We discovered that the older version failed to operate under low-pressure conditions—apparently, it couldn’t reliably draw liquid through the silicone tubing, and even when it did manage to dispense material, the flow was intermittent and unreliable. After experimenting with reducing the needle’s diameter to match the inner bore of the silicone tubing’s retaining fixture, we found that this approach worked to some extent—but it didn’t fully resolve the issue. In a stroke of serendipity, we ended up using a slightly oversized fitting to secure the needle, only to realize that the problem lay in air leakage around the needle itself.

Wrapping raw Teflon tape around the needle’s mounting point on the old version solved the problem—what a roundabout solution!

Here are my test prints…

From left to right: the original design, the original design with raw Teflon tape, and the latest iteration.

The test pressure settings are shown in the diagram below:

In summary, if your system is operating at low pressure and struggling to function properly, simply wrapping raw Teflon tape around the needle’s mounting point can often do the trick. For the older version, applying raw Teflon tape proved effective; for the latest iteration, we leveraged a snug fit achieved through 3D printing—feel free to choose whichever method suits your preferences. Additionally, using silicone O-rings can provide a slight improvement in sealing performance.

This design was modified from the original, with the following changes:

Added a textured, non-slip surface to the model.

Offered three different diameters for the needle holder: 4.0 mm, 4.1 mm, and 4.2 mm.

Introduced a wider‑opening cap 2, designed to enhance airflow (though testing showed the original cap was sufficient—if you encounter any issues, feel free to experiment with this option).

Increased the diameter of the silicone tubing’s mounting area to 4.6 mm for improved retention. While a 4.0‑mm inner‑diameter PTFE tube may be more challenging to install, you might consider using a 4.1‑mm inner‑diameter PTFE tube instead.