In our recent blog post, Five Reasons SPC is Nearly Impossible for Liner Operation, we determined that:
“For all of its importance, liner weight is an extremely difficult metric to manage – and it turns out that SPC is no help whatsoever!”
And as we unraveled all the reasons why, we determined:
“QC Holds are inevitable.”
That’s Not Good News!
In the industry, QC Holds are often referred to as HFI’s (Hold for Inspection), and they present a host of issues. First, HFI’s can jeopardize timely shipments – and that can be a real problem. Imagine Campbell’s not having cans to put their next batch of soup in!
Moreover, some customers require reporting of HFI’s. It’s a way for them to identify and manage their risk, as well as to evaluate their packaging suppliers. In these instances, HFI frequency can mean the difference between holding on to hard-earned business and losing it.
But that’s not the worst of it…
HFI’s are Expensive
The normal method for dealing with HFI’s is to sort. The problem with this approach is that it takes time. Lots of time.
In addition, it generates a lot of scrap. And while that’s not cheap, it’s a far cry better than taking the risk of shipping product that could potentially be rejected which, as we note in our post, Why Customer Returns are the Worst for Can Makers:
“A single rejected lot of cans can cost a manufacturer 30 to 50 times the profit made on that sale, or more!”
So What Are We To Do?
Turning back to our post, Five Reasons SPC is Nearly Impossible for Liner Operation, we determined that:
“The answer is a real-time, in-process control strategy that can make these sparse data points relevant…”
But in this process, the orifice is fixed. Pressure is already regulated in real-time. And gun timing is controlled electronically, which is as good as being in real-time. The only parameter left to place under proactive, real-time process control is viscosity.
But, while it is possible to measure viscosity in real-time, modifying the viscosity by changing the formulation of the compound in real-time – just as it reaches the nozzle – is not practical (if it is even possible). Fortunately, there is another way. We have demonstrated that the compound changes viscosity as a function of temperature. In fact, the manufacturer’s lab data shows it to change from 2800 cps at 60°F to 2400 cps at 90°F – a change of nearly 15% over that 30°F window – which equates to a rate of change of roughly 0.5%/°F. It’s even fairly linear over that temperature range.
Now that’s a relationship you can control with!
Stable Temperature = Stable Viscosity
So the key to control, then, is to stabilize the temperature of the compound as it reaches the point-of-application. And that is both possible and practical. The key is to bring the material to the proper temperature at exactly the right point in the process, then hold it at that temperature until it reaches the point of dispense.
Hold the temperature at a specified point – hold the viscosity at a specified point.
It’s really that easy!
While this does require some specialized devices, and the knowledge of how to apply them, this can be done with virtually no downtime, minimal mess, and at a reasonable cost.
Reduced HFI’s = Increased Business
Stabilizing compound temperature at the point-of-application stabilizes the process, and that means fewer HFI’s. In fact, we’ve seen reductions of HFI’s in excess of 50%!
Driving down HFI’s controls your cost and improves your image. At the risk of being trite – it’s a win-win!
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