The article is talking about how to improve plastic injection molding accuracy.
1. Plastic Injection Mold processing quality includes processing accuracy and surface quality
Machining accuracy is the degree of conformity between the actual size, shape, and position of the three geometric parameters of the surface of the processed part and the ideal geometric parameters required by the drawing.
Ideal geometric parameters are average sizes for size; for surface geometry, they are absolute circles, cylinders, planes, cones, and straight lines; for mutual positions between surfaces, they are absolutely parallel. , Vertical, coaxial, symmetrical, etc. The deviation of the actual geometric parameters of the part from the ideal geometric parameters is called the machining error.
Machining accuracy and machining error are both terms used to evaluate the geometric parameters of the machined surface. Machining accuracy is measured by tolerance grade, the smaller the grade value, the higher the accuracy; the processing error is expressed by numerical value, the larger the numerical value, the greater the error. High machining accuracy means small machining error and vice versa.
The actual parameters obtained by any machining method will not be absolutely accurate. From the perspective of the function of the part, as long as the machining error is within the tolerance range required by the part drawing, it is considered that the machining accuracy is guaranteed.
The quality of the machine depends on the machining quality of the parts and the assembly quality of the machine. The machining quality of the parts includes the machining accuracy of the parts and the surface quality. The machining accuracy refers to the actual geometric parameters (size, shape, and position) and the ideal geometry after the parts are processed the degree to which the parameters match.
The difference between them is called machining error. The size of the machining error reflects the level of machining accuracy. The greater the error, the lower the machining accuracy; the smaller the error, the higher the machining accuracy.
2. The main aspects that affect processing plastic injection molding accuracy
2.1 Dimensional accuracy of the plastic injection molding accuracy
Refers to the degree of conformity between the actual size of the processed part and the center of the tolerance zone of the part size.
The dimensional accuracy is controlled by dimensional tolerances. The dimensional tolerance is the allowable amount of variation in the size of the part in the cutting process. In the case of the same basic size, the smaller the dimensional tolerance and the higher the dimensional accuracy.
2.2 Shape accuracy of the plastic injection molding accuracy
Refers to the degree of conformity between the actual geometric shape of the surface of the processed part and the ideal geometric shape.
There are 6 items for evaluating shape accuracies, such as straightness, flatness, roundness, cylindricity, and line profile. The shape accuracy is controlled by the shape tolerance. The shape tolerances are divided into 12 accuracy levels except for the roundness and cylindricity divided into 13 accuracy levels. Level 1 is the highest and level 12 is the lowest.
2.3 Position accuracy of the plastic injection molding accuracy
Refers to the actual position accuracy difference between the relevant surfaces of the parts after processing. There are eight items for evaluating position accuracy: parallelism, perpendicularity, inclination, concentricity, symmetry, position, circular runout, and full runout. The position accuracy is controlled by the position tolerance, and the position tolerance of each item is also divided into 12 accuracy levels.
Generally, when designing machine parts and specifying the machining accuracy of parts, attention should be paid to control the shape error within the position tolerance, and the position error should be smaller than the dimensional tolerance.
That is, precision parts or important surfaces of parts, the shape accuracy requirements should be higher than the position accuracy requirements, and the position accuracy requirements should be higher than the dimensional accuracy requirements.
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