8 Design Considerations for Manufacturable Plastic Parts

Written by Rahul Verma | Updated: February 12, 2026

Principles of Designing Plastics

When designing a plastic component for manufacturing, it is crucial to consider factors such as geometry, tooling, materials, and the manufacturing process. These factors include temperature, resistance to degradation, approvals from regulatory bodies, compliance with assembly procedures, surface quality, and cost.

When designing a plastic component for manufacturing, there are various considerations that must be given to the part’s geometry, its tooling, the materials used, and the manufacturing process itself. The first step is to design and construct components with the intended function in mind. To decrease costs and increase speed to market, it is important to think about minimizing product weight, removing unnecessary fabrication and assembly procedures, enhancing structural components, and eliminating waste. Here are eight things to keep in mind as you design your plastic parts to ensure a smooth manufacturing process:

Relevant Factors

Plastic grades are generally chosen by manufacturers based on past experience with that grade in a similar application or on supplier recommendations. The resins you pick for this method might work, but they won’t be the best. Plastic selection is a difficult process that needs to take numerous factors into account, including:

Temperature: The potential for exposure to high temperatures during assembly, finishing, and transport, as well as under normal and harsh use conditions
The resistance of a component to degradation caused by chemical interaction with a solid, liquid, or gas
Approvals from regulatory bodies: public and private benchmarks for qualities like durability, safety around fire, and functionality in electrical and mechanical contexts
Compliance of the plastic with all assembly procedures, including bonding, mechanical fasteners, and welding
Surface quality as it emerges from the mold, including gloss, smoothness, and other aesthetic characteristics
Manufacturing, upkeep, assembly, disassembly, and other expenditures are all factored into the final price tag, from labor savings to savings on tools and materials.
Obtainability, or the resin’s accessibility in terms of the quantity required for manufacturing

Radius

The thickness of a part should be calculated with the radius in mind so that stress concentrations and potential failure points are avoided. As a rule of thumb, the corner thickness should be between 0.9 and 1.2 times the nominal thickness of the part.

The thickness of the walls

Many manufacturing errors can be avoided if the part is designed with a consistent wall thickness. Melted plastic tends to pool in low-resistance regions. Melt may flow into thick portions first (depending on gate placements) if your part has varying thicknesses. If this happens, the gaps might not get filled up correctly. In addition, flaws like voids or sinking occur more frequently in thicker regions because they cool more slowly. The molding process will go more smoothly if your part’s design incorporates rounded corners.

Gate Number Four

If you want smooth resin flow into the mold, gates are a must-have. These tiny design elements are what channel resin from the runners into the part’s interior. The effectiveness and reliability of a part are greatly affected by the gates used and where they are located.

Draft

The quantity of draft in the plastic part’s vertical walls indicates how much they taper. Without proper draft, a mold’s portion may not eject or may be damaged in the process. Draft angles of 1-2 degrees are typically necessary, though this range is subject to change according to the particulars of the part in question.

Ribs Are a Part of It

If the wall thickness of a plastic component is kept to a minimum during the design process, the part will be weaker than if it were made with a thicker wall. Sink marks can be avoided by keeping the rib thickness between 50 and 70 percent of the corresponding part thickness. The likelihood of defects is reduced by coring out material during design to prevent sinking.

Mold Contracting

Plastic parts can lose as much as 20% of their volume during the molding process. Most thermal shrinkage occurs in crystalline and semi-crystalline materials. Shrinkage is less of an issue with amorphous materials. Here are some simple strategies for preventing mold shrinkage:

Change the formula around

Take into account the anticipated shrinkage when designing the mold to achieve the desired size.
The molding temperature, melt temperature, injection speed, injection pressure, injection time, and cooling time should all be optimized.

Unique Characteristics

The mold tool should be able to effortlessly open and eject the plastic portion. The halves of an injection mold split apart in the opposite direction when a part is released. It may be necessary to add side actions to the design when holes, undercuts, or shoulders prevent the release from occurring.

Coring is pulled in the opposite direction of the mold separation by side actions. This increases the mold’s cost and design freedom for the part.

Many problems can be avoided in the design and development phases by working with a seasoned plastic injection molder and engineering team. A successful product launch on time and under budget can be achieved by keeping the above considerations in mind during the design phase and teaming up with an experienced plastics engineer.