Transparent plastic sheets are widely used in packaging, printing, decoration and other fields. Transparent appearance, no impurities, and no crystal dots are the core standards for product quality inspection. In production, small crystal dots and fish eyes are the most common quality defects, which not only reduce the light transmittance of the sheet, but also lead to product degradation and scrap. The majority of crystal point issues are not related to raw materials, but rather to inadequate control over details such as plasticization, filtration, and temperature control. Benk Machinery has compiled a set of highly practical techniques for de crystallization points based on their experience in debugging transparent sheet equipment.

Optimize raw material processing to reduce crystal points from the source

1. Strictly dry and dehumidify

Transparent PP, PVC, and PET sheet materials are highly hygroscopic, and when water containing materials are extruded, microscopic bubbles are generated, which form pseudo crystalline dots after cooling. Before production, constant temperature dehumidification and drying must be completed to thoroughly remove moisture from the raw materials and prevent crystal defects caused by water vapor.

2. Eliminate the mixing of miscellaneous materials

Mixing impurities of different materials and melting points, which cannot be melted and plasticized synchronously, will form permanent crystalline hard blocks. Production requires separate materials, standardized feeding, and regular cleaning of the material bin to avoid cross mixing pollution.

Adjust the extrusion plasticization process

Uneven plasticization is the core reason for the formation of crystal dots in transparent sheets. The temperature is too low, the material is not fully plasticized, and unmelted particles form crystal dots; The temperature is too high, causing slight decomposition and coking of the material, resulting in fine focal points. Segmented gradient temperature control should be adopted to maintain uniform and stable temperature of the machine body and mold head, combined with low shear screws for uniform plasticization, allowing the material to fully melt and homogenize.

Upgrade the melt filtration system

The insufficient filtration accuracy of ordinary filters cannot intercept small unmelted particles, which is the key cause of frequent occurrence of crystal dots. The production of transparent sheets requires the use of multi-stage precision filtration combinations to shorten the screen replacement cycle and timely intercept impurities and unmelted particles. The transparent sheet production line of Benk Machinery is equipped with a high-precision screen changing filtration system, which can effectively filter out small impurities and greatly reduce the production of crystal dots and fish eyes.

Fine control of equipment and molding processes

Long term use of screws and barrels will result in residual carbon deposits and aging materials, and continuous production will continuously drop particles to form crystal dots. It is necessary to regularly disassemble and clean the extrusion system and die head material accumulation. Simultaneously stabilizing the roller speed and temperature to ensure uniform sheet forming and avoid visual crystal defects caused by stress concentration.

Conclusion

The core of removing crystal points from transparent sheets lies in the purity of raw materials, uniform plasticization, precise filtration, and clean equipment. By effectively controlling the details of each stage, we can completely solve the problems of crystal dots and fisheye, and improve the transparency of the sheet and the qualification rate of the finished product. Benk Machinery can customize high-precision sheet production lines and process optimization solutions based on transparent sheet materials and production capacity requirements.

FAQ

Q1: What are the main reasons for the high number of crystal dots on transparent sheets?

A: Mostly caused by moisture in raw materials, uneven plasticization, insufficient filtration accuracy, or equipment carbon deposition.

Q2: Can simply increasing the temperature eliminate crystal points on the sheet?

A: No, blind high temperature will cause material decomposition, but instead produce coke particles and new defects.

Q3: Why does the crystal point of the sheet decrease significantly after changing the mesh?

A: Precision filters can effectively intercept unmelted particles and impurities, preventing the formation of crystal points from the melt end.

Q4: Will insufficient drying of raw materials produce crystal dots?

A: Yes, water vaporizes to form microscopic bubbles, which form pseudo crystalline dots and pinholes after cooling.

Q5: Does Benk Machinery support customized transparent sheet production lines?

A: Support, can provide fully automatic sheet extrusion line equipment with high transparency and low defects.

Why Choose Benk Machinery?

From individual machines to complete production lines, Benk Machinery provides reliable and customized plastic processing solutions. Since 2012, we have focused on plastic extrusion, nergy-saving plastic recycling machine, and automated compounding centralized feeding systems, helping customers build efficient and cost-effective production facilities.

• Complete Extrusion Solutions: Professional expertise in plastic pipe, profile, sheet, plate and board extrusion lines.
• Customized Project Solutions: Equipment and production lines can be configured according to your materials, products, capacity and factory requirements.
• Stable & Cost-Effective Equipment: Reliable machine performance, efficient production and optimized energy consumption help reduce operating costs.
• Professional Service: From technical consultation and production to installation, commissioning and after-sales support, our team provides complete project assistance.

Contact Benk Machinery:

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