Longwei is a professional manufacturer of glass bottles and lids with over 20 years of production experience.
Language
Longwei is a professional manufacturer of glass bottles and lids with over 20 years of production experience.
Causes and classification of defects in molding
Forming is an important process in the bottle glass manufacturing process. The root causes of molding defects come from many aspects. Therefore, the real cause of defects can only be found after fully understanding the characteristics of the molding method.
The concept of defect origin and classification
Only defects of a general nature are presented here. They may be related to the properties of the glass itself, or may be formed before or after molding or during the molding process. Due to the similarities between various molding defects, the causes of their formation may also belong to the same type.
To analyze the defects in the manufacturing process of bottle glass, the following two basic essentials should usually be grasped:
1. The cause of the defect:
① Defects caused by molten glass;
② Defects caused by impact;
③ Defects caused by operation;
④ Defects related to molds.
2. Classification of defect causes:
Classification by manufacturing defects
①Heat defects;
②Cold defects;
③Defects with poor mechanical adjustment.
Classified by user acceptance criteria:
For the defects of manufactured products, there are three defect levels in accordance with user acceptance standards that are generally accepted internationally:
①Dangerous defects;
②Important defects;
③General defects.
Source of defect
1. There are many glass defects in the bottle glass manufacturing process, and some defects cannot be solved by the operator of the determinant bottle making machine, for example, defects such as stones or glass that is easy to be torn.
However, most of the defects come from the drip feeder or row bottle making machine.
There may be operational problems, or there may be problems with the quality of the machine itself in terms of manufacturing or performance.
2. In order to better understand the problems related to the causes of forming defects and discuss practical prevention measures, first of all, it is necessary to determine which physical parameters of the glass in terms of forming performance and at least briefly introduce the glass bottle determinant bottle making machine operating principle. Of course, the focus is on discussing which molding defects are closely related to the molding process itself, that is, defects whose cause can be found in the molding process.
3.Various forming methods require accurate control of the physical properties of the glass in stages. In the forming process, it is required that the glass can flow on the wall of the mold at the beginning, but after a certain shape, due to economic (and time) reasons, it is hoped that the glass can be solidified as quickly as possible. The forces (gravity, compression, tension, etc.) applied to the glass gob exceed the molecular resistance inside the glass gob. Such as viscosity, surface tension, etc. will make the glass flow. The forming process is closely linked to the continuous reduction of heat contained in the glass. The viscosity of the glass is closely related to the temperature, which means that the heat conduction and heat radiation of the glass become other important physical properties in the forming process.
3. The three physical properties of viscosity, surface tension, heat transfer and radiation are closely related to each other, all of which are determined by the composition and temperature of the glass. Among them, the change of viscosity is particularly important to the molding method and molding process. In actual production, it has long been customary to describe the tendency of glass with "long material properties" and "short material properties" of glass frit. The so-called "long material properties" means that the glass can maintain the required plasticity within a longer processing time; while "short material properties" means that the glass solidifies quickly.
5. If the heat radiation performance of the glass is not considered at the same time. It is also impossible to make glass meet the specified requirements according to its viscosity change. The relationship between the properties of glass (viscosity and heat radiation) and the mechanical forming process of bottle glass is very close. For example: the edge portion of the green glass blank solidifies faster than the white glass blank. The latter will be strongly heated by the inside of the glass due to its strong radiation transmission ability during reheating.
6. Another interfering property of glass is the crystallization tendency. For example, in the part of the feeder, viewed from the direction in which the molten glass flows. The stagnant glass liquid next to the flowing glass melt will produce crystallization at a certain temperature. If these crystals (mostly in the shape of needles or small rods) are brought to the product (inside the wall of the bottle) during the molding process, especially Containers subject to internal pressure are prone to damage.
The way to eliminate devitrification is to change the composition of the glass frit, or reduce the residence time of the glass frit in the feeder (that is, increase the throughput per hour) and control the temperature (avoid the "crystallization temperature"), these are Something so easy to do every day.
Ways to Find Defects
To find the root cause of forming defects, the melting and glass processing process experienced by glass should never be ignored, but more efforts should be made on the properties of glass melt and glass as the "potential" source of defects.
Longwei is proud of its rich experience in glass packaging industry. We’ve served over 100 baby brands across the world.
