[Technical article] Sharing successful cases of mold flow analysis: Moldex3D allows ACER to manufact
Time：20240530 08:01:35 / Popularity： / Source：
Outline
Thin and light tablet computer products are current trend, plastics with glass fiber (PC+GF) and appropriate product design can maintain required rigidity of product. Most tablet computer products are decorated using an inmold roller (IMR) process. However, IMR process is prone to product defects such as ink flushing and stress marks. Therefore, Acer used design of experiments (DOE) method of Moldex3D expert analysis module to examine problems in IMR process, optimize process conditions and design.
Challenges and solutions
Main challenges faced in this case are "back cover of thin tablet computer product has ink flushing (Figure 1)", "there are obvious stress marks near gate" and "product thickness cannot exceed 0.8mm".
Figure 1: There is ink flushing on the back cover of tablet computer product.
In response to abovementioned challenges, Acer decided to use Moldex3D experimental design method to find highquality gate design and process. Benefits are as follows:
Successfully optimized gate design, reduced shear stress and solved ink flushing problem;
Thickness of product is reduced by 48%;
Product weight reduced by 40%.
In response to abovementioned challenges, Acer decided to use Moldex3D experimental design method to find highquality gate design and process. Benefits are as follows:
Successfully optimized gate design, reduced shear stress and solved ink flushing problem;
Thickness of product is reduced by 48%;
Product weight reduced by 40%.
Case study
Original product of ultrathin tablet computer in this case has partial ink flushing at gate position (Figure 2). Purpose of this case is to solve this problem. Acer found through Moldex3D that product had high shear stress (Figure 3).
Figure 2: Original gate design
Acer set up 11 sensing nodes at product gate position (Figure 3), then used Moldex3D flow analysis function to detect shear rate at each node, analysis results were compared with experimental results. It was found that shear rate at defective location of product was higher. Therefore, ink flushing problem can be corrected later based on shear rate analysis results.
Acer set up 11 sensing nodes at product gate position (Figure 3), then used Moldex3D flow analysis function to detect shear rate at each node, analysis results were compared with experimental results. It was found that shear rate at defective location of product was higher. Therefore, ink flushing problem can be corrected later based on shear rate analysis results.
Figure 3: Shear rate analysis results of original design during filling stage
In order to reduce shear stress from gate to mold cavity, Acer first designed 7 gates with different positions and sizes and conducted Moldex3D flow analysis. After comparing shear rate results, 4 more optimal designs were selected.
Then Moldex3D DOE was used to analyze four optimally designed mesh and gate types, two quality factors of "shear stress distribution" and "inlet gate injection pressure value" were set as small characteristics. Find four control factors and four levels according to Taguchi method, and analyze signaltonoise ratio (S/N Ratio) (Table 1).
In order to reduce shear stress from gate to mold cavity, Acer first designed 7 gates with different positions and sizes and conducted Moldex3D flow analysis. After comparing shear rate results, 4 more optimal designs were selected.
Then Moldex3D DOE was used to analyze four optimally designed mesh and gate types, two quality factors of "shear stress distribution" and "inlet gate injection pressure value" were set as small characteristics. Find four control factors and four levels according to Taguchi method, and analyze signaltonoise ratio (S/N Ratio) (Table 1).
Quality Factor  Characteristic  Weighting(%) 
FillingSheer rate distribution 1/sec  The Smaller the Better  50% 
Sprue injection pressure value / Mpa  The Smaller the Better  50% 
Order & Control Factor  Level 1  Level 2  Level 3  Level 4 
Mesh  A1  D3  E2  F2 
Melt Temp.(℃)  290  300  310  320 
Mold Temp.(℃)  45  50  55  60 
Max. Flow rateprofile value (%)  20  25  30  35 
Table 1: DOE analysis results of quality factors and control factors
According to analysis results in Figures 4 and 5, signaltonoise ratio shows that material temperature and flow rate are main controlling factors that affect ink flushing phenomenon.
Filling Shear rate distribution (Mpa)
According to analysis results in Figures 4 and 5, signaltonoise ratio shows that material temperature and flow rate are main controlling factors that affect ink flushing phenomenon.
Filling Shear rate distribution (Mpa)
Control Factor  A. Mesh  B. Melt Temp.  C. Mold Temp.  D. Max Flow rate 
1  2.23945  0 3266  1.223  4.0065 
2  5.45684  2.29562  2.13897  2.98867 
3  1.5981  2.73937  3.00874  5.51633 
4  2.72897  4.11881  4.90261  4.32866 
B/N Ratio  7.05494  4.44546  6 12558  9.52283 
Factor Response Plot
Figure 4: Signal zz noise ratio of shear stress distribution during filling stage
Spure injection pressure value (Mpa)
Spure injection pressure value (Mpa)
Control Factor  A. Mesh  B. Melt Temp.  C. Mold Temp.  D. Max Flow rate 
1  38.199  40.437  38.521  38.121 
2  38.648  38.998  38.401  38.073 
3  38.073  37.516  38.177  38.345 
4  38.216  36.185  38.038  38.598 
B/N Ratio  0.57522  4.25226  0.48371  0.52553 
Factor Response Plot
Figure 5: Signaltonoise ratio of inlet injection pressure value during filling stage
Moldex3D expert analysis module also provides highquality process conditions (Figure 6). After comparing the worst and best groups, Acer found that the worst group had a significantly steeper shear rate curve at gate edge, while the best group had a fairly flat curve (Figure 7). Acer then changed gate design and remanufactured product based on this analysis result, successfully solving the ink flushing problem (Figure 8).
Moldex3D expert analysis module also provides highquality process conditions (Figure 6). After comparing the worst and best groups, Acer found that the worst group had a significantly steeper shear rate curve at gate edge, while the best group had a fairly flat curve (Figure 7). Acer then changed gate design and remanufactured product based on this analysis result, successfully solving the ink flushing problem (Figure 8).
A. Mesh 

C. Mold Temp. 

Shear Stress(Mpa)  Sprue Injection Pressure value (Mpa)  
Worst Run  F1  300  50  25  2.40365  87.3878 
Best Fun  D3  320  60  30  0.432175  65.6163 
Figure 6: Comparison of best and worst groups
Figure 7: Shear rate curves for the best and worst groups
Figure 8: After optimization of product, ink flushing problem has been greatly improved.
Result
Virtual mold trial function provided by Moldex3D can help Acer quickly find highquality mold designs in a short period of time, and enable processes that were previously considered to produce failed products to produce qualified products. Thickness of lower cover of original tablet computer was 1.3~1.55mm. After optimization to 0.8~0.95mm, weight of product can be reduced by 24%~40%; thickness of product has been reduced by 26.9%~48.4%. This achievement has brought intuitive economic benefits to Acer and also enhanced industrial competitiveness.
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