Grease III (not even close to the musical)
The Blob Returns, A Study In Horror
Barbara Kanegsberg
Rejoicing pervaded the Fabrication Facility. All the machine shops had
switched over to water-soluble lubricants. Rejoicing extended to
final assembly and
to all industrial and critical cleaning processes. Rejoicing swept over
all Sub-Contractors and Suppliers, because it was decreed from Corporate
that
Sub-Contractors, too, were to use water-soluble lubricants. All problems
were solved – no worker exposure problems, no environmental issues,
no assembly issues. Suddenly, a dark, ominous cloud appeared over Corporate,
prompted by an even more ominous Blob on the assembled product.
Panic set in. There were, sad to say, multiple Blobs on multiple products.
Products failed, customers roared, Corporate roared, Official Inquiries
were assembled, heads rolled, vacations were cancelled.
The Laboratory Wizards were summoned. After extensive analysis, they
ascertained that while the Blobs contained many soils, the lifeblood
of the Blobs consisted
of residue of water-soluble lubricant.
Prevent this “Study in Horror” from happening in your Fabrication
Facility. Water-soluble lubricants can be very effective, but plan and monitor
the process change. When you change any single step of a manufacturing process
- cleaning, coating, polishing, metalworking, whatever - you can’t
assume that other steps in the process will stay the same.
About Water-soluble metalworking fluids
Water-soluble metalworking fluids are indeed water-soluble at the
start of the process. However, this does not mean that the fluids
left on
the parts
will remain water-soluble forever.
One reason is that all metalworking fluids contain complex, balanced
blends of chemical additives. As with all soils, the additives
in water-soluble lubricants become chemically modified and more
adherent
under conditions
of
• high force
• elevated temperature
• time
Further, with very complex parts, tight spacing, and blind holes, extra
effort and careful process design may be needed to remove the residue
completely.
In addition, people who formulate metalworking fluids are usually
not focused on how to remove the lubricant. Instead, they
are focused on
such technical
issues as surpassing the required performance specifications,
meeting safety and environmental requirements, achieving a long shelf
life, and producing
a cost-effective product. When we have posed the question,
at least
some formulators of metalworking fluids have taken umbrage
at even the concept
that residue of their carefully-formulated fluid might
sometime or other have to be removed from the product. Some large
suppliers of
lubricants
do have applications labs or customer service groups to
provide
guidance with
the task of removal. However, for complex builds, the most
direct approach is to carefully observe your own process.
Banish the Blob
Here are three steps you can take to avoid residue from water-based
lubricants. These steps apply to all phases of assembly
and to sub-contractor activities.
Observe, document, and optimize the machining process. Get input from the most skilled machinists; and be
sure that
you have documented
their
best
techniques for your applications. With complex, miniature
configurations, when there are changes in metalworking
fluids, if the technique
is not adjusted appropriately, there can be a problem
with entrapped metal fines.
Clean the part immediately after machining, adjusting
the initial cleaning process. The most economical
step you
can take is
to invest time in
immediate cleaning. Otherwise, lubricant residue
becomes even more adherent, leading
to more Blobs.
Accompanying the switch to water-based lubricants, there
is often a change from a hydrocarbon-based cleaning
agent to an
aqueous
cleaning agent.
Soaking or sloshing the part in a dish of solvent may
be effective; using the same
approach with aqueous cleaners may not be adequate.
If aqueous processes are used, the cleaning step may require
a full
process consisting
of
washing, rinsing, and drying.
Coordinate the process change with your subcontractors.
If you adjust the process but your subcontractors
do not, there
are
still likely
to be Blobs
on the parts you receive from them. The longer
those Blobs remain on the surface, such as during shipment,
the more
adherent they
become.
For Parts I and II of “Grease” go to:
Part
1
