Injection molding tolerances also be known as platic injection molding tolerances, which are a very important part of injection molding design. They are ” given by designer to designed dimensions”. Molding manufacturers should define the plastic injection molding tolerances to made the design dimensions fit the assembly requirements. It is a necessary detail to consider for every molding designer.
Tight tolerances can help designers a lot to develop complex plastic injection parts and products, especially when they are used in high-quality requirements industry such as medical, automotive, or defense applications. There has no chance to making up for mistake, especially when designer design critical-use parts, which the margins are as slim as +/- .001 inches.
How to Make Tie Tolerances During Injection Molding?
If you want to make tight tolerances, you must design them early in the part design phase. Here are some suggestions for you to achieve the tight plastic injection molding tolerances.
Start with design: Molding design engineers must consider the requirements of part geometry, overall size, and wall thickness. These factors will influence tolerance control. The thick walls may have shrink rates within the thick sections, and with the rate, it is difficult to hold tight tolerances, because the variable shrink within the section may change.
Consider the complexity of parts: The correct complex design of parts can make control of tight tolerances. Usually, complex designs have issues such as shrinking and warping. If the issues of complex designs are too lots, the part may not be repeatable. Therefore, it is necessary to consist of product design with manufacturing teams.
Injection Molding Tolerances Guide
There is a brief injection molding tolerances guide, which aims to help you know the tolerances of plastic injection molded parts. This guide is made of dimensional tolerances, straightness/flatness tolerances, hole diameter tolerances, blind hole depths tolerances, concentricity/ovality tolerances, and all of these tolerances were measured by mm.
|Dimension||1 to 20 (+/-mm)||21 to 100 (+/-mm)||101 to 160 (+/-mm)||for each 20mm over 160 add|
|PA 30% GF||0.060||0.120||0.240||0.080|
|PBT 30% GF||0.060||0.120||0.240||0.080|
|PC 20% Glass||0.050||0.100||0.200||0.080|
|PP 20% Talc||0.125||0.170||0.375||0.100|
|PPS 30% GF||0.060||0.120||0.240||0.080|
|Dimension||0-100 (+/- mm)||101-160 (+/- mm)|
|PA 30% GF||0.150||0.200|
|PBT 30% GF||0.150||0.200|
|Polycarbonate, 20% Glass||0.130||0.180|
|Polypropylene 20% Talc||0.850||1.500|
|PPS 30% GF||0.150||0.200|
Hole Diameter Tolerances
|Dimension||0-3 (+/-mm)||3.1-6 (+/-mm)||6.1-14 (+/-mm)||14-40 (+/-mm)|
|PA 30% GF||0.050||0.050||0.080||0.080|
|PBT 30% GF||0.050||0.050||0.080||0.080|
|PC 20% GF||0.050||0.050||0.080||0.080|
|PP 20% Talc||0.050||0.080||0.150||0.150|
|PPS 30% Glass||0.050||0.050||0.080||0.080|
Blind Hole Depths Tolerances
|Dimension||1-6 (+/-mm)||6.1-14 (+/-mm)||Over 14 (+/-mm)|
|PA 30% GF||0.050||0.080||0.100|
|PBT 30% GF||0.050||0.080||0.100|
|PC 20% GF||0.050||0.080||0.100|
|PP 20% Talc||0.100||0.120||0.150|
|PPS 30% Glass||0.050||0.080||0.100|
|Dimension||up to 100 (+/-mm)|
|PA 30% GF||0.150|
|PBT 30% GF||0.150|
|PC 20% GF||0.130|
|PP 20% Talc||0.250|
|PPS 30% GF||0.130|