Friday, October 10, 2025
Tips On Etching Tips
I got some actual 316L stainless steel wire and some Nichrome 80, after the "Art of Bulshito" non-stainless non-steel wire incident. I decided to try etching them in either 1% nitric acid or 5% salt solution using the rig and instructions here on Printables. Using 3xAAA batteries for power, immersing the wires 8mm into the liquid, and with a stainless steel spoon/cathode 40mm from the liquid's surface. Blimey, wasn't expecting this:
Using nitric acid seems to produce a very robust probe tip, with an almost foamed shaft. There was indeed no cloudy precipitate during etching, but the tips of the wires did not fall off. What you see in the top photos is just the eroded end of the wire.
The salt was as cloudy as ever. The 0.12mm Nichrome dropped off at the meniscus. The 0.3mm Nichrome parted about half way down the immersed section.
The tips were gently rinsed with water and sprayed with isopropyl alcohol to remove any remaining liquid.
It appears that nitric acid is best for creating a robust tip. Nichrome creates extremely fine tips, but using wire as fine as 0.12mm diameter produces a very short tip that appears uneven and particularly delicate.
I think the most impressive tip of this batch was the very fine, spire-like tip produced by the 0.3mm Nichrome in salt. The tip is exceptionally small (too fine for the camera), the length has a gentle taper, and the sides look like they would hold a good dose of resin by capillary action. Here's an image zoomed in on that fine tip, with a piece of 0.3mm wire (almost in focus - sorry, it's hard) for scale.
That tip though is really fragile, and finer than I need - I had to make a jig to protect it during assembly. I wanted something half way between nitric and salt in dimensions. Well, lets put about 5ml of 1% nitric and 35ml of 5% salt solution together and... interesting. That stops the precipitate forming, and I can see the point sharpening nicely - hydrochloric acid might do the same and is easier to get, which I'll try later.
Anyway, that combination allows me to get a good tapered point, and tune its thickness to my requirement of the day. Now to join it to the μRepRap and see if I can deposit an even smaller resin Jolly Wrencher with it.
