transparent plastic parts injection moud design points

Transparent plastic parts injection mould design

Transparent plastic parts injection mould design overview:

Design points of injection mold require verification to ensure the surface quality of the product. At The YuanCheng Mold, we injection molded a range of products, including items such as household products mould, industrial products mould, and home appliance mould for one of the leading companies in the injection mould industry. A customer had reached out to us hoping that we could provide a solution to their problem. Which is about the Design points of injection mold for transparent plastic parts. 

Figure 1 Transparent Plastic Parts Injection Moud Design Points

Transparent plastic parts injection mould design


Transparent plastic parts injection mold necessary to adjust the mold temperature, injection pressure, and injection speed in order to achieve a high-quality surface. During injection molding, fine adjustments to process parameters such as degree are made so that the mold cavity can be filled quickly. This will ensure that the product won’t be deformed and cracked by internal stresses. 

The most common transparent plastics are polymethyl methacrylate (commonly known as acrylic), polycarbonate (codenamed PC), AS, and PS.

Figure 2 Acrylic

Transparent plastic parts materials

Transparent plastic parts injection mould design:

Analysis of plastic parts

Figure 3 Analysis Plastic Parts

As shown in Figure 1, the transparent panel is part of the electronic sphygmomanometer. An edge of the plastic part has a small boss with a thickness of 1mm, two arc gaps, and two round holes. The smaller end has a small boss with a thickness of 1mm. One side of the product has two arc gaps, and the product measures 55.07mm x 43.01mm. Silkscreen boundary lines appear on the plastic parts’ fronts. Although the rectangular hole has a silkscreen, the entire area is screen printed. It is made of PMMA plastic. PMMA’s transparency leads to high light transmission, but poor fluidity.

When injection molding is not done properly, stress builds up inside the product. This stress is difficult to detect during injection molding, but it can damage during screen printing.

Key points of mold design

1. Find out how many mold cavities are needed for the product dimensions and thickness

In order to balance the flow channel, a hole is cut in the transparent panel. The number of cavities that can be opened depends on the mold cavity volume. However, more than four cavities make the mold difficult to adjust, and defects increase.

2. To leave the plastic part in the movable mold, the parting surface is generally selected along the edge of the plastic part. Check whether the parting surface of the plastic part has a small R at the parting slope, and check the demoulding slope of the edge.

3. Picking the right injection point is crucial. 

PMMA injection molds should have an S-shaped runner with a cavity for cold material. You can adjust airlines and glue lines easily. As the gate is located at the big end of the plastic part, glue lines are the least noticeable. Unlike transparent molds, PC molds need thick, short runners. The runner should be polished brightly and have a trapezoidal shape.

4. The design of the exhaust position. 

For transparent lenses with thimble marks, an auxiliary flow channel is needed. It also serves as an exhaust channel. The general rule is to provide exhaust where corners are excessive.  Choosing the steel correctly and selecting it for the application, then polishing it after it has been finished, will result in a wonderful result.

5. For plastic parts ejection, transparent thimbles are generally not allowed. At each gate position, a thimble is designed, and a pin is added to the small boss on the small end of the plastic part, and the plastic deforms smoothly under the pins’ ejection.

6. Separate cooling systems are designed for front and rear molds to ensure injection parameters are adjusted. Reverse pulls cannot be designed for cold slug wells facing the main channels. Transparent parts cannot be made with cold slug wells with inverted buckles.

7. It is best to use a mechanical button machine to open the mold for transparent products made with three-plate molds to prevent rubber powder from entering the cavity.

8. The nozzle must be flushed on a manual punch when the batch is large enough to be sheared. A pair of electric heating pliers can also be used to cut small batches of water outlets.

Transparent plastic parts injection mould design-Result

Based on the results of the mold trial, there is no doubt that the design of the mold is reasonable and fully meets the requirements of transparent plastic products. The transparent mold can be used as a reference when designing transparent molds in the future.

Related reading: China plastic injection mould maker

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