Other Waste Reduction Options for Wood Finishers
Laundering Staining Rags
Industrial laundry services and uniform leasing companies also lease towels which can be used for staining operations. During the laundering process solvent washwaters may be generated and are difficult to manage. Laundry services may require rags to be spun in a centrifuge before they accept them. Reputable laundry services have industrial wastewater permits and properly manage their waste streams.
Optimizing Cleaning Solvents
Pine-Tique began reusing the solvent used to clean mixing equipment, disposing of it when the solids content becomes too high. Fresh solvent is used to flush pressure pots, lines and guns because the solids would plug the in-line strainer on the spray gun.
MnTAP tested the ability of a paint strainer to remove solids from old cleaning solvents so the solvent could be used as a first wash. The strained cleaning solvent was pumped though equipment and no solids were detected in the gun screen. This practice could have cut Pine-Tique’s solvent waste stream in half with a few modifications to solvent collection and use. In addition, Pine-Tique could have let solids settle periodically to prevent the paint strainer from getting clogged. Reusable strainers can also be fabricated and then back-washed into the solids container.
Operator Training
All finishing companies can improve finishing material transfer efficiencies by focusing on training operators. Many times production-push conflicts with the pace necessary to do the job right. This often results in increased overspray and lower material transfer efficiencies. Training on good spray techniques should be given to veteran and new spray operators periodically. Spray operators should share improvements on techniques or their “tricks” for spraying particular pieces, including sharing between shifts. Videotaping and reviewing the tape with spray operators may also help improve spray techniques. Additional information, including links to LaserPaint are available on the transfer efficiency Web page.
Good spray techniques include the following:
- Hold the spray gun perpendicular to the surface of the part being sprayed. This reduces the chance of the coating coverage being uneven.
- Trigger the gun slightly before and after each pass to minimize overspray.
- Overlap each stroke by 50 percent to achieve a uniform coating thickness.
- Maintain a consistent distance between the gun tip and the part. This ensures the best spray pattern. The distance is dependent on the spray equipment, coating and operating pressures.
- Spray with a suitable speed to give a full, wet coat with each stroke, without causing the coating to run.
- Adjust the air and fluid pressures, and select the correct tip size for the coating and gun being used. This minimizes overspray and avoids wasted material.
Uniform coating thickness is stressed because applying too much coating wastes material and may pose quality problems. Too little finish may produce a reject part both wasting time and creating refinishing costs.
One tool to assist spray painters is a laser pointing attachment for spray guns. This tool assists painters in targeting and aiming the spray gun. It shows the painter that the correct gun-to-part distance is achieved when the two laser beams cross at the part to show one dot.