Transparent z-axis touch plate

Hi, I’ve seen some great designs and videos for z-axis touch plates and I plan to take some of the concepts and try something different. I have the components and am planning to build a transparent z-axis touch plate to zero the axis using circular pieces of indium tin oxide glass. So far in conductivity testing it performs very well. My only design quandary is finding the best method of applying a cross-hair on the underside of the glass to allow perfect alignment with the start point and I’d appreciate some ideas. I wondered how I was going to reliably connect wires to the indium tin oxide glass until I found some 50mm/0.5mm copper rings which I think are more commonly used in the manufacture of jewellery, so the glass will sit below with the wire soldered to the copper ring.

Now, it took me a while to figure out how I could consistently have mill-ends of various sizes align to the center of the cross-hair each time until I realised I could re-wire the cabling on the backside of the z-axis gantry to remove the connector strip, and mount small neodymium magnets there instead. That would allow me to clip on the z-axis touch plate assembly for calibration and remove it afterward with ease. I’ll need to to make the assembly adjustable when first applied so that it aligns with the spindle center but I think I have figured that out. The up and down movements will be controlled using 8mm stainless steel rods and linear bearings to minimise movement.

I’m interested to know if anyone has tried something like this before. Might it work or am I wasting my time?

@JonLake

You could try the Mark 15 variant of this:

http://www.edmundoptics.com/test-targets/image-analysis-test-targets/experimental-grade-reticles/26037/

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You could always engrave the cross hair on it

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As long as it has continuity you will be fine. Look into engraving the crosshairs from underneath. I would be interested in buying one if the price was reasonable :slight_smile:

I know what you mean Phil but the idea, whether sensible or practical, is to line up the zero/start position precisely on the cross-hairs and reliably have the mill-end come down onto that point. Arguably OCD on my part but I thought I’d try it.

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Hi Eric, I hadn’t thought of engraving but it’s a bloney good idea! I have a few pieces of the conductive glass and micro-mill-ends so I’ll give it a go. Thanks for the idea; I’d followed a line of thought without considering that option. This is why it’s great to have a forum like this to make you look at things differently.

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You could also buy/make a vinyl stencil and get the crosshair sand blasted onto it.

A friend had this done to some glass for a trophy cabinet with an elaborate design and the results were perfect, and it was literally done in a few minutes (obviously the crosshair would take no time at all). The guy that did it asked for a fiver as a token payment.

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You’re probably spot on Phil, but I have this crazy idea and am desperate to see how it’ll turn out. Plus, I have to come up with at least a part rational purpose for buying the conductive glass. My better half is convinced I’m loosing the plot every time she makes the mistake of looking in the workshop. She doesn’t seem to understand that all the odd bits and pieces I have scattered around isn’t (as she puts it) a mess but is actually organised creativity.

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I have that. I just can’t remember where I put it. I know it’s here somewhere.

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Precisely Larry! I got a look earlier (you know the look) just because I’d borrowed two pairs of scissors from the kitchen. How was I supposed to know that they were only to be used for kitchen related tasks? Okay, maybe scissors which are (apparently) designed to cut herbs and leafy vegetables aren’t supposed to be used to cut 1.5mm x 75mm neoprene but how was I supposed to know that? There’s no warning label and as it turns out they cut neoprene almost as well as they cut spring onions and fresh lettuce.

My wife used that same logic when she used my left-hand twist drills to mount a kitchen do-dad. She complained that they needed to be sharpened as she had to press extremely hard to get the holes drilled. :weary:

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Just make sure the crosshairs aren’t too big, or you will limit how the ITO glass works.

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