This means that there is almost no chance that this dimension will be out of tolerance.Ī. The difference between minimum and maximum tolerance is 10% from dimension.ĭ. There is no way that a material expected to shrink 2% will shrink 6.9%.Ĭ. Shrinkage from mold size to minimum dimension is also impossible. Cavity dimension is smaller than the allowed maximum dimension on drawing (negative shrinkage).ī. Shrinkage from mold size to maximum is impossible. See Figure 3.įigure 3: Shrinkage of the part that is needed to reach the tolerance limit.Īnalysis of shrinkage to tolerance limits:Ī. Now we can check what the shrinkage should be for each dimension in order to reach the limits. On our simple part, each dimension can reach the tolerance limits. See Figure 2.įigure 2: Mold dimension to receive nominal part dimension.ĭimensions of the cavity in the mold are fixed so shrinkage will be calculated from these dimensions. In the same part we have another dimension, no 2, (200.0☐.1). Cavity dimension will be 2.0/0.98=2.0408 mm, meaning: in order to meet the nominal dimension (2.0) the cavity dimension will be 2.0408mm. In order to achieve this dimension on the product, we add shrinkage for mold production.
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#IRONCAD DEFAULT DIMENSION PRECISION HOW TO#
This article discusses how to analyze the dimensions, tolerances, and ranges in injection molded parts in a more accurate and practical way to help the designer know in advance about production capability.
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The designer, most of the time, does not take into account the ability to produce the designed part. However, this is a general recommendation that cannot always be achieved in injection molding. Standards like DIN 16901 (and others) define general tolerances for different materials and different locations on the produced part. These tolerances are to ensure that all dimensions fit the assembly requirements. It is impossible to produce identical parts therefore, the designer defines tolerances for the design dimensions.
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Dimensions are required for functionality or correct fit in an assembly. The design of a product includes dimensions. By Amos Shavit, Plastokit, Member of Rion Group