Table of contents:
- Faster to the better bottle
- The challenge: the production of lighter, more stable bottles
- Lighter bottles reduce costs
- Overengineering ensured robustness
- Internal tensions reduce stability
- Knowledge from experience
- Simulation increases know-how
Video: Get Very Close To The Ideal With Simulation
From the point of view of multidisciplinary simulation, transforming a molten glass bill into a solid - technically still liquid - glass bottle is one of the most complex tasks. The manufacture of a glass container encompasses all types of heat transfer as well as the structural and fluid mechanics of a material that changes its viscosity by seven orders of magnitude during processing.
Faster to the better bottle
The Italian company Bottero Spa specializes in systems for the production of high quality glass products; the “Hollow Glass” business unit develops and manufactures machines for bottle and container production. Bottero's goal is to enable its customers to develop new, very light glass products that are at the same time much more stable and therefore more durable than previous products. At the same time, the production should cost less raw material and energy, both when melting the glass and when transporting the finished container. This enables a better quality product with lower overall costs.
The challenge: the production of lighter, more stable bottles
Even though most believe that glass is a solid, in reality it is a supercooled liquid, the viscosity of which is so high that the molecules cannot move freely and form crystals. Controlling the process in which the glass is cooled down to its (almost) solid state is crucial for the strength of the resulting glass container.
Lighter bottles reduce costs
Simply put, a bottle is made by first pouring a blank, called a preform, from a certain amount of melted glass - which is exactly enough for one bottle. This preform is then slowly cooled and at the same time brought into its final shape. This is done by inflating with compressed air and a number of other processes.
“Our goal is to make lighter bottles that use less raw material and less energy to melt, which in turn means lower manufacturing costs. However, glass is a sensitive material, so we have to make sure that the bottles are as stable as possible,”says Ferrari. "The most important property of a bottle is not to break."
Overengineering ensured robustness
In the past, the robustness of the glass containers was ensured by "overengineering" by increasing the wall thickness. But this led to heavier vessels that were less customer-friendly and more expensive to produce. In the past 20 years, the weight of a typical glass bottle has been reduced by more than 40 percent thanks to advances in production technology and the combined influence of customer preferences and economic requirements. And that without loss of stability or greater fragility. As we will see later, modern, lighter bottles are often even more stable than their heavier predecessors.
Internal tensions reduce stability
“If you want to produce a structurally stable bottle, two stages of the process are crucial: In the first step, molten glass is poured into the preliminary bottle shape. Then the bottle is brought into its final shape in a different form,”says Marcello Ostorero, Head of Development and Design, who introduced engineering simulation at Bottero. “Precisely hitting this final shape is extremely important to ensure the structural stability of the bottle. If the shape is not hit exactly, the bottle can break under normal use."
In the course of the manufacturing process, the glass is cooled from over 1,000 ° C to ambient temperature, which increases the viscosity by seven orders of magnitude from 100P to 1e9P. If the bottle is cooled too quickly or unevenly, internal tensions develop in the walls of the vessel, which reduce its stability.
Knowledge from experience
The biggest problem is that the processes around the molten glass take place inside the production machine and cannot be observed. So far, the usual way to assess this incredibly complex process has been to examine the finished product and the distribution of the glass. It took a lot of experience to imagine what might have gone wrong in the form.
"The stability of the glass depends very much on how the glass is cooled during production," says Ferrari. “Even if we can measure the temperature of the mold in the glass factory, without simulation we have little or no knowledge of what the temperature of the glass itself is like. The typical approach in the industry is trial and error. Decommissioning the manufacturing process for months is time-consuming and very expensive. And yet you still don't get any real insight into the processes."
Simulation increases know-how
A large bottle factory can produce more than two million bottles a day or 25 bottles a second. The costs for these trial-and-error attempts or unresolved problems in production cause high costs. For this reason, Bottero decided to use engineering simulation to obtain detailed insights into the manufacturing process. With these simulations, on the one hand the process and on the other hand the quality of the manufactured vessels can be optimized.
Content of the article:
- Page 1: Get very close to the ideal with simulation
- Page 2: The solution: multidisciplinary simulation with Star-CCM +
- Page 3: The result: More stable and lighter bottles
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