For plastic injection machines, a larger screw diameter usually means a larger injection volume, but this is not an absolute relationship and other factors need to be considered comprehensively. Below is a detailed introduction of the following points:

1. Basic relationship between screw diameter and injection volume
A larger screw diameter results in a larger volume: The larger the screw diameter, the more molten plastic it pushes per rotation or advance, resulting in a larger injection volume (volume or weight) per unit time.
The "injection volume" of an injection machine is usually measured in grams (g) or cubic centimeters (cm ³), which is directly related to the diameter and stroke of the screw.

2. The larger the screw diameter, the lower the injection pressure may be
The injection pressure is inversely proportional to the area: under the same cylinder thrust, the larger the screw diameter, the larger the force area, resulting in a decrease in pressure per unit area.
Suitable for large and thin-walled products: large screw injection volume, low pressure, suitable for producing large volume but low wall thickness products;
Not suitable for high-pressure products: For precision or thick walled products that require high injection pressure, oversized screws may not be sufficient to provide sufficient injection pressure.

3. Screw diameter affects plastic melting efficiency
A larger screw requires stronger heating capacity: a larger diameter means a larger volume of plastic melt, which consumes more energy and takes longer to melt;
Higher temperature control requirements: If the temperature is uneven, it can easily lead to uneven plastic melting, affecting the quality of the product.

4. The injection volume is not only affected by the diameter of the screw, but also limited by the injection stroke
Injection stroke length: refers to the pushing length of the screw during the injection process. Even if the diameter is large, the stroke is short and the overall injection volume may be limited;
Effective injection volume=cross-sectional area of screw x stroke length.

5. The selection of injection machines should comprehensively consider product size and screw specifications
Small product size: Using small-diameter screws is beneficial for precise control of injection volume and avoiding waste;
Larger product size: When a larger injection volume is required, choosing a large-diameter screw can improve production efficiency;
When producing multiple products alternately, it is more flexible to choose injection machines with medium screw diameter or screw replacement function.

6. Increasing the diameter of the screw will also bring about changes in equipment structure and cost
Larger equipment volume and higher energy consumption: The material barrel, heater, and drive system matched with the large screw need to be stronger, resulting in an overall increase in machine size and cost;
Increased maintenance complexity: Larger screws are more difficult to disassemble and clean, especially during frequent material changes in production.