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Rapid Prototyping for EPB development

Service Detail from RPWORLD

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The customer needed a few prototypes of EPB housings within 35 days, and required full-dimensional inspection, overmolding sheet metal Pin. If applying mass production, the molds’ lead time of other supplier is around 70 days. RPWORLD came up with Rapid-Tooling solution and manufacturing arrangement to deliver the high-quality parts within the required time, ensuring the smooth testing for customer’s prototypes.

 

1. The Complete Technical Proposal
Early DFM analysis
We provided the specific DFM analysis, and informed customer about potential manufacturing risks and proposals after we carefully checked their 3D and 2D drawings, compared the samples’ quality provided by customer and analyzed their functional requirements. In addition, we offered simple mold drawings to facilitate customer better understand gate, parting and top-out mode.
Simulated analysis
The top shell was made of glass fiber reinforced material. The products with this material are more prone to deformation than non-filled materials due to the inconsistency of the shrinkage rate in the vertical and flow direction and the change of fiber orientation.
 
During the T0 sample stage, it could be seen, that the deformation both happened at interface position and the welding datum plane of housing, the deformation value at datum plane as large as 1.9mm, which wouldn’t meet functional requirements. Normally there are several solutions to relieve the plastic part’s defects, weakened from A to F based on the workload and improvement effect:
 
A. Modify the design to reinforce the structure;
B. Optimize the mold gate to improve the fill pressure and fiber orientation at deformation position;
C. Make pre-deformation to increase or decrease the material at the deformed position;
D. Adjust the cooling lines to improve the cooling effect;
E. Adjust the machine to try other combinations of injection parameters;
F. Correct the deformation of jig after injection molding.
 
With overall evaluation and the simulated analysis, we decided to try Plan B—Adding a gate to interface position and sent customer the proposal, which turned out was satisfying and relieved for them. After several days work, we improved the warpage from the initial 1.9mm to 0.5mm, saving more time and cost in production tooling.
2. Rich Experience in Mold Manufacturing
Based on the drawings requirements and products application, we treated the mold as precision tooling manufacturing, and has taken every consideration into account: the hardened and anti-corrosion materials, shrinkage rate testing, mold, conversion of dimensional tolerance of inserts and 2D design, manufacturing equipment, dimensional inspection, reserving the manufacturing space for polishing, etc. The molds consist of two kinds: injection mold and sheet metal mold. The followings are the introduction of these two kinds of molds.
3. Standardized Parameter Control and Tailored Transparency Solutions
The top and bottom shells were required to be welded together by laser welding, which needs high laser transparency for top shell. However, the instability of laser transparency of the material assigned by customer is a common problem in the industry. While ensuring the laser transparency, we had to cut down glass emergence on the surface and maintain the tight tolerances. But those requirements narrowed down the molding window of the product. To address the issue, we got two solutions as the following:

a. Strict control for injection molding parameters
Referring to the parameters recommended in material datasheet, we made small-scale adjustments to meet above quality demand. In addition, injection molding parameters of each product are recorded to be referred in future repeated production.

b. Customized laser transparency testing instrument
We learned that this injection molding material is also transparent to ordinary light source, and the laser transparency can be detected indirectly through the transparency of ordinary light source. We tailored a special gauge and standardized the quality inspection procedures. Finally, the top and bottom shells inspected under the tailored inspection method and testing instrument all meet the customer’s requirements.
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