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[March 3, 2014] The seemingly simple task of cleaning precision machine parts may appear on the surface to be rather mundane and unworthy of much attention on the CNC machine shop floor. Nothing however, could be further from the truth. The surface preparation of a part actually is an integral step in the milling and machining process. Whether for cosmetic purposes alone, prepping a part for surface finishing, or as a precursor to the job of penetrant inspection, proper cleaning methods ensure that all undesirable materials are removed. Cleaning operations are as varied as the machines and materials we work with, and the variety of fluids used in high speed machining mean there is no catch all solution. At APM's CNC machining center, based on the jobs we run, trial and error has resulted in some time-tested techniques and the incorporation of new technology to get the job done.
By its very nature, precision machining is a dirty job. Milling machines for example, produce contaminants that end up on precision machine parts including: coolants, oils, grease, cutting fluid, metal smearings, scale, smut and other residue from metalworking fluids. Contaminants can either be soluble, insoluble or mixed. Solubles, such as coolants and oil, are easily broken down in a solvent. Insolubles, such as dirt, paint and burs can't be broken down chemically and must be removed mechanically. The cleaning process itself can either be manual, mechanical or automated. Manual cleaning is a simple, yet effective solution. A finished part can be simply washed with water and toweled off prior to packaging, or a solvent containing dish soap, vinegar, denatured alcohol, acetone etc. can be applied then rinsed away. Caution should be given to the caustic properties of your solvent and its possible reaction with softer metals. For example, some soaps can be too alkaline in nature and damage or discolor aluminum.
In many cases, the addition of some form of mechanical energy is used to hasten and improve manual cleaning methods. Spray cleaning is straightforward; a pump and nozzle direct a cleaning solvent directly at a part, and works great on larger parts. Immersion cleaning is another alternative, and is more effective on small parts or larger batches. Finished products are immersed in a solution containing the cleaning agent, and mechanical agitation is typically applied. Introducing ultrasonic sound waves into the immersion tank further improves results. Advanced Precision Machining now 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 to create bubbles in the cleaning solvent. When these bubbles come into contact with the part being cleaned, they burst and release energy that boosts cleaning power, and this action reaches into every nook and cranny.
For more aggressive cleaning applications like removing rust, thermal oxides or burrs, other automated machines may be called upon. Certain very high-pressure spray wash systems have the ability to perform deburring tasks and are great for difficult-to-reach locations. The post fabrication method of passivation is a cleaning method that brings out the natural corrosion resistance properties in stainless steel. Vibratory finishing machines, tumblers, power sanders and other deburring tools are all utilized in other cleaning applications. With precision maching, it is important to remember in the end that the customer wants nice, clean parts. A proper cleansing may also be a precursor to secondary operations such as surface treatments and penetrant inspections. Know 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 need, 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 partnered with his friend and colleague, Kirk Tuesburg, currently APM’s machine shop manager, together launching 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.