Analysis of the top ten elements of high-gloss seamless injection mold design

First, the principle of high-gloss seamless injection molding

Higher temperature

Molding requires a higher temperature (generally 80 ° C -130 ° C), after the injection into the pressure holding, use cooling water to reduce the mold temperature to 60-70 ° C. The higher pressure temperature of the mold temperature is beneficial to eliminate defects such as weld lines, flow marks, and internal stress. Therefore, the mold needs to be heat treated during operation. In order to prevent heat loss, a heat insulation board is usually added on the fixed mold side.

2. The cavity surface is extremely bright (generally mirror level 2 or higher)

The products produced by Gaoguang Mould can be directly used for installation (assembly) without any surface treatment. Therefore, it has high requirements for mold steel and plastic materials.

3. Hot runner system has more hot nozzles

Each thermal nozzle must have a sealing needle and a separate air passage. It can be individually controlled by a solenoid valve and a time relay to realize time-divisional feeding, thereby achieving the purpose of controlling or even eliminating the welding mark, and the control method is complicated.

4. Heating method

The way in which the mold is heated is usually water vapor (hot water) heating and electric heating rod (tube) heating. The steam (hot water) heating method is to input steam (hot water) into the mold during the injection molding process through a specific temperature control machine, so that the mold is rapidly heated; after the injection molding, the mold is cooled by cold water to rapidly cool the mold. The electric heating method and the water heating temperature control machine are the same in principle, that is, the heat source is different, the electric heating is the secondary energy, the water heating is the three energy sources, according to the principle, the electric heating energy loss is small, the utilization rate is high, Energy saving benefits are good. Easy to use, so say: If it is a flat (face) product or electric heating method.

Second, the mold material

1. The mold material for the general requirements of the product surface is available: NK80 (Japan Datong), etc.;

2. High light requirements materials: S136H (Sweden), CEANA1 (Japan), etc.;

3. NK80 can be quenched without treatment; S136H should be quenched to 52 degrees after roughing; CEANA1 itself has 42 degrees and does not require quenching treatment (it is recommended to use this steel, as it does not affect subsequent processing or modification);

4. There is also a good choice in the German Gritz brand: CPM40/GEST80

Third, mold waterway design

1. Water channel aperture size design

The water channel adopts a hole diameter of 5-6mm; the nozzle uses 1/8 or 3/8 teeth (mold side), the other side uses 3/4 inch thread (old-fashion connection); the pipe material is made of stainless steel tube; now we change Into one out and one out, the split port is preferably made in the mold, and the interface is connected by DN25, so that the heat energy loss is small, the operation is convenient, and the interface is convenient.

2. Product design

The side of the waterway is generally 5-6mm away from the product surface; the large selection has an effect on the heating time of the mold, and the selection of the small has an influence on the strength of the mold. Parallel product surfaces of waterways must be evenly arranged (15mm equidistant distribution in the center of the original material). Thermocouples should be designed in the middle of the two waterways. The depth should be more than 50mm, and the maximum should not exceed 100mm. Each set of mold PT100 is one-fitted. To maintain its accuracy, it must be inserted into the mold cavity and fixed. Use a lead to connect to the outside of the mold and connect to the thermostat socket.

3. Mold waterway joint design

The mold waterway joint must be designed on the upper and lower side ends or the rear side end of the mold; the operation side (station side) is not allowed to have water inlet and outlet or water pipe arrangement to avoid the pipe rupture and hurt the production personnel.

4. Mold inlet and outlet nozzle design

The water inlet and outlet nozzles are designed with a splitter plate. The water-heat mold temperature control system has only one inlet and one outlet interface to reduce excessive water pipe connection and reduce unnecessary loss of heat energy; and achieve energy saving. And the outer surface of the bellows is wrapped with heat-insulating tape to maintain the heat preservation effect.

5. Mold construction holes

The construction hole of the mold (not the hole) should be blocked with the plug to ensure no leakage and leakage. The method is to block the copper first, then use the taper throat to add the high temperature resistant rubber seal; the arrangement of the high light mold to the cooling water channel is compared. Pay attention to (the hydrothermal mold channel is shared), good water channel arrangement can not only greatly improve the injection efficiency, but also play an important role in improving product quality. The water channel of the high-gloss mold should not only be uniform but also must be sufficient (to have a sufficient amount).

