About the design of injection drawings

2021/04/20

1 Subject content and scope of application

This standard specifies the content and expression specifications that should be expressed in product drawings, which is conducive to improving the quality of mold drawings and better guiding production. This standard applies to the design of product drawings of the mold design of the company's product development department.


2 content

2.1 Two-dimensional drawings

2.1.1 Two-dimensional drawings must comply with national standards for mechanical drawing.
2.1.2 Use PRO/E software to produce two-dimensional drawings, and the file configuration content should be unified.
2.1.3 The line width, font size and line of the drawing should be uniform, the line width of thick solid line, thick dotted line is 0.5mm, thin solid line, wavy line, double polyline, thin dotted line, double dotted line is thick 1/3 of the solid line, the dashed line width is 1/3 of the thick solid line, the line segment length is 4mm, and the line segment interval is 1mm. The font (numbers, text) has a height of 3.5mm and a line width of 0.35 mm.             
2.1.4 The drawing scale is in accordance with national standards, and the actual scale of the printed drawing should be consistent with the scale noted in the title bar, and scaling is not allowed. According to the size and complexity of the product structure, the proportion of customized drawings should be selected reasonably, and the view is not allowed to be too small and the structure is not clear. Do not allow the dimension lines to be distributed too densely and difficult to identify.            
2.1.5 Drawing dimensions:             
2.1.5.1 The product datum should be noted in the figure, and the size marking should be a unified datum.             
2.1.5.2 The drawings should be complete in size, correct, clear and reasonable, without missing sizes, and reasonable distribution of the size lines. The dimension marking should be conducive to mold processing.            
2.1.5.3 Tolerances should be marked for important assembly dimensions, important parts, positioning dimensions, and required inspection dimensions. Other dimensions are not marked with tolerance level.
2.1.5.4 The required inspection dimensions are the key dimensions of the product assembly and appearance. A serial number should be added after the required size, and the serial number is in the form of a number plus a circle. The serial numbers should be arranged in order, from left to right, top to bottom, for easy reference.             
2.1.5.5 Three-dimensional curved surfaces that are not easy to mark are marked with the maximum external dimensions.
2.1.6 Reinforcing ribs must be marked with the size of the large and small ends, and the size of the inclined part must be clearly stated whether the marked size is the large end or the small end.             
2.1.7 The graphic representation is clear and clear, and unnecessary arc tangent lines are removed.
2.1.8 The technical requirements should include: unfilled wall thickness, unfilled corners, unfilled demoulding slope, appearance requirements (such as mirrors, transparent parts, spray paint, etching, etc.), assembly relations and gaps, mandatory inspections Dimensions and other special requirements, etc.
2.1.9 Mark the area or range with a dotted line if the appearance needs to be textured.
2.1.10 For appearance parts, use a thick double-dot chain line to indicate the position of the appearance surface in the figure.
2.1.11 A thin solid line shall be used to mark the position of the parting surface in the two-dimensional drawing and explain with text.
2.1.12 The position where the gate is not allowed and the position where the ejection marks are not allowed are indicated in the figure.
2.1.13 If the mold ejection direction is inconsistent with the product assembly direction, generally draw the picture according to the product mold ejection direction, and use the arrow on the drawing to mark the product assembly direction and reference, and text description.
2.1.14 The state of the drawing shall be indicated, and the replacement drawing shall be specially marked.
2.1.15 The two-dimensional drawing should be consistent with the three-dimensional drawing. If the 3D graph is changed, the 2D graph should be updated simultaneously.
2.1.16 In order to facilitate the identification of the drawings, add a three-dimensional side view in the appropriate position of the two-dimensional drawing.           
3.1 Three-dimensional map
3.1.1 All structures of three-dimensional three-dimensional drawings shall be expressed in solid (Solid), and no missing structures or inconsistencies with two-dimensional drawings shall be allowed.
3.1.2 The inner and outer surfaces of the product that are perpendicular to the ejection direction, the sliding block and the core-pulling movement direction on the three-dimensional drawing should be added with a demolding slope. The slope should be 0.5°~1º. Before adding the slope, the position of each parting surface of the product and the assembly and appearance requirements of the product should be clarified to determine the direction and size of the slope. The position to be inserted should add an inclination of 1º to 3º. Where permitted, the greater the slope, the better. The stiffener should ensure the strength. Usually the mold design task book is proposed by the structural designer and the mold designer based on the task book of the molded plastic product, and the mold designer designs the mold based on the task book of the molded plastic product and the mold design task book.
3.2 Collect, analyze and digest original data
Collect and organize relevant parts design, molding process, molding equipment, mechanical processing and special processing materials for use when designing molds.
⑴ Digest the drawings of plastic parts, understand the purpose of the parts, analyze the technical requirements of the plastic parts, such as the processability and dimensional accuracy. For example, what are the requirements for plastic parts in terms of appearance, color transparency, and performance, whether the geometric structure, slope, and inserts of the plastic parts are reasonable, the allowable degree of forming defects such as weld marks and shrinkage holes, and whether they are coated or not. Post-processing such as assembly, electroplating, bonding and drilling. Select the size with the highest dimensional accuracy of the plastic parts for analysis, and see if the estimated molding tolerance is lower than the tolerance of the plastic parts, and whether the plastic parts that meet the requirements can be molded. In addition, we must understand the plasticization and molding process parameters of plastics.

(2) Digest the process data, analyze whether the molding method, equipment model, material specification, mold structure type and other requirements proposed in the process task book are appropriate and can be implemented. The molding material should meet the strength requirements of plastic parts, and have good fluidity, uniformity, isotropy, and thermal stability. According to the purpose of the plastic parts, the molding material should meet the requirements of dyeing, metal plating, decorative properties, necessary elasticity and plasticity, transparency or opposite reflective properties, adhesiveness or weldability.             

Three, choose molding equipment

 Molds are made according to the type of molding equipment, so you must be familiar with the performance, specifications, and characteristics of various molding equipment. For example, for an injection machine, the following should be understood in terms of specifications: injection capacity, clamping pressure, injection pressure, mold installation size, ejection device and size, nozzle hole diameter and nozzle spherical radius, sprue sleeve positioning ring size, The maximum and minimum mold thickness, template stroke, etc., please refer to the relevant parameters for details. It is necessary to preliminarily estimate the size of the mold and determine whether the mold can be installed and used on the selected injection machine.