In order to ensure the mold and the injection machine designed for the owner have a good match, and the relevant data between the two must be checked, and the mold and the model of the injection machine can be designed accordingly.

The areas to be checked for data are: injection volume, injection pressure, clamping force, mounting size, mold opening stroke, and ejection device. (Specially designed designers should take it seriously)

1. Injection volume check

Whether the mold cavity can be filled with the maximum amount of injection allowed by the injection machine. If the finished product is partially deficient, the most likely cause is the insufficient injection volume. Therefore, when designing the mold, it should be ensured that the total amount of melt required by the mold is within the range of the actual maximum injection volume of the injection machine. 80% of the rated injection volume of the injection machine, so there are: nm1+m2≦80%m

M1---the mass or volume of a single finished product

M2---the quality or volume of plastic required for the gating system

m --- maximum injection volume allowed by the injection machine (g or cm3)

n --- number of cavities

Note: n is related to the plasticizing rate of the injection machine, the maximum injection volume and clamping force, the precision of the finished product, the economics of production, etc. Generally speaking, the size accuracy of the finished product is 4%~8% lower for each additional cavity. The higher the cost of the mold. For example: gears or blades can only be designed with a maximum of 1*2.

2. Injection pressure check

This is to verify whether the maximum injection pressure of the injection machine can meet the needs of molding the plastic part. The injection pressure required for the finished product is determined by factors such as the type of injection machine, the form of the nozzle, the fluidity of the plastic, the flow of the casting system and the flow of the cavity. Insufficient injection pressure will actually form a short shot.

Generally speaking, whether the injection pressure is full or not can be controlled by the adjustment personnel. It cannot be adjusted to be too large, so that the pressure at the gate or the strength of the mold is not damaged or the mold cannot be divided.

3. Clamping force check

When injection molding, the projected area of the plastic part on the mold parting surface is the main factor affecting the clamping force, and the clamping force is proportional to the projection surface. If the clamping force provided by the injection molding machine is not enough, the clamping force will be The mold parting surface is not tightly closed, and the cutting and inserting are not sufficient, so that the burr or the flashing phenomenon is directly formed. The tonnage model of the injection molding machine is determined by the clamping force, and the formula for quickly calculating the tonnage required for the clamping force of the injection molding machine is:

F1=(n A1+A2) P

A1---Maximum projected area of finished product, total length * total width Unit: cm2

A2---Projection area of the gating system Unit: cm2

P --- Pressure coefficient (high pressure: 0.75 tons / cm 2 general pressure: 0.5 tons / cm2)

F1---Resin pressure Unit: ton

F1≦80% F F---Clamping force of injection molding machine

4. The installation size check

In order to ensure the smooth installation of the mold, it is very important to check the installation size. In this part, the designer often neglects the problem of over-reliance on the computer operation. As a result, the mold cannot be tested on time.

4.1 Nozzle size:

Between the aperture dn of the nozzle and the aperture dp of the sprue bushing, and between the convex spherical radius Rn of the nozzle and the radius Rp of the bushing surface, the following relationship must be satisfied.

Dp=dn+1.0mm, dn, Rn value, please refer to the specific injection machine data

Rp=Rn+1.0mm

The effective length of the injection of the nozzle (the length that can be extended into the mold) and the mold (especially the hot runner system), the sinking depth of the sprue bushing should be well matched to prevent the nozzle head from being able to abut the bushing

4.2 Positioning ring size:

The purpose of the positioning ring is to ensure that the center line of the mold can be overlapped with the nozzle and the center rod of the injection machine after the mold is installed, so that the injection molding must be carried out smoothly. A certain gap is used between the positioning circle dH and the center hole dj of the injection setting plate: dj=dh+(0~0.2mm). The positioning ring has a thickness of 10mm and contact with the center of the pallet.

4.3 Mold thickness:

Mold thickness H (also known as closing height) must meet: Hmin < H<Hmax

Hmin---the minimum opening distance between the moving and fixed pallets

Hmax---Maximum mold thickness allowed by the injection machine

The thickness of the clamping die of the machine is a range, and its value can be adjusted.

4.4 Molding and fixed dimensions of the mold:

The mold is placed between the columns of the injection machine on the injection machine. The safety relationship between the total width Wm of all the molds and the total width Wj between the columns is:

Wm≦Wj-50mm

If the Wm value of the mold is affected by Wj and there is no larger model to choose from, you can try to change the "work" model into a straight mold design.

There are two common forms of fixing molds:

One is to fix with a screw (when the plate is in the form of a screw hole in a fixed position);

The other is fixed by screws, pressure plate (or automatic pressure plate) (the tray is in the form of “T” groove). When fixing with the pressure plate, it must be ensured that the difference between the front and rear plate clamping edges is less than 5mm, so as to be easy to use. The same type of pressure plate.

4.5 Checking the mold opening stroke:

The mold opening stroke refers to the distance that the movable mold fixing plate moves during the opening and closing of the mold, and its size directly affects the height of the finished product that can be formed by the mold. If it is too small, the finished product cannot be taken out.

Simple method of weighing: When the opening stroke of the injection machine is less than 2 times the total height of the finished casting system, the finished product is difficult to take out. In actual calculation, the safety margin of the finished product should be 30~50mm. Suitable for robotic movement, and the mold opening stroke is independent of mold thickness

4.6 Checking the ejector device:

2.4.6.1 Verify the position of the KO hole opened on the mold according to the specific machine, and whether the hole diameter is matched with it.

2.4.6.2 Verify that the ejection distance of the injection machine can meet the needs of the mold ejection action, especially in the secondary ejection mold structure, the ejection amount is insufficient, or the length of the plunger is not enough. Supporting columns on two ejector plates

2.4.6.3 In the ejector mechanism of the forced return, verify whether the mold screw is matched with the screw hole of the top of the injection ram