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[October 17, 2019] While the seemingly simple task of cleaning and preparing newly precision machined parts for delivery may appear to be somewhat mundane and undeserving of much attention, nothing could be further from the truth. At Advanced Precision Machining’s Colorado machine shop, the surface preparation of a part is actually an integral step in the milling and machining process and plays a key role in meeting our client’s needs for accurate, on-time and on-budget delivery. Whether for imparting aesthetic qualities, preparing a part for surface finishing applications or as a precursor to penetrant inspection techniques, proper cleaning methods ensure that all undesirable materials are removed. As varied as the machines and materials we work with, precision machined part cleaning operations don’t rely on one catch-all solution. This is a direct result of the many different fluids used in high-speed CNC machining, turning and grinding processes. Based upon the jobs run on APM’s shop floor, trial and error have resulted in some time-tested cleaning applications, innovative techniques, and the incorporation of new technology to get the job done.
Let’s face it, despite the refined and polished look of the finished end product, the very nature of precision manufacturing is a dirty job! For all of their technological wonder and advancements, today’s CNC machining centers still produce a host of contaminants that end up machined parts including coolants, oils, grease, cutting fluid, metal smearings, scale, smut and other residues from metalworking fluids. These unwanted and leftover visitors are categorized as being either soluble in water, insoluble, or in some instances, both. For part cleaning purposes, solubles such as machine coolants and oils are easily broken down by commercially available cleaning solvents. Insolubles, such as dirt, leftover paint, and burs, are chemically impossible to break down and clean and therefore must be removed through mechanical means.
Whether removing soluble or insoluble contaminants, the part cleaning process itself and the labor employed can be either manual, aided by means of a mechanical device, or fully automated. Although the simplest of all available options, manual cleaning is perhaps utilized most often and is a tried and true, effective cleaning technique. A finished part can be simply washed off with water and then towel dried prior to packaging, or a solvent containing dish soap, vinegar, denatured alcohol, acetone, etc. can be applied then simply rinsed away. A word of caution; Some solvents have caustic properties associated with them and an adverse reaction can occur when used on softer metals. For example, some soaps can be too alkaline in nature and damage or discolor aluminum.
When good old fashioned elbow grease doesn’t cut through leftover contaminants, some form of mechanical energy can be used to hasten and improve upon manual cleaning methods. Spray cleaning is a common, yet highly effective method of utilizing a pump, nozzle and high pressure to direct a cleaning solvent directly at a part, and it works great on larger parts. Immersion cleaning is another alternative. More effective on smaller parts and larger batches, recently machined parts are immersed in a cleaning agent solution, then some form of mechanical agitation is applied. The introduction of ultrasonic sound waves into the immersion tank can further improve upon results. APM’s Colorado machine shop employs an Ultrasonic Power Corporation cleaning tank in its arsenal using Brulin Formula 815 GD as a cleaner. Ultrasonic part washers utilize the power of high-frequency sound waves that create bubbles in the cleaning solvent, and when they contact the part being cleaned, they burst and release energy that boosts cleaning power.
For more aggressive cleaning applications on insoluble contaminants such as rust, thermal oxides or burrs to name a few, more automated machines may be called upon. Certain very high-pressure spray wash systems have the ability to perform deburring tasks and are great at reaching into difficult-to-reach nooks and crannies. The post-fabrication method of passivation is a cleaning method that brings out the natural corrosion resistance properties in stainless steel, aluminum, and other ferrous materials. Vibrating finishing machines, tumblers, power sanders, and other deburring tools are all utilized in other cleaning applications.
Throughout the entire precision milling and machining process, what’s most important to remember is that in the end, the customer simply wants nice, clean parts. A proper cleansing may also be a precursor to secondary operations such as surface treatments and penetrant inspections. Keep in mind that there is no best way to clean a part; so much depends on the material, geometry, the type of contaminant, finishing applications and the demands of the customer. Stay educated and open to all possible methods.
Want to learn more about the cleaning methods we use, or need help with an upcoming project? We're happy to discuss any machining needs, so please contact our Colorado machine shop.
Gerry Dillon is a co-founder, current owner and certified CNC machinist at Advanced Precision Machining (APM), a full-service machine shop located in Longmont, Colorado. Before making his home in the United States in 2000, Gerry was born and raised on the emerald isle of Ireland and took an interest in milling and machining from an early age, ranking #1 in the Irish National Apprenticeship Program. In 2005, he and a partner began what’s grown into a leading Colorado machine shop. Gerry brings over 30 years of machining experience to the shop floor and is certified in all aspects of geometric dimensioning and tolerancing.