Multi-way pipe joint products are shown in Figure 1. Products are divided into two types: AB. Maximum dimension of A is 137.5 mm * 76.30 mm * 129.00 mm, average thickness of plastic parts is 2.00 mm, material of plastic parts is PP, and shrinkage rate is 1.013 , weight of plastic parts is 64.50 grams. Maximum external dimension of B is 145.0 mm * 47.30 mm * 92.00 mm, average thickness of plastic parts is 2.00 mm, and weight of plastic parts is 51.50 grams. Technical requirements for plastic parts are that there shall be no defects such as peaks, underfilling, flow lines, pores, warpage deformation, silver lines, cold materials, and spray lines.

 

A product

 

Product B
Figure 1 Multi-way pipe joint diagram

 

Figure 2 Mold Design Ranking Diagram

 

Figure 3 Combination diagram of rear die slider
As can be seen from Figure 1, plastic part A is a complex six-way pipe joint, one of which is threaded on outer diameter of edge of mouth, and the other is inclined. Plastic part B is a three-way pipe joint, and inner hole core pulling distance is longer. Difficulties in the design of multi-pass pipe joint molds are as follows: 1. Direction of mold opening, that is, analysis of both sides of movable and fixed molds of plastic part, and analysis of which side slider is facing. 2. Determination of cylinder core-pulling and inclined guide column core-pulling. 3. Combination analysis of slider in inner hole, that is, neutron junction cannot hinder neutron movement, neutron junction can not have a drape, neutron cannot be bent and deformed under pressure of injection.
In this set of molds, analysis of mold opening direction of plastic parts is the key. For plastic part A, orient slanted joint towards movable die, as shown in Figure 2. For plastic part B, turn cruciate position toward movable mold and maximum core pulling direction toward outside. Mold design cavity ranking is 1+1, mold base is a standard mold base 4060, and gating system is a latent gate.

 

Figure 4 Analysis of mold ranking
According to structure of plastic parts, mold opening direction is determined and ranking is done. Slider core pulling of this set of molds adopts hydraulic cylinder core pulling. In the mold of multi-pass pipe fittings, it is often necessary to do a good job of the two neutrons in inner hole when inner hole is cored. Generally speaking, when core-pulling distance exceeds 70, oil cylinder must be used for core-pulling. If inclined guide post is used for core pulling, strength and rigidity of inclined guide post are insufficient, length of inclined guide post is too long and protrudes out of mold. Another reason is that core pulling of oil cylinder is convenient to control timing of core pulling, so that neutrons touching each other can well seal glue.
Precautions for cylinder core pulling are as follows;
1. Do a good job of guiding slider. Guide post and guide sleeve can usually be designed to guide piston rod and increase rigidity. It can also be used as a guide on the bead, such as this set of molds.
2. For connection of oil cylinder, piston rod of oil cylinder cannot be directly connected to slider. Instead, screw a ring on the head of piston rod. Snap ring into T-slot at the end of slider.
3. Confirmation of cylinder core pulling stroke. It is usually necessary to design a travel switch at the initial two positions of stroke to control operation of cylinder.
4. Selection of cylinder size. To design core pulling of cylinder, it is necessary to confirm that piston rod exerts pressure in rod cavity or in rodless cavity. If necessary, it needs to be selected by calculation.
5. For some molds, it is necessary to analyze whether cylinder is pushed out or retracted. That is, slider core-pulling action required for mold core-pulling.
6. When cylinder is cored, molding cycle of mold will be affected, so it needs to be confirmed by customer.
7. When designing mold for core pulling of oil cylinder, oil pipe needs to be properly fixed to prevent action of mold from being affected. If mold operation balance is required, oil collector is designed to uniformly enter and exit oil inlet and outlet joints.
8. When cylinder is cored, oil temperature needs to be kept stable. Cylinder core pulling should be used with caution in high temperature molds.
9. When cylinder is core-pulled, shovel base must be used to lock cylinder. Core-pulling of particularly small holes can be unlocked and locked by power of oil cylinder itself.