Plastic Mold Factory Gives An Introduction of Rules

    1. Radius

    Plastic mold factory said that a design with corners always needs to accommodate large radii. Sharp corners spell stress thereby affecting the manufacturability of parts. Corners such as the attachment between bosses and surfaces which are often overlooked require scrutiny.

    Sharp Corners in Injection MoldingThe radius should always be with regards to the part thickness thereby eliminating the prospects of high-stress concentration and resulting in the breakage of the plastic part. General guideline suggest that the thickness at the corner should be in the range of 0.9 times the nominal thickness to 1.2 times the nominal thickness of the part.

    1. Wall Thickness

    Given the different nature of the composition of plastics, plastic parts should always have walls with uniform thickness. Swerving away from the recommended would give rise to unfavorable results such as shrinkage and warpage. Apart from this, uniform wall thickness gives the assurance of minimum manufacturing cost. This further ensures quick cooling which in turn lets one produce more parts in a short span of time and optimum utilization of resources which is much sought after. And lighter parts have never been considered inconvenient.

    Uniform Wall Thickness

    General guidelines suggest that wall thicknesses for reinforced plastic materials should be between the range of 0.75 mm to 3 mm and those for unfilled materials should be 0.5 mm to 5 mm.

    1. Determine an apt location for gate

    While it is recommended to have a plastic design with a uniform wall thickness, we understand the need to have variations in few designs. In such unavoidable situations, having a proper gate location would decide the success of the part. Experts recommend designs with the gate at a location at which the melt enter the thickest section of the cavity only to flow out of a narrower region.

    1. Draft

    Plastic heavily relies on mold draft in the course of its removal from the mold. Due to which plastic parts are to be designed with a taper (or, draft) in the direction in which the mold moves. In such case, the lack of an appropriate draft would make the removal of plastic parts almost impossible.

    Minimum Draft Angle in injection molded plastic parts

    A design with sufficient draft is always considered to be a good practice. 1.5 degrees for a depth of 0.25mm is usually recommended by design experts. General guidelines suggests that a draft angle of 0.5 degrees is recommended for core and 1.0 degrees for cavity

    1. Ribs

    Recommended Rib ParametersA known aspect of plastic is its stiff nature. Given this, the inclusion of ribs in a design is often recommended which adds to the bending stiffness. Ribs are pocket-friendly and a convenient option, the end result of which is often well received by both the designer and the manufacturer.

    But a plastic designer should always take the wall thickness into consideration at the time of including a rib in a plastic design. Thick and deep ribs can cause sink marks and filling problems respectively. Rib thickness of a part should never exceed the wall thickness.

    General guidelines suggests that rib thickness at its base should be around 0.6 times nominal wall thickness of the part. Failing to include a proper rib would eventually lead to the distortion of the plastic part.

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