My company is implementing a cleanliness requirement from our biggest customer. The parts with the requirement are fuel valve components and assemblies for automotobile engines. The requirement is called "Millipore cleanliness testing". The Millipore part is actually the name of a company that pioneered the testing methodology, and is in the business of providing the equipment.
We ended up purchasing the necessary equipment from Millipore because it was a designed system that fits together right out of the box.
The test process is called gravimetric filtration. Basically, you clean the parts in a solvent (we are using kerosene). You collect the kerosene the parts were brushed clean in, and filter it through a specified filter under vacuum pressure. Since you weighed the filter before use, and weigh it again after drying it out, you get the weight of the contaminants present from the difference between the weights.
Our initial testing to shake out the process indicates that we are compliant to the basic requirement, which is less than 3.0 mg of contaminant per part on the part we are currently testing. We fall short on the maximum particle size allowed (.010" x .008"). I have been finding particles as large as .017" x .019".
We have improved component storage to reduce our atmospheric contaminant exposure. We improved on the overall contaminant weight, but the particle sizes were not affected. We have filtering and preventive maintenance systems in place in our part cleaning operation that should prevent this particle contamination from that source. We will be auditing those systems to see if there are problems there. The parts are cleaned prior to assembly, and assembled in a room separated from the production floor to maintain cleanliness. The containers the components are kept in during assembly are cleaned in the same cleaning process as the parts themselves.
The cleanliness testing results are consistent across batches, so the problem is likely to come from the system, not some special cause.
Any ideas?
We ended up purchasing the necessary equipment from Millipore because it was a designed system that fits together right out of the box.
The test process is called gravimetric filtration. Basically, you clean the parts in a solvent (we are using kerosene). You collect the kerosene the parts were brushed clean in, and filter it through a specified filter under vacuum pressure. Since you weighed the filter before use, and weigh it again after drying it out, you get the weight of the contaminants present from the difference between the weights.
Our initial testing to shake out the process indicates that we are compliant to the basic requirement, which is less than 3.0 mg of contaminant per part on the part we are currently testing. We fall short on the maximum particle size allowed (.010" x .008"). I have been finding particles as large as .017" x .019".
We have improved component storage to reduce our atmospheric contaminant exposure. We improved on the overall contaminant weight, but the particle sizes were not affected. We have filtering and preventive maintenance systems in place in our part cleaning operation that should prevent this particle contamination from that source. We will be auditing those systems to see if there are problems there. The parts are cleaned prior to assembly, and assembled in a room separated from the production floor to maintain cleanliness. The containers the components are kept in during assembly are cleaned in the same cleaning process as the parts themselves.
The cleanliness testing results are consistent across batches, so the problem is likely to come from the system, not some special cause.
Any ideas?