Shot volume in an injection molding machine is the total amount of molten plastic that the screw injects into the mold during a single cycle, measured in volume or weight.
It is a critical factor in achieving high-quality plastic parts, as an incorrect shot size can lead to defects like underfill or overfill.
The shot volume is determined by the combined volume of the part, the runner system, and the sprues, plus allowances for material shrinkage.
Shot volume injection molding is the amount of molten plastic injected into the mold cavity per cycle in injection molding.
Typically measured in weight grams per ounce or volume cubic centimeters per cubic inch.
Shot volume
Shot volume in injection molding machine is the maximum charging(storage) space for materials(resin) in the barrel.
That is why the shot volume also will be named shot size, and injection capacity,shot volume injection molding.
The shot volume is fixed, as the space between the barrel and screw can not be changed.
However, the injection weight will be changed if the material is different.
The shot Volume has not changed, weight changes with density.
The injection capacity is the same as the capacity of charging.
After the screw sucks back to the end, the charging space in the barrel is the volume of the shot.
Shot size formula in injection molding
Injection molding is a method for manufacturing plastic parts in high volumes that involves injecting molten material into the mould cavity.
In plastic injection molding, the raw material enters the barrel, melts.
And the plastic gets injected into the mould cavity for cooling and solidification after mould closure.
And finally, the mould opens and ejects the parts.
Refer to figure (i) for the diagram indicating an injection molding process.
How to calculate shot volume？
The calculation method for theoretical injection shot volume is usually the product of the screw head area and the maximum stroke.
The specific formula of shot volume is as follows:
Theoretical injection volume=π× (D/2)² × S
Among them:
D：D is the diameter of the screw (in centimeters or millimeters).
>S： S is the maximum stroke of the screw (in centimeters or millimeters).
π： π is pi, which is approximately equal to 3.14159.
Screw diameter D: The diameter of a screw is the maximum width of its cross-section,
Usually measured in millimeters (mm) or centimeters (cm).
Screw stroke S: Screw stroke refers to the maximum distance that the screw can move during the injection process,
Usually measured in millimeters (mm) or centimeters (cm).
Screw head area: The screw head area is the cross-sectional area of the screw, calculated using the formula π× (D2) 2 π× (2D) 2.
In practical applications, manufacturers usually use the theoretical injection volume to select the appropriate injection molding machine model.
In addition, the theoretical injection volume also helps evaluate the injection capacity and production efficiency of injection molding machines.
How do selection criteria？
Calculate the total injection weight and check if the machine shot volume can charge more material.
- Meet product requirements
- Do not exceed the maximum value
- Consider the characteristics of the raw materials
Meet product requirements
Firstly, the theoretical injection volume required needs to be determined based on the weight of the product and the requirements of the gating system.
In general, the total amount of material used in the product should be less than or equal to the theoretical injection volume.
Do not exceed the maximum value
When selecting an injection molding machine, it is necessary to ensure that the theoretical injection volume of the selected machine is greater than the total material consumption.
But at the same time, it cannot exceed the maximum theoretical injection volume of the machine, otherwise it will result in material waste or equipment damage.
Consider the characteristics of the raw materials
Different plastic materials may have different requirements for injection volume.
For example, for polystyrene (PS), the theoretical injection volume needs to meet a specific proportion range (such as between 20% and 75% of the product weight+gate system weight).
Haichen machine
Haichen is the manufacturer of injection molding machines, with an injection volume from:60 cm² to 43904 cm².
The shot volume of the injection molding machine is the space for the material charging.
The injection capacity means injection shot volume.
The theoretical injection volume is not only one of the key indicators but also affects production efficiency and product quality.
