# Presentation: 149512

## Objectives:               Determine constitutive equations and develop software tools for accurately and efficiently predicting pattern tooling and casting dimensions for all types of investment castings.  Key program considerations include:

**Predicting Pattern Tooling & Casting ****	****    Dimensions for Investment Casting - Phase I**
**Srinath Viswanathan & Adrian Sabau**
***Oak Ridge National Laboratory***

**Objectives:****               **Determine constitutive equations and develop software tools for accurately and efficiently predicting pattern tooling and casting dimensions for all types of investment castings.  Key program considerations include:
- Thermal expansion
- Mold restraint on the wax and alloy
- Thermo-mechanical behavior, such as plastic, creep, and elastic deformation of wax, shell, and alloy materials during solidification and subsequent cooling.
- The computational models also will take into account the solidification and crystallization characteristics of the alloy wax and alloy, respectively.
**Sponsors:**
- American Foundry Society Des Plaines, IL
- Accu-Cast, Inc., Chattanooga, TN
- DOE Office of Industrial Technology
- Howmet Corp., Whitehall, MI
- Johnson & Johnson, Inc. Raynham, MA
- M. Argueso & Co. Mamaroneck, NY
- MINCO, Inc., Midway, TN
- PED Manufacturing Ltd. Oregon City, OR
- Precision Metalsmiths, Inc. Cleveland, OH
- Spokane Industries Spokane, WA
- UES, Inc., Annapolis, MD
**Problem/Opportunity:**
- As tools for predicting pattern tooling to achieve casting dimensions are very limited, trial and error approaches during the first article production is used.  Pattern modifications required to tune the process increase lead times and raise costs.** **To date, technical literature has been limited to experimental, phenomenological studies aimed at obtaining empirical correlations for application in industry. In this project will develop standardized material property measurement tests and computational methodologies for accurately predicting pattern tooling and casting dimensions, taking into account the characteristics of the pattern wax, shell mold, and alloy solidification.

## Future Potential:

- The development of constitutive equations for wax, shell, and alloy materials based on experimental measurements will provide a sound base for casting packages.  Future efforts will focus on filled waxes, shell, and alloy materials. To facilitate adoption by industry, tutorials on the use of investment casting models for production castings will be developed. Workshops will be conducted for industry sponsors and the results will be disseminated through trade press and industry conferences.  For more information visit:
- _http://www.ms.ornl.gov/researchgroups/process/PROCESS.HTM_

**Action/Implementation:**
- Guidelines for pattern handling are currently available but cannot be used to predict wax deformation. Phase I focuses on measuring wax properties and predicting wax pattern dimensions based on thermal expansion/contraction and viscoelastic properties of the wax during its crystallization and subsequent cooling.
- Models that seek to predict investment casting and tooling dimensions must include heat transfer, solidification, stress build-up due to the restraint of wax and alloy geometrical features.  Thermo-mechanical properties of the alloy (elastic, viscoplastic) and wax (viscoelastic) must be considered.
- Pressure and temperature measurements can be used to determine the maximum dwell time and the onset of gate freezing.
- Temperature data near the die interface was used to estimate the heat transfer coefficient

- The shrinkage factor is dimension dependent.
- Shrinkage of the pattern length is larger for the restrained pattern.
- There is a good agreement between experimental data and numerical simulation results of wax pattern distortion.

*   **Test methods used to characterize polymeric materials were used to quantify wax deformation properties.*
*   **Stepped wax patterns, with and without mold restraint, were made.*
*   **Analysis procedures for computing the wax dimensions were developed.*

- Shrinkage [cm]