Define your component

• Provide a clear drawing. It is important that the incoming dimensions and tolerances be clearly shown.
• State the base material and its code. Highlight any parts with mixed materials, including braze, weld, inserts, helicoils or adhesives.
• Show its heat-treatment condition, and its sensitivity to possible embrittlement, tempering or distortion. Show the hardness and UTS values for such sensitive components.
• Its manufacturing history, cast, wrought, etc
• Its machining history, turned, milled, spark-eroded, ground, etc
• Indicate any prohibited pre-treatments steps, such as acid etching (embrittlement concerns) or aggressive roughening by blasting (contamination, distortion concerns)
• Indicate its function
• For large parts, their weight

Define your coating needs

• Show on the drawing the area that must be coated.
• Indicate if the part can (or must) be coated all over, or if there are some areas that MUST remain uncoated. Remember that, in most cases, it is more expensive to mask such areas than to coat the part all over. In particular, indicate internal areas or bores that must be coated, where special processing fixtures may be needed to coat such areas (when access may be restricted). Consult the supplier on the practicalities.
• Indicate where the part can be held on a jig, either for support and/or for the provision of a sound electrical contact. Remember that such a holding point may show a witness mark where the coating is thinner or not present. If it is a heavy part, indicate the allowed lifting points.
• Show the required coating thickness and a tolerance band. If the requirement is to coat the part to attain a specified finish size, then specify that size and its tolerance. Remember that the coating process itself will have its own tolerance band (consult the supplier), so that such tolerances are ADDITIVE with the incoming size tolerance.
• Indicate any features such as holes or threads that need to be protected, have special tolerances or may trap processing chemicals.
• Show any requirements for the as-coated surface finish, that is assuming that no further finishing operation (grinding, polishing, etc) is planned
• If colour or appearance matching is required, specify the standards. Remember that colour matching may be expensive and difficult with an engineering coatings.
• If a finishing operation is specified as part of the coating service (e.g., grinding), then provide details of the required final size and tolerance, as well as the required surface finish and tolerance.
• For sensitive parts, agree the required pre-coating stress-relieving and post-coating de-embrittlement heat-treatment times and temperatures.
• Agree any requirements for Quality Control testing or sampling, either non-destructively on finished parts or destructively on sacrificial parts or test coupons. Properties such as hardness, thickness, surface finish, etc can be within this requirement.

Define the commercial issues

• Provide a clear purchase order. Include clear references to the supplier's quotation paperwork, to repeat orders and to individuals in the supplier's company who have technical knowledge of your application
• Show the number of parts to be processed. Wherever possible, agree with the supplier sensible batch sizes that fit efficiently with rates of processing and the number of parts that can jigged and coated simultaneously.
• Agree on your scheduling. Ensure that delivery time to the supplier allows him to process your parts to meet your final deadline requirements. The coating step is often the final step in the manufacturing route, a point where impossible demands to 'catch up' on slipping time schedules are often made. Make sure you understand the timing of the various processing steps that your coating supplier must follow, and agree on any extra charges relating to processing out of hours to shorten delivery times.
• Clearly define any specifications or approvals demanded for the job. Ensure beforehand that the supplier can meet and demonstrate such approvals.

Poeton Industries Ltd. Head Office, Eastern Avenue, Gloucester GL4 3DN, England, UK   Tel: 01452 300500  Fax: 01452 500400
Production facilities in Cardiff & Gloucester and in Wisconsin. USA.