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.
Issue link: https://pf.epubxp.com/i/830013
PARTS CLEANING BY DAVID GOTOFF CHEMETALL 32 JUNE 2017 — PFonline.com Optimizing Aqueous Cleaning Requires Proper Design and Maintenance A well-designed and proactively managed aqueous washer system provides premium performance. Effective cleaning of manufactured parts is the critical founda- tion of a manufacturing operation. Optimum performance of an aqueous washer can be achieved if there is an understanding of the capabilities and limitations of the chemistry, along with the mechanics. Proper equipment design, coupled with appro- priate product selection and process control, assure sustainable and cost-effective performance. A robust preventive mainte- nance program makes the performance consistent over time. An aqueous cleaning system must provide reliable removal of all soils, which prepares parts for the subsequent operation. Over-cleaning may be costly, but under-cleaning, or inadequate corrosion protection, puts the entire process at risk. Therefore, it is important to find a proper balance. The following informa- tion explains how each area of a process should be optimized. System Design and Mechanical Action When designing a cleaning system, the required productivity rates and configuration of the part being cleaned should be addressed. Parts with recessed areas or blind holes require immersion programs to allow complete contact with the chemistry. The highest productivity is obtained with a spray washer and when a belt or conveyor is used. Regardless of the design, mechanical action is a key param- eter of aqueous cleaning. This can be achieved with impinge- ment in spray washers, eductor agitation in the immersion process and with ultrasonic energy. The mechanical action should be maximized and maintained during operation. Using TACT Four key "pillars" that a cleaning program relies on and impacts cleaning efficiency are referred to as "TACT," by Chemetall. TACT stands for contact Time, physical Action, product Concentration and solution Temperature. If one or more of these TACT parameters change, the remaining must be adjusted to optimize the overall cleaning performance. Chemistry Selection Identifying the ideal cleaning and rust preventing chemistry can be challenging. First, the chemistry selected must be compatible with the substrates being cleaned and with the washer construction materials. It also needs to perform well in the washer design. Alkaline cleaners are compatible with ferrous alloys, and when properly formulated, they are also compatible with aluminum and galvanized surfaces. Alkaline chemistry is extremely efficient for removing organic soils such as oils, waxes and greases—typical constituents found in many metalworking and rust preventing fluids. However, where inorganic soils are present, such as oxides from welding, plasma cutting or corrosion, often an acidic cleaner is more effective. Some applications require multiple stage programs where both alkaline and acid chemistries are used to effectively process a part. Before choosing an aqueous washer, perform small-scale process simulations in a laboratory or pilot environment using real production parts. Doing so can determine the optimal cleaning system for an application. Identify, Measure and Control Key Performance Indicators (KPIs) that are applicable to a process need to be identified, measured and controlled. KPIs include metrics to determine product concentrations, rinse quality, soil loads, part cleanliness and washer performance (validating the mechanical action). KPIs should be monitored on a regular basis and suitably logged. Collecting this data is a good way to recognize performance trends. An operation manual documenting these procedures should be developed, taught and used as part of a continuous improvement program. Monitoring and automation technology increases a washer's effectiveness. Technology can be as simple as using a sensor or probe to measure the solution and activate the metering pump, or it can be more sophisticated systems with multiple inputs collecting data and displaying it in multiple locations. Some units allow for data logs and facilitate troubleshooting with real-time alert systems for the operator when a problem occurs. Soil Management To have effective soil management, operators must under- stand the nature of the soils present on the part and how they interact with the cleaning solution. Soil loading should be