Playing the cleaning game means tallying up the costs and benefits.
MicroCare Corp. W hen it comes to selecting a new, long-term clean- ing process, pity the poor production engineer. They are always expected to clean more with less. Regulators are imposing new air quality
regulations (fewer VOCs); new shipping, handling, and storage
regulations (fewer hazmats); and new waste treatment rules
(fewer dead fish). In some locations, a lack of water or rising
energy costs are huge problems (less again). These conflicting
demands severely restrict a company’s cleaning options.
Despite all the problems, a production engineer needs a
cleaning process that is fast, safe, sustainable, versatile, and
affordable. While this is a challenging objective, there is a
procedure engineers can use to select the optimal solution
between these conflicting demands. Here at MicroCare, we call
it a “cleaning scorecard.” But first, a word of caution!
The cleaning scorecard
When people talk about football, baseball, or golf, the score
pretty much says it all. The same is true with cleaning. But you
have to pick the correct score.
Most people believe the cleaning game begins and ends with
the cost of a machine or a drum of solvent. They think the lowest
priced machine or the lowest “cost per liter” is the best choice.
This is completely wrong. In most instances, those two costs are
(almost) completely irrelevant. There are many other factors far
more important than the cost of the “juice” and the “box.”
Smart engineers need a score or a cleaning index to mea-
sure the economics of cleaning. In my experience, the best
cleaning index is total cost per part cleaned. This focuses
everything on one, paramount question: how can we clean the
product at the lowest total cost?
So here’s your sound bite: stop caring about just the solvent
cost. It’s not the cost-per-liter that really matters, it’s the total-cost-per-part-cleaned. That’s where your profits will be made or lost.
I’m glad we cleared that up. Now, here are some numbers
to put on your cleaning scorecard.
Take a practice swing
When you buy a golf club, you need one that fits your swing.
Similarly, cleaning machines come in all different sizes. But
don’t grab the tape-measure yet—the size of a cleaning machine
isn’t measured in inches. The best fit is measured in production
capacity or cleaning capacity. And just like a new golf club, car,
or suit, you have to select the machine that fits best.
The “cleaning fit” can be measured several ways. The least
precise (but often adequate) method is to measure the number of
units which have to be cleaned: 300 boards per day, 500 pieces per
week, and so on. Another option is to estimate the total surface
area of all the parts to be cleaned. This is most useful when there
are a large variety of parts with many different shapes. Keep an
eye on the extremes: very small or very fragile components may
have different cleaning requirements than larger pieces.
Now that you have defined the capacity you need, you can
evaluate which type of cleaning technology is best for your
situation. For example, benchtop cleaning machines are slow,
but small and cheap. High-volume systems are larger, more
capable, usually more efficient and always more expensive.
Consider all your options.
Then, take the systems which appear to have the best fit-out for a test drive. Prepare a batch of typical products and
have each manufacturer run them through their cleaning
systems. The manufacturer should be able to produce a brief
written report that describes the process, solvents, temperatures, times, and results. Be sure the systems perform to your
standards. Do this testing first, because this is the easiest part
of the selection process.
Now comes the hard part: computing which system produces clean parts at the lowest total cost. A list of the major
costs is included with this article, but each project may require
other items be added to the list.
On the first tee: Computing throughput
When comparing different cleaning technologies, engineers
need to estimate the average productivity of the system in
terms of assemblies per hour. This is crucial to computing the
cost-per-part-cleaned because operational and labor expenses
usually are tabulated as hourly costs.
Start with the cycle time. This is defined as the duration of
one complete cleaning cycle, including loading and unloading.
A machine that cleans twenty boards simultaneously in a forty
minute cleaning cycle has a throughput of one board every
two minutes, or an average throughput of thirty boards/hour.
Your vendors should be able to provide benchmark numbers.
Many factors affect throughput. For example, loading
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