Mold design refers to those who are engaged in the digital design of enterprise molds, including cavity molds and cold stamping dies, based on traditional mold design, and fully apply digital design tools to improve mold design quality and shorten mold design cycles.

Lots of software are suitable for mold design, such as UG, Pro/Engineer, AutoCAD, Cimatron, PowerMill Hypermill, Solidworks, WORKNC, Solid Edge, CATIA, etc.
For simple molds, CAD software is fast and easy to use; for molds with a messy structure and more curved surfaces, Pro-E, UG, Mastercam, Solidworks are good choices. Pro-E or UG is commonly used in drawings and production. Each software has its own characteristics. The important factor for choose is which one the mold designer is better at or prefers to use.

In the actual design process, according to the requirements of the design content, we need to consider the sequence of 2D drawing(s) or 3D drawing(s). Our mold design steps are listed as below FYR.

1.According to the customized plastic parts 2D and 3D drawings, we will organize the design data, analyze the structure, shape, and assembly dimensions of the plastic product (for example, analyze the rationality of the demolding angle during the molding process), in order to confirm whether the parameters of the injection molding equipment matches the relevant dimensions of the mold, cavity, production batch, steel requirements, etc., and then convert the data into design instructions.

2.We will determine the mold type, overall structure, mold cavity number, and layout of the cavities.

3.The parting surface will be confirmed by using 3D modeling for parting or 2D drawing for post-modeling).

4.We will decide the type of injection system, conduct Moldflow analysis, and confirm the gate form, location, and numbers.

5.To determine side core pulling structure and inclined top mechanism.

6.To confirm the mosaic structure.

7.Design of ejection and early return system.

8.Cooling and heating system design.

9.Guiding and positioning system design.

10.Selection of mold base (size of the template, cavity, core, etc.). Make the assemblies diagram of the mold base, and try to design according to the standard mold base.

1. The overall layout of the mold is reasonable
2. Parting surface selection
3. Layout of 3 runners, selection of glue inlet
4. ejection device
5. water transport arrangement
6. exhaust options
7. Pay attention to the draft angle when parting the mold, the extraction of inserts, the treatment of the rubbing angle, and the selection of material shrinkage
8. Processing drawings should be detailed, but simple.
All in all, mold design must consider the ability to demold! Easy to process and to eject!

Reasonable mold design is mainly reflected in the following four aspects.
1.The quality of the manufactured plastic products (both appearance quality and dimensional stability).
2.Convenient, fast, concise, saving money and manpower during processing and manufacturing, as well as leaving room for mold correction and improvement.
3.Safe, reliable, and easy to maintain the mold during usage.
4.In injection molding, sometimes there is a shorter molding cycle and longer service life, also a reasonable mold manufacturing process.

For mold design, the gate design is usually based on experience, and the size of the gate depends on the cross-sectional area and gate length:
1. The cross-sectional area of the gate is as small as possible, and the length of the channel is as short as possible to ensure the appearance of the finished product and reduce the pressure loss when the plastic passes.
2. The gate must be narrow to facilitate the cold formation and prevent excessive plastic from flowing back, so the gate is in the center of the runner.

For mold design, in order to obtain the best filling condition, the type of gate must be selected carefully. Common gates have the following types: sprue gate, edge gate, overlap gate, fan gate, diaphragm gate, ring gate, film gate, pin-point gate, submarine gate, tab gate, and hook gate, etc.

In-mold design, the side gate is a commonly used type, and its structure is the simplest one. It is only processed on one side of the mold. And this gate connects the runner and the finished product.
Here are several reasons for choosing an edge gate for mold design.
1.The section area is simple and easy to process.
2.The size is easy to accurately control and quickly improve.
3.When plastic is filled, the finished product is easy to control.
4.It is easily affected by the cooling and solidification of the gate and all plastics.

Fan gate is one of the gates types for mold design. And here are some advantages of this gate type for your reference.
1.It is suitable for large-scale and thin-walled plastic injection products.
2.When the resin flows into the mold, the plastic flows from the thinness and expands to form the plastic with good fluidity, reducing the flow pattern and the water trapping pattern.
3.Fan gate is appropriate for any plastic, especially PMMA, except for rigid PVC.

The requirement of the ejector system is to demould the product without deformation and accurately within the specified time. Here are 7 points to be considered for mold design.

1.The ejection stroke generally stipulates that the ejected product is 5~10mm away from the mold. For some simple cylindrical products with a large demolding slope, the stroke can be 2/3 of the product depth. Don’t be too long, because the ejector rod is very thin and has a long stroke, which is easy to damage the ejector rod.

2.The reset rod (return rod) must be set in the ejection system to help the ejector rod return. During the ejection process, the ejector backing plate bears great ejection pressure. When the strength and rigidity are insufficient, the flexible deformation affects the ejector movement. Pay attention to the screw connection (need to be screwed in from the backing plate to the fixed plate) to avoid insufficient wrench space Difficulties.

3.The relationship between the top of the ejector pin and the plane of the core (or cavity) should theoretically be on the same plane, which is convenient for mold manufacturing and assembly. In practice, most of the end surface of the ejector pin exceeds or lowers the core (or cavity) plane by 0.05~0.1mm, Negotiate with the designer to obtain the permission of the inner surface of the product with bosses and pits.

4.The shape and size of the ejector pin. Unless the shape of the product is limited, other ejector pins must be used. Generally, cylindrical ejectors are used, and elongated ejector pins with a diameter less than 3mm should be avoided.

5.Due to the large size of the ejector pin fixing plate and the backing plate, the span between the movable mold backing plate is enlarged. Under higher injection pressure, the movable mold backing plate may be deformed, causing the ejector pin to move poorly or jam In addition to increasing the thickness of the movable mold backing plate to enhance its rigidity, a support column can also be set between the movable mold fixing plate and the backing plate.

6.When the output of the product is large or the ejection stroke is long, use a thinner ejector pin, and when the ejector tube is used for ejection and the movable mold fixing plate is equipped with an elongated core, it is used to protect the ejector pin (or long core). Its movement is stable, the ejection system needs to be equipped with a guiding device, and there are positioning pins between the movable template and the seat cushion bar and the movable mold fixing plate to ensure positioning accuracy.

7.Where the product has plastic surrounding the steel part, it will be difficult to demold. This is caused by the phenomenon of “holding” the steel part due to the shrinkage stress of the plastic melt after cooling. Therefore, these places (ribs, columns) are Should be considered.

In mold design, the injection mold exhaust system is the exhaust of the cavity and the gating system, which mainly includes the air in the cavity, the air in the runner, and the steam of the moisture in the plastic at high temperature. These gases must be discharged in time to avoid affecting the quality of the plastic parts. The exhaust method in the injection mold includes the following 7 ways: ① Parting surface (including venting groove); ② Insert fitting surface; ③ Fitting surface of pushrod or push tube and inner mold insert; ④ Exhaust of side core pulling mechanism; ⑤ Adding a vent needle or insert to exhaust the trapped air; ⑥ Ventilate steel exhaust; ⑦ Exhaust valve.