In modern foundry education, the traditional teaching of sand casting has long relied on theoretical explanations and simple demonstrations, which often fail to provide students with a comprehensive and tactile understanding of the real casting process. As a result, we have developed an interactive virtual training system for gravity sand casting based on the Unity3D platform. This system uses virtual reality technology to simulate the complete process of producing sand casting parts, from mold preparation to final solidification, thereby offering a safe, low-cost, and highly engaging learning environment.
Our system is built upon a well-defined pipeline that integrates powerful three-dimensional modeling tools, animation software, and a robust game engine. The main objective is to help learners visualize and practice every step involved in manufacturing high-quality sand casting parts. In this article, we describe the theoretical background, system architecture, implementation details, and final deployment of the virtual training environment.
Current Challenges in Sand Casting Education
Sand casting remains one of the most widely used metal-forming processes in the industry. It offers excellent flexibility for producing sand casting parts of varying complexity, size, and alloy composition. However, educational institutions face several obstacles when teaching this process. Laboratory setups are expensive, occupy large spaces, and introduce safety risks such as molten metal splashes, high-temperature burns, and fume inhalation. Most current classes therefore rely on instructor demonstrations or video recordings, which limit student interaction and do not encourage hands-on experimentation.
To overcome these issues, we propose a virtual reality-based training system that simulates manual molding and gravity pouring. The system allows students to interact with three-dimensional models of flasks, patterns, rammers, ladles, and sand casting parts in a virtual scene. They can follow procedural steps and observe the results of their actions in real time. This not only improves knowledge retention but also reduces the overall cost and risk associated with physical instruction.
System Architecture and Development Workflow
The development of the virtual training system follows a clear and modular workflow. We use UG NX for solid modeling, 3ds Max for animation and rendering, and Unity3D for system integration and interaction. In addition, a finite element module is used to simulate the temperature field during solidification, which enhances the realism of sand casting parts production. The overall workflow is summarized in the table below.
| Stage | Tool | Purpose | Output |
|---|---|---|---|
| 1 | UG NX | Create 3D solid models of all equipment and sand casting parts | Model files (e.g., .prt, .stl) |
| 2 | 3ds Max | Generate motion sequences, assign materials, render animations | FBX animation clips |
| 3 | HZCAE (IntelliCAST) | Simulate temperature distribution during pouring and cooling | Temperature field images/videos |
| 4 | Unity3D | Integrate assets, write scripts, design UI, implement interaction | Executable virtual training application |
The development pipeline is designed to be reusable and scalable. By separating content creation from interaction logic, we can easily update the simulation of sand casting parts for different mold geometries or casting processes. The system is ultimately published for Windows platforms, and it can be linked with the HTC Vive headset for a fully immersive virtual reality experience.
Gravity Sand Casting Process Overview
Before describing the technical implementation, it is important to outline the main steps in gravity sand casting that we simulate. The process begins with pattern preparation, then sand molding, core setting, mold closing, pouring, solidification, and finally shakeout and cleaning. Each step directly influences the quality of the final sand casting parts. Our virtual system guides the learner through these stages with animated actions and explanatory text.
One of the most critical phases is solidification, where the molten metal cools and develops its microstructure. The temperature field evolution can be modeled by the transient heat conduction equation:
$$
\frac{\partial T}{\partial t} = \alpha \nabla^2 T + \frac{\dot{q}}{\rho c_p}
$$
where \(T\) is the temperature, \(t\) is time, \(\alpha = k/(\rho c_p)\) is the thermal diffusivity, \(k\) is the thermal conductivity, \(\rho\) is the density, \(c_p\) is the specific heat, and \(\dot{q}\) represents the internal heat generation. The solidification time of sand casting parts can also be estimated using Chvorinov’s rule, which relates the solidification time \(t_s\) to the volume-to-surface-area ratio:
$$
t_s = B \left( \frac{V}{A} \right)^n
$$
where \(V\) is the volume of the casting, \(A\) is the cooling surface area, \(B\) is a mold constant, and \(n\) is an exponent typically around 1.5 to 2. These theoretical equations are integrated into the virtual simulation to compute realistic cooling rates and visualize temperature contours on the surface of sand casting parts.
