Finishing Cannulae

4 Points for Cannula refinement

A sharp tip is by no means the only thing important in cannula or needle manufacturing. In fact the tip design has nuanced regions that must be addressed in different ways to both improve it’s effectiveness and ensure patient wellbeing.

• Anti-coring

• Anti-skiving

• Texturing for overmolding

• Echogenic finish

Let’s dive into the details.

If instead the cannula is only sharp at the tip and dull at the heel, it will cut a “C” shape. This will both prevent the coring, and provide a flap of skin to cover the entry point which is better for healing.

MicroBlasting method

To avoid coring, the cannula needs specific treatment from the blasting process which is most effectively achieved through automation. Blasting is localized at the heel region, away from the tip. Glass bead slightly rolls this portion of the grind, dulling it. Dulling about 15% of the cutting edge creates an effective flap. Nozzle angle and distance are critical components of the process for anti-coring.

Anti-Skiving

A sharp edge on the back end of the point will scrape along the inside of the catheter wall as it is pushed through it. An unblasted cannula peels up ribbons of material along the way.

MicroBlasting Method

A cutting abrasive, focused on the outside of the tube applies a slight radius to the heel of the back edge. Once this sharp edge is removed, the cannula glides smoothly through the catheter. The localized edge break is best achieved through automation.

Texturing for Overmolding

A textured surface has a greater surface area, the peaks and valleys of which provide more contact points for a stronger bond.

MicroBlasting Method

A sharp, cutting abrasive, like aluminum oxide or silicon carbide quickly and efficiently textures the surface. Blasting properties can be controlled to match the specific surface requirements to best bond with a hub.

Echogenic Finish

Ultrasound uses high-frequency sound waves to create detailed images allowing a medical professional to see the cannula as it travels through the body. If the surface is shiny, specular reflection causes those waves to reflect in a singular direction that may miss the receiver, impeding proper imaging. By creating series of satin bands along the needle shaft, diffuse reflection ensures some of the reflected energy finds its way back to the receiver for proper imaging.

MicroBlasting Method

Using glass bead with the Ring Nozzle is ideal for creating a series of bands on cannula; the abrasive flows uniformly around the circumference imparting a satin finish. This not only eliminates the need to rotate the part during the blast, but also creates a sharp delineation on both ends of the band.