High-precision tool solution for dental dilators

Geometric Complexity: Challenging Length-to-Wall-Thickness Ratios

The requirements for this component represented a technical challenge even at the design stage. With a total length of approximately 127 mm (5.0″), the tube features a wall thickness of only 0.75 mm and an inner diameter of just 1.32 mm. A detailed part drawing containing all geometric product specifications and a corresponding 3D model served as the engineering foundation for the mold design.

The Challenge: Core Stability Under Injection Pressure

Achieving a process-reliable result with such a small inner core diameter over a length of 127 mm is impossible using conventional injection molding techniques and standard tool sequences. The primary obstacle occurs during the injection phase: as the plastic melt fills the cavity, the mass never distributes perfectly evenly at these dimensions. Due to the uneven load during filling and the high injection pressure, the long, fragile inner core would inevitably deflect or even break. A solution had to be found to keep the core stable.

Innovative Core Guidance: Integrated Support Sleeve as a Stabilizer

Success was achieved through a specialized tooling solution. While a metal inner core in a steel mold is typically guided only at the rear end and otherwise remains unsupported, we integrated an additional support sleeve. This sleeve is significantly more rigid and initially occupies the free space that is later filled with plastic.

During the actual injection process, the support sleeve is retracted in a controlled manner, successively releasing the cavity volume. This mechanical support stabilizes the core during the critical injection phase, effectively preventing any bending or breakage.

Process-Reliable Implementation and Validation

To ensure the customer could perform in-house production seamlessly, RKT handled the entire sampling and tool validation process. Validation included “Pro-Op”—a weight-based statistical method used to establish a stable injection molding process for optimal plastic filling. The tool was fine-tuned based on these results. During the initial trial runs, the customer joined us on-site to verify part functionality and provide critical feedback. We also provided on-site support during the final implementation of the mold into the customer’s machine.

Dimensional Accuracy and Technological Scalability

The project’s success was measurable: the dental dilator was produced with consistent process stability within strictly defined dimensions and tolerances, resulting in full customer satisfaction. With this specially developed tooling technology, we are now positioned to reliably solve similar challenges involving long, extremely thin-walled hollow bodies in the future.