies with AMS 2431/1.
In order to meet customer requirements Volvo Aero Norge AS has to do a sieve analysis and hardness test for incoming materials on a yearly base. In most cases the certificate and result of VAN’s receiving control do not show the same result. The hardness generally is outside of the specification. The specification requires that not less than 90% of the readings shall fall within the range of 45-52 HRC. In most cases four or five readings fall outside out of a total number of twenty readings.
VAN has evaluated a lot of media suppliers but most of them failed the tests performed in-house. VAN receives very strict requirements from its customers. A co-operation between VAN and a media supplier Pometon S.P.A. made it possible to get media according to this specification, but it required a conditioning of 60 to 100 times to remove internal defects such as cracks, hollows and shrinkage.
The AMS 2431/1 allows not more than 15% of these defects. The tests performed by the supplier and VAN show that the defects must be reduced to a minimum (lower than 15%) if the shot is going to have a chance of passing the hardness test.
A very important result of the conditioning (100 times) of the shot, is that the process is reproducible.
Do not trust the certificate issued by the supplier. Perform a receiving test.
Work together with your supplier
Ask for conditioned shot (min. 60 times, best 100 times)
Make sure suppliers read the specifications
Hardness test: Not less than 90% of the readings shall fall within the range of 45-52 HRC
Volvo Aero Norge AS