July 2025 - Jan 2026

Modular S-Pen Grip Sleeve
Iterative Mechanical Design & FDM Prototyping

A modular, 3D-printed grip sleeve designed to improve S-Pen ergonomics through constraint-driven mechanical design, threaded interfaces, and real-world durability testing.

Quick Facts

  • Role: Designer & Fabricator
  • Tools: Onshape, Bambu Studio, Bambu Lab A1 Mini
  • Process: Iterative prototyping, failure analysis
  • Focus: Ergonomics, durability, manufacturability

    • Problem Statement

    The Problem

    Modern styli like the Samsung S-Pen prioritize precision and compactness, but their slim form factor can cause discomfort and grip fatigue during extended writing. Existing third-party grips—often silicone—stretch, deform, or lack consistent retention.

    Goal

    Design a non-destructive, modular grip sleeve that improves ergonomics without sacrificing precision or manufacturability.

    Design Constraints

    Key Constraints

  • Must fit securely without adhesives or permanent modification
  • Must not interfere with writing tip or sensing functionality
  • Must be printable on consumer-grade FDM hardware
  • Small-scale geometry limited by nozzle resolution
  • Durability required under daily use (install/removal + backpack transport)

    • These constraints frame every other design decision that follows.

    Concept Evolution

    Early Two-Piece Design

    Early partial-coverage design used to isolate attachment mechanisms.

    Slide-Lock vs Threaded

    Slide-lock concepts failed at FDM scale, prompting transition to threaded interfaces.

    Threaded Modular System

    Threaded attachment enabled reliable retention and modular iteration.

    Engineering Decisions

    Key Engineering Decisions

    Threaded Interfaces

  • Chosen over slide-locks due to FDM resolution limits
  • Tolerant to print variation
  • Scalable across modular components
    • Result: Reliable attachment without adhesives

    0.2 mm Nozzle Adoption

  • Improved thread fidelity at small diameters
  • Increased print time but enabled viable designs
    • Result: Printable threads at stylus scale

    Modular Architecture

  • Grip geometry separated from retention interface
  • Allowed rapid ergonomic experimentation
    • Result: Multiple grip variants without redesigning the entire sleeve

    Ergonomic Exploration

    Grip Geometry Variants

    Faceted, knurled, and smooth profiles were evaluated to explore tactile feedback, rotational stability, and subjective comfort.

    Failure & Iteration

    Durability-Driven Iteration

    Failure Example

    Early failures at threaded interfaces revealed stress concentration and insufficient wall thickness.

    Fix Example

    Thread relief and increased engagement redistributed stress and improved durability.

    Key Takeaway:

    Durability emerged as a dominant constraint only after extended real-world use.

    Results & Tradeoffs

    Outcomes

  • Improved comfort during extended writing
  • Reliable, repeatable attachment
  • Manufacturable on consumer-grade hardware

    • Known Tradeoffs

  • Partial obstruction of S-Pen side button
  • Magnetic storage compatibility not preserved
  • Durability improved, not “indestructible”

    • What This Project Demonstrates

    Skills Demonstrated

  • Constraint-driven mechanical design
  • Iterative prototyping & failure analysis
  • Small-scale threaded design for FDM
  • CAD parameterization (Onshape)
  • Manufacturing-aware design decisions

    • Optional Extras

  • Full Design Case Study (PDF)
  • Makerworld - Body Components
  • Makerworld - Grip Modules

    • This model is split into two MakerWorld uploads due to different print process requirements. Body components prioritize dimensional accuracy and thread strength, while grip modules prioritize surface finish and ergonomics.