RepRap: Blog

There is now an attachment, provisionally called the Probe Dipper, in https://github.com/VikOlliver/RepRapMicron/blob/main/pika/pika_probe.scad that attaches to a Z Axis Driver (the Driver is now very easy to remove and re-attach). The Probe Dipper has a ridged bar to which a length of wire can be held with a croc clip thus:

The electrolyte and so forth have changed slightly. It's sufficiently acidic that you don't want to leave the spoon in overnight:

56ml H20, 2.5g NaCl, 1.5ml fuming HCl. Wire is 0.3mm dia., cut to 80mm for convenience.

Initial depth of etch 15mm, current ~50mA for 30 sec.

Probe then zeroed to point of contact with meniscus to within 10μm.

Etching time purely dependent on Z axis speed of  15mm/min. Probe dipped and immediately retracted to provide agitation of electrolyte:

0.5mm 3x - Reduce roughened surface

100μm x4 - Create annular grove and fine pitting

Contact x4 - Shape and smooth tip

 

The result of the first attempt has the desired features of a roughened shaft, an annular indent, and a vaguely ogival tip:

Just how essential these features are remains to be seen, but I can't explore them until I have a repeatable method of making probes. The above process was used because I estimated that's what I was doing manually to make a probe that worked (minus the nitric acid). How many of these steps are accurate or indeed actually necessary is unknown.

And so, the next task is to repeat the probe electrolysis on another day. If it is repeatable, I can think about optimizing the shape by changing steps/depth/timing, know that I'll be able to replicate it on demand, and produce a method for making probes as good as or better than the ones I make by hand.