Bài giảng Thiết kế khuôn mẫu: Chương 5 - TS. Nguyễn Công Nguyên

The design of plastic products, particularly those manufactured through injection molding, necessitates a meticulous approach to geometry to ensure functional integrity, aesthetic appeal, and manufacturing efficiency. This chapter delves into the critical aspects of "geometric design of plastic products", highlighting how fundamental elements like draft angles, wall thickness, and fillets directly influence the quality and manufacturability of the final product. Understanding and correctly applying these principles is paramount for engineers and designers to preempt common defects, optimize production processes, and achieve robust, high-performance plastic components.

Kỹ sư thiết kế, kỹ sư sản xuất, chuyên gia khuôn mẫu, sinh viên ngành kỹ thuật vật liệu và cơ khí quan tâm đến thiết kế sản phẩm nhựa và công nghệ ép phun.

This academic content systematically addresses the essential geometric design principles for plastic products, focusing specifically on applications within "injection molding" processes. It commences by outlining a design cycle that prioritizes process parameter and "plastic material" adjustments before altering "product geometry" when encountering defects like incomplete filling or warping. The core of the discussion then elaborates on three critical geometric features: "draft angles", "wall thickness", and "fillets (góc bo)". For "draft angles", the document emphasizes their necessity for efficient demolding, providing specific angle recommendations based on mold depth, material type, and product size. It details how inadequate draft angles lead to excessive friction, product sticking, and surface damage. The section on "wall thickness" highlights its profound impact on product rigidity, electrical insulation, heat resistance, aesthetics, and manufacturing cost. It thoroughly discusses common "product defects" arising from inconsistent or overly thick walls, such as sink marks, voids, warpage, and weld lines, advocating for uniform and appropriately thin sections to optimize cooling, minimize shrinkage, and reduce internal stresses. Finally, the role of "fillets" is examined, underscoring their importance in promoting uniform cooling, reducing "warpage", easing material flow during filling, and mitigating stress concentrations. Recommendations for optimal inner and outer fillet radii relative to wall thickness are provided, alongside illustrations demonstrating how proper fillet design prevents issues like cracking and surface defects. In essence, this document provides practical guidelines and theoretical insights, enabling designers and engineers to create plastic products that are not only aesthetically pleasing and functionally sound but also cost-effectively manufactured with minimal defects. By applying these "geometric design of plastic products" principles, industries can significantly enhance product quality and production efficiency.