How to design the demoulding slope for plastic mold ? The demoulding slope is the slope designed on both sides of the die cavity for the convenience of demolding. The orientation of the demolding slope for plastic mould depends on the inner and outer dimensions of the plastic part.
The size of the demolding slope of the plastic part is related to the properties, shrinkage rate, friction factor, wall thickness and geometry of the plastic part. Rigid plastics have a larger demoulding slope than soft plastics; plastic parts with more complex shapes or more forming holes take a larger demoulding slope; plastic parts with large height and deep holes take a smaller demoulding slope Slope; the wall thickness increases, the force of the inner hole to wrap the core is large, and the drafting slope should also be larger.
How to design the demoulding slope for plastic mold
Sometimes, in order to keep the plastic part in the die or on the core when the mold is opened, the slope of the edge is intentionally reduced or the oblique edge is enlarged.
There is no certain criterion for the size of the draft angle, most of which are determined by experience and the depth of the product.
In addition, the method of molding, wall thickness and choice of plastic are also considered. In general, for any side wall of the molded product, a certain amount of draft angle is required to allow the product to be removed from the mold. The size of the demolding slope can vary from 0.2° to several degrees, depending on the surrounding conditions, generally 0.5° to 1° is ideal.
The following points should be paid attention to when selecting the demolding slope:
(1). Take the direction of the inclination. Generally, the inner hole is subject to the small end, which conforms to the drawing. The inclination is obtained from the expanding direction. The shape is subject to the large end, which conforms to the drawing. As shown below.
(2). Where the precision of plastic parts is high, a smaller demoulding slope should be used.
(3). For higher and larger sizes, smaller draft angles should be used.
(4). If the shrinkage of the plastic part is large, a larger slope value should be selected.
(5). When the wall thickness of the plastic part is thick, the molding shrinkage will increase, and the demolding slope should adopt a larger value.
(6). Under normal circumstances, the demoulding slope is not included in the tolerance range of plastic parts.
(7). The demoulding slope of transparent parts should be increased to avoid scratches. Under normal circumstances, the demolding slope of PS material should be greater than 3°, and the demolding slope of ABS and PC material should be greater than 2°.
(8). The side wall of the plastic parts with leather grain, sandblasting and other appearance treatments should be added with a demoulding slope of 3°~5°, depending on the specific bite depth. Required draft angle for reference. The deeper the bite depth is, the larger the demolding slope should be. The recommended value is 1°+H/0.0254° (H is the biting depth). For example, the pattern drafting slope of 121 is generally 3°, and the pattern demoulding of 122 is generally 3°. The slope is generally 5°.
(9). The slope of the insertion surface is generally 1°~3°.
(10). The draft angle of the shell surface is greater than or equal to 3°.
(11). Except for the outer shell surface, the draft angle of the other features of the shell is 1° as the standard draft angle. In particular, it can also be taken according to the following principles: the draft angle of the reinforcing ribs below 3mm is 0.5°, 3~5mm is 1°, and the rest is 1.5°; the demolding angle of the cavity below 3mm is high. Take 0.5° for degrees, 1° for 3~5mm, and 1.5° for the rest
Plastic parts must have sufficient draft angle to avoid top white, top damage and dragging. The demoulding slope is related to the properties of the rubber compound, the shape of the rubber part, and the surface requirements.
Recommended values for minimum draft angles for commonly used plastics have been published. For the parts that do not have drafting slope requirements in the 3D file of plastic parts, refer to the general drafting slope requirements in the technical description. The appearance surface of the plastic part requires a smooth or textured surface, and its demolding slope is also different. The slope values are as follows:
(1) The demoulding slope of small plastic parts with smooth surface on the outer surface is 1°, and the demolding slope of large plastic parts is 3°;
(2) Ra < 6.3 draft angle/3° on the etched surface of the outer surface, Ra/6.3 draft angle/4°;
(3) Ra < 3.2 draft angle/3˚ for outer surface fire pattern surface, Ra/3.2 draft angle/4˚.
For the plastic parts of the built 3D model, use Pro/E to check the demoulding slope. The steps are as follows:
Analysis ® Surface Analysis ®
Draft Check® [Given the maximum slope value, select Analysis
Part or Surface, determine the direction surface corresponding to the analysis] ® Compute.
