History of the Small Bottle (SB) Rotary Blow Molder

The Story of Wilmington’s Small Bottle (SB) Blow Molding Wheel

We had a customer visit a couple of weeks ago and asked the question about how and why was the SB technology developed. Wilmington Machinery was the first company to specifically design a high speed rotary extrusion blow molding system for small bottles and there was a very specific reason for that.

First let me start by explaining the SB technology refers to Wilmington’s exclusive technique of blowing a bottle with a capture neck parison (no flash around the neck) and a mold design with no bottle knockout devices, no cut off knives between the molds and no bottle takeout mechanism. The bottles are spin trimmed and do not require deflashing. Reaming of the neck internal diameter is optional as a secondary operation.

Several years earlier while doing development work in our lab, a customer wanted to conduct multilayer trials on a small container in a typical neck-to-neck configuration. These containers were being retorted and sidewall paneling was a particular problem so material distribution was critical as was the statistical significance of certain wall thickness measurements. As hard as we tried, we could never get the top and bottom container perfectly identical and we always had a bi-modal statistically distribution of wall thickness at the base of the bottles.

So the idea was born to build a wheel with small clamps that could handle much smaller molds than had ever been done before on wheel machines. Individual bottles could be placed in each mold and all bottles oriented in the same direction. This would guarantee that every bottle would be identical because they were blown from a single parison using the same tooling and same parison profile. The first wheel manufactured was for drinkable yogurts which had 24 stations and could make 240 BPM. It stood only 6 feet tall and everyone was amazed at how many bottles it could produce for such a small machine.

The next challenge was that the majority of the small single serve bottles were concentrated in the dairy, juice, drinkable yogurt and the growing nutritional / supplement market. These bottles were light weight and some could run at very fast cycle times with some in the 5-6 second range. This meant bottles would be discharged from the wheel at possible speed up to 1000 parts per minute and a traditional bottle takeout system had never been built to handle these speeds. Based up on some previous experience of trimming bottles in the mold, a very unique mold design was developed that would both trim and discharge the bottle to a bulk conveyor without the need of pneumatic knockout system, no cut-off knives between the mold and no complicated bottle takeout device. This was made possible because the mold and process design also blew and cooled 100% of the flash eliminating the risk of the bottles sticking together prior to trimming.

Today the technology has been expanded in to multi-layer and dual parison applications with plans on the board to extend to 3 parison configuration. To learn more and understand if this technology could be applied to your application, contact Jeff at Wilmington Machinery.