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 rate, etc.

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.

Justification

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.

Your Point?

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 (http://gpreeves.com).
Find more information at greasedispensing.com.
Questions or comments? Email Ken