The nylon five-star base of the office chair is made of nylon and fiberglass injection molding, a plastic product produced by injection molding, and is attached to the gas cylinder.
After reinforced and modified with glass fiber (GF), the strength, hardness, fatigue resistance, dimensional stability and creep resistance of nylon PA are greatly improved. It makes the chair base more resistant and durable.
However, in the actual production process, the dispersion and bonding strength of glass fiber in PA resin matrix have great influence on the product performance. Glass fiber reinforced PA injection molding products usually have various defects.
We have decades of experience in injection molding and as manufacturers we would like to share our thoughts:
We will divide this topic into two parts, including the injection molding process of fiberglass reinforced PA and the causes and solutions for defects. In this article, we will introduce the injection molding process.
Glass fiber reinforced nylon injection molding process
After determining the plastic raw material, injection molding machine and mold, the selection and control of injection molding process parameters is the key to ensure the quality of parts. The complete injection molding process should include the preparation before molding, injection molding process, parts after processing, etc.
1. Preparation before molding
In order to make the injection process go smoothly and ensure the quality of the plastic nylon office chair base, some necessary preparations should be made before molding.
(1) Confirm the performance of raw materials
The performance and quality of plastic raw materials will directly affect the quality of plastic nylon office chair base.
(2) Preheating and drying of raw materials
During the plastic molding process, residual water in the raw material will evaporate into water vapor, which will remain inside or on the surface of the base.
This can then form silver lines, marks, bubbles, pitting, and other defects.
In addition, moisture and other volatile low molecular weight compounds will also play a catalytic role in the high heat and high pressure processing environment. This can cause PA to be cross-linked or degraded, affecting surface quality and severely degrading performance.
Common drying methods include hot air cycle drying, vacuum drying, infrared drying and so on.
2. Injection process
The injection process usually consists of the following steps: feeding, plasticizing, injection, cooling and de-plasticizing.
(1) Feeding
Since injection molding is a batch process, a quantitative (constant volume) feed is required to ensure stable operation and even plasticizing.
(2) Plasticizing
The process by which the added plastic is heated in a barrel, transforming the solid particles into a viscous fluid state with good plasticity, is called plasticization.
(3) Injection
Regardless of the type of injection molding machine used, the injection molding process can be divided into several stages, such as mold filling, pressure holding, and reflux.
(4) The door is cooled after freezing
When the melting of the gate system is frozen, it is no longer necessary to maintain pressure. As a result, the plunger or screw can be returned and the pressure on the plastic in the bucket can be relieved. In addition, new materials can be added while introducing cooling media such as cooling water, oil or air.
(5) Demoulding
When the part is cooled to a certain temperature, the mold can be opened, and the part is pushed out of the mold under the action of the ejection mechanism.
3. Post-processing of parts
Post-treatment refers to the process of further stabilizing or improving the performance of injection molded parts. This usually includes heat treatment, humidity regulation, post-treatment, etc.
Another chair base
In addition to nylon, there are other materials, aluminum metal and chrome metal materials, which have their own advantages and disadvantages.
Without a doubt, the Nylon chair base is the most used on the market.
Post time: Nov-28-2022
