Yeah, I think they got the blow-balance perfected, and have not changed it. Think how long you've been seeing the same bottles on the store shelves.
Altho, I specifically recall a time when the clear bottles ALL had a BLACK or GREEN or RED opaque base element, glued to the bottom to avoid wobble or tip-over. I guess those extra parts were phased-out after the first 20 million or so bottles proved to be "stable enough".
I remember, (probably 25 years ago – perhaps 1987), when a designer associate of mine returned from visiting a potential New supplier, who did Plastic injection molding. He brought back a sample part, which was the molded slug used for placement into the blow-molding application you have showcased here. This injection molded part had the molded-in threads for the bottle cap, and the precise volume and shape of the material needed to 'seed' the blow-molding operation, as you have described. As my associate passed around this clear, threaded, solid, phallic-looking slug, several 'guesses' were offered as to what it was – but no-one guessed correctly; that it was the seed-part for a blow-molded Coke Bottle!!
TJ, it is also possible that there are others who read this blog, or write for Design News, or read it, who may be in a position to do such a write up. and it may be possible that the bottling company wouldlike a chance to show off their superior technology.
And there also exists the possibility that some automation company that produces bottling equipment or bottle producing equipment wouldappreciate a chance to tell a lot of folks how great their systems are.
TJ, the first machine that I worked on had a cycle timeof ten seconds, for a gallon PE bottle. My guess is that the soft drink machines are a whole lot different. That wold make a good writeup, if anybody is seeking hints for topics.
Like most folks,Ihad not considered the complexity of the blowmolding process until I was called upon to do a major upgrade replacement oof the parison controllers on some blowmolding machines. The process is quite complex, since that glob of hot plastic, ( called the parison), is extruded with a variable thickness from a carefully controlled size shot of hot plastic, which is delivered by a mechanism sort of similar to an injection molding machine. The thickness is set at close intervals, either by time or by the displacement of the injector piston. At each point the opening of the injection control valve poppet is monitored and set according to the program. And that setting can be set, typically for every 2% to 5% of the bottles height. And since the control is done before the bottle mold is closed, the process is often iterative, starting with an educated "best guess", at least in some bottle plants. so the whole process would certainly benefit from greater understanding, and possibly closer control.
Nice discussion of all the multiple process variables encountered during bottle molding. Its amazing how we take for granted these everyday processes and don't realize just how much engineering goes into them. Did not consider that frictional heat effects could also have a significant influence on this process.
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