An inventor recently contacted DMS Group-TW in Taiwan with a new consumer coupling product that required engineering refinement before entering tooling and mass production. The customer provided an initial design concept, and our team was asked to evaluate the prototype and recommend improvements to ensure a stable, secure locking function using spring-loaded steel balls, instead of O-rings.
During prototype testing, our engineers identified two main issues that affected stability and overall performance.
Problem 1: Wobble Caused by Outwardly Tapered Inner Wall
The lower receptacle of the coupling set featured an outwardly angled inner wall. After machining the first prototype, we discovered that this tapered geometry created excessive internal clearance, causing the upper mating piece to:
sit loosely,
wobble when inserted, and
weaken the spring-ball engagement.
This instability would negatively impact user experience and long-term durability.
Problem 2: Thin Wall Thickness Limited the Internal Groove for the Spring-Ball System
The lower component’s wall thickness was too thin, leaving insufficient room to machine:
the internal groove required to capture the steel balls,
secure seating surfaces for the spring-ball mechanism, and
stable engagement points for locking the top piece.
With such thin walls, the locking balls did not seat firmly, which caused inconsistent locking force.
Engineering Solutions by DMS Group-TW
1. Straight Inner Wall for the First 10 mm to Improve Stability
We modified the lower receptacle so that the first 10 mm of the inner diameter is perfectly straight (not tapered).
This adjustment achieved:
1 a tighter initial guiding fit 2 reduced wobble during insertion
3 more consistent alignment of the spring-ball locking points
This change significantly increased the overall stability of the coupling mechanism.💡 Tip: A reliable supplier will openly share quality reports and machining parameters.
2. Increased Wall Thickness for a Stronger Spring-Ball Groove
For a detailed view of our manufacturing process, see our related article:By slightly increasing the wall thickness and adjusting the internal diameter, we created enough space to machine:
1 a deeper and more stable ball-retaining groove, 2 improved seating for the steel balls, and 3 a stronger structure to withstand locking forces during repeated use.
This allowed the locking balls to engage more securely with the upper mating piece.
3. Re-engineering the Mating Part for Better Ball Engagement
The original mating component had a tapered outer surface. This caused the steel balls to slide inconsistently along the taper during insertion.
We redesigned the upper mating part so that the first 10 mm of the outer surface is straight, providing:
consistent contact with the spring-loaded steel balls
a firmer locking action
smoother insertion and removal
This improved the tactile feel and reliability of the coupling system.
A Successful Partnership
This project demonstrates how DMS Group-TW combines design insight with precision CNC manufacturing to help innovators develop manufacturable, high-performance mechanical products. Through close collaboration, we transformed the initial concept into a secure and reliable spring-and-ball coupling system ready for production.
We look forward to supporting more inventive product development and custom CNC projects worldwide.
2025/11/18