How to improve the precision of plastic molds?

2019-11-19

1. Plastic mold mold processing quality including processing accuracy and appearance quality

Machining accuracy is the degree of conformity between the three geometric parameters of the actual dimensions, shape and orientation of the appearance of the part after machining and the ideal geometric parameters required by the drawing.

The ideal geometric parameters are uniform scales in terms of scales; positive circles, cylinders, planes, cones, and straight lines in terms of external geometry; in terms of mutual orientation between external surfaces, Definitely parallel, straight, coaxial, symmetrical, etc. The violation of the part's actual and ideal geometric parameters is called machining error.

Machining accuracy and machining errors are terms used to evaluate the geometric parameters of machining appearance. The processing accuracy is measured by the service level. The smaller the level value, the higher the accuracy. The processing error is expressed by a numerical value. The larger the value, the larger the error. High processing accuracy means small processing errors and vice versa.

The practical parameters obtained by any machining method are not necessarily accurate. From the perspective of the function of the part, as long as the machining errors are within the official service range required by the part drawing, the machining accuracy is considered to be guaranteed.

The quality of the machine depends on the machining quality of the part and the assembly quality of the machine. The machining quality of the part includes the machining accuracy and appearance quality of the two parts. The machining accuracy refers to the actual geometric parameters (size, shape and orientation) and ideal geometry after the machining of the part. The degree to which the parameters agree. The differences between them are called processing errors. The size of the machining error reflects the unevenness of the machining accuracy. The larger the error, the lower the machining accuracy, and the smaller the error, the higher the machining accuracy.

2. The first aspect that affects the precision of plastic mold processing

2.1 scale accuracy

Refers to the degree of conformity between the actual scale of the processed part and the center of the service belt of the part scale.

Scale accuracy is controlled using scale official service. Scale service is the allowable variation in the size of the part during cutting. In the case of the same basic scale, the smaller the scale is, the higher the scale accuracy is.

2.2 shape accuracy

Refers to the degree to which the actual geometric shape of the processed part matches the ideal geometry. There are 6 items to evaluate the accuracy of shape, such as straightness, flatness, roundness, cylindricity, and line summary. The shape accuracy is controlled by the shape official service. In addition to the roundness and cylindricality, there are 13 accuracy grades, and the rest are equally divided into 12 accuracy grades. Level 1 is high, level 12 is low.

2.3 bearing accuracy

Refers to the difference in actual azimuth accuracy between the appearances of the parts after processing. The items for appraising azimuth accuracy include parallelism, straightness, inclination, coaxiality, symmetry, azimuth, circular runout and full runout. The azimuth accuracy is controlled by azimuth service, and each intentional azimuth service is also divided into 12 accuracy levels.

Generally, when designing machine parts and specifying the machining accuracy of parts, care should be taken to control the shape errors within the azimuth service, and the azimuth errors should be less than the scale service. That is, precision parts or important appearances of parts should have higher shape accuracy requirements than azimuth accuracy requirements, and azimuth accuracy requirements should be higher than scale accuracy requirements.

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