In this way, the mold is heated up quickly; at the same time, the long water pipe is used to directly transport the mold core out of the water without using a sealing ring, which can prevent the mold from working at a high temperature for a long time, resulting in aging of the sealing ring and reducing the maintenance cost of many molds. It is worth mentioning that the water pipe of the high-gloss mold must use a high temperature resistant material (250 ° C) bellows. High-pressure 1.6Mpa bellows to prevent bursting of water pipes under high temperature and high pressure. For round products, circular water is used; for long products, parallel water channels are used. For the products with large height difference, the water well form is adopted; for the special-shaped product, the three-dimensional water transportation method with the appearance of the product is adopted.

Fourth, mold insulation system

1. Mold core design

The mold set core or the movable mold insert shall be hollowed out on all four sides; the mold frame and the insert core shall have a certain gap (depending on the thermal expansion coefficient of the mold material, 1 mm on one side). Prevent the expansion of the mold frame to reduce the contact surface of the mold core on the mold frame, so as to minimize the loss of heat energy; the lock of the mold core and the mold frame adopts the oblique type or the like, and the front end adopts the dust resin with obvious heat insulation effect or Other materials (such as asbestos board).

2. Die frame design

The detailed structure of the mold frame and the core, the cooling water of the mold frame is very important. In order to prevent the heat energy in the mold core from being transmitted to the mold frame, a water circulation is arranged at a position close to the guide column.

3. Guide sleeve design

The moving part of the guide sleeve should be made of graphite material as far as possible or the front end of the guide post should be avoided. It is enough to ensure the length of the joint is 25mm.

Five, mold gate design

The mold gate design is designed to minimize weld lines and to facilitate venting and shear reduction. For the mold using the water heating temperature control machine, the gate size should be larger and the large gate should be used as much as possible. The gate should be shortened as much as possible without affecting the product function and molding efficiency.

1. The gate is too small

If the gate is too small, it is likely to cause defects such as insufficient filling (short shot), shrinkage depression, and weld line, and the molding shrinkage will increase.

2. The gate is too large

If the gate is too large, residual stresses may occur around the gate, resulting in deformation or cracking of the product port, and difficulty in removing the gate.

It is best to use a gate unless the flow ratio exceeds the actual limit. The flow length plot of the resin will provide the flow length of the material under certain defined forming conditions. Multiple gates often produce weld lines and weld lines. In addition to long, narrow products, the use of a single gate will ensure a more consistent material, temperature, and pressure distribution for better fit.

Six, mold exhaust

As far as possible, 10mm apart for the product, a uniform distribution of the exhaust groove, the depth is 0.15mm; the product intermediate veneer also needs the exhaust design.

Seven, the mold parting surface matching

Because the temperature of the high-gloss mold has a large drop, the veneering requirements are higher, and at the same time, the area of ​​the veneer is reduced. It is enough to have a 10mm fit around the parting surface.

Eight, heating rod (tube) high light mold design

1. There should be electric heating rods (tubes) on the upper and lower sides of the gate. The cooling water holes are generally 6mm (larger and better); the distance between the two water holes is 15-20mm; the distance between the heating rod walls and the product surface is 5mm, two The center distance between the heating rods is 20 mm; the distance between the cooling water and the heating rod wall is 6-8 mm, and it is better to intersperse with the electric heating rod if necessary.

2, the inner mold cavity water can be sealed with high temperature sealing ring or hard sealing.

3. The diameter of the heating rod is 4.92mm, and the mold is designed to be 5mm. Before assembling the heating rod, the burr of the heating rod is removed with a 5mm thimble grinding edge.

4. The mold inlet and outlet nozzles adopt the same manifold design (cooling water) as the steam heating mold, because the electric mold control system only has one inlet and one water pipeline.

Nine, Gaoguang mold requirements for products

The high-light mold has strict requirements on the product structure. The more sensitive the product is, the more sensitive it is to the light. The surface is slightly defective and will be discovered soon. Therefore, how to solve the shrinkage problem is the primary problem of high-gloss products. The thickness of the general product ribs does not exceed 0.6 mm of the thickness of the main body glue and does not shrink, or the shrinkage is small and is not easy to be found, which can be ignored. However, for high-gloss products, such requirements are far from enough. The thickness of the product ribs should be reduced to not more than 1 times the thickness of the main body glue. For the screw column, a crater-type sloping roof structure must also be used.

Ten, high light mode selection of plastic materials

At present, commonly used high-gloss plastic materials are generally ABS+PMMA and ABS+PC, PMMA, ASA, etc. As a commonly used casing material, ABS+PC products are better than HIPS in terms of impact resistance, surface gloss and hardness, so in the production of high-gloss products, high-gloss ABS materials are usually used. If weather resistance is required, the ASA can be selected and the PMMA alloy material may be selected for hardness.