Plastic Blow Molding
Plastic blow molded products have outstanding advantages, among which seamless products, high bottom strength, precise mouth size, and clear surface text and patterns are their most prominent features. They can be used to make large containers with surface markings.
Blow Mold Problems & Solutions
The proposal of blow mold solutions greatly reduces the risk of problems and defects during design and processing, helping manufacturers provide better blow molding services. Plastic blow molding mold is the most important tool in blow molding technology, and a well-designed mold directly determines the shape and quality of the workpiece.
Nowadays, manufacturers with excellent blow mold solutions have exported blow molding molds and products to many countries, such as Vietnam, the United States, Japan, South Korea, etc., and have conducted extensive international trade exchanges.
Blow Mold Manufacturing Solutions
The proposal of blow mold solutions has provided a new direction for the manufacturing of blow molding molds, resulting in better quality and design accuracy.
The first point of a blow mold manufacturing solution is to choose the right materials. Manufacturers can choose blow molding materials with higher cost-effectiveness. The bottleneck mold embedded in the blow molding mold requires extremely high precision to make the assembly of the core rod more appropriate. When embedding it into the blow molding mold, can allow the billet to be smoothly inserted, preventing deformation of the billet during rotation. If the gap is too large, the blow molding mold will leak air, causing dimensional changes in the product, which is not conducive to the solution of the blow molding mold. This type of blow molding mold does not have a cutting-edge area. To allow the air trapped in the mold cavity to be discharged smoothly, the solution is to add several exhaust holes. If the bottom of the product is too low and concave, the solution for such blow molding molds is to process the bottom of the mold into a convex shape. Due to the extremely high requirements for size and accuracy of blow-molded products, the processing of blow-molded molds must be extremely accurate, and the blank molds are the main bearers of injection pressure, so manufacturers often have more stringent requirements for them.
If there is a problem with the exhaust system of blow molding molds, many blow mold solutions cannot be implemented, so manufacturers should pay attention to the design of the exhaust system of blow molding molds. To achieve the best cooling effect, minimize the time, and improve the efficiency of blow molding, the design of the cooling water channel should be as close to the mold cavity as possible. Unlike the solution for extrusion blow molding molds, the cooling medium flow channel of injection blow molding molds is usually perpendicular to the mold cavity, which can greatly reduce the width of the mold. The cooling medium for blow molding molds is generally water (around 5-15 ℃), and a small number of designs may use oil. When designing a larger rectangular plane, it is easy to encounter problems of shrinkage and concavity. The blow mold solutions can be to minimize the design of arch shapes as much as possible.
The bottom plug of the blow molding mold cavity is usually symmetrical in two halves, and each half of the mold is cooled by water, which is usually used to shape the bottom of the product. For general plastics, such bottom plugs require a plastic part to be pushed out 5mm or more to successfully detach from the mold; For other hard plastics, successful demolding can be achieved after the ejection amount reaches 0.8mm. If the volume and depth of blow-molded products are large, the blow-mold solutions can design a bottom plug with a retractable structure. The bottom plug and blow molding mold can be made of the same material.
Blow Mold Product Solutions
The proposal of blow mold solutions has also reduced the risk of product defects to a certain extent.
- Uneven Vertical Wall Thickness of Blow-molded Products
-Reason: The cause of this defect may be the loosening of the billet or a significant difference in diameter between the two cross-sections of the product. The reasons for this defect are very complex.
-Solutions: At this point, this problem can be alleviated by reducing the temperature of the blow molding mold and improving extrusion efficiency. In addition, the solutions to the problem of blow molding mold can also be chosen to solve it from the root, such as changing the design concept of the product.
- Orange Peel-like Lines or Black Spots Appear on the Surface of the Product
-Reason: The cause of this defect may be poor design of the exhaust pipe of the mold or poor plasticization of the blank; The standard air pressure blown out is not enough, the speed is relatively slow, and the blow out is relatively small. The blow mold solutions are relatively complex.
-Solutions: Firstly, blow molding manufacturers can sandblast the blank of the mold to increase the exhaust holes of the mold; Reduce the screw speed ratio of the equipment and increase the heating temperature of the extruder; These type of blow mold solutions also includes cleaning the compression safety channel, checking for leaks in the blowing rod, removing the top block and core, and increasing the inflation rate of the blank.
- Unclear Appearance or Surface Pattern of Blow-molded Products
-Reason: The main cause of this defect is the poor exhaust pipe of the mold or low inflation pressure; The solid solution temperature of the mold is slightly lower, and the plasticizing effect of the raw materials is poor; The cooling temperature of the mold is relatively low.
-Solutions: The blow mold solutions mainly include maintaining the sandblasting process of the mold mother mold or adding exhaust pipe slots; Increasing the standard inflation pressure; Moderately increasing the temperature of the extruder and engine; Adding appropriate plastic filling masterbatch if necessary; In addition, the temperature of the mold can also be raised above the leakage point.
- Blow Molded Products with too Many or too Thick Burrs
-Reason: Insufficient locking pressure of the blow molding mold; Mold damage or displacement of positioning pins and blocks; When blowing the mold, the mold itself tilts; The mold body started inflating too early.
-Solutions: The manufacturer’s solutions for this type of blow molding mold mainly include: adjusting the appropriate locking pressure and reducing the inflation standard pressure; Correct or replacing the mold positioning pins and blocks; Repair the mold and increasing the depth of the slide or blade; Adjust the inflation time of the mold blank appropriately. The implementation of solutions for such blow molding molds requires meticulous operational skills.
- Blow-molded Products Rupture
-Reason: It may be because the cutting edge of the mold is too sharp; There are residues or bubbles in the blank; The blowing ratio is too large; Insufficient length during billet extrusion; The wall thickness of the tubular billet is too thin or uneven; Insufficient inflation time of the container caused it to rupture when coming out of the mold; Insufficient locking force.
-Solutions: There are various forms of blow mold solutions, which can apply dry and cold raw materials, apply them after air drying, and clean the raw materials; Replace or disassemble the top block and core of the mold to reduce the scrap rate of the mold; Re select more suitable raw materials and replace the previous ones to moderately reduce the solution temperature; Check the operating equipment parameters of the extruder or discharge cylinder engine to reduce adjustments and changes in the main processing parameters; Adjusting the gap of the mold, whether it is too large or too small, can have negative consequences; Adjust the time or delay time for air injection.
- Difficulty in Forming Blow-molded Products
-Reason: The cooling time of the product is too long, and the cooling temperature is relatively low; Poor mold design with burrs or other defects on the surface; During mold opening, the movement speed of each template is unbalanced; Incorrect mold installation or maintenance methods.
-Solutions: At this point, the manufacturer can appropriately shorten the mold expansion time and increase the mold temperature; Redesign or repair the mold; Reduce the depth of grooves and the inclination of convex ribs; Use film removers appropriately, but do not overly rely on them; Repair the locking equipment, adjust the locking force, and ensure that the movement speed of each template is consistent; Reassemble the mold according to the correct method.
- Uneven Quality of Blow Molded Products
-Reason: the wall thickness of the billet suddenly changes; Uneven mixing of recycled materials; 3. The feed section is blocked, causing fluctuations in the feed of the extruder; The temperature fluctuation during heating is significant.
-Solutions: Maintain billet control equipment to maintain consistent billet dimensions; Select appropriate materials and equipment; reduce the use of recycled materials; Remove clumps at the material outlet and keep the discharge port unobstructed; Reduce the temperature of the material outlet.
The proposal of blow mold solutions has largely solved the production difficulties of many manufacturers and has crucial practical significance.
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