3D Modeling with UG NX
UG NX is a highly capable CAD software that allows us to build precise solid models. We modeled every component required for the gravity sand casting system, including different types of wooden or metal patterns, match plates, flasks, cope and drag, pouring basin, sprue, runner, gate, riser, and the final sand casting parts. The table below lists the main model categories along with their purpose.
| Model Category | Examples | Function in Simulation |
|---|---|---|
| Molding tools | Rammers, trowels, slickers, bellows | Use for compacting sand and finishing mold surfaces |
| Flasks | Cope flask, drag flask | Contain the sand mold and create the parting line |
| Patterns | Split pattern, loose pattern | Form the cavity that defines the shape of sand casting parts |
| Gating system | Pouring basin, sprue, runner, ingate | Direct molten metal into the mold cavity |
| Casting products | Flange, gear blank, valve body | Simulate the final sand casting parts to be produced |
After building the models, we applied mesh simplification to reduce the number of triangles while preserving visual fidelity. This is essential for smooth real-time interaction in Unity3D, especially when rendering multiple sand casting parts and tools simultaneously.
Animation Generation Using 3ds Max
With the solid models prepared, we imported them into 3ds Max to create the keyframe-based animation of the casting sequence. The animation covers the entire procedure: placing the pattern, ramming sand, removing the pattern, cutting the runner and gate, setting cores, closing the mold, pouring the liquid metal, waiting for solidification, and finally shaking out the casting. We paid special attention to the correct chronological order and overlap of these actions to reflect real practice.
In 3ds Max, each object’s transformation is controlled by position, rotation, and scale keyframes. The animation is exported in FBX format, which Unity3D can natively read. For a clean integration, we split the continuous animation into discrete clips during the export. A common way to handle time progression is to define the frame rate and duration according to the following relationship:
$$
F_r = \frac{N_f}{T_d}
$$
where \(F_r\) is the frame rate in frames per second, \(N_f\) is the number of frames, and \(T_d\) is the animation duration in seconds. For our virtual training, we set the frame rate to 30 frames per second, which provides a smooth visual experience while keeping the file size manageable for sand casting parts demonstrations.
Material assignment is equally important. We applied realistic textures to the sand, molten metal, and metallic tools. The rendering in 3ds Max ensures that the shadows and reflections are accurately computed, resulting in high-quality visual assets for the final virtual environment.
Temperature Field Simulation with HZCAE
To make the virtual training even more scientifically accurate, we incorporated a finite element casting simulation module that computes the temperature field during pouring and cooling. This module, known as HZCAE, was developed at our laboratory and has been refined through years of industrial practice. The finite element equation for transient thermal analysis is:
$$
[K] \{T\} + [C] \{\dot{T}\} = \{Q\}
$$
where \([K]\) is the conductivity matrix, \([C]\) is the heat capacity matrix, \(\{T\}\) is the nodal temperature vector, \(\dot{T}\) is the time derivative of temperature, and \(\{Q\}\) is the heat source vector. Solving this system at each time step yields the temperature distribution in the casting and the mold.
We export the thermal results as image sequences, which are then integrated into the Unity3D scene. These images are applied as textures on the three-dimensional model of sand casting parts, allowing students to watch the temperature gradient evolve on the casting surface in real time. This hybrid approach combines the visual richness of virtual reality with the physical accuracy of numerical simulation. The table below summarizes some key properties used for a typical steel casting simulation.
| Parameter | Value | Unit |
|---|---|---|
| Thermal conductivity of sand | 0.6 | W/(m·K) |
| Specific heat of sand | 800 | J/(kg·K) |
| Density of molten steel | 7800 | kg/m³ |
| Latent heat | 270000 | J/kg |
| Pouring temperature | 1550 | °C |
| Initial mold temperature | 25 | °C |
The resulting temperature contour maps clearly show the hot spots and cooling rates, enabling learners to understand how different regions of sand casting parts solidify at different times, which is critical for predicting shrinkage defects.
