Effectively cleaning parts improves bottom line

What are the final steps to a machining job at your shop? Removing the burrs? Measuring and recording dimensions? Marking with serial numbers? Cleaning?

At my family’s shop, deburring, measuring and marking were considered important activities. Cleaning, however, was something of an afterthought.

As the shop grew and brought in new customers, we occasionally had to conform to cleaning specifications, such as those from a food equipment manufacturer. But most of the time, our lackadaisical attitude toward cleaning did not cause any serious problems. Therefore, we never developed a comprehensive cleaning program.

Cleaning Automotive Parts

After I left the family machine shop to work for a Tier 1 automotive supplier, though, I began to fully understand the importance of cleaning parts.

I worked for a company that manufactured hydraulic power steering gears. Our QC plan included measuring cleanliness of machined parts. They were collected three times each shift, then taken to a lab where the parts were put through an extensive test that evaluated cleanliness. Each part was cleaned for a specific amount of time in a custom washer with a virgin mixture of water and cleanser.

Image courtesy of Ecoclean Inc.

After the cleaning cycle, the water was filtered through pre-weighed filter discs to remove any solids. Filters were then dried in an oven and weighed again. Parts were considered unclean when the filter weight exceeded the specification. If part cleanliness was found to be out of spec, every part that had been manufactured since the previous acceptable evaluation would be returned to the line to be cleaned again. There was little margin for error: only 300mg.

We ran about 8,000 parts per day, and all had to conform. By purchasing custom parts washers, we were able to conform to the rigorous requirements. These washers, each costing about $75,000, were configurable to the various parts that were run on a line. Much like other machines, they had part-specific fixtures, along with special nozzles pointed at critical areas. Washers were programmable—temperature, motion and duration had to be controlled or monitored.

Maintaining cleanliness also required extravagant filtration units capable of removing particles as small as 1µm (0.00004″). Finally, just like machining centers, each new machine went through a runoff; the cleaning process was needed to meet Six Sigma capability.