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Haptic Ramming Tool

Project team member(s): Ashley Davidson, Becky Miller, Jeremy Merritt, Zachary Larson

The motivation for this project stems from the challenges novice students face when learning manual green sand compaction in the foundry. Our goal is to create a haptic-augmented foundry rammer that provides real-time vibrotactile feedback to alert users when they have reached the proper force for each layer. This tool aims to quantify and standardize the historically subjective task of knowing when sand has been rammed "hard enough". Ultimately, we hope to determine if this haptic augmentation provides a measurable improvement in helping students properly compact sand molds.

Introduction

We are all Product Realization Lab (PRL) course assistants who specialize in the foundry, where teaching the sand casting "ram-up" process is a significant part of our work. This process requires students to compact sand layer-by-layer around self-designed patterns, with forces needing to increase sequentially to achieve proper compaction. Because instructing this subjective technique can be challenging, we believe a haptic device providing feedback on actual forces would be a highly appropriate educational tool to help novices learn the necessary feel for the process.

Background

Current literature lacks direct examples of vibrotactile feedback integrated into manual foundry tools, so our theoretical framework relies on core haptics research. Papetti et al. (2017) demonstrated that human sensitivity to vibrations shifts dramatically depending on how hard a hand actively pushes. As participants press harder, the physical contact area of their finger increases, triggering "spatial summation" in the skin's Pacinian channel and increasing overall sensitivity. This suggests that as users apply more force to our tool, they will become better conductors for the mechanical waves.

Additionally, Veliky et al. (2024) explored low-cost load cells for haptics in surgical training. Their success in building cheap, disposable-friendly haptic components validates our approach to building a cost-effective training tool rather than a precision lab instrument. Finally, Bast et al. (2009) investigated the non-linear behavior of moulding sand under stress. Their methods for analyzing sand compaction help us model system dynamics under force and establish the target forces that should be applied using the tool.

Methods

Hardware Design and Implementation

The design integrates a 50kg capacity load cell (TAS606 disc) into a standard foundry butt peen. Because this specific load cell only allows mounting on one side, we designed the handle to thread into one side of the sensor while the other side utilizes a sliding fit over the handle. The system is powered by a microcontroller (Arduino Uno) and utilizes an HX711 amplifier and a motor driver circuit. For the physical feedback, we mounted Eccentric Rotating Mass (ERM) vibration motors to the handle.

System Analysis and Control

The microcontroller translates analog compressive force data from the load cell into real-time vibrotactile feedback using the ERM motors, which are tuned to approximately 250 Hz. The system isolates the complex haptic feedback into a single, controllable degree of freedom: downward compressive force.

Demonstration / Application

• (To be completed after final user testing and open house)*

Results

Preliminary force testing was conducted to determine the ideal target forces required for proper compaction at different mold depths. Based on participant-balanced averages, the target force for Layer 1 is set to 47.85 lbf, and the target force for Layer 2 is set to 75.66 lbf. Further results regarding the device's qualitative efficacy with novice users will be documented following open house testing.

Future Work

• (To be completed detailing how the system could be improved or applied in other PRL tooling)*

Acknowledgments

• (Optional: List anyone who helped with your project here)*

Files

• CAD Models: [Link to be added]
• Arduino Code: [Link to be added]
• Bill of Materials: [Link to be added]

References

1. Papetti, S., Järveläinen, H., Giordano, B. L., Schiesser, S., & Fröhlich, M. (2017). Vibrotactile sensitivity in active touch: Effect of pressing force. IEEE Transactions on Haptics, 10(1), 113-122. 2. Veliky, Madison, Garrison L. H. Johnston, Ahmet Yildiz, and Nabil Simaan. "A Feasibility Study of a Soft, Low-Cost, 6-Axis Load Cell for Haptics." arXiv preprint, 2024. 3. Bast, J., Kadauw, A. & Malaschkin, A. Optimising of Moulding Parameters for Green Sand Compaction by Computer Simulation and a New Compaction Measuring Device. Inter Metalcast 3, 55-65 (2009).

Appendix: Project Checkpoints

Checkpoint 1

1. Project Hardware Status We are currently a little behind schedule, as our primary hardware order is still in transit. To maintain our overall project timeline and continue progress, we shifted our immediate focus to prototyping mechanical integration risks, specifically regarding the sensor mounts and actuator selection.

2. Load Cell Integration & Sliding Shaft Prototype The primary mechanical constraint we are working around is that our specific load cell only allows for single-sided mounting. Cantilevering a load on a single-sided mount risks introducing off-axis moments that would severely skew our force readings.

To solve this, we designed and physically prototyped a sliding shaft assembly to mechanically isolate the sensor. The shaft constrains the movement to a single axis, ensuring that any lateral or torsional loads are absorbed by the housing rather than the sensor. We integrated a retaining spring to hold the two sliding halves captive; this keeps the assembly securely mated under dynamic movement while ensuring the force transfer directly into the load cell remains strictly linear.

3. Haptic Actuator Selection For the haptic feedback loop, we established a two-stage testing plan to guarantee the user receives an adequate tactile response.

High-Output Contingency: Anticipating that the mass of our final mechanical assembly might damp the vibration of the smaller coin motors, we also sourced heavier-duty Jameco 256365 vibration motors.

Once the hardware arrives, we will run immediate A/B testing on both setups. If the standard disc motors lack the necessary amplitude to cut through the mechanical inertia of the device, we will immediately drop in the larger Jameco units to ensure clear haptic communication.

Photos here: https://drive.google.com/drive/folders/1upN5CkKifeXnWkuOm3mj9HftDyzQGwNk?usp=sharing

Checkpoint 2

• (To be filled out during the next checkpoint phase)*