Stewart Manufacturing LLC’s quality and manufacturing engineers in Hermansville, Michigan, needed to take action after one of their best customers ratcheted up the cleanliness requirements for a family of cast iron turbo bearing housings that Stewart manufactures for them.
The tighter cleanliness specifications meant that particles larger than 500µm were no longer acceptable, gravimetric weight gain would be restricted to 25mg, and no amount of abrasive material – in this case residual honing grit – would be allowed.
Bill Westbrook, North American operations manager for MecWash Systems Ltd., explains, “Where 10 years ago particle sizes of 1,000µm captured in a millipore patch test might have been acceptable, today it is not uncommon for heavy equipment OEMs to demand maximum particle sizes of 500µm or even less, as this customer required, as well as the new gravimetric limits on components that are critical to the fuel, oil, and airflow inside of engines, pumps, and compressors.”
After honing, Stewart had cleaned the turbo bearing housings inside a spray cabinet washer in a 15-minute cleaning cycle. However, cycle times were inexact because the spray washer sometimes needed multiple 15-minute passes to successfully clean the parts.
Engineers at Stewart, recognizing that it already took two wash cycles to clean housings, realized they needed a high-performance cleaning system to meet the increased cleanliness standards. They determined the ideal solution would flood drilled passages of housings multiple times during a cleaning cycle and could engage ultrasonics to evacuate cast iron filings and all grit retained in the bearing housings after the honing process.
Stewart’s customer had purchased a MecWash aqueous parts cleaning system 2012 and recommended the UK-based company’s cleaning machines as a solution to meet their demanding needs.
Randy McLeod, Stewart’s vice president of manufacturing, says, “When an important customer is pleased enough with your finished product to give you increasingly more business, you don’t hesitate to dedicate the resources necessary to create a winning situation for both parties. As for the more rigorous cleanliness standards, our belief was that our customer was probably achieving them inside their own manufacturing operations, so we inquired with our contacts there.”
Westbrook adds, “At first, Stewart was interested in buying a MecWash Midi, which they believed would achieve their cleaning throughput and also meet the new cleanliness requirements. The MecWash Midi is a highly versatile, aqueous single-chamber, rotational cleaning system that features ultrasonic flood wash-and-rinse, immersion wash-and-rinse, spray wash-and-rinse, hot air dry, and vacuum dry to evaporate any retained water in small blind holes of components with more complex geometries. Stewart’s family of cast iron bearing housings had blind holes, so a vacuum dry function was going to be an important part of an effective cleaning process.”
As negotiations continued on the new cleaning system, Stewart’s customer increased its orders, spurring the supplier to consider the larger MecWash Maxi. The Maxi performs the same functions as the Midi, but has a much larger 24" x 24" x 40" cleaning chamber.
MecWash Managing Director John Pattison explains, “Critical to successfully cleaning these cast iron bearing housings was the requirement to be able to hold them firmly in place during the full rotation for the entire cleaning cycle. For this, MecWash designed four different purpose-built holding fixtures that would securely retain bearing housings measuring several different diameters. For the smallest housing, the MecWash Maxi cleans 26 housings on two fixtures per 15-minute cleaning cycle. For the largest, the Maxi cleans 12 housings on two fixtures per 15-minute cycle.”
Depending on the sizes of the houses, the MecWash Maxi cleans an average of 84 turbo bearing housings per hour – topping Stewart’s 80-parts-per-hour cleaning goal. The MecWash Maxi was installed and commissioned about a year ago and, and has since been cleaning turbo bearing housings on every shift virtually non-stop.
MecWash Systems Ltd.
IMTS 2016 Booth #NC-432
Stewart Mfg. LLC