Thermal Spray Operator Acceptance Contd

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In a previous post, we had introduced the concept of Operator Acceptance for thermal spray shops. Thermal spray coatings operations have some similarities to other manufacturing operations that have implemented Operator Acceptance programs and yet have some subtle differences. Being almost the last in the sequence of operations, thermal spray coaters are usually pressured to ship parts with shortened lead times. Implementing an Operator Acceptance quality program in your thermal spray coatings operation can significantly increase profitability levels and improve lead time deliveries if done properly. Let us consider some key elements involved in implementing such a program for your thermal spray coatings operation.

The Operator Acceptance quality program must be very well documented and must be part of the Quality Manual for your thermal spray facility. All of the procedures need to be written down and strictly adhered to. Check lists and such must be maintained and filed accordingly. The following headings will hopefully guide you towards establishing such a program and developing the associated procedures for your thermalspray coatings operations.

1. Training: The first step in implementing an operator acceptance program is documented training of the thermal spray operators in inspection and test equipment, procedures and documentation. Without proper training and its documentation, there could be doubts and confusing interpretations of testing and acceptability requirements.

2. Scope of Testing: Procedures must outline exactly what each operator is and is not allowed to test himself. For example, the procedure could explicitly state that listed thermal spray coatings operators are allowed to do visual testing and acceptance for proper coatings coverage and dimensional testing for proper coating thickness using calipers, micrometers, height gages, etc; but are NOT allowed to perform metallographic test acceptance of coating quality or on the spot dye penetrant testing for crack evaluation. Similarly procedures for thermal spray masking operators must outline for example that they are allowed to check and accept for proper masking scribe lines and overspray masking protection, etc.

3. Developing Operator Trust: This procedure allows for “trusting” a thermal spray operator, masking operator, deburrer, etc with testing his own work. The procedures will have to state for example, for what period of time will the operators and inspectors perform dual testing to ensure consistency in acceptability testing – will it be three months, six months, etc. Check lists will have to be generated with dual signatures to verify duplicate testing performances. Upon completion of the 100% duplicate testing, procedures need to be written to outline reduced duplication frequencies and duration. For example, you could have 100% duplicated testing for 3 months followed by 50% duplicated testing for 3 more months ( whereby the inspector and operator will both test every other part ) followed by 25% duplicate testing for 3 months and then complete Operator Acceptance program would be in place; thus taking 9 months for implementation.

4. Follow-up testing, Corrective Actions and Penalties: Procedures need to be in place for inspectors to spot check operators periodically to ensure the integrity of the operator acceptance program. Procedures should also state what would happen in case of discrepancies between the operator and inspector results after the program has been in place. For example, procedures could state that if one discrepancy is found then 25% duplicated testing would ensue; if two discrepancies are found then 50% duplicated testing would ensue and if three discrepancies are found then the operator would be removed from the operator acceptance program, etc. In each case though, proper corrective actions need to get generated and addressed.

5. Same Platform testing: Operator Acceptance programs can be extended to allow for operators to do testing on similar platforms for other operators. For example, there could be procedures in place to allow a bonafide thermal spray operator that performs self testing on his own parts by visual and micrometer testing to be able to accept another thermal spray operator’s parts by visual and micrometer testing. These are considered testable subjects on the same platform. The said operator however will not be allowed to test and accept for masking scribe lengths for masking testing.

As denoted above, operator acceptance programs are heavily dependant on proper procedural standards to be in place to avoid confusion on limits of testing allowability by individuals. Without strong procedures and checklists, such programs may end up with problems. With good controls in place operator acceptance programs can go a long way in reducing lead times and increasing profitability for your thermal spray operations. It may also be advisable to submit your operator acceptance programs to your key customers and get their approval to use such testing on their hardware.