Optimizing Scanner Components' Design Before Injection Molding

Scanner covers are usually comprised of grid structures that have very small features (as shown in Figure 1). This is poses a challenge during the injection molding process as it can easily create weld line and short shot problems. To save on tooling and design modifications, it is thus important that manufacturers have a better understanding of a product's moldability during the early design stages. Furthermore, the gear of the scanner requires precise dimensional requirements in order to function as well as a good surface finish (e.g. gate area) during the manufacturing process.

Moldex3D enables early analyses of various molding defects and offers optimized molding performance.

The scanner cover with grid structure and tiny features is challenging during injection molding.

Figure 1. A scanner cover with grid structure and minute features presents certain issues during the injection molding process.

Challenges

  • To optimize mold design and scanner gear parts to meet dimensional specifications
  • To assess potential short shots in scanner covers with a different gating design

Solutions

Moldex3D's Filling analysis is used to assess flow imbalance and potential short shot problems, while also utilizing packing and cooling analyses to accurately determine the impact of over-packing and part shrinkage.

Benefits

  • Identifying the cause of dimensional inaccuracies, enhanced part-shrinkages and heat accumulation issues
  • Identify potential short shots early in the manufacturing process

Case Study

A recent study carried out by Foxlink sought to evaluate whether modifying the gating designs could help in resolving short shot issues caused by small features in a grid structure. This research also aimed to predict the final dimensions of a molded scanner gear and identify any major issues relating to design modifications.

Initially, a Moldex3D simulation was used to assess two gating designs for the scanner cover (Figure 2, from the center area or grid structure). The simulation found similar short shots in both cases, thus prompting the designer to mold the component parts individually (Figure 3).

The short shot issues on different gating design are evaluated through the flow front result in Moldex3D Filling analysis.

Figure 2. Short shot issues on different gating designs were evaluated using flow front results from Moldex3D's filling analysis.

It shows short shot risk no matter which gating design was applied, hence, it was suggested to mold as two separated parts.

Figure 3. Short shot risks occurred regardless of which gating design was applied. Thus, a decision was made to mold as two separated parts.

As there is no possible solution to solve the short shot problem, Foxlink decided to mold the scanner cover components individually.

In the case of the scanner gear, the simulation results revealed over-packing and flow imbalance issues, which led to part deformation and a failure to meet dimensional criteria (Figure 4). Foxlink thus recommended three design modifications to enhance part deformation (Figure 5).

The difference of the upper and lower part (Ø X and Ø Y) of the scanner gear has to meet required dimension criteria.

Figure 4. The difference between the upper and lower part (Ø X and Ø Y) of the scanner gear must meet required dimensional specifications.

Three different revised designs were proposed to improve the part deformation of the scanner gear.

Figure 5. Three different revised designs were proposed to improve the part deformation of the scanner gear.

After confirming the original design and modified designs using Moldex3D Filling/Packing/Cooling processes, Foxlink found that parting face shift, gating relocation, and part design change on local thickness were needed to effectively overcome the over-packing and flow imbalance issue on the molded scanner gear and lead to significantly enhanced dimensions after deformation. The actual molding results revealed that Type C can enhance filling pressure, lead to less packing pressure losses, enhance heat accumulation, and irregular part shrinkage.

The actual molding results showed that, between the lower and upper part of the gear opening (Ø X and Ø Y), the difference shrunk by 0.03 mm. This met the design criteria and matched up with the prediction made by the simulation. (Figure 6).

The packing and part deformation simulation results of the revised designs.

Figure 6. The packing and part deformation simulation results of the revised designs.

Results

Moldex3D can help achieve tooling at a low cost, while offering early analyses of molding defects, such as sink marks, short shots, warpage, and air traps. Other benefits include saving considerable amounts on production costs and mitigating risks prior to actual production.

This information has been sourced, reviewed and adapted from materials provided by Moldex3D.

For more information on this source, please visit Moldex3D.

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