How to avoid defects such as bubbles, flow marks, and deformation in the production process of golden acrylic sheets?
(I) Avoid bubbles
Raw material control
Golden acrylic sheet materials contain tiny gold sequins to create a luxurious effect, and the quality of raw materials directly affects the generation of bubbles. When purchasing raw materials, suppliers are strictly screened to ensure that the acrylic raw materials used are of high purity and few impurities. For the additives of gold sequins, strict testing is also carried out to ensure that they have good compatibility with acrylic raw materials. For example, before each batch of raw materials enters the factory, sampling and testing are carried out, and key indicators such as moisture content and molecular weight distribution in the raw materials are tested through professional chemical analysis instruments. Only raw materials that meet strict standards can enter the production link, reducing the possibility of bubbles caused by raw material problems from the source.
In terms of raw material storage, a special constant temperature and humidity warehouse is set up. Acrylic raw materials are sensitive to environmental humidity. Excessive humidity may cause the raw materials to absorb moisture, and the moisture is heated and vaporized to form bubbles during the processing process. The warehouse is equipped with advanced temperature and humidity control equipment to control the temperature at 25℃±2℃ and the humidity at 40%±5%, ensuring that the raw materials are always in good condition during storage.
Production process optimization
In the casting process of acrylic sheets, a vacuum degassing process is used. In the raw material mixing stage, the mixed materials are placed in a vacuum environment, and the air in the materials is extracted by a vacuum pump. By precisely controlling the vacuum degree and degassing time, the vacuum degree generally reaches -0.095MPa to -0.1MPa, and the degassing time is controlled from 30 minutes to 2 hours according to the material quantity and equipment performance, which can effectively remove the bubble nuclei in the material. For example, in large-scale production equipment, the vacuum degree and degassing time are monitored in real time by an automated control system to ensure the stability and consistency of the degassing process.
In the injection molding stage, the injection molding parameters are optimized. Too fast an injection molding speed can easily cause air to be drawn into the material to form bubbles. Therefore, the company's technical team has determined the optimal injection molding speed curve for gold acrylic sheets after a large number of experiments. At the beginning of injection molding, a lower injection speed is used to allow the material to slowly fill the mold cavity and reduce the chance of air being drawn in. As the cavity is gradually filled, the injection speed is appropriately increased to ensure that the material can quickly fill the entire cavity. At the same time, the injection pressure and holding time are accurately controlled to avoid the shrinkage of the material and the generation of bubbles due to insufficient pressure or too short holding time.
Equipment maintenance and cleaning
The cleanliness of production equipment also has an important impact on the generation of bubbles. After the end of production every day, the injection molding machine, mold and other equipment are thoroughly cleaned. Use special cleaning agents and cleaning tools to remove the residual materials on the surface and inside of the equipment. For molds, regular disassembly and cleaning, especially the runners, gates and other parts of the mold, to ensure that there is no material accumulation and impurities remaining. For example, using ultrasonic cleaning equipment to deeply clean the mold can effectively remove tiny particles and dirt that are difficult to clean on the mold surface, preventing these impurities from becoming the core of bubbles during the production process.
Regularly maintain the equipment and check the sealing performance of the equipment. If there is a problem with the sealing performance of the barrel, screw and parting surface of the injection molding machine, air can easily enter the material and generate bubbles. The technicians check and replace the seals of the equipment at regular intervals to ensure that the equipment always maintains a good sealing state during the production process.
(II) Avoid flow marks
Mold design optimization
The mold is one of the key factors affecting the quality of acrylic sheet molding. The runner design of the mold adopts a balanced runner system to ensure that the material can be evenly filled into each cavity of the mold. The cross-sectional shape and size of the runner are accurately calculated, and generally a trapezoidal or circular cross-section is used. The runner diameter is between 6mm and 12mm depending on the product size and injection volume. For example, for large-scale golden acrylic sheet molds, when a multi-cavity design is adopted, the flow of the material in the runner is simulated by CAE simulation analysis software, and the runner layout is optimized to make the flow velocity and pressure distribution of the material in each cavity uniform, thereby reducing the generation of flow marks.
The gate design of the mold is also crucial. According to the shape, size and appearance requirements of the product, select the appropriate gate type. For golden acrylic sheets with high surface quality requirements, point gates or latent gates are usually used. Point gates enable materials to enter the cavity at a higher speed, reduce gate marks, and help control the flow direction of materials. Latent gates can automatically cut off the gate when the product is demoulded to avoid leaving obvious gate scars on the surface of the product. The location and number of gates are carefully designed, and the best location is determined through simulation analysis, so that the material can smoothly fill the cavity and avoid flow marks caused by poor material convergence.
Injection molding process adjustment
The injection molding temperature has a direct impact on the fluidity of the material, which in turn affects the generation of flow marks. The optimal injection molding temperature range for golden acrylic sheets was determined through experiments. Generally, the injection molding temperature is controlled between 210℃ and 230℃. Within this temperature range, acrylic materials have good fluidity, can evenly fill the mold cavity, and reduce flow marks caused by poor material flow. At the same time, during the production process, the temperature of each section of the barrel is monitored and adjusted in real time through the temperature control system of the injection molding machine to ensure temperature stability.
