How Do You Operate and Maintain Plastic Injection Molds?
When compared with other tools, the plastic injection mold is more complicated and precise, with higher requirements for operation and maintenance. As a result, throughout the entire production process, their correct use and meticulous mold maintenance are of great significance to maintain the normal production and improve the efficiency of a company. 1. Select the right molding equipment, and determine the reasonable process conditions. If the injection molding machine is too small, it will not meet the requirements; if too large, it will waste resources. Also, it may damage the mold or the mold plate due to the improper adjustment of the clamping force, while at the same time affecting the production efficiency. When selecting the injection molding machine, check … Read more
What Causes Short Shot in Plastic Injection Molding?
Short shot refers to incomplete filling of a mold cavity which results in the production of an incomplete part due to the insufficient plastic fluidity. The main causes are the inappropriate injection pressure and speed (including excessive pressure loss caused by resistance), which are mainly affected by the following aspects: I. Injection Molding Machine: (1) Insufficient injection molding capacity – This is caused by an overestimation of the capacity of the injection molding machine, which may also occur due to insufficient plasticizing capacity or insufficient injection volume. Among them, the insufficient plasticizing capability can be increased by extending the heating time, increasing the screw speed and raising the backpressure. If the injection volume is not high enough, the injection machine … Read more
VDI 3400 Mold Texture and Drafting Angle
Bayer Plastics has some good Information about surfaces and injection molding available on their web- Site. According to a (German) Document the VDI 3400 texture surfaces correspond to the following Ra / Rz Values and require the following drafting angles: VDI3400 Ra Rz DA-PA DA-PC DA-ABS 12 0.40 1.50 0.5 1.0 0.5 15 0.56 2.40 0.5 1.0 0.5 18 0.80 3.30 0.5 1.0 0.5 21 1.12 4.70 0.5 1.0 0.5 24 1.60 6.50 0.5 1.5 1.0 27 2.24 10.50 1.0 2.0 1.5 30 3.15 12.50 1.5 2.0 2.0 33 4.50 17.50 2.0 3.0 2.5 36 6.30 24.00 2.5 4.0 3.0 39 9.00 34.00 3.0 5.0 4.0 42 12.50 48.00 4.0 6.0 5.0 45 18.00 69.00 5.0 7.0 6.0 DA-PA = … Read more
What Causes Flow Lines in Plastic Injection Molding?
Definition of Flow Lines: Flow lines, also known as flow marks Linear marks on the surface of a molded product, which indicates the flow direction of the molten plastic. Injection Molding process 1．Insufficient Pressure / Holding Pressure The injection pressure and the holding pressure are not high enough to press the solidified layer against the mold surface, thus leaving flow lines along the melt flow direction. Increase the injection pressure and the holding pressure, to press … Read more
What causes silver streaks or marks during injection molding?
Definition of silver Streaks: Silver streaks are also referred to as silver marks, which appear like burst blisters on the surface of injection molded parts, mostly in the shape arrows pointing to the gate. Causes of Silver Streaks: I. Equipment 1. The nozzle hole is too small, the material leaks or draws at the nozzle, or the barrel or the nozzle is obstructed, and the material decomposes due to the frictional heat caused by high-speed melt flow; 2. The barrel and the screw wear, or melt flow dead ends exist in the screw cap and collar, which are decomposed due to long-time heating. 3. The heating system is out of control, causing the temperature to be too high and resulting … Read more
What causes air bubbles or voids in injection molding?
According to the cause of air bubbles or vacuum voids , the solutions to the defects are described as below: (1) When the wall thickness of the product is large, the outer surface is cooled down faster than the center portion. Therefore, as the cooling progresses, the resin at the center portion is expanded toward the surface while shrinking, so that the center portion is insufficiently filled. This situation is referred to as air bubbles, to which the main solutions are: a) Determine the proper gate and runner size based on wall thickness. Generally, the height of the gate should be 50%-60% of the product wall thickness. b) A certain amount of supplementary injection material is retained until the gate … Read more
PC/ABS injection molding defects and solutions
Seven Common Defects and Solutions for PC/ABS injection molding Products Flow Lines The flow lines are caused due to the poor fluidity of the material. Unlike silver streaks, it is not caused by moisture or material decomposition, thus resulting in a different look. Solution: The flow lines can be eliminated by raising the material temperature so as to improve the fluidity. Appropriate increase of mold temperature and decrease of injection speed can also solve the problem. Pitting The shrinkage cavities are caused by short shot in the mold cavity. Solution: Increase mold temperature and material temperature appropriately to improve material fluidity; extend the injection / pressure holding time, and raise the injection speed to improve the mold filling, or increase the … Read more
How to Control the Dimensions Tolerance of Injection Molding Products
Due to the greatly varied market demands for molds and molded products, there are many kinds of changes and thus high requirements for us in such aspects as shape, size, material, structure and more, causing us many problems and difficulties in the production process of molds and products. How to effectively control the geometric dimensions of the mold and the product is just one of them. For different types of molds and products, there are different control techniques and methods for dimensions control. Personally, I usually start from the following aspects. Mold Design Control Firstly, we have to fully understand the technical requirements for the mold structure, material, hardness, and precision, etc., including whether the shrinkage rate of the plastic … Read more
PVC injection molding plastic resin
PVC plastic is a heat-sensitive material that features a poor injection moldability, for which the reason is that an excessively high melt temperature or an excessively long heating time easily causes PVC decomposition. Therefore, the key to molding the PVC products lies in the control of the melting temperature. The heat sources for melting the raw PVC material are usually from two aspects, i.e., the shear heating generated by screw motion and the resistance wire heating provided by the outer wall of the barrel, among which, the former is the main source, while the latter is mostly provided during machine operation. Due to the unsatisfactory heat transfer property of the PVC material, although the outer portion is heated, the inner … Read more
Mold steels P20,718 and H13 comparison
P20 Mold steel Overview:The P20 Mold Steel is a type of mold welding consumable, and the earliest is P20, followed by P20H and P20Ni. The P20 Steel is applicable to the production of molds for plastic materials, as well as those for diecasting low melting point metals. This steel material features great machinability, as well as mirror polishing properties. Chemical composition： Element C Si Mn Mo Cr Ni （%） 0.28~0.40 0.20~0.80 0.60~1.00 0.30~0.55 1.40~2.00 0.80~1.20 How to Use: The P20 Steel is pre-hardened to 285-330HB (30-36HRC), which is equivalent to 618 of Sweden and GS-2311 of Germany. It can be directly used for molding, and boasts a great dimensional stability. Pre-hardened steel is able to meet the requirements for … Read more