Several techniques of plastic mold design


Plastic mold design standard, universal plastic design form, super complete. In the design, the design of the gate is particularly important. In order to simplify our design, we often need to summarize some common standard forms. When you use it, you can call it directly. Here are some common gate types and numerical requirements, specifications, I hope to help everyone.

1.Direct gate

This gate directly enters the product surface, there will be traces where the product enters the glue, and the gate needs to be removed later. Everyone is familiar with the phrase “Mould is the mother of industry”. The importance of molds is increasingly recognized by people, and mold design and mold manufacturing technology have also made great progress.
The innovation of mold processing technology, the wide application of various new mold materials, and the standardization and specialization of mold parts have forced us to adapt to the development of mold faster and more.
The speed increase requires that the design section can be completed to the post section in about 3 days: improve accuracy; in the design process, the processing methods of each part should be considered, and the cost of high-precision and low-processing processing methods should be used as much as possible.
The increase in accuracy and speed is consistent. The increase in speed inevitably requires an increase in precision, and the increase in precision inevitably leads to an increase in speed.
The main flow path refers to the cross section from the injection nozzle nozzle to the mold contact portion to the branch flow path.

2. Design considerations

  • (1). The shape of the end face of the main channel is usually round.
  • (2). In order to facilitate demoulding, the main road is generally made of slope, but if the main passage passes multiple planks at the same time, you must pay attention to the slope of the opening and the size of each opening.
  • (3). The design of the mainstream flow channel size should be based on the flow characteristics of the plastic material.
  • (4). Most mainstream road designs are conical. (As shown), note:
    a. Small head diameter d2 = d1 + (0.5 ~ 1mm)
    b. Small end ball radius r2 = r1 + (1 ~ 2mm)
    (Where d1 and r1 are the injection outlet diameter of the injection machine and the sphere radius of the injection head, respectively)

3. Gate cover

Because the main channel contacts and collides with the high-temperature plastic and the nozzle, the main channel portion of the mold is usually designed as a removable replacement bushing, called a casting sleeve or gate bushing.

(1). Its main functions are:

  • a. When the mold is installed, it is easy to enter the positioning hole, the nozzle of the injection molding machine is well positioned on the injection molding machine, can withstand the back pressure of the plastic, and will not be extruded from the mold.
  • b. As the mainstream of the pouring system, the plastic in the barrel is transferred to the mold to ensure that the flow reaches the cavity forcefully and smoothly. There should be no plastic overflow during the injection process, and it is convenient to prevent the main liquid flow. Aggregate W.

(2) The structural form is integral split

  • Integral: the shoulder is combined with the main body of the main road
  • Split type: the shoulder is made separately from the main body
  • Japanese Industrial Standard: JIS
  • China Industrial Standard: SJB

(3)Split flow channel:

Definition: a section between the main road and the gate. It is the transitional section of molten plastic flowing into the cavity from the main channel. By changing the cross-sectional area and plastic turning, the plasticity can be transformed smoothly, which is the transition section of the pouring system.

(4)Sectional design

  • a. The overall design part is round
  • b. Generally speaking, u-shaped, v-shaped, trapezoidal and regular hexagonal shapes are designed from the perspective of convenient processing.
  • c. The cross-sectional shape and size of the flow channel should be determined according to the molding volume of the plastic part, the wall thickness of the plastic part, the shape of the plastic part, the process characteristics of the plastic used, the injection speed, and the length of the flow channel. Endoplasmic factors.

The layout of the runner is balanced feed and unbalanced feed. The balanced feed is to ensure that the feed port feeds at the same time. Unbalanced feeding means that the feeding ports cannot be fed at the same time, usually evaluated by the mold flow analysis method.

(5). door

1. Definition: Gate is also called inlet or inner runner. It is the narrow part between the runner and the plastic part, also known as the shortest part of the pouring system;

2. Function: Accelerate the flow speed of molten plastic conveyed by the flow channel, forming an ideal flow state and flow sequence. It can also quickly fill the cavity, and by closing the cavity to prevent the melt from flowing back, it is easy to separate the gate from the plastic part after molding

Gate form:

  •  Inner door
  • Ordinary side door (side door)
  • Exterior doors
  • Fan gate: commonly used to form large-width sheet plastic parts
  • Flat seam gate
  • Ear muffs
  • Gap gate
  • General point gate

The lurking door (most people in our company use this method)

  • Ring gate
  • Spoke door
  • Claw gate
  • Garden Gate

4. Gate position selection

  • (1) Select the gate closest to the barrier.
  • (2) The size and position of the gate should be selected to avoid spraying and crawling.
  • (3) The gate should be opened at the thickest part of the plastic part.
  • (4) The location of the gate should be selected so that the plastic flow is the shortest and the flow direction is the smallest.
  • (5) The choice of gate location should be conducive to the discharge of gas in the cavity.
  • (6) The choice of gate location should reduce or avoid the weld of plastic parts to increase the welding firmness.
  • (7) The gate position should be selected to prevent the water flow from deforming the cavity, core and insert.
Plastic Mold
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