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Where Liner Temperature Variations Come From and How They Affect Your Delivery, Quality and Cost Structure

Posted by Mike Bonner

Jul 18, 2016 9:00:00 AM

Image of can lids. Manufacturing process control, temperature control, and coating technology can help manufacturers overcome temperature issues.

Can making facilities are large.

We cut our teeth in the automotive industry and still, these places are pretty big. Big enough that, in extreme climates like the south and the west, it would be cost prohibitive to air condition them – especially in a low-margin industry like can manufacturing.

A Constantly Varying Environment

Because there is no climate control, the temperature in the plant varies. It varies from morning-to- evening as the sun rises and sets. It varies from season-to- season as the earth pivots on its axis. Inside the plant, the temperature is in a state of constant flux – sometimes too hot – sometimes too cold – sometimes just right.

But not very often.

So who cares – besides the folks that have to work there?

The Cans Care!

For some manufacturing systems, like steel or glass making, a constantly varying environment doesn’t matter much.

But can making is different.

The modern can depends on advanced coating and sealing technologies in order to do its job. And the temperature at which these materials are applied makes a big difference in how they perform.

In this series, we’ve been focused on the end liner application. The point in the process where “compound”, a form of rubberized sealer, is applied to the can end to ensure that the can does not leak when it is assembled.

The Fixed Orifice System

In our post, The Impact of Temperature and Pressure on Liner Weight Consistency, we defined this process as being of the “Fixed Orifice” variety. This means that the size of the orifice (often called a nozzle) is determined by a machining operation as opposed to an adjustment. Furthermore, in Variation in Liner Placement Impacts Delivery, Quality, and Cost, too!, we established that the position of the nozzle is fixed by its mechanical mounting with regards to distance and angle to the groove in the end. Between these two posts we also demonstrated that both the volume and the position of the compound in the groove is directly related to the viscosity of that compound, which is a function of the temperature at which it is dispensed.

It Has to be Just Right, Goldilocks!

So, as the temperature in your plant varies, so does the temperature of your compound – and so does your dispense. When it is too cold, you dispense too little compound into the groove. Furthermore, it is too “thick” (viscous), so it does not flow out the way it should to create a reliable sealing surface and profile.

When it is too warm, you dispense too much compound into the groove. This will create leaking cans just as too little compound will – plus it is costing you more to manufacture because you are using too much material. Not to mention that, because the compound is too “thin” (less viscous), it tends to be pulled out of the groove by centrifugal force of the rotating end as it is being applied, which creates a whole host of other quality issues. Even the right amount of compound put in the wrong place is bad.

And now you can add scrap to the list of excess costs in this scenario…

You Can’t Sell What You Can’t Ship

With your quality questionable, you have to determine if you can even ship the product to your customer. If not, will you miss a scheduled delivery and leave your customer with product to package and no cans to put it in?

What will that do to your relationship? And what are your options?

Do you sort and add more cost? Perhaps you’ll make delivery, but there goes your margin.

Do you ship and risk a return? In our post, Why Customer Returns are the Worst for Can Makers, we noted that, “A single rejected lot of cans can cost a manufacturer 30 to 50 times the profit made on that sale, or more!” This is definitely not an option…

Do you have any palatable options?

You do. But you have to start thinking about it, and doing something about it, well before you get into this situation. You need to assure that you dispense your compound at the optimal viscosity (read: temperature), every time – regardless of the ambient environment.

But that’s the subject for another day…

Download our free Process Excellence Diagnostic to more closely evaluate the operation costs, maintenance, overall performance, and product quality of your liner process.


Topics: Coating Technology

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