1. Design purpose of injection molding cooling waterway
Waterway design purpose:
Purpose of waterway design is to cool product evenly and eject it into shape in a short time. Quality of waterway arrangement directly affects molding quality and production cycle (cost) of product.
·Impact on quality: Water channels are used to control mold temperature during molding, mold temperature and its fluctuations have an impact on shrinkage deformation, dimensional stability, mechanical strength, stress cracking and surface quality of product. Main appearance is: surface finish, residual stress, crystallinity, thermal bending.
·Influence on production cycle: A molding cycle is mainly divided into following parts. Shortening cooling time is to improve molding efficiency.

 

2. Mold cooling system:

 

3. Relationship between cooling system water hole diameter spacing and mold cavity

 

Cooling water circuit layout
1) Cooling water circuit should be set to make cooling effect uniform; close to the place with more heat; away from the place with less heat.

 

2) Shengdu water channel standard: straight through on both sides, single-side loop is not allowed,

 

Note: 1. Length of water circuit cannot be too long: temperature change of coolant from inlet to outlet of water pipe should be within 5°; more precise products should be controlled within 3”.
2. Large molds with more water circuits should indicate INOUT and it is best to use a water distributor.
1. Water well cooling
a. Fountain

 

Parallel water path features
Advantages: Suitable for cooling around inlet; high flow rate can be achieved under low pressure
Disadvantages: Different flow rates of each branch, different cooling effects of each branch, easy to silt and clog.
b. Partition plate

 

c. Spiral baffle
Features of spiral baffle
1. Efficient cooling = improved production efficiency
Since it can make cooling water rotate and flow to increase contact between cooling water and mold core, it has higher cooling efficiency than conventional baffles.
Because it is made of plastic, it will not cause cooling hole to be blocked due to rust.
2. Easy to assemble and adjust - shorten working time
With conventional baffles, it is difficult to insert baffle when upper and lower cooling holes are misaligned. Since spiral baffle adopts a split type, assembly operation is simple, and cooling water can flow smoothly even if upper and lower cooling holes are slightly misaligned. (See right picture)
It can be cut and easily adjusted to length and front shape by aligning with cooling hole. However, it contains glass fiber and is difficult to break. (Tensile strength is about 490N/mm2){50kgf/mm2})
·When removing baffle, scale attached to cooling hole can be removed at the same time.

 

2. High thermal conductivity material embedded cooling

 

3. Spiral insert cooling water channel

 

Single spiral insert cooling water channel is suitable for some relatively large round inserts without holes in the middle.

 

Double spiral insert cooling water channel is suitable for some relatively large round inserts with holes in the middle.
4. Water connection of different inserts
Applicable to molds with large parts area, small mold core thickness, and mold core that is not integral (trouble to arrange water wells)

 

5. Lifter cooling

 

When lifter is large, cooling water channel cannot be ignored. Absence of cooling water channels will extend injection cycle or cause lifter molding to deform during demolding.
6. Slider cooling

 

Cooling water channels are required not only on slider, but also on slider insert if necessary.
7. Special style of cooling circuit

 

1. Cooling and warping deformation

 

2. Cooling optimization example 1

 

Cooling optimization example 1---Optimization process

 

3. Cooling optimization example 2

 

Cooling optimization example 2---Optimization process

 

1. Water temperature heating: Mold temperature requirements below 80°:
Most plastic raw materials (except high-temperature materials) require mold molding temperature: 20°~90°. If surface finish of parts is required to be high, or mold structure makes molding difficult, a water temperature machine must be used for heating.

 

Note: 1. Select hoses according to cooling water temperature:
2. These hoses are dedicated to cooling water (not applicable to oil);
3. General water temperature machine is set at 70~80°. If it is higher than 80 degrees, there are safety hazards.
2. Oil temperature heating: Mold temperature requirement is 90~150°.
After adding glass fiber GF to PP, PC, nylon (PA66, PA6, PA46), POM, etc., mold temperature is required to reach 120° and can be controlled by an oil temperature machine; molding temperature of PET and PPS is 130~150°, and must be controlled by an oil temperature machine.

 

Note: High-temperature mold water circuits require high-temperature special joints, water stoppers (throat plugs) and other accessories.
3. Heating rods and thermocouples: PET, PPS and other materials have high crystallization temperatures (130~150°). Heating rods and thermocouples must be used to ensure rapid heating and flexible temperature control of mold.

 

4. Heat insulation board: prevent excessive heat dissipation from mold to ensure constant cavity temperature, thereby ensuring stable quality of molded products.
For crystalline resins such as nylon, PBT, and PET, changes in surface temperature of mold cavity have a great impact on crystallinity, size, appearance quality of parts, and heat insulation boards need to be installed.

 

Note: 1. When processing heat insulation board, use a dust collector to absorb dust (containing glass fiber, which will irritate skin and cause itching: adhering to machine will affect accuracy):
2. It is easy to break when processing with a drill bit, so be careful when processing (customized processing is available);
3. It is not suitable for thread processing and 3D processing.
5. Comprehensive application of heating equipment