Metrology Tool Case

Project Overview

A precision-engineered storage solution designed to organize and protect measurement instrumentation, specifically a Starrett 799 digital caliper and steel ruler. This project demonstrates iterative CAD design methodology and additive manufacturing techniques to create a functional enclosure with appropriate geometric tolerances and ergonomic features.

Development Timeline

Initial Design Phase

The design process commenced with feature extraction from the Starrett 799 Digital Caliper technical diagram. The caliper's geometric profile was digitized in CAD through direct tracing of the provided engineering drawings. Similarly, the steel ruler's dimensional constraints were analyzed to establish custom-fit retention geometry for both measurement instruments.

• Extracted geometric features from Starrett 799 Digital Caliper technical documentation
• Digitized caliper profile through CAD-based reverse engineering of engineering drawings
• Analyzed steel ruler dimensional constraints to establish retention geometry
• Optimized spatial layout to minimize footprint while maintaining structural integrity

Version 1: Initial Prototype

Post-manufacturing evaluation of the first prototype revealed critical design flaws: the caliper retention feature exhibited an interference fit, preventing tool insertion, while the steel ruler groove depth was insufficient for proper seating. This iteration highlighted the necessity of implementing appropriate manufacturing tolerances and clearance fits in the design specification.

• Fabricated initial prototype via fused deposition modeling (FDM)
• Identified interference condition in caliper retention feature—negative clearance preventing insertion
• Quantified insufficient groove depth for steel ruler flange engagement
• Recognized requirement for systematic tolerance analysis and clearance fit implementation

Version 2: Refined Design

The second iteration addressed the identified failure modes through geometric modifications: the steel ruler groove depth was increased to ensure proper flange engagement, while the caliper retention feature was offset to establish an appropriate clearance fit. This resulted in a functional enclosure that maintains secure tool retention while enabling ergonomic extraction.

• Increased groove depth to accommodate full steel ruler flange engagement
• Applied geometric offset to caliper retention feature, establishing clearance fit with appropriate tolerance
• Optimized retention mechanism to balance secure tool constraint with extraction force requirements
• Validated design through functional testing, confirming proper accommodation of both measurement instruments

Version 3: Ergonomic Refinement

User experience evaluation revealed that caliper extraction required excessive force due to limited grip clearance. To improve ergonomics, a finger relief groove was integrated into the caliper retention feature, providing mechanical advantage for tool removal. Additionally, the steel ruler groove was widened to accommodate the flanges with increased clearance, reducing insertion resistance.

• Integrated finger relief groove (pinch feature) into caliper retention geometry to reduce extraction force
• Widened steel ruler groove clearance to accommodate flange geometry with improved tolerance
• Enhanced ergonomic accessibility through strategic removal of material at grip interface
• Optimized user interaction through mechanical design modifications reducing manual force requirements