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Injection Mold & Molding

Intronics (Shenzhen) Technology Development Co., Ltd

Design Guidelines

Injection Molded Product Design Guidelines

There are some very specific design features that must be considered in the design stage in order to avoid molding issues, and subsequent Design changes will add time and cost to an injection-molding project, especially when the issues are not discovered until the Design For Manufacturability review. ITTD offers a free mold design guide as well as guidance from our team of experts to help bring your product to life.
These design features showing below should be in the forefront of every engineer’s mind when starting the design process.

NO.	Design features
1	Part Wall Thickness	Part should have uniform wall thickness throughout. This will help ensure the even distribution of the plastic during the injection molding process. Uniform wall thickness will also provide better structural stability.And you also The following table shows the wall thicknesses designed for the commonly used materials.
2	Gate Location	The gate, is the spot in the mold where the plastic resin is injected ,will leave a mark on the finished part.A good designer will place the gate in a location that is easy to remove, or better yet, in an inconspicuous spot so that it does not have to be removed. Eliminating the need for post processing will help reduce overall project costs.
3	Draft Angle	Good draft angles can save a lot of time and money for customer A positive draft angle will allow the part to be ejected from the mold easily. This will save wear and tear on the part and the mold and injection-molding machine. Generally,Draft angles should be around 1° to 2° and be considered for every wall on the part. But like MINIMUM FOR LIGHT TEXTURE (PM-T1/T2),the draft angle needs to be 3° or greater.
4	Bosses	notes：Proper bosses should have connecting ribs and be positioned away from sidewalls. Tthe designers should avoid merging bosses with sidewalls as they can form thick sections that lead to sinking. Bosses are a common feature in many plastic parts used as points for assembly. suggests setting the outside diameter of bosses at 2.0 to 2.4 times the outside diameter of the screw or insert to avoid Shrinking and cracking .
5	Shrinkage	All injection-molded pieces will have some shrinkage. The amount of shrinkage will depend on several factors but will mostly come down to the type of material being used. Shrinkage will happen to every plastic injection molded part because plastic will contract as it cools. During the design process, engineers must consider the shrinkage rate of material and accurately determine the shrinkage rate of the materials in order to prevent the products from being significantly larger or smaller than the intended size.
6	Ribs Features	Generally, the thickness of the Ribs should be the same as or slightly thinner than the wall thickness. If the Ribs are too thick, then obvious shrinkage marks will appear on the outer surface, and the Ribs should not be too deeper; otherwise, it will cause the mold to stick during mold release.
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Material:

The material should always be the first item to consider. Where and how the part is used will largely determine the appropriate material. Will the part need to withstand extreme environments? Will the part be painted? etc. The material cost must be considered. Will a less expensive material be suitable for the intended application? The experts at ITTD will be happy to help with all material considerations.
Different materials will also be designed with different wall thicknesses. The following table shows the wall thicknesses for the commonly used materials.

Materials	Wall thickness recommended	Remarks
ABS	1.15mm - 3.55mm
PC	1.00mm - 3.80mm
PP	0.63mm - 3.80mm
PE	0.76mm - 5.08mm
PS	0.90mm - 3.80mm
Nylon	0.76mm - 2.92mm

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Undercuts:

Undercut molding is an important process for creating hooks, grooves and other elements that have a direct impact on the functionality of the part. And it is used to handle complex shapes and designs to prevent the part from any damage of part being removed from the mold. The undercut features in injection molding usually increase the overall complexity and related costs of any design, but they can also be avoided with some techniques to reduce their complexity and costs (As shown in the example on the right---in order to simplify mold structure and reduce cost, make a slot under undercut feature. ). ITTD engineers have rich experience in mold and product design and will do their best to solve the problems for you.