Products Finishing

OCT 2013

Products Finishing magazine is the No. 1 industrial finishing publication in the world. We keep our readers informed about the latest news and trends in plating, painting, powder coating, anodizing, electrocoating, parts cleaning, and pretreatment.

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CLINIC PARTS CLEANING Parts Handling Optimization Q. We currently clean, phosphate and adhesive-coat metal parts used in the automotive industry, producing in excess of three million parts per day. We process under lean principles, but due to the volume, we process in controlled batch sizes. We are continuously improving our processes and are researching new equipment technology. We are interested in cleaning and coating equipment that will eliminate part-to-part contact. I am not sure if this means racking systems or one-piece flow. The define stage of our project begins soon. Do you have any suggestion for where we might look for equipment to meet our needs? —W.B. A. One-piece flow is sometimes proposed as an ideal state for almost all materials-handling issues in manufacturing as a whole, not just cleaning. One-piece flow is a simple concept in principle since it targets handling and delivering one part at a time, in the right condition, to the right place at exactly the time it is needed. While this should be a goal to consider with any cleaning and materials-handling system, practical constraints and cost often will require deviation from this ideal state. Two of the most significant factors related to materials handling will be part size and geometry. Obviously, handling three million tiny parts is generally less expensive from an investment and footprint standpoint. Geometries with large surface areas that contact and nest or may have blind holes will be more difficult to handle and, specifically, to clean and circulate cleaning fluid and rinse through. Practical considerations for today's parts handling will often involve the use of a rotating barrel for cleaning and handling of smaller, more intricate parts. While this will not keep parts from touching, it will minimize the contact time in any specific area, enabling the cleaning and coating to take place more uniformly. True one-piece flow would be more likely and necessary the larger the parts you are dealing with. Washers utilizing hanging or flat conveyorized movement are well-equipped to handle most medium to large parts. I would recommend you gather part sizing and geometry information to discuss with suppliers along with details regarding your current process (stages, chemicals, effectiveness and desired changes). Then check the information on the Products Finishing site, PFonline.com, under the Suppliers tab to find some businesses that can assist you. Tape Test for Cleaning Efficiency Q. I want to learn about test methods to check efficiency of degreasing. Do you know anything about a Ford Scotch Tape test? How does it work? How reliable are the results? —B.K. A. I could not find any information specific to the Ford Scotch Tape test, but there is a well-established test method under the global International Standards Organization (ISO) procedure 8502-3, Preparation of Steel Substrates Before Application of Paints and Related Product—Test for the 86 OCTOBER 2013 — pfonline.com pfonline.com/experts Assessment of Surface Cleanliness— Part 3: Assessment of Dust on Steel Surfaces Prepared for Painting (Pressure Sensitive Tape Method). While the title suggests this may only be applicable to steel, in practice it could be used on almost any substrate as a semi-quantitative measure for surface particle cleanliness. It uses a specified tape that is applied to the surface of interest. The tape is removed DAVID S. PETERSON / Consultant and examined by partscleaning@pfonline.com comparison to a standard, both visual and descriptive, that classifies the residue on a scale of 0 to 5, with 0 being the best (no particulate visible under 10× magnification). The other classes have a greater density and size of residue. For instance, a rating of 1 describes particulate of no more than 50 microns. At the far end of the spectrum, a rating of 5 describes particulate of greater than 2.5 mm. This test is only effective for the evaluation of particulate on the surface and would not be applicable to evaluate the removal of organic contaminants, unless the residue was so heavy that it would simply not allow the adhesion of the tape to the substrate. A quick check of the Products Finishing suppliers revealed that there are a few companies that carry kits for this evaluation. Mechanical Cleaning Effectiveness Q. We are coating nuts and fasteners with nickel alloys for corrosion resistance. We currently do mechanical cleaning before electrochemical cleaning but would like to eliminate this mechanical cleaning, as the system is not efficient. Could you give us information on a new process? —J.H. A. It is not clear from your question why your mechanical cleaning process is inefficient, however, I would venture to guess that since you are performing an electrochemical cleaning process, the mechanical cleaning is not being done to remove oxides or scale. If you are attempting to degrease your parts, a mechanical cleaning process would not be effective. A chemical cleaning process such as a solvent or aqueous detergent would be advisable prior to entering the electrocleaning process. Since the electrocleaning is also an aqueous process, an aqueous pre-cleaning followed by thorough rinsing would be significantly more efficient than the mechanical cleaning process.

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