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What are the causes of defects in glass packaging products? - Maypak

March 30, 2024

Glass Packaging products have the advantages of non-toxic, odorless, transparent and beautiful, good barrier properties, pressure resistance, high temperature resistance, etc. Compared with plastic, paper, metal and other packaging materials, glass packaging materials have relatively stable chemical properties and are the safest at this stage. A kind of packaging material. Usually we can divide it into: Cosmetic Glass Bottles, Perfume Glass Bottles,Lotion Glass Bottles, Spray Glass Bottles, etc.

During the reproduction process, there are many types of product defects caused by molds, and there are many reasons. They can be roughly summarized as follows: mechanical defects, temperature defects, molding process defects, and mold defects.

Common mold defects caused by molds mainly include the following six types.

   1. Insufficient Capacity   

01. Possible Reason

• The mold cavity does not conform to standard dimensional tolerances.

• Design capacity is low.

• The bottle is overweight and the capacity is low.

• The bottle is not blown enough.

02. Actions That Can Be Taken

• Detect bottle size tolerances.

• Correct the mold cavity size and increase the bottle capacity.

• Reduce material weight.

• Adjust the positive blowing pressure and time to ensure that the exhaust hole is suitable and smooth.

   2. Capacity Is Too Large   

01. Possible reasons

• The mold cavity does not comply with the standard tolerance; it has been used for a long time and has been worn excessively, and the mold cavity has become larger.

• The design capacity is on the high side.

• The bottle is deformed.

• The bottle material is light.

02. Measures That Can Be Taken

• Detect cavity size tolerances.

• Revisit the design and reduce the bottle capacity.

• Adjust process parameters, especially positive blowing pressure and time.

• Control the verified material temperature.

   3. Seam Lines Are Too Thick, Too Sharp, And Come Out Of Corners   

01. Possible Reasons

• The seam lines don't fit well.

• Old mold, badly worn.

• The mold is not tightly closed or there is broken glass or dirt on the seam line.

• The positive blowing pressure and time settings are improper, and the mold is opened.

• The edges and corners of the mold seams are damaged, nicked, and missing corners.

• The axes of the initial mold and the final mold are asymmetrical, and the double seams are misaligned.

02. Measures That Can Be Taken

• Check seam line fit tolerances.

• Replace with new mold.

• Check the switch mechanism and remove broken glass and debris.

• Reduce the positive blowing pressure and adjust the positive blowing time to prevent the mold from opening when the pressure is too high or the positive blowing time is too long or too late to blow after the mold is opened.

• Replace new molds or damaged molds (the parts that are often easily damaged are the corners of the initial mold, the corners of the neck of the finished mold, the bottom corners of the finished mold and the mold, and the seam line, etc.).

• Correct the initial mold and mold axis.

   4. The Smoothness Of The Bottle Body Deteriorates   

01. Possible Reasons

• The mold has been used for too long, and the surface has become oxidized and peeled.

• Mold cavity lubricating oil and lubricating paint accumulate dust.

• Poor lubrication.

• Material temperature and material shape changes.

02. Measures That Can Be Taken

• Replace the mold.

• Remove accumulated dust and replace and clean if necessary.

• Apply lubricating oil or paint to lubricate the mold in a timely manner.

• Correct material temperature and material shape.

   5. Bottle Head Size Tolerance Does Not Meet Requirements   

Here we mainly consider mold factors:

01. Possible Reasons

• The inner diameter of the bell mouth is too small, and the punch size (straight position and mouth ring) design is unreasonable.

• There are burrs, the material weight is too heavy or the punch charging position is too low.

• Notch, the material weight is too light or the punch cannot press in place.

• The mouth is oval, the material is closed, and the mouth mold is opened improperly and deformed (other technological reasons).

• The head and neck are fat, the molding air pressure is too high, the blowing head and the blowing tube are inappropriate, and the material is damaged.

• Deformity, poor cooperation between the die and the initial mold, bad material, inappropriate machine speed (other technological reasons).

• Insufficient threads, dust accumulation in the die, grease, and broken glass (other technological reasons).

• Other temperature, mechanical and process reasons.

02. Measures That Can Be Taken

• Redesign and modify the punch.

• Reduce the material weight, raise the punch charging position and adjust the charging time.

• Increase the material weight and increase the punch pressure.

• The opening speed and opening of the die should be appropriately reduced, the material temperature should be lowered, and the lubrication of the die should be enhanced.

• Reduce the positive blowing pressure and adjust the blowing head and trachea.

• Correct the die to match the initial shape, lower the material temperature, and adjust the machine speed.

• Remove dust and broken glass from the mouth and replace it if necessary.

• Solve other temperature, mechanical and process defects.

   6. Uneven Thickness   

01. Possible Reasons

• The design of the preliminary mold cavity and punch is unreasonable (especially the press-blow method).

• The extension is too long or too short.

• Machine speed is too fast or too slow.

• Material weight is light.

• The material temperature and material shape are inappropriate.

• Other technological and mechanical reasons.

02. Measures That Can Be Taken

• Correct the initial mold cavity and punch to improve glass material distribution.

• If the extension is too long, the length of the initial mold cavity can be shortened or a linear bulkhead or bulkhead can be used. • If the extension is too short, a deeper bulkhead can be used. At the same time, the speed of the molding machine can be appropriately reduced and the material temperature can be increased.

• Adjust the molding process time and machine speed of each step, especially the "reheat" process.

• Strictly control the weight of materials.

• Control the appropriate material temperature and material shape.

• Solve other process and mechanical problems.

The Future Of Glass Molds

The design of glass bottles is a relatively complex process. Domestic glass mold design is still mainly based on experience and manual design, lacking mature design theory. Each company also focuses on its own production, lacking exchanges and communication within the industry. .

In the past ten years, the United States, Germany, etc. have successively developed software related to glass mold design. Based on CAD systems, bottle shapes and molds are designed and modified, and finally products and molds that meet the requirements are obtained. In this way, not only can the two-dimensional engineering drawings and three-dimensional solid models of the bottle shape and mold parts be clearly and accurately given by the plotter, but they can also be transmitted to the machining center (CAM) in the form of data through the network to produce the mold. The application of these professional design software frees designers from a large number of complicated calculations in the past, improving work efficiency and accuracy. Therefore, it is increasingly urgent and necessary to improve the mold design and mold processing and manufacturing levels of practitioners, and to fully utilize computers for glass mold design.

*Maypak packaging is Glass Packaging Manufacturer and has been focusing on Glass Packagings for more than 17 years and was established in 2006,the company enjoys a good reputation at home and abroad. If you have any questions about lipstick tubes, please contact us.

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