Factors affecting the appearance of injection molded parts

Nowadays, injection molding can be said to be an important part of the plastic processing industry, and it is necessary to control the process parameters skillfully when processing injection molded parts, otherwise, the quality of injection molded parts cannot be guaranteed. For an injection molded part, the appearance quality is an important part to measure the value of the product, and the success of the product we design is often affected by its visual appearance. In addition to visual appearance, the appearance of plastic parts also affects the sense of touch, and quality judgments usually depend on how the product feels when held or touched. Therefore, it is important to ensure the appearance quality of injection molded parts.

So what factors will affect the appearance quality of injection molded parts in the specific injection molding process?
 
There are four main factors in the appearance of a part: the geometry of the part, the choice of material, the design of the mold (or tooling), and the processing parameters during injection molding. These drivers are cross-coupled with each other and have other design factors, such as strength and durability. While the part designer has complete control over geometry and resin selection, they typically require only a small amount of input into the mold design.
 
1. Part Geometry
 
Part geometry can affect many aspects of an injection molded part. With so many possible geometries, if the geometry of an injection molded part is inherently unreasonable, the quality of the appearance of the injection molded part will not be guaranteed. The shape and size of the injection molded parts need to be designed by strictly calculating each mechanical parameter and combining with the structural strength of the plastic material itself, unreasonable structural design will only make the appearance of the injection molded parts much lower quality.
 
2. Material Selection
 
The resin you choose will have a dramatic effect on the appearance. The most obvious effect is color, but there are many aspects beyond color that are influenced by material choice. Material selection includes base resins, colorants and fillers.
 
The quality of the appearance of the injection molded part depends to a large extent on its color effect. Some resin materials are less compatible with colorants, and the subsequent coloring effect is not guaranteed, so naturally it is not possible to obtain a satisfactory appearance quality. At the same time, the coloring ability of colorants is also very important, manufacturers should pay attention to check the quality of colorants when choosing colorants, do not use poor quality colorants.
 
Remember that the mold polishing level is specified and standardized for the mold surface and not the resin surface. The appearance of parts made in a mold can be very different for different resins. If you are considering trying out a new resin, ask your molder for samples made from the resin or a similar resin.

3. Mold Design
 
The mold also has a great influence on the appearance quality of injection molded parts. Some molds are made at a low level, and if the inner wall is not smooth enough or the dimensional design is not good enough, the appearance quality of the produced injection molded parts is definitely not satisfactory. The surface of injection molded parts made by rough mold surface will also be rough.
 
In most cases, the mold designer proposes the gate and vent locations and thus the resin flow. The goal is to select the gate and vent locations that will produce the best part, but as with other aspects of part design, gating may require compromise. Without your input, the mold designer cannot know your goals, which is why you will be asked to approve the gate and ejector layout prior to building the mold. If desired, the mold designer can use an injection molding simulation program to simulate the solidification flow of the resin.

 
4. Cross-coupling variables
 
Many problems are usually caused by a trade-off between two or more factors. Some common appearance problems and their causes are shown, as well as some ways to solve them. Sometimes solving one problem can exacerbate another.

For injection molded parts to ensure its appearance quality is a very important aspect, to achieve a very good appearance quality is a problem that every injection molding processor should pay attention to, and at the same time, as a buyer, when making purchases, it is also necessary to pay great attention to all aspects of the performance indicators of injection molded products.