The complexities of engineering a plastic part or product for use in a critical-use application must translate to moldability. If a molder is inexperienced in mold design and process optimization, there’s a good bet they won’t be familiar with methodologies essential for creating a highly efficient production process such as scientific molding and, more specifically Design of Experiments (DOE) within scientific molding. This article discusses key steps tool and process engineers take to ensure consistent and repeatable manufacturability of flawless molded parts.
Why does the process matter?
Why are scientific molding and DOE important to your critical-use application or injection molding project? Simply put, they take the injection molding process to a much higher level of precision, helping to save costs in the long run by allowing for identification and correction of tooling problems prior to production.
Experienced injection molders use scientific molding and DOE as the foundation for a robust and optimized injection molding process that leads to the successful manufacture of critical-use plastic parts and components by introducing a series of progressive checks and balances.
Steps to Process Optimization
When making decisions about process optimization, tool engineers and process engineers work together to proactively identify and correct any tooling weaknesses.
1. Mold functionality examination
Every aspect of the injection mold’s mechanical functionality is assessed to make sure everything works as designed, using the material settings provided by the supplier of the material to be molded.
2. Short shot testing
Dynamic pressure loss and, in a multiple-cavity mold, cavity imbalance are determined and documented using sample parts. Also, the rheology curve (or viscosity curve) is established to indicate the best fill rate and pattern.
3. Gate seal studies
Both the pressure curve and weight of the sample parts are observed to see if the gates fully seal, and at what point on the mold cavity (or cavities in multiple-cavity molds) sealing occurs.
4. Sample parts evaluation/data recording
All defects are examined and recorded, along with recommendations for any adjustments in the process or the tool in order to correct the defects. Likewise, data is recorded with regard to melt temperature, fill time, mold temperature, coolant flow, cycle time and pressure curves.
5. Quality control
The sample parts go to quality control for examination and documentation of their measurements, shot-to-shot consistencies and overall quality.
6. Tool adjustments
Based on information gathered during quality control, necessary tool adjustments are made, and new sample parts are made.
7. New sample creation/quality control testing
The new sample parts are subjected to the same quality testing and more adjustments are made, if necessary.
8. Process parameter/performance ranges verificationThe quality testing and adjustments continue until all process parameters meet their performance ranges. Once verified, the mold is ready for use and the process is deemed optimized.
By leveraging scientific molding and DOE, experienced complex injection molding engineers understand each phase of development — from mold design and flow analysis to process monitoring and quality control. The result? The most efficient and robust process possible for manufacturing the complex injection molded plastic parts and products you need for critical-use applications from medical devices to heavy trucking parts.
Read about how we applied scientific molding principles to optimize a complex production process for a life-saving device in our recent case study, Why Molder Experience Matters in Life-Saving Applications. Click the button below for your free copy.