Processing analysis and mold design of low⁃pressure injection molding of trim panel on front A⁃pillar of automobiles

doi:10.19491/j.issn.1001-9278.2025.04.018

Abstract

Abstract:

In view of the complicated structure of the trim panel on the front A⁃pillar of a car with many internal reinforcement bars， inverted buckle features， snap seats and support structure base， and other structures， and the exterior surface needs to be covered with fabrics. In this case， a low⁃pressure injection overmolding process is adopted， and a pair of one⁃mold and a two⁃cavity valve hot runner low⁃pressure injection overmolding inverted molds were designed. Owing to the low⁃pressure injection overmolding， the hot runner could not feed the glue from the cavity side. Therefore， a direct gate was opened on the B⁃side （the core side） of the molded part， and the Moldex 3D mold flow analysis software was used to verify the reasonableness of the pouring system and analyze the possible defects in the molding process. For the inverted feature， a “spring+slider” side core extraction mechanism was adopted. The “inclined top bar+inclined top block” and “cylinder+slider” mechanisms were adopted for the support structure base and snap seat structures， respectively. The “oblique top bar+oblique top block” and “oil cylinder+slider” mechanisms were designed for the support structure base and snap seat structures， respectively， and used for lateral core extraction and demolding. The ejector mechanism was driven by an oil cylinder to eject the molded parts by the “straight top block+straight top bar+ejector pin” mechanism together with other components. Before the mold starts to work， it is necessary to lay the fabric flat on the one side of the cavity at first and then close the mold and injection molding. When the mold is opened， the lateral core⁃extraction mechanism moves to both sides under the action of cylinders and springs. After the core extraction， the ejector cylinder can provide a power to drive all the ejector parts to eject. As a result， the plastic parts， cold runners， and excess overflow material can be smoothly demolded from the mold. The mold structure is reasonable and can be operated stably and safely， and the obtained products produced can meet the design standard.

Key words: automotive front a-pillar upper trim panel, low-pressure injection overmolding process, Moldex 3D, inverted mold structure, lateral core pulling mechanism

CLC Number:

TQ320.66⁺2

ZHANG Wenchao, WU Di, ZHANG Han, MIAO Lei, CUI Enming, WANG Mingwei, YE Xinghui, YU Junwei. Processing analysis and mold design of low⁃pressure injection molding of trim panel on front A⁃pillar of automobiles[J]. China Plastics, 2025, 39(4): 104-110.

Figures/Tables 12

Fig.1. Automotive front A⁃pillar upper trim panel molding diagram

Fig.2. Design of casting systems

Fig.3. CAE meshing results

Fig.4. CAE mold flow analysis results

Fig.5. Fabric crimping and positioning mechanism

Fig.6. Molded parts design

Fig.7. Lateral core pulling mechanism

Fig.8. Ejection mechanism

Fig.9. Cooling system

Fig.10. Automotive front A⁃pillar upper trim panel Three⁃dimensional mold drawing

Fig.11. Automotive front A⁃pillar upper trim panel two⁃dimensional assembly drawing

Fig.12. Automotive front A⁃pillar upper trim panel moldings

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