The design of an injection mold for a chair typically involves several key points, including:

1. Part design: The first step is to design the chair itself. This includes determining the shape, size, and thickness of the different parts that make up the chair.

2. Material selection: The type of plastic used for the chair will impact the design of the injection mold. The plastic must be able to flow easily into the mold and solidify quickly to produce a strong, durable chair.

3. Gate location: The gate is the point where the molten plastic enters the mold. The location of the gate is critical for ensuring that the plastic flows smoothly into the mold and fills all areas of the mold evenly.

4. Cooling system: Cooling channels are built into the mold to ensure that the plastic solidifies quickly and evenly. The cooling system must be designed to provide sufficient cooling while avoiding warping or other defects in the finished product.

5. Ejection system: Once the plastic has solidified, the finished chair must be ejected from the mold. The ejection system must be designed to release the chair from the mold without damaging the finished product.

6. Mold construction: The mold itself must be constructed to withstand the high pressures and temperatures involved in the injection molding process. The mold must also be designed for easy maintenance and repair.

7. Quality control: Finally, the injection molding process must be carefully controlled to ensure that each chair is produced to the desired specifications. This includes monitoring the temperature, pressure, and timing of the injection molding process, as well as inspecting each finished chair for defects.