Adjust the coordination of injection molding pressure and speed. During the injection molding process, changes in injection molding pressure and speed will affect the flow state of the material in the cavity. The company's technical personnel formulate reasonable injection pressure and speed curves according to the actual situation of the product. In the early stage of filling, a lower injection speed and appropriate injection pressure are used to allow the material to enter the cavity slowly and smoothly, avoiding the high-speed impact of the material on the mold cavity wall to produce jet marks. As the cavity is gradually filled, the injection speed is appropriately increased, and the injection pressure is adjusted at the same time to ensure that the material can quickly fill the entire cavity, and in the pressure holding stage, through reasonable pressure control, the material can fully compensate for the volume change caused by cooling shrinkage and reduce the appearance of flow marks.
Mold surface treatment
The finish of the mold surface has a great influence on the surface quality of the gold acrylic sheet. Advanced polishing equipment and technology are used to reduce the roughness of the mold surface to between Ra0.01μm and Ra0.05μm. The smooth mold surface can make the material flow more smoothly during the process, reduce the friction between the material and the mold surface, and thus reduce the possibility of flow marks. For example, for the core and cavity surface of the mold, the diamond paste polishing process is used. After multiple processes of fine polishing, the mold surface achieves a mirror effect, which effectively improves the surface quality of the product.
When applying the release agent on the mold surface, strictly control the coating amount and uniformity. The main function of the release agent is to help the product demold smoothly, but if it is not applied properly, it may cause flow marks. The company uses professional release agent spraying equipment to ensure that the release agent is evenly coated on the mold surface by accurately controlling the spraying pressure, flow rate and spraying time. At the same time, select a release agent with excellent quality and good compatibility with the golden acrylic sheet to avoid the release agent from having adverse effects during the material flow process.
(III) Avoid deformation
Product structure design optimization
For large-area golden acrylic sheets, the rib structure is reasonably designed. The layout and size of the ribs are accurately calculated, which can not only improve the strength of the product, but also effectively prevent the product from deforming due to uneven shrinkage during the molding process. For example, when designing a large golden acrylic decorative panel for luxury interior design, a certain number and height of reinforcing ribs are evenly distributed on the back of the panel according to the size and usage scenario of the panel. The height of the reinforcing ribs is generally between 3mm and 5mm, and the width is between 2mm and 3mm. Through this structural design, the rigidity of the product is enhanced and the risk of deformation is reduced.
Control the uniformity of the wall thickness of the product. Uneven wall thickness is one of the main reasons for the deformation of acrylic panels. When designing products, try to keep the wall thickness of the product consistent. For some products with special shapes, avoid sudden changes in wall thickness through reasonable transition design. In the mold design stage, the wall thickness of the product is optimized and analyzed using CAE simulation analysis software to ensure that the wall thickness uniformity reaches the best state while meeting the functional requirements of the product. For example, for a golden acrylic display stand with a special-shaped structure, the shape of the mold core and cavity is adjusted during design to control the wall thickness deviation of the product in each part within ±0.2mm, effectively reducing the possibility of deformation.
Injection molding process optimization
The design and control of the cooling system have an important influence on the deformation of the golden acrylic panel. An efficient cooling system is designed in the mold. The layout of the cooling water channel is carefully planned to ensure that all parts of the mold can be cooled evenly. The diameter of the cooling water channel is generally between 8mm and 12mm. Through reasonable arrangement and distribution, the temperature difference on the mold surface is controlled within a small range. For example, in large injection molds, a circulating cooling method is adopted to control the cooling water flow rate and water temperature so that the mold can be cooled evenly during the injection process. The cooling water flow rate is generally controlled between 1.5m/s and 2.5m/s, and the water temperature is controlled between 20℃ and 30℃, so that the product can shrink evenly during the cooling process and reduce deformation.
Optimize the holding process. The choice of holding time and pressure is directly related to the shrinkage and deformation of the product. Through experiments and simulation analysis, the company has determined the optimal holding parameters for gold acrylic sheets of different sizes and thicknesses. During the holding stage, the holding pressure is gradually reduced to avoid excessive compression of the product due to excessive pressure, which causes rebound deformation after demolding. At the same time, the holding time is reasonably controlled to ensure that the product is fully cooled and shaped in the mold. Generally, the holding time is between 10 seconds and 30 seconds according to the thickness of the product. For example, for a gold acrylic sheet with a thickness of 3mm, the holding time is set to about 15 seconds, and the holding pressure is set to 60% to 70% of the injection pressure at the beginning, and then gradually reduced to 30% to 40% during the holding process.
Post-processing process
Proper post-processing of the molded gold acrylic sheet can further reduce deformation. Put the product in an oven at a specific temperature and keep it at a certain temperature for a period of time to release the stress inside the product. The heat setting temperature is generally controlled at 10℃ to 20℃ below the glass transition temperature of acrylic, that is, between 100℃ and 110℃, and the holding time varies from 30 minutes to 2 hours according to the thickness and size of the product. For example, for a 4mm thick golden acrylic sheet, keeping it in an oven at 105℃ for 1 hour can effectively eliminate the residual stress inside the product and reduce the risk of deformation.
Take appropriate protective measures during product packaging and transportation. Use customized packaging materials such as foam boards, bubble films, etc. to package the golden acrylic sheet in layers to ensure that the product is not squeezed and collided by external forces during transportation. At the same time, when designing the packaging, consider the shape and size of the product, arrange the placement of the product reasonably, and avoid deformation caused by mutual squeezing of the products in the packaging. For example, for a golden acrylic sheet with a standard size of 1250 x 2450 mm, use a specially designed wooden packaging box, and set up appropriate support and cushioning materials in the box to ensure the integrity of the product during long-distance transportation.
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