What is projected area in plastic injection molding
The total projection area is determined by adding up the projected areas of the cavities and runners in relation to the parting surface. As such, this value is subject to variation based on the number of items being molded and the layout of the runners. It is important to keep these factors in mind when calculating the total projection area.
Below is the guide for how to calculate the projected area for injection molding. This process is crucial for ensuring that the mold can be properly created and that the final product meets the necessary specifications or help you to pick the right injection molding machines for the mold in production.
Step 1: Determine the parting line of the mold.
This is the separation line between the two halves of the mold and is typically the highest point of the part. It is also where the part is ejected from the mold.
Step 2: Identify the areas that will create undercuts.
Undercuts are areas of the part that create a recess or projection that would prevent the part from being ejected from the mold. Undercuts need to be addressed during the design phase to ensure the mold can be properly created.
Step 3: Calculate the total area of the part.
Measure the length and width of the part and multiply them to get the total area. If the part has any holes or cutouts, subtract the area of those features from the total area.
Step 4: Calculate the projected area of the part.
The projected area is the area of the part that is visible from the direction that the mold will be filled. To calculate the projected area, measure the height of the part and multiply it by the total area of the part.
Step 5: Account for any draft angles.
Draft angles are angles built into the part to aid in its ejection from the mold. The projected area calculation assumes that the part is perfectly vertical, so if there are any draft angles, they need to be accounted for by multiplying the projected area by the cosine of the draft angle.
Step 6: Calculate the projected area of the mold.
The projected area of the mold is calculated by multiplying the projected area of the part by a mold factor, which is typically between 1.5 and 3.
Step 7: Calculate the clamp force required.
The clamp force required to hold the mold closed during injection is proportional to the projected area of the mold. The formula for calculating clamp force is:
Clamp force = projected area of the mold x injection pressure / number of cavities
Where injection pressure is the pressure required to fill the mold and number of cavities is the number of parts that will be produced in each cycle.
