What are the requirements for drawing all parts in mold design?

 

Introduction

What is Mold Design and the Significance of Drawing Parts

Mold design is a crucial aspect of the manufacturing industry. It involves creating a detailed plan for the production of molds, which are used to shape various materials into specific products. These molds can be made from a variety of materials such as metal, plastic, or rubber, and are used in processes like injection molding, die - casting, and extrusion.

Drawing all parts in mold design is of utmost importance. Firstly, it serves as a visual representation of the entire mold structure. Just like an architect's blueprint for a building, a detailed drawing of mold parts allows manufacturers to understand the shape, size, and how each component fits together. This understanding is fundamental for the actual manufacturing process of the mold. For example, in injection mold manufacturing, the accurate drawing of the cavity and core parts helps machinists to precisely machine these components, ensuring that the final plastic product will have the correct dimensions and shape.

Secondly, drawing parts plays a vital role in quality control. By having clear and detailed drawings, quality inspectors can easily check if the manufactured parts meet the design specifications. Any deviation from the drawing can be quickly identified, whether it's an incorrect hole diameter, a misaligned surface, or a wrong angle. This early detection of defects helps in reducing production waste and costs. For instance, if a mold part is produced with a dimension that is 0.5mm off from the drawing in a high - precision mold for medical device production, it could lead to non - compliant final products, and detecting this error early through drawing inspection can save significant rework or scrap costs.

Moreover, in a team - based manufacturing environment, drawings are an essential means of communication. Designers, engineers, machinists, and quality control personnel all refer to the drawings. They can discuss modifications, improvements, or potential issues based on these visual representations. For example, during a new mold project kick - off meeting, the design team can present the part drawings to the manufacturing team, and together they can identify any manufacturability issues, such as areas that might be difficult to machine or need special tooling.

Different Parts in Mold Design and Their Drawing Requirements

Core and Cavity

The core and cavity are the most critical parts in a mold as they directly determine the shape of the final product. The core forms the internal features of the product, while the cavity creates the external shape.

Size Precision: In the drawing of the core and cavity, the dimensional accuracy requirements are extremely high. For example, in a high - precision plastic injection mold for electronic components, the dimensional tolerance of the core and cavity may be required to be within ±0.01mm. Any deviation from this tolerance can lead to products with incorrect dimensions, which may not fit properly with other components in the final assembly.

Surface Roughness: The surface roughness of the core and cavity also needs to be clearly marked on the drawing. A smooth surface finish, often expressed as a low Ra value (such as Ra 0.2 - 0.4μm for optical - grade plastic products), is required for products that demand a high - quality surface appearance. If the surface roughness is not specified accurately in the drawing, the machined core and cavity may have a rough surface, causing defects like surface scratches or uneven texture on the final product.

In a die - casting mold for automotive parts, the core and cavity may have more complex shapes. When drawing these parts, special attention should be paid to the draft angles. These angles, usually in the range of 0.5° - 2°, are essential for the easy ejection of the cast part from the mold. If not properly drawn and accounted for during manufacturing, the part may get stuck in the mold, leading to damage to both the part and the mold.

Runner System

The runner system, consisting of the sprue, main runner, and sub - runners, is responsible for delivering the molten material (such as plastic in injection molding or metal in die - casting) from the injection unit to the cavity.

Diameter and Length: The diameter and length of each part of the runner system need to be precisely drawn. For instance, in a medium - sized injection mold, the diameter of the main runner might be 8 - 12mm, while the sub - runners could have a diameter of 4 - 6mm. These values are not arbitrary; they are calculated based on factors like the volume of the cavity, the viscosity of the material, and the injection pressure. If the diameter is drawn too small in the design, it can cause high - pressure drops, leading to incomplete filling of the cavity. On the other hand, an overly large diameter can result in excessive material waste and longer cooling times.

The length of the runner should also be optimized. A long runner may increase the pressure loss and cooling time, so it needs to be as short as possible while still ensuring even distribution of the material. For example, in a multi - cavity mold, the runner length to each cavity should be designed to be equal to ensure simultaneous filling.

more What are the requirements for drawing all parts in mold design?