Quality of temperature control system design has a great impact on molding cycle and product molding quality of mold, which is especially important for automobile door panel injection molds with high appearance requirements. One of design principles of cooling water channel is that distance from cavity surface should be roughly equal to achieve a roughly balanced temperature in all parts of mold cavity. Temperature control system of this mold adopts a combination of "straight-through water pipe + inclined water pipe + water well", as shown in figure below. This combination is to give priority to use of straight-through water pipes, supplemented by inclined water pipes, and only use water wells as a last resort. Its advantages are uniform cooling of plastic parts, short molding cycle, high molding quality, it is suitable for molds with high requirements and high appearance performance.

 

Design key points of cooling water channel of automobile injection molds are as follows:
(1) Fixed and movable molds need to be fully cooled. Heat is concentrated in straight top, lifter, slider, hot nozzle areas, and they need to be cooled intensively. However, cooling water channel must be kept at least 10mm away from ejector pin, straight top, and lifter holes.
(2) Spacing between water channels is 50-60mm, distance between water channels and cavity surface is 25-28mm.
(3) If cooling water channel can be made into a straight hole, do not make an inclined hole. Inclined holes with an inclination of less than 3 degrees should be directly changed to straight holes.
(4) Length of cooling water channel should not differ too much to ensure that mold temperature is roughly balanced.
(5) Cooling area should be at least 60% of projected area of plastic part. (excluding areas outside plastic part).
(6) Principle of priority for conformal cooling water: cooling water of fixed and movable molds should be designed to conform to shape as much as possible. Distance between water channel and glue surface is 25-28mm. When some areas of plastic part cannot be drilled to carry out conformal water transportation, appropriate water wells can be drilled for uniform cooling. Distance between water well and glue surface is 25-28mm; diameter of water well is Ø24mm; considering problem of processing deviation, cooling water channel of this mold is kept at least 10mm away from push rod, lifter and other holes.
(7) Principle of similar length: Length of cooling water channel is roughly equal, ensuring that temperature difference between cooling water inlet and outlet is roughly equal, thereby ensuring that mold temperature is roughly balanced. Large lifter, large straight top and four sliders of this mold are all designed with cooling water, thereby ensuring molding quality of plastic parts. For cooling water on lifter and straight top of car dashboard, it is preferred to design it to be disassembled from parting surface to facilitate assembly work of fitter.
(8) Water pipe joint of mold must not be installed in code groove to avoid interference with code screw.
(9) Try not to use offset connection method for water holes. It is difficult to clean iron filings. In addition, if the offset is too much, water flow will be reduced.
(10) Sufficient cooling should be designed for the runner and runner insert, glue inlet, and hot nozzle area. When designing mold, flow of cooling water and thermoplasticity should be balanced, and temperature difference of plastic part during demolding should be less than or equal to 10 degrees under working conditions.
(11) Layout of water channels requires that grid of water channels should be well balanced and arranged as much as possible according to shape of plastic part.
(12) Water channels should preferably be internally connected. For thermoplastics, water channels must be internally connected. In narrow conditions or when internal connection is not possible, external connection can be considered. If plastic part has deformation defects, water channels should be adjusted and optimized to avoid deformation.
(13) Water channel design must ensure uniform cooling of plastic part, especially for automotive interior and exterior trims. Water channel design must be evenly spaced, ensuring that a group of cooling water is designed between 50-60mm to ensure sufficient cooling of plastic part. If there is interference with other components, water channel spacing should also be roughly same.
(14) For areas where plastic part temperature is high and difficult to cool, such as inserts and hot nozzles, a separate group of water channels should be designed.
(15) Uniformity of cooling system: Considering wall thickness of product, thick wall should be cooled more to prevent deformation after shrinkage. Considering complexity of product, cavity with high and low undulations should be cooled more. Gate of product has high heat and needs to be cooled more.
(16) 3-meter principle: The total length of cooling water channel (serial length) should not be too long. It is best to be within 1.5-2 meters. Considering deep hole drilling processing, maximum length of large automobile bumper molds cannot exceed 3 meters. Dead water level length should be as short as possible and controlled within 20mm.
(17) Cooling water channel should avoid weld mark position and thin-walled area of product as much as possible to avoid affecting weld strength of product and avoiding injection defects.
(18) Under no circumstances should water channel pass through hot nozzle fixing hole to prevent poor sealing from damaging hot runner. Cross-sectional flow amplitude of water channel should not fluctuate.

∅D = water channel diameter. Small molds have diameters of 6/8/10/12mm, medium- and large molds have diameters of 12/15mm, and bumper molds can reach 19mm.
K1 = distance from water channel to product edge. Small molds have diameters of 12-15mm, and medium- and large molds have diameters of 20-25mm.
Water channel should be designed to cover 85-90% of product area, maximizing coverage. Minimum distance between water channel and each standard component should be 5-10mm. Each hot nozzle should be cooled in a group to ensure adequate cooling around hot nozzle.

 

Method 1 is the most commonly used. Hole is directly drilled using a deep-hole drill, then plugged with a 2mm thick copper baffle. However, it's important to avoid excessive clearance between baffle and hole, otherwise desired effect won't be achieved.
Method 2 is spiral drain. This is commonly used for circular molds, sprue bushing cooling, and other applications. This method offers the best and fastest results. Inner side is a standard plastic part.

 

Method three uses a fountain-style waterway, using standard components or steel pipes on inside. This method is typically used for narrow, sloping roofs with a single waterway inlet and outlet.
Method four utilizes a cooling rod. We typically use standard flow fittings or beryllium copper rods, connecting waterway to cooling rod to achieve desired cooling effect.

 

First, let's look at hole in Figure 1. For this type of hole, we should use Standard Part 2, which features a sealing ring and provides excellent water blocking. Looking at Figure 2, H represents required plug depth. Each plug has a specific height, so when selecting, we must ensure sufficient thread depth. In this case, we use Standard Part 1. Standard Part 3 cannot be used in either Figure 1 or Figure 2.

 

Water hole in Figure 3 is relatively deep, but needs to be isolated. To do this, we can use HASC0 standard plug (standard part 4). This expandable plug requires specialized tools for tightening, providing excellent water isolation and pressure resistance.
Lower right image shows a waterway connection block. This method can be used when space for waterway connections is limited. It can be used on any surface of mold, providing great flexibility.

 

Faucets in image above represent commonly used standards. If no specific requirements are met, a quick-connect faucet is generally chosen. DME standard is currently the most widely used by some domestic OEMs. For international clients like DME, HASCO, and STAUBLI, countersunk holes are generally required, with only a few clients opting for them. Importantly, ensure a minimum spacing of 35mm between faucets.

 

Manifolds pictured above are the most common. The first type is machined directly from 45# material. Some customers require separate inlet and outlet ports, with separate nozzles. The second type is a standard part and is currently the most commonly used. Made of stainless aluminum, it's affordable and highly practical. Third type is STAUBLI manifold, which is typically ordered upon customer request and is more expensive.