PRACTICAL ROTO TIPS

R. Dru Laws, Brigham Young University - Idaho

Anyone who has ever been to one of my seminars knows that I have a favorite tip for rotomolders everywhere. So, it seems appropriate to begin this RotoWorld® Practical Tips series with this gamechanging perspective.

You see, too many of us begin our rotomolding journey with the wrong vantage point. We go to work and see the process externally. We watch closed molds rotating in the open air while in a visible station or watch them rotating as they enter or exit an oven or enclosed cooling bay. And the only time we get a boring peek inside the mold is when it is stationary while unloading molded parts or loading raw materials. It’s this limited time we get to see inside the mold that is the problem.

The only thing we should care about is what is going on inside the mold, but we spend our entire roto experience watching what is going on outside the mold. And, because we can’t actually take a ride inside, maybe the most appropriate approach is to employ some creativity and imagine ourselves inside the mold.

Truth be told, you CAN see what is going on in the mold if you have one of the many real-time temperature logging devices available today, but that is looking through the lens of a thermocouple. Or you could do like Rodney Syler did so many years ago and destroy a fleet of camcorders in the pursuit of his in-mold videos (now owned by ARM and hosted on their website).

However, without these instruments, I invite you to simply “imagine”. Doing so will change the way you think about the rotomolding process. It will make you a better machine operator, a better QC/QA technician, a better supervisor, a better manager, a better engineer.

It’s time to flip the script and image the rotomolding process from the inside out. When you do this, you will quickly realize that blowholes should actually be called suck-holes. With rare exception, they always occur after the mold has left the oven and air is being sucked back into the mold as the internal air cools.

When you imagine yourself in the mold during the oven portion of the cycle, you can more clearly “see” how rotation conditions change the powder behavior. When you use this new perspective, you can “watch” bridging occur in the corners when you mold with powders that have poor dry-flow characteristics.

When you get good at using this inside-out approach, mold release makes more sense, venting becomes less confusing, and mold design becomes more meaningful. In fact, as you improve your ability to imagine yourself inside the mold, troubleshooting most problems is less artisan and more strategic.

If you’ll join me, then yesterday was the last day you will have pictured our wonderful rotomolding process from an exterior perspective. Replace your subjective thinking with a more robust and objective interior vantage point!