Kruse Training
November 6, 2023

Maximizing Efficiency and Quality: The Critical Role of Design of Experiments (DOE) in Injection Molding


Design of Experiments (DOE) is a vital tool in the injection molding industry, playing a crucial role in optimizing processes and ensuring product quality. Here are some key points highlighting the importance of DOE in injection molding:

  1. Optimization of Process Parameters: Injection molding involves numerous variables, such as temperature, pressure, cooling time, and material flow. DOE helps in systematically exploring these variables and understanding their interactions. By doing so, it enables the identification of optimal process settings that yield the best product quality and efficiency.
  2. Cost Reduction: By using DOE to fine-tune the injection molding process, manufacturers can significantly reduce waste and improve yield. This directly reduces production costs, as less material is wasted, and fewer defective products are produced.
  3. Quality Improvement: DOE is instrumental in enhancing product quality. By understanding how different variables affect the final product, manufacturers can make adjustments to produce parts with higher precision, better aesthetic qualities, and improved structural integrity.
  4. Faster Time-to-Market: With DOE, the time required for process development and troubleshooting is significantly reduced. This accelerated process development means products can move from concept to market more quickly, providing a competitive advantage.
  5. Scalability and Reproducibility: DOE helps in creating robust processes that are scalable and reproducible. This is crucial for large-scale production, where consistency across batches is essential.
  6. Risk Management: By identifying the critical factors influencing the process and product quality, DOE aids in risk management. Manufacturers can proactively address potential issues, reducing the likelihood of defects and failures.
  7. Innovation and Experimentation: DOE encourages a structured approach to experimentation, fostering innovation in product and process design. By systematically exploring various combinations of parameters, new and more efficient ways of injection molding can be discovered.
  8. Customer Satisfaction: Improved product quality and consistency lead to higher customer satisfaction. DOE’s role in ensuring product reliability and meeting specifications is vital in maintaining and enhancing customer trust.
  9. Regulatory Compliance: In industries where injection molded parts must meet strict regulatory standards, such as medical or automotive, DOE is crucial in ensuring compliance. It provides a documented and systematic approach to validating process capabilities and product qualities.

Kruse Training Tip: The Five Stages of DOE

Experimental design techniques can be utilized by anyone with a fundamental understanding of injection molding.

There are five primary stages for conducting a designed experiment. These are planning, selecting the tests to run, conducting the experiment, analyzing the data, and then confirming the results.  Here is an overview of each stage:

Step 1- PLAN

The first step is planning the experiment. This includes defining the objective, selecting the factors to be studied, and determining the settings, or levels, for each factor. In this phase, we also determine the response of interest. The response of interest is the variable we are trying to determine by running the experiment. We will refer to this simply as the “response” throughout these lessons.


The second step is selecting the series of tests to be performed. In this phase we also need to determine the number of repeat samples for each experiment.  In a designed experiment a mathematical set of tests, referred to as orthogonal array (O.A.), are used for this step.

Step 3 – CONDUCT

The third step is conducting the experiment. It is important to have a written plan or protocol in place and that someone from the team is present while the trials are being conducted to note any deviations from the experiment protocol.

Step 4 – ANALYZE

After conducting the experiment, the fourth step is to measure the responses of interest and analyze the results. In this stage you will utilize the graphs and charts along with the statistical output generated from the software used for the experiment.

Step 5 – CONFIRM

The fifth and final step is the confirmation phase. By making a prediction of the best setting for each factor and then trying this setting one or more times, you can confirm the results.  Verifying the optimized process set up is essential for maintaining part quality.

In summary, DOE is an essential practice in the injection molding industry for its ability to optimize processes, reduce costs, improve quality, and accelerate product development, ultimately leading to increased competitiveness and customer satisfaction.