Improve LSR injection molding mold temperature and warpage with special-shaped oil circuit and mold

Time：2023-09-16 20:08:10 / Popularity： / Source：

Due to rapid development of 3D printing technology, designers can use 3D metal printing to design more in line with requirements of oil circuit, which can be close to contour of product when designing, so as to solve dead angle and heat accumulation of product. The more complex geometric shape of product will be more obvious, and this type of waterway design is usually called Conformal Cooling.
Using 3D metal printing to make heating oil circuit will effectively reduce heating time and evenly give mold heat. Reduction of heating time can shorten the entire production cycle and increase production efficiency; evenly giving mold heat can make temperature distribution in mold more even, so as to avoid warping. Therefore, heating oil circuit is made by 3D metal printing to effectively improve above two points, thereby achieve purpose of reducing heating time and improving product quality.
This study uses oil as heating fluid for products of same size under different piping designs, different conditions and parameter settings. After observing product through oil heating and maturing, compare different oil circuit designs, maturation speed, temperature change and volume shrinkage rate after maturation to find optimal tubing design.

Research purposes

In injection molding process, cooling time often accounts for more than half of molding cycle. However, traditional water routing is often difficult to close to geometric shape of product due to its processing method, it is easy to cause product to accumulate heat in mold cavity, resulting in uneven cooling temperature distribution of product, therefore prone to warping. In order to reduce cooling time and reduce warpage, designer uses 3D metal printing to design a waterway that meets requirements to solve dead angle and heat accumulation of product.
This study uses CAE mold flow analysis software to analyze use of oil as a heating fluid under different pipeline designs, observe products after being heated and matured by oil, compare different oil circuit designs, maturation speed, temperature changes and body shrinkage changes after maturation to find optimal tubing design.

Research methods & direction

Compared with special-shaped waterway, traditional waterway is difficult to get close to product geometry, so temperature distribution of traditional waterway will be poor, so its volume shrinkage rate will also be poor. Same problem is also reflected in degree of maturation. This study mainly discusses configuration of different pipelines, compares their respective maturation degree and volume shrinkage rate of product, and finds a suitable plan from it.

Model geometry

Research items of model geometry can be subdivided into "product geometry", "material analysis", "oil circuit design", and "parameter setting".
• Product geometry: Name of product part is "half-round spherical shell", diameter of spherical shell is 20cm, and thickness is 8mm. Product size is shown in Figure 1. Mesh type is Moldex3D-Mesh, and its total mesh number is 396169. Mesh model of product is shown in Figure 2.

Figure 1: Product size drawing

Figure 2: Finished mesh model diagram
•Material analysis: LSR2070 material is selected for Moldex3D material analysis.
•Oil circuit design: This study compares conversion rate of finished product at different times with traditional oil circuit and special-shaped oil circuit. Figure 3 and Figure 4 show design of special-shaped oil circuit.

Figure 3: External special-shaped oil circuit

Figure 4: Internal special-shaped oil circuit
• Parameter setting: In order to detect conversion rate of traditional oil circuit and special-shaped oil circuit, compare according to parameters in Table 1.

Spherical shell	Temperature	Flow	Coolant
Traditional oil circuit	150℃	120cm3/sec	Oil
Traditional oil circuit	175℃	120cm3/sec	Oil
Traditional oil circuit	200℃	120cm3/sec	Oil
Double spiral oil circuit	150℃	120cm3/sec	Oil
Double spiral oil circuit	175℃	120cm3/sec	Oil
Double spiral oil circuit	200℃	120cm3/sec	Oil

Table 1: Parameter setting of heating oil circuit

Results and discussion

From Figure 5 and Figure 6, we can clearly know that cold runner in mold can ensure that liquid silicone is in injection molding process, avoiding high mold temperature and causing gate to solidify, at the same time, we can understand temperature distribution of traditional oil circuit and special-shaped oil circuit mold. .

Figure 5: Temperature distribution of traditional oil circuit mold

Figure 6: Temperature distribution of special-shaped oil circuit mold

Finished product conversion rate distribution

Figure 7, Figure 8, Figure 9 are conversion rate distribution diagrams of special-shaped oil circuit. From the three pictures, it can be known that from oil temperature, as temperature increases, conversion rate of finished product is better.

