Edited by Earl Wang, Engineer at Technical Support Team, Moldex3D

Summary

In this project, the engineers at the Dongguan WISE Plastic Products were tasked with improving the part flatness of a drawer slide part. The main function of the drawer slide part is to ensure the smooth opening and closing action of the drawer. Therefore, the manufacturing of the part can be challenging with strict flatness specifications. In addition, the wear-resistant POM material used in this project tends to have high shrinkage rates, which must also be taken into consideration. Moldex3D allowed WISE Plastic Products to evaluate important factors and considerations affecting the part flatness prior to actual manufacturing. This helped them save time and cost and successfully achieved mass production.

Challenges

• Strict flatness specification
• To improve part warpage
• To shorten cycle times

Solutions

WISE Plastic Products engineers used Moldex3D to evaluate and determine suitable gate and cooling channel designs. With the help of Moldex3D Pack analysis, the engineers were able to identify the dominant cause of warpage, which is uneven shrinkage. The engineers also used Moldex3D Cool analysis to investigate the effect of uneven cooling on part warpage and estimate the mold cycle time. Finally, the engineers used Warp analysis to examine the amount of displacement in the X, Y, and Z directions and achieved optimal design proposal to reduce the part warpage.

Benefits

• Saves time and revision costs
• Reduced mold cycle time by 55%
• Reduced X-direction displacement by 300%

Case Study

The most important parts of drawers are drawer slides. The main function of the slides is to guide the drawers to slide smoothly. It requires high precision for the slide size and any deformation is not tolerable. The key factor to achieve accuracy of the part is to make the part shrink evenly in every area during the molding process.

In this case, WISE utilized Moldex3D Professional solution to simulate the molding scenario of the original design with the traditional injection molding method (Fig. 1). In the warpage analysis results, the deformation was very close to the real part, in which high deformation was observed (Fig. 2). To solve this issue, WISE needed to find the factors of deformation. Through Moldex3D, they found that the temperature difference between the two sides of the slide was large. It caused a larger shrinkage rate inside than outside and finally caused the deformation (Fig. 3). In addition, in the original design there were three gates but the flow rate was low in the two sides. It led to an unbalanced flow.

Fig. 1 The original design using traditional injection molding method to simulate the process	Fig.2 Original design with deformation issues

Fig. 3 According to the cooling analysis of the original design, when the part reached ejection temperature,
heat was accumulated in the thick-wall area, where high volume shrinkage was observed.

In order to solve these issues, WISE changed the design from three gates to one gate. This change not only solved unbalanced flow in one part but also eliminated the weld line caused by three gates (Fig. 4). Moreover, WISE also changed the part design by making the thickness of the two sides of the slides more even (Fig. 5) so that the two sides will cool down simultaneously.

 Fig. 4 Weld lines were observed in the original design (left). After changing the gate design, the weld line issue was solved (right).

Fig. 5 The thickness of the two sides was revised and made even.

However, the deformation in Z direction was not only caused by uneven shrinkage but also uneven cooling. Considering that improving the deformation in Z direction needed to revise the whole design including the mold and cooling system, WISE decided to compensate the deformation in the Z direction.

Lastly, WISE conducted a series of optimization experiments through Moldex3D. In comparison to the original design, the volume of the optimal design has been reduced by 50% on the runner volume. The warpage in X direction was lowered by more than 300%. Through the compensation in the Z direction, it hardly caused deformation (Fig. 5, 6). The cycle time in whole injection molding was also decreased by 55%.

Fig. 6 Moldex3D simulation analysis accurately predicted the deformation in the X direction

Fig. 7 After revision and verification, the deformation was resolved and the real product was closed to the simulation result.

Results

Through Moldex3D analysis, WISE could clearly identify the factors of deformation and further revise and verify the product quality. Thus, they were able to shorten the development time and successfully manufacture more reliable products.