PRM Industry Plastic injection molding production and use of technology

   Plastic injection molding Repair bad surface
Semi-crystalline engineering plastics (such as POM, nylon, PBT) is used mainly as they have excellent mechanical properties, thermal and electrical performance. Compared with amorphous plastics, they have better resistance to chemicals and resistance to stress cracking performance advantages. In a number of specific applications, but also the appearance of high-quality surface. This article will focus on how to remove the surface defects that may exist.
Positioning and definition of surface defects
In order to solve the problem of surface defect, the defect must first be accurate positioning. Suggested that attention to the actual injection molding process observed on the surface, a description of the following:
* Defects will appear when each injection or irregularly appear?
* Does each injection, the total defect in the same cavity?
* Whether the defects in products every time the same general location?
* Fill in the mold of whether the defect has been able to predict?
* Whether the sprue surface was defective?
• When using a new batch of plastic, the defect occurs whether there is a change?
* Defect occurs only on one machine or other machines have?
Analysis of the possible causes surface defects
Surface defects may be caused by the following factors:
Plastic materials mixed processes: drying, mixing with the quality of materials, the presence of impurities (foreign substances)
Injection processing conditions: melt temperature, injection speed, and changes - all of the above.
Injection machine conditions, such as wear and corners.
Hot runner design (flow, materials, blocking, etc.)
Mold design, gate location and gate cross-section, injection of cold feed block, exhaust, etc.
Pigments and other additives
Molding compounds contain special polymers.
The conclusion from the surface defects
Rules of local defects
If the surface defects is always a regular appearance in the same position, it indicates that the injection nozzle or hot runner nozzle problems. Flow channel, gate, or the shape and design of their products, such as sharp edges, sudden changes in wall thickness may be relevant. Another reason is that processing conditions, such as injection technology curve and change.
Irregular local defects
If the surface defects always appear in different positions, it may be mixed with the plastic special material problems in the process (with mixed quality, the presence of dust). Other factors, such as low melt temperature, back pressure, screw speed and the screw speed and so may have a major impact on this.
Large area of ​​surface defects
This deficiency always appear in the product surface, often you can see the flaws in the mainstream trail. At this time the melt to be checked whether there has been decomposition. Melt can be injected into a group of open container and observe to see if there is air bubbles. For the hot runner system, the method difficult to achieve. Melt degradation or decomposition of additives may also be due to high temperature or long duration. For the moisture absorption of plastic, if the processing of materials is not fully dry, the plastic may occur hydrolysis.
General recommendations
Semi-crystalline engineering plastics with products made excellent surface appearance if required, are not suitable for hot runner injection molding method with processing. Recommend the use of auxiliary flow method, this method will nozzle and injection products, insulation, reducing the possibility of producing
PRM Industrysurface defects.
From the injection or hot runner nozzle head out of the cold material, it should be opposite the main channel using a special cold-slug well to retain it live. The following table lists the various surface defects and removal of their methods. In practice, different defects may also occur, which makes them more difficult to analyze and remove.