DB9 Strain Relief
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I needed a simple strain relief for a DB9 connector I had this is my solution to that.
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Model information
- Source
- Printables
- Category
- Electronics
- License
- Creative Commons — Attribution — Share Alike
This details the design and implementation of a custom 3D-printed internal strain relief insert designed to fit seamlessly inside standard DB9 plastic connector backshells. Traditional DB9 shells often rely on basic metal clamps or loose rubber grommets that can allow wire fatigue, pull-outs, or sharp bending right at the solder joints. This internal insert captures the wiring bundle securely inside the housing, providing robust mechanical strain relief and extending cable lifespan.
Key Design & Functional Features
Internal Housing Integration: Designed to seat precisely into the designated slot of an existing DB9 plastic shell assembly, preserving the original exterior footprint and latching hardware.
Two-Part Clamping Assembly: The strain relief mechanism consists of two 3D-printed halves that join together directly around the cable bundle.
Integrated Cable Collar / Grommet: Features a contoured exit collar (shown in green) that supports the conductor bundle as it exits the rear port, preventing tight bend radiuses and chafing against the outer shell.
Mechanical Strain Relief: Securing the two printed halves around the wiring isolates all tensile pull forces away from delicate DB9 pin solder cups or crimp terminals.
Bill of Materials (BOM) & Hardware Integration
Component | Specification | Function |
Strain Relief Assembly | 2-piece custom 3D-printed collar/insert (TPU or PETG recommended) | Clamps around the cable bundle and slides into the DB9 shell's internal slot. |
DB9 Shell / Hood | Standard 2-piece plastic DB9 backshell with jackscrews | Houses the connector, printed strain relief insert, and wiring assembly. |
Insert Fasteners | M2x8 Fluted Screws | Joins the two 3D-printed halves together around the cable before seating into the shell slot. |
Shell Fasteners | Standard shell assembly screws | Fastens the outer DB9 plastic hood halves together. |
Assembly Instructions
Wiring Prep: Strip outer jacket and solder or crimp conductors to the DB9 connector terminals.
Strain Relief Assembly: Place the two 3D-printed halves around the cable jacket directly behind the solder connections. Fasten the two printed halves together using the M2x8 fluted screws.
Shell Seating: Slide the assembled 3D-printed strain relief unit into the designated internal slot of the DB9 plastic shell half.
Final Closure: Place the top half of the DB9 plastic hood over the assembly and secure with the outer shell screws.
I included the fusion 360 model if you need to adjust the clearance.