Making plastic molds – how important is the process of polishing molds?

Plastic mold manufacturing is the need of many manufacturing enterprises. Plastic products increasingly occupy an important position in production and consumption. The plastic mold manufacturing process consists of many stages, in which the mold polishing part is an important stage that determines the gloss and smoothness of the plastic product surface.

What technique does polishing in plastic mold fabrication require?Plastic mold fabrication - mold polishing stage

– General requirements:

  • The face surface is treated satisfactorily, ensuring the quality of the product when using the mold in accordance with the customer's requirements.
  • Know the factors that affect the mold polishing: the technique of polishing each type of mold, steel quality, heat smelting.
  • Dust-free plastic mold polishing environment. The space is as clean as possible.
  • Use the right polishing tool, the right type of chemical with every detail, part in the mold.

– Separate requirements:

  • Ensure the surface tolerance requirement according to the original mold design drawing.
  • Pay attention to the parts and details of plastic molds used for optical plastic products. The surface needs to be polished requires high accuracy, high technique with the finished product is a glossy surface like a mirror, spotless.

3 stages in the process of polishing plastic molds

Stereotypical polishing is a long process. However, it can be summarized in the three stages below:

  • Rough grinding stage.

After CNC machining is completed, the surface of the face may have many scratches, ripples. Rough grinding will help the surface flatter, the polishing process then also happens faster. This stage uses high-rough materials for grinding.

  • The grinding phase.

The surface of the face after rough grinding has been relatively flat. Only scratches are left caused by the rough grinding process. Refined grinding uses grinding paper and diamond powder measuring 15 to 25 microns. The surface is finely sharpened.

  • Polishing phase.

In the final polishing stage or also known as surface finishing, there will be many different methods for polishing depending on the shape of your mold. However, the final gloss should be achieved of this mold surface finishing process should usually be at 6-3 microns (almost mirror) for the mold to reach the highest quality.

6 polishing methods in plastic mold fabrication

Stereotypical polishing now has the support of polishing tools such as polishing machines. However, it must depend on the type of mold and size to choose the right method. Make polishing plastic molds simpler and faster.
Previously, polishing plastic presses was classified into 3 methods:
  • Polished entirely by machine
  • Polishing combined machine and craft
  • Polishing is completely manual.
Plastic mold fabrication - mold polishing stage
Machine mold polishing for high gloss

Currently, many mold polishing technologies are developed. Grading methods are classified including:

Mechanical Polishing

This method is equivalent to manual polishing. Use items such as grinding stones, sandpaper, wool wheels, turntables …

This method depends quite largely on the skill of the polisher. Long polishing time leads to low polishing productivity. The quality is also uneven because it depends on the experience and technique of the polisher. For highly complex stereotypes, it is not appropriate.

Chemical polishing

Hearing about chemistry, we immediately thought of using chemicals in mold polishing. In this way of polishing, chemical solutions are corrosive substances. Use them to erode the gaping part of the surface of the face. After abrasion, the roughness at the general surface of the mold is 10μm.

Although the gloss is not as high as manual, but it is suitable for products with complex shapes, a variety of different types of molded embryos. The usage is also simple should be applied quite a lot in the mold.

Electrolylyted Polishing

This is a popular and easy-to-operate metal polishing model. Electrolyzing is an electrochemical process. Dissolve the rough part on the surface to form a bright and glossy plane.

This method has the advantage of superiority over the above two pattern polishing methods. Not only in terms of product quality, but also reduced processing time, saving human labor.

Ultrasonic Polishing

Ultrasonic Wave Tool Washing Machine Breed

The workpiece is soaked in abrasive solution and placed in the same ultrasonic field. For ultrasonic oscillations, abrasives conduct grinding and polishing on the surface of the workpiece. Small ultrasonic machining forces will not cause embryo deformation, but having limitations in the manufacture and installation of tools is difficult.

