Automated Greasing Improves Product Quality
Automating a process such as greasing a part or assembly is certainly not trivial,
there is definately cost and effort involved. Preferrably this can be minimized by
"embedding" the greasing process into some other assembly operation. That
way the cost of the fixture, part handling, etc, is shared between those operations.
Either way, by using automation rather than a manual method the payback is in the
quality of the products produced.
In the quality - conscious production environment of today, the application of
grease is often overlooked or an afterthought. Even when methods such as "continuous
improvement", "zero-defect" and "ISO900x" are employed, production greasing is
still accomplished with outmoded and unreliable processes. When done well, automated
greasing will help complete the product quality picture.
The Bad and the Ugly
There are many ways to apply grease to products in production. Probably the most
common methods involve an operator using a brush or a syringe to apply the grease
manually. When any process is operator-dependent, there the risk of parts being
overlooked, and not greased at all. The parts that are greased, can have a large
variance in the amount of grease applied, depending on the operator, mood, production
Others try to automate the dispensing by using a timed method of releasing grease through
a nozzle. The result is an unknown amount of grease, and no way to sure that any
grease was dispensed at all (the nozzle could be clogged).
Still others automate the greasing process using the relatively cheap equipment
that is intended for greasing bearings on presses and similar rotating machinery.
Most bearing greasers do provide a consistent volume, and some even provide basic
confirmation that a dispense cycle did occur. The problem is,bearing greasers are not
designed for the high cycle rates encountered in automation. Slow cycle times and
short component life are common.
In most cases, failure to apply grease during assembly will result in premature
product failure and must be considered a manufacturing defect. Since all of the
above methods are likely to produce at least some defective product, they are not
suitable for production use.
Is enough too much?
Another common practice is to specify a volume of grease that is much greater than
is really needed. Since the above application methods are so inaccurate and unreliable,
overcompensating is one way to try to assure that enough grease gets on most
of the parts. This can result in grease migrating out onto cosmetic surfaces, as
well as adding unnecessary cost.
We Can Do Better
How can we overcome the weaknesses in the systems described above? Make a list of
the attributes that a good dispensing system should have:
- Automated: To eliminate human error as a common cause of defects,
the grease should be applied in an automated process.
- Poke Yoke: The greasing operation should be embedded in some other
assembly operation where the part(s)are sensed to make sure they are physically
present. This makes sure that the greasing operation is not skipped.
- Measured Volume: The grease dispenser(s) should eject an acurate,
measured volume every time they are actuated. The measurement should be by
mechanical means, or electronic positioning, not timed.
- Airless: The dispensing equipment should detect and reject
air in the grease, or at least generate a fault when air is present.
Dispensing air on the part is a defect, as the grease volume
will be reduced by the air volume.
- Confirmation: The machine should have a means to confirm
that the grease actually arrived at the nozzle, and therefore was deposited
on the part. Any failure in the dispensing system should be detected, and
generate a machine fault.
- Fast: The dispense cycle includes ejecting the measured grease volume
plus recovery time to be ready for the next shot. The compete cycle time for the
automated greasing equipment must match the production rate.
- Industrial Rugged: Production rates in automation are often as high
as 1 part every six seconds. To stand up to these high cycle rates, the dispensing
equipment should be designed for long life.
- Self Checking: The automated greasing system should detect the failure
of its own components. No component failure should ever allow parts to be
processed through without being greased.
Clearly an automated greasing system will have a higher initial cost than the "old
ways". This initial cost will be offset with savings on grease by using the
optimal amount for the product design. Further savings can be realized in reduced
labor time over applying the grease manually. Finally the big payoff - Elimination
of warranty returns and recalls due to ungreased product making it out to customers.
Spending more up front to properly integrate automated greasing into an assembly
operation will provide a short term return on investment and long term profit. Even
more important - a reputation for providing quality products or assemblies.
About the Author
Ken Hirst has been a controls designer and machine integrator since 1977 and is
currently employed by G. P. Reeves Inc. in Holland, Michigan
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Questions or comments?