Precautions for the angle and thickness of injection molded parts
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November 26 13:21:23, 2020
1. Demoulding slope of plastic parts:
The size of the draft angle is mostly determined empirically and according to the depth of the product. In addition, the choice of wall thickness and plastic choice is also under consideration. In general, a certain amount of draft is required for any side of the molded product so that the product can be smoothly removed from the mold. The magnitude of the draft is generally 0.5 to 1 °.
The specific selection of draft angle should pay attention to the following points:
For large shrinkage of plastic parts, a larger slope value should be used.
Higher, larger size, based on actual calculations, take a smaller draft.
When the wall thickness of the plastic part is thick, the molding shrinkage will increase, and the draft angle should be larger.
The surface of the plastic part is smooth, the dimensional accuracy is high, and the shrinkage is small. A small draft angle, such as 0.5°, should be used.
The stripping angle of the transparent part should be increased to avoid scratching. Under normal circumstances, the draft of the PS material should be no less than 2.5 ° -3 °, and the draft of the ABS and PC materials should be no less than 1.5 ° -2 °.
The sidewall of the plastic part with appearance treatment such as dermatoglyph and blasting should be taken at a peeling angle of 2°-5° depending on the specific conditions, depending on the specific depth of the dermatoglyph. The deeper the grain depth, the larger the draft should be.
When the structure is designed to be inserted, the insertion surface slope is generally 1°-3°.
Take the direction of the slope. Generally, the inner hole is based on the small end, which conforms to the pattern. The slope is obtained by the expansion direction. The shape is based on the big end and conforms to the pattern. The slope is obtained by reducing the direction.
In general, the draft angle is not included in the plastic part tolerance.
The outer surface of the outer casing is at a slope of 3° or more. Except for the outer surface of the outer casing, the draft of the remaining features of the casing is drafted at a standard of 1°. In particular, it can also be taken according to the following principle: the draft of the ribs below 3 mm is taken as 0.5°, the 3-5 mm is taken as 1°, and the rest is taken as 1.5°; the cavity of the cavity below 3 mm is stripped. Take 0.5°, take 1° for 3-5mm, and take 1.5° for the rest.
2. Determination of wall thickness of plastic parts and wall thickness treatment
It is important to determine the wall thickness of the plastic part reasonably. The wall thickness of the plastic part is determined first by the requirements of the plastic parts: including the strength, quality cost, electrical performance, dimensional stability and assembly requirements of the parts. The general wall thickness has empirical values, which can be determined by reference.
The points to note are as follows:
The wall thickness of the plastic parts should be as uniform as possible, avoiding too thin, too thick and abrupt wall thickness. If the plastic parts require wall thickness changes, gradient or arc transition should be used, otherwise the plastic parts will be deformed and affected due to uneven shrinkage. Forming process problems such as the strength of plastic parts and the influence of fluidity during injection molding. The thickness difference should be controlled within 25% of the basic wall thickness as much as possible. The minimum wall thickness of the whole part should not be less than 0.4mm, and the back side of the part should not be A-level appearance surface, and the required area should not exceed 100mm2.
The wall thickness of the plastic part is generally in the range of 1 to 5 mm. The most commonly used value is 2 to 3 mm.
Try not to design the ribs and screw columns too thick. It is generally recommended to take half of the wall thickness of the body to be safer, otherwise it may cause appearance problems such as microcosm.
Try not to design the part as a separate flat plate. The size is small, otherwise the deformation will result in uneven parts.
The recommended values ​​for the minimum wall thickness and common wall thickness of plastic products are as follows: