outstanding mold surface quality can have positive affact on the molded parts
by Lushi-Molding  | September 21th. 2019  |  Tags: Injection Tool, Plastic Injection Molding

The Impact of Mold Surface Finish on the molded parts

When it comes to injection molded parts manufacturing, the mold surface finish is an essential thing to consider if you want to deliver a quality and precise result. Before designing a mold surface, the most important factors to consider are the actual customer stipulated dimensional tolerance, as well as the material to be used for the mold creation.

To get the desired performance of plastic molded parts accurately, you need to consider some impacts of Mold surface finish as bellow:

Mold Surface finish affects Material Flow

The Injected materials are expected to get to every part of the cavity when injected into mold, but if the surface finish is not adequately designed to allow this material fill in the space, then it is evident that there would either be deformation in the molded parts or deficient filling pressure.

However, these could be prevented by first simulating the mold filling with the help of MoldFlow, to know if the mold surface design will produce the desired output. In most cases, this is done by just entering in the preferred mold parameter like dimensions, undercuts, thickness variations, as well as the draft angles in the MoldFlow software.

molfflow can simulate the material flowing in the cavity of injection tool

Substandard Mold Surface finish causes Splay

Splays are silver stripes marked on the surface of molded parts, after the mold has been released. This happens as a result of tiny gas bubbles that are also pressured along with the elements as it enters the cavity image. As these materials are heated before being shot into the mold, they produce wet substances that when shot it together into the mold, create these little bubbles around the surface of the injected material. In substandard surface finishing, these bubbles coagulate at the surface will create the silver streaks to damage the quality of the molded part.

However, there are varied ways to curb this situation as it could significantly affect the appearance of product and as well adversely affect the scheduled cost of production. Therefore, a proper mold surface finish needs an effective dryer to ensure that this moisture is appropriately expelled from the surface of the molded part before cooling. Besides having a vent in the mold surface finish is the best way to release gas bubble off the surface of the cavity of a mold to reduce the splays. This can be also solved by simulation the vent design.

Impacting on the ejection

Presently, most high-performance of the thermoplastics needs a quality surface finish to molding efficiently. After molding, the ejection mold supposed to release after the clamping unit quickly. However, with a faulty or substandard mold surface finishes, this will be difficult to puff the parts out. To prevent this from happening, primarily if it would be used on materials that have higher tendencies of sticking to the mold, and this is where the addition of textures is necessary to loosen the surface further as it might occur in high-quality molds too.

tooling steel have big affact on the surface quality of parts

How to achieve an excellent mold surface finish

Achieving an excellent mold surface finish even high gloss is important to get an accurate and precise molded part and is one factor that must be taken seriously in the molding process. Below are a few ways to attain an excellent mold surface finish.

Mechanical Polishing

This is a manual polishing process where welds and contaminants are smoothened off the mold surface through the process of grinding, buffing and polishing. It is used to polish mold surface to a preferred level of roughness with the using materials like sandpaper or oil stone strips. Presently this machining process will be taken by robotic to save time and expensive manpower.

High-quality manual grinding

High-quality manual grinding is used to achieve high precision on surface finishing. Manual grinders make use of stationary magnetic chucks under the grinding wheel, which rotates horizontally, and then the head is lower unto the mold surface. As the head frictionally rubs on the mold in a make and forth movement, excess materials, weld paths and spiral grind marks are rubbed off the surface, resulting in a highly efficient mold surface finish.

Nevertheless, there are many factors that influence the quality of the molded part, it is obvious that surface quality is one of the most important factors for excellent molding in the efficient injection molding process. What needs to be considered in the design of the injection mold and in the production process.


More Infos Please Contact Us:

Email: jonas@lushimold.com
Jonas Zhan
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Blog Tags:

Injection Molding Tool

Plastic Injection Molding

Molding Technology

Mold Design

Injection Molding Process

Additive Manufacturing

Plastic Materials

Industrial applications

Chinese Tooling

Industry 4.0


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