Development of the Virtual Training System in Unity3D
Unity3D is the core platform for our virtual training system. It provides a powerful scene graph, animation state machine, and an extensive UI framework. We used C# for scripting, which is both stable and feature-rich. The scripts in our system control character movement, camera switching, scene transitions, animation triggering, and object highlighting. A summary of the principal scripts is shown in the following table.
| Script Name | Function |
|---|---|
| CameraControl.cs | Enables free navigation and orbit around the virtual scene |
| SceneManager.cs | Loads and unloads different scenes such as menu, tutorial, and simulation |
| AnimationTrigger.cs | Plays and stops the designated animation clip for each process step |
| UIManager.cs | Handles button clicks, text updates, and progress tracking |
| ObjectHighlighter.cs | Highlights the currently relevant model to direct the user’s attention |
| TemperatureOverlay.cs | Updates the temperature texture on sand casting parts during solidification |
The user interface was designed with clarity and ease of use in mind. The main menu provides access to several modules, including an introduction, a procedural guide, a safety notice, and an interactive practice mode. We created the UI elements as PNG images using Photoshop to ensure that text remains legible and responsive at different screen resolutions. A typical welcome screen and the main menu are shown in the following table of scene snapshots.
| Scene | Content |
|---|---|
| Welcome Scene | Background image, system title, “Enter” button |
| Main Menu | Buttons to start training, view theory, check safety, and quit |
| Process Flow | Step-by-step animation of the gravity sand casting sequence |
| Safety Notices | List of important precautions when handling molten metal and sand casting parts |
| Part Library | Selection of different sand casting parts to simulate |
One of the most challenging tasks was to split the long animation into several short clips that correspond to individual operational steps. In Unity3D, we imported the FBX file and divided it using the Animation window. We set the start and end frames for each clip and assigned them to the Animator controller. This allowed us to play each action separately, such as “ramming sand” or “pouring metal”, when the user clicks the corresponding button. The relationship between button presses and animation playback is managed by an event-driven system that contributes to the overall interactivity index:
$$
I = \frac{N_{\text{interactive steps}}}{N_{\text{total steps}}} \times 100\%
$$
where \(N_{\text{interactive steps}}\) is the number of steps where the user has to perform an action or click a button, and \(N_{\text{total steps}}\) is the total number of procedural steps. In our system, nearly all steps are interactive, giving a high interactivity score and making the training of sand casting parts more engaging.
System Publication and Deployment
After completing the integration and testing, we published the virtual training system as a standalone Windows application. Unity3D’s Build Settings allow us to choose the target platform and scene list. The build process generates an executable file along with a resource folder. Both must be present to run the application correctly. The final product can be operated with a mouse and keyboard, or with an HTC Vive headset for a full immersive VR experience. In the VR mode, the user can walk around the virtual foundry, pick up tools, and interact with the sand mold in a more natural manner.
The published system was tested on multiple computers. We measured the average frame rate to ensure smooth performance. The frame rate can be estimated by the following equation:
$$
FPS = \frac{1}{t_{\text{render}} + t_{\text{update}}}
$$
where \(t_{\text{render}}\) is the time required to render a frame and \(t_{\text{update}}\) is the time for script updates and physics calculations. The optimized models and efficient scripts keep the value above 60 frames per second in most scenes, even when displaying complex sand casting parts with temperature overlays.
Educational Benefits and Future Prospects
The virtual training system offers multiple benefits over traditional education. It reduces the need for expensive foundry equipment and consumables, eliminates safety hazards, and allows unlimited repetition of the casting process. Students can explore the internal structure of the mold, measure dimensions, and inspect the impact of process parameters on the quality of sand casting parts. Moreover, the system can be extended to other casting processes, such as investment casting or die casting, by changing the models and animations.
We believe that the integration of virtual reality with numerical simulation is a promising direction for advanced manufacturing education. The current system already demonstrates the feasibility of teaching gravity sand casting through a fully interactive environment. In the future, we plan to add more realistic physics, such as fluid flow simulation during pouring, and to incorporate haptic feedback for even greater immersion. These enhancements will further improve the training outcomes and help more students master the production of high-quality sand casting parts.
Conclusion
In this paper, we have described the development of a virtual training system for gravity sand casting based on Unity3D. The system was created using UG NX for modeling, 3ds Max for animation, HZCAE for temperature field simulation, and Unity3D for system integration and interaction. Through this workflow, we successfully built an immersive and interactive learning environment that covers the entire process of manufacturing sand casting parts. The system has significant potential to improve modern foundry education by making the learning process safer, cheaper, and more efficient.
We have also presented several mathematical models related to heat transfer and animation control, which are embedded into the system to increase its fidelity. The use of tables in this paper summarizes the key development stages, model lists, script functions, and simulation parameters, offering a clear reference for other developers who wish to build similar virtual training platforms for sand casting parts or other manufacturing processes.