Ultrasonic polishing can be combined with chemical or electrolyzed methods. The corrosive and electrolytic solution then the solution is stirred and ultrasonic vibration is applied causing the dissolved substance on the surface of the mold workpiece to leave.

Polished with liquid

You've probably heard the phrase "Water flows." In this case, that's what it is. Based on the speed of the flow erodes the excess positions on the surface of the face.

Magnetic polishing

This is a polishing method using a magnetic polishing machine. Use magnet-generated magnet magnets to move polishing instruments on the surface of the face. High efficiency, quality achieves roughness of 0.1μm. Suitable for polishing plastic press molds.

Tools and supplies used to polish molds

Depending on the mold requirements, the process of each manufacturer, the quality of the workers' workmanship, the practical experience that each mold manufacturer will use different ways as well as materials for polishing differently. However, in general, the following materials, materials, tools and machines are widely used in the field of stereotypical polishing.

Precision polishing tools – grinding

1 Steel Dung – Diamond Dung

Like nail polish, the tincing used in mold polishing is used to grind the excess metal. Used in rough grinding.

Designed in a variety of shapes to polish a variety of contact locations, the use of courage can control hardness and roughness directly.

Making plastic molds - polishing molds with steel cans

2 Ceramic Bars

English ceramic is ceramic. In mold manufacturing, ceramic is a grinding stone, used to grind steel molds. Small grinding stone rods are suitable for grinding at hard-to-grind positions.

Ceramic is a hard, durable material. Can be used in manual mold polishing or shared with polishers.

Plastic mold fabrication - polishing tools

Some other common mold polishing tools such as:

  • Wooden sticks, polished softwood cotton with many different shapes.
  • Mold Polishing Broom
  • Soft paper
  • Whetstone
  • Neglecting to hit the ball…

Each instrument has its own advantages and disadvantages, depending on the polishing position requirements to choose from. The ultimate goal is to get the mold polished perfectly.

Types of polished supplies

1 Polished Diamond Powder

Polished diamond powder is the highest quality polishing material today. With its large hardness characteristics, the highest cutting capacity of diamonds, it is the first choice of mold manufacturing companies.

You may not know: Diamond powder is used to polish the diamonds themselves.

In mold production, polished diamond powder can give a mirror-like gloss or may be better at the size of particles of 1-3 microns. The size of ordinary nuts uses between 1 micron and 160 microns.

Plastic mold fabrication - mold polished diamond powder
Diamond powder is stored in cylinders for ease of use

In terms of rules, just using diamond powder to polish is enough. However, if so, the price will be very high. Therefore, mold manufacturing companies will use support solutions to save money. In addition, the solution also helps to increase the ability to cut and clean the mold after polishing. Thanks to this solution, using diamond powder can be cheaper than other polishing materials.

2 Other powders

In addition to diamond powder, there are also many other materials used to polish molds. However, the gloss is not compared to when using diamond powder and the polishing time is longer. But these materials are cheaper. Suitable for use for molds that do not require high gloss.

For example, alloys of aluminum oxide, silicate.

The machines used to polish molds

1 Mold Polishing Machine

Mold polishing machines are often designed in the form of vibration, can be attached to other mold polishing tools such as Wood, Fabric, Shake … to help the polish faster, save labor costs.

Mold shake polishers have adjustable speed, many different designs to serve different types of molds.

2 Mold welding machine:

After a period of use, it will not be inevitable that the case of cracking, … Then the mold welding machine is more effective equipment than reworking another mold.


Coming to VCC Molds, you can be completely assured of the mold quality, mold design service as well as the price that we offer.

Vietnam Capacity Precision Mold Joint Stock Company

Address: Lot B2-3-3b, Nam Thang Long Industrial Park, Thu Phuong, Bac Tu Liem, Bac Tu Liem, Hanoi

Phone: (+84)24 6687 8283


Hotline/Zalo: 0934683166


Google map: