Because plastic products have a variety of useful characteristics, there is a great demand for plastic products in modern world. One of the most popular methods of manufacturing plastic products is through injection molding process. In order to produce desired shape, a mold is required.
Focus of this article is molding of electrical enclosure connectors. Composition material is polybutylene terephthalate filled with 30% glass fiber. Ordinary molding is sufficient to produce  this device. For a better understanding, we conducted the first part of research and design.
Before manufacturing tools, conceptual design is required, because manufacturing requires design and drawings as references. Taking into account physical and thermal characteristics of material, mold flow analysis can better understand precise parameters required for mold design, such as good gate positions, runner cross-sections, etc.
Tool design starts from extracting core cavity and cavity, then designing other elements. Software used for design is NX.11, and software used for analysis is NX Easy Fill Advanced. Tool design should be economical, accurate and designed according to machine specifications. Therefore, tools should produce accurate products for required production and tool life.

Plastic is one of the most widely used materials in countless applications. They are versatile, lightweight and durable. There are several processes for converting plastic raw materials into final products. The most famous and widely used process is injection molding. Raw material plastic is melted in injection molding machine and then injected into mold through gate. Then it cools and solidifies, finally finished product is ejected. Equipment used to mold and mold device is called an injection mold. Process cycle of injection molding mainly includes four stages-melting, injection molding, cooling and injection molding.
In melting stage, mold is closed, plastic particles in hopper are gravity fed into heated barrel and rotating screw. Particles are caused by high pressure, friction and temperature. Injection is stage of forcibly injecting molten plastic into mold cavity through a rotating screw. Maintain pressure throughout process until material is fully filled and cooled. Next step is cooling of device, which is usually achieved through a cooling circuit in mold. Water circulates in these circuits to cure device and maintain mold temperature. As screw retreats, final ejection stage occurs when mold is opened, ejection mechanism pushes device out of mold. When mold is closed for next cycle, this will complete a complete cycle.

As number of electrical and electronic products increases, electronics industry is exponentially increasing demand for manufactured devices. Circuit consists of many devices, including wires and cables. A connector is a device that serves as an interface connecting two circuits. Male connector is called a plug and female connector is called a socket. Connector has a housing and a terminal, wherein housing for stability is made of plastic material, and terminal is made of conductive material. This article focuses on injection mold design and verification of housing connector socket. Device is made of 30% glass filled polybutylene terephthalate, with black masterbatch added to produce corresponding color composition. According to customer’ requirements, regrind can reach 25%.
Material properties of polybutylene terephthalate 30% GF:

 

This model was studied from 2D drawings. Device has ten contact cavities, a pin protector and two guide column cavities at diagonal end. It has four fins on socket side to improve stability and strength. 3D model was completed using NX11.0 software. Unless any draft is not mentioned in  drawing, draft must be placed vertically so that it can be easily ejected from mold and avoid jams. Key issues involved in this device include ten contact cavities and pin protectors.

 

Figure 4.1: Connector core side

 

Figure 4.2: Connector cavity side

 

Figure 4.3: Time before melting

 

Figure 4.4: Average temperature

Mold flow analysis is a simulation of plastic material flow, which helps to evaluate device, parameters and mold design to produce high-quality devices. Analysis can give results such as filling time, cooling time, flow pressure, etc., and can indicate defects such as weld position, air pockets, short circuits, burn marks, etc. Reducing solder joints in device is one of the important ones because these defects in critical areas may cause failures. Welding line is a V-shaped notch, which is caused by poor adhesion area close to surface, and shrinks due to extremely high molecular orientation caused at the end of filling.

 

Figure 4.5: Welding line
Using flow analysis software, the best gate location can also be determined. Arrow shows approximate location of door. Here, software is used to determine gate location so that it can completely fill device and avoid defects as much as possible. We have conducted several experiments and placed gate position in different positions to achieve position that provides the best results.
Test 1:

 

Figure 4.6: Device fill time running 1

 

Figure 4.7: Device welding line operation 1
In the first trial, gate location is given on the top surface of device. It can be seen from results that device is not completely filled and a large number of welds in critical area may cause device to fail. Therefore, gate position will be moved to the other side of device and simulation operation is completed.
Test 2:

 

Figure 4.8: Device fill time running 2

 

Figure 4.9: Device welding line operation 2
In second test, gate position is given on the side of device. It can be seen from results that complete filling can be achieved by reducing number of welds. Therefore, this location is considered the best gate location and has been implemented in design.

When designing device tools, please note following:
Number of cavities: 4
Gate type: tunnel / buried gate
Tool type: 2 discs
Ejection system: top pin
We also need to consider other factors, such as design appearance, production orders, shrinkage, material usage, etc. Fixed part and moving part of mold are separated at parting line. After studying device, the most suitable is plane division.
The first step after designing a device is to extract core cavity cavity of a single device and then multiply it by four cavities. Extraction can also be done using layers and surface modeling in NX11.0 software. It is important to extract main plug-in and 10 contact plug-ins separately. This is due to high output and high accuracy. Contact insert is manufactured separately and has a shoulder in main insert. These cavity inserts exist on both the cavity and core cavity sides. Size of contact inserts is very critical. If they are broken or worn, only a specific insert can be easily replaced, not entire insert.
Next step is design of device feeding system. Feed system is composed of gates, runners, sub-runners and gates. Plastic material first flows through sprue bushing from nozzle to core cavity and cavity, then fills runner and gate.
Door:
Gate is channel through which molten plastic flows from runner to device cavity. Size of gate is usually smaller than runner, allowing plastic to flow under high pressure. This avoids formation of welds, short fills and other defects. There are various types of gates, such as sprue, edge, ring, buried wire, fan, precise positioning, etc.
Type of gate depends on various factors. Gate should not be located in area with device function. This is because gate cut from device leaves certification mark. Similarly, size of certification mark depends on type and size of gate. Client specifies before design whether he does not want to place gate certification marks on the area. Then determine type of gate based on production speed and size allowed by certification. Then flow analysis and defect analysis to determine the best gate location, type and size.
We used Submarine gate in this mold. This is to avoid extra degumming work, automatic degumming system can be incorporated into two-plate mold. Gate starts with a runner with a larger diameter, and then contacts device at an angle between 30 and 60 degrees to decrease. Compared with other gate types, certification mark left is also smaller.
Gate size can be determined by gate calculation or experience. However, opening size of door is considered from the smallest point of view, if there are any defects, it can be increased later.

 

Picture 4.10: Buried wire gate

In an injection mold, there are usually two halves, fixed half contains cavity insert, and movable half contains core cavity insert. Since ejection system is located on core side, devices should be stuck on same side. Use NX11.0 software to extract core cavity, and extract ten contact cavities respectively.

 

Figure 4.11: Core cavity and half cavity

 

Figure 4.12: Half cavity

A mechanism is always needed to push device out of mold. This is called eject system. Demoulding can be done in many ways, such as pin demolding, sleeve demolding, plate demolding, air demolding, etc. For this type of mold, a common type of mold is used, that is, pin demolding. This is to force device out through round steel rod of ejector pin. Pin faces head and facilitates insertion into ejector plate supported by ejector rear plate. Ejector pin slides in mold plate with a good sliding fit.

We have designed a complete tool device. Elements such as locating ring, sprue bushing, guide post, guide bushing and sprue puller are designed according to available standard shapes and sizes, which can guide elements for easy movement and precise guidance. Z-runner puller is used to keep cast blank in core cavity of mold during mold opening process. There is a REST button between rear panel and bottom panel of eject button to leave a gap between them to avoid clogging caused by dust or other particles.

 

Figure 4.13: Complete tool assembly

This article has completed tool design and analysis of 10 drawer type housing connectors in NX 11.0 software.
Manufacture a complete injection mold according to design, set parameters according to given conditions. Manufacturing various mold components such as top plate, bottom plate, core cavity inserts, ejection plates, guide posts and bushings. Some standard devices are purchased from market. It is necessary to test mold and check whether device is defective. If there are any defects due to mold, please make minor corrections and check.