Mastering Press Size Calculation:  Essential Tips for Successful Plastic  Injection Molded Projects ..
                     Mastering Press Size Calculation: 
Essential Tips for Successful Plastic 
Injection Molded Projects
Choosing the right press size is a critical factor in the success of any plastic injection molded 
project. The press size determines the capacity and capabilities of the machine to produce 
high- quality parts. In this article, we will discuss essential tips and considerations for 
calculating the right press size for your project.
•Understand Your Project Requirements
Before calculating the press size, it is crucial to have a clear understanding of your project 
requirements. Consider factors such as the type of plastic material, part dimensions, 
production volume, and desired quality standards. These requirements will help determine the 
appropriate tonnage and clamping force needed for the project.
•Calculate Required Clamping Force
Clamping force refers to the pressure applied to hold the mold closed during the injection 
process. To calculate the required clamping force, consider the projected area of the part, the 
type of material being used, and the number of cavities in the mold. This calculation ensures 
that the press can exert enough force to securely hold the mold and prevent flash or other 
defects.
•Determine the Shot Size
The shot size refers to the volume of material injected into the mold. It is important to 
calculate the shot size accurately to avoid overfilling or underfilling the mold. Consider factors 
such as  the part weight, material density, and desired part characteristics. A larger shot size 
may  require a press with a higher injection capacity.
•Consider the Mold Size and Design
The size and design of the mold also play a crucial role in determining the appropriate press 
size. Evaluate the mold dimensions, including the mold base size, maximum mold opening, 
and mold thickness. Ensure that the chosen press can accommodate the mold size and has 
enough space for mold installation, cooling, and ejection.
•Evaluate Machine Specifications and Features
When selecting a press size, it is important to consider the specifications and features of the 
machine. Look for features such as injection speed, injection pressure, mold open/close 
speed, and the ability to control temperature and pressure accurately. These features 
contribute to the overall performance and efficiency of the injection molding process.
•Factor in the Material Properties
Different plastic materials have varying flow characteristics and require specific injection 
molding conditions. Consider the melt flow rate (MFR) or viscosity of the material, as it can 
impact the injection pressure and fill time. Materials with higher MFR may require higher 
injection pressures and larger press sizes to achieve proper flow and fill the mold adequately.
•Account for Projected Volume
The projected volume of your production plays a significant role in determining the 
appropriate press size. If you anticipate high-volume production, it may be beneficial to select 
a larger press to accommodate increased production speed and reduce cycle times. However, 
for low-volume projects, a smaller press may suffice.
•Take Part Complexity into Account
The complexity of the part can influence the required press size. Parts with intricate 
geometries, thin walls, or multiple undercuts may require higher clamping forces to ensure
proper mold filling and ejection. Evaluate the part design and consult with a mold designer or 
engineer to determine the necessary press size based on part complexity.
•Consider Future Expansion
If you anticipate future growth or plan to expand your production capabilities, it's advisable to 
consider a press size that allows for scalability. Choosing a press with slightly higher tonnage 
than your immediate requirements can provide flexibility for future projects without the need 
for immediate press replacement.
•Seek Expert Advice
When in doubt, it is always beneficial to seek advice from a custom injection mould 
manufacturer. A professional molder can provide valuable insights, conduct thorough analysis, 
and recommend the most suitable press size based on your specific project requirements. 
With expertise an experienced molder can help ensure optimal performance, efficiency, and 
cost- effectiveness in your cheap injection molding process.
Conclusion
Calculating the right press size is a crucial step in ensuring the success of your injection 
molding solutions. By understanding your project requirements, calculating the required 
clamping force and shot size, considering the mold size and design, and evaluating machine 
specifications, you can make an informed decision. Consulting with the best injection molding 
company can provide valuable insights and expertise to help you select the appropriate press 
size for your project. Making the right choice will result in efficient production, high-quality 
parts, and  overall project success.