bepps

The best way to explain what all goes on here regarding rotational molding is to describe what all happens to the plastic from beginning to end.

When we get the plastic it comes in beads about 1/8" dia er so. We then grind it up into a powder with a granule size that's the approximate size of sugar. It's weight is much less than sugar so it has almost the consistency of flour.

Here's a lousy picture of the powder coming out of the pulverizer.


After it's ground to the granule size that we want then it's put in those drums and moved over to a guy who weighs out exactly how much powder will be used.

With the mold not moving it's opened up and the powder is poured in. The mold is closed and it's put into the oven (we use vice grips to hold the mold shut because Howard likes his operations to be ghetto). The ovens look really ghetto because they get covered in plastic powder over the years, but in actuality they're pretty advanced and just all around awesome. They go from room temperature to 800 deg F in about less than 60 seconds. The burners use more fuel per second than a Boeing 737 on takeoff. When these things fire up in the morning to preheat the oven it's really impressive. Think F-16-taking-off-at-night.

While the mold is in the oven it's rotated around in two different directions. Every time it's rotated around once it's about a quarter turn. I belive the original machine that Howard and Dave built back in 1959 used 4.11:1 ratio. They took an old truck rear end and hacked the axles off it. Howards shed in his back yard became the oven.

Here's a video of our smaller machines rotating around. Noir calls the molds Spinning Coffins.



As it rotates around inside the oven the mold is heated to slightly above the melting temp of the plastic. As it rotates around some of the powder will stick to the walls and melt. Each time it rotates around a few more plastic granules stick to the wall and melt. It does that until all of the powder is stuck to the walls.

After the part "cooks" in the oven for however long it's supposed to, the oven doors are opened and the entire machine is rotated around. Right outside there are fans to blow room temp air on the molds. Sometimes we spray a mist on it to cool it down super fast.

Once the part is cooled enough to where it can be handled the mold is opened up and the part's taken out.

Here's a lil video I took with my phone of the small square spa rotating around in the cooling phase.

But yes, those are two full sized spas rotating around. The sheer size of this stuff moving around is insane. As crazy as that is though, Dave wanted to rotomold entire above ground pools! The oven was going to be 6 stories tall. He always had a hard on for building super big shit. Howard was seriously considering it. I thought they was nuts but that's one cool thing I like about these guys. They run the numbers and see if something's profitable and if it is they go for it. Even if it doesn't make much profit at all as long as it pays for itself they'll do it just for bragging rights. Me I like my molds like I like my women. Way tiny and easy to pick up and move around.

Each mold weighs about 2000lbs. The "spiders" (that's actually short for Spider Webs because that's what Dave thought they looked like) weigh around 1000lbs each. The weight of all that stuff rotating around was breaking the original machines that they used when I started working here so they had me design up a different type of machine. Dave actually designed up a machine for his brother in law who does rotomolding as well so we used that basic concept. His actual machine design was friggin crazy though so I redesigned it and made it a little more practical to build and use. That was actually a really big project. Most of the construction of the actual arms were done by this machinist guy we got in Adelanto. He's just a regular ol' machinist who turns handles and creates parts from print, not really a designer.