Mold design

Mold Design Definitive Guide

In order to let more people understand the process of mold design and its importance, Ecomolding will share the design experience and process of the mold industry, so that everyone can have a deeper understanding of mold design to promote the follow-up project.

Chapter 1: What are Mold Design?

Chapter 2: What are the considerations for Mold Design?

Chapter 3:The example of Mold Design process?

What are mold design?

Mold design is basic but important part in injection molding, regardless of the size and position of the gate, the size of the shear edge, flow assist, cooling and ejector technology, all affect the final mold injection results . It is no exaggeration to say that mold design has a significant impact on the cost-effectiveness and quality of molded parts and your products.

The mold design is started with a 2d layout, basic information will be draw out, such as mold size, gating type, parting line, ejection way, cavities layout, mechanical design, accessories used, steel of each component used, etc.

3D design in details and NC programming will follow after the 2d design is approved by the customer. Depends on the complexity, a complete mold design would need 3-7 days. Some of the complex molds require mold flow analysis or several updates as per feedback from customer, it could take much more time.

mold design

There are many other design issues that must be considered in the design of the molds. Firstly, the mold must allow the molten plastic to flow easily into all of the cavities. Equally important is the removal of the solidified part from the mold, so a draft angle must be applied to the mold walls.

The design of the mold must also accommodate any complex features on the part, such as undercuts or threads, which will require additional mold pieces. Most of these devices slide into the part cavity through the side of the mold, and are therefore known as slides, or side-actions.

The most common type of side-action is a side-core which enables an external undercut to be molded. Other devices enter through the end of the mold along the parting direction, such as internal core lifters, which can form an internal undercut. To mold threads into the part, an unscrewing device is needed, which can rotate out of the mold after the threads have been formed.


Building a high-quality mold is the core focus of Eco molding.We have 10 highly experienced mold designers, who have significant experience in resin characteristics, and mold structure.

Before we start a design, Our designer will run a Mold Flow Analysis, This analysis is reviewed by the designer, together with tool shop and injection molding shop. This avoids potential manufacturing issue and provides an opportunity for troubleshooting.

The collaboration of our departments provides a strong guarantee that Eco molding can provide high-quality mold in a short lead time.

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What are the considerations for mold design?

Currently, the plastic injection mold industry is faced with fierce competition. The mold cost and injection molding price has become a topic of great concern to every mold maker. Plastic injection mold manufacturers must consider how to lower the cost while ensuring a high efficiency in the mold design process. How can we achieve this target? When designing a plastic injection mold, the following factors need to be taken into consideration:

  1. Injection Molding Cost

Determine product arrangement and the number of cavities according to the size of the machine and the cost of each shot. The larger the number of products ejected, the lower the injection molding cost, because in the plastic injection molding process, the cost is calculated by the number of shots.

  1. Product Appearance

Determine the parting surface according to the appearance requirements of a product. The location of the parting surface has to facilitate mold processing, venting and mold release, etc. The more cavities, the more likely for appearance problems to occur.

  1. Gate Type

Determine the shape, size and venting orientation of the sprue and runners. Hot runner molds cost a lot but save on runner material. Each type has its own advantages and disadvantages, depending on how the user decides.

  1. Mold Release

Determine the ejection method and the placement of ejector pins. The more the ejection pins, the higher the mold cost.

Plastic injection mold design also involves the considerations on product shrinkage and injection time, as well as determination of cooling / heating method and the placement of the cooling channel. In addition, consider the service life of the mold, determine the hardness, thickness, size and processing difficulty of the mold material, and identify the splitting of the molding parts and the shape of the wire cutting structure. As long as all the above steps are integrated, with more comprehensive analysis and considerations made, the cost can be effectively saved.

The example of mold design process?

PRJ02_PROTO_BODY 2-Plate Direct gate 1X1 ABS/PC 1.005

1.Define the parting line, avoid the parting line affect the appearance of product.

2.Decide the gate type and gate position

3.Decide the ejector position

4.Thickness analysis, find where sink mark will occur

5.Draft angle analysis. if the draft angle is too small, it is easy to cause scratch.

6.Design lifter and sliders to release the undercuts if needed

7.Complete mold assembly drawing

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