Figure 7: Temperature distribution of finished product curing time 40 seconds

Figure 8: Temperature distribution of finished product aging time of 50 seconds

Figure 9: Temperature distribution of finished product curing time of 60 seconds

Conversion rate distribution of traditional oil circuit and special-shaped oil circuit

According to distribution of conversion rate of traditional oil circuit and special-shaped oil circuit in Fig. 10, Fig. 11, and Fig. 12, it can be seen from numerical value that conversion rate of special-shaped oil circuit is relatively higher than that of traditional oil circuit.

Figure 10: 150℃ conversion rate curve

Figure 11: Conversion rate curve at 175℃

Figure 12: Conversion rate curve at 200℃

Temperature Distribution

Table 2, Table 3, and Table 4 show respective cooling temperature distributions of different oil circuits at same oil pipe temperature. From perspective of temperature difference and standard deviation, the smaller value, the more even temperature distribution, and the better temperature uniformity.

Spherical shell	Temperature range (℃)	Temperature difference (℃)	Standard deviation
Traditional oil circuit	140.007℃-145.571℃	6.492℃	1.305
Double spiral oil circuit	145.129℃-147.201℃	2.072℃	0.308

Table 2: Temperature distribution of oil pipe temperature at 150 degrees

Spherical shell	Temperature range (℃)	Temperature difference (℃)	Standard deviation
Traditional oil circuit	162.948℃-169.440℃	6.492℃	1.475
Double spiral oil circuit	169.171℃-171.591℃	2.42℃	0.370

Table 3: Temperature distribution of oil pipe temperature of 175 degrees

Spherical shell	Temperature range (℃)	Temperature difference (℃)	Standard deviation
Traditional oil circuit	186.574℃-193.689℃	7.115℃	1.726
Double spiral oil circuit	193.214℃-195.969℃	2.755℃	0.437

Table 4: Temperature distribution of oil pipe temperature at 200 degrees

Volume shrinkage

Displays percentage of volume change from cooling under high temperature and high pressure to normal temperature and pressure. A positive value represents volume shrinkage, while a negative value represents volume expansion that may be caused by excessive holding pressure. Figure 13 shows distribution of volume shrinkage of two waterway configurations. Table 5, Table 6, and Table 7 show distribution of volume shrinkage of different oil circuits at same oil pipe temperature. From point of view of standard deviation and difference, the smaller standard deviation, the more uniform volume shrinkage rate, uneven volume shrinkage rate distribution will cause warpage and demoulding deformation of plastic part.

Figure 13: Distribution of volume shrinkage rate

Spherical shell	Volume shrinkage rate (%)	Difference (%)	Standard deviation
Traditional oil circuit	6.752%-7.126%	0.374%	0.074
Double spiral oil circuit	6.448%-6.675%	0.227%	0.054

Picture table 5: Volume shrinkage distribution of tubing temperature 150 degrees

Spherical shell	Volume shrinkage rate (%)	Difference (%)	Standard deviation
Traditional oil circuit	7.782%-8.259%	0.477%	0.106
Double spiral oil circuit	7.999%-8.345%	0.346%	0.086

Picture table 6: Volume shrinkage distribution of tubing temperature of 175 degrees

Spherical shell	Volume shrinkage rate (%)	Difference (%)	Standard deviation
Traditional oil circuit	8.841%-9.367%	0.526%	0.123
Double spiral oil circuit	9.055-9.453%	0.398%	0.099

Picture table 7: Volume shrinkage distribution of tubing temperature at 200 degrees

In conclusion

Through this experiment, following three conclusions have been drawn, which are described as follows:
•By Moldex3D analysis and simulation of special-shaped oil circuit compared with traditional oil circuit, it can be known that contact area of special-shaped oil circuit is larger, so heat conduction effect is better.
• Higher oil temperature can increase maturation rate of molded product and reduce product production cycle.
•According to analysis results, it can be known that under same oil temperature, special-shaped oil circuit can evenly conduct heat energy to molded product, maturation distribution is more uniform, and volume shrinkage rate is small. ■
This article was co-authored by Professor Zeng Shichang, Liao Jianhe and Lin Yuqi, and was translated by Gud Mould Industrial Limited.

Gud Mould Industry Co., Ltd