Multi Axis Caliper (MAC) (aka "3D caliper")

Please be aware, that this has marginal accuracy but if you need to measure a 3d object it can be very helpful.

It is a 3D-printed multiple-axis caliper. I designed it to document the shape of larger and odd-shaped objects (like a wine glass for example). It can measure 2 and 3 dimensions at the same time. It does work (albeit with a few caveats). And, honestly, trying to measure 3 dimensions at one time might just be ridiculous. But 2 dimensions at the same time is awesome and I have already put this to good use.

I wanted this entire assembly to be collapsable since I knew I would only need this from time to time. So I have made the Z and X axis folding and collapsable BUT with the folding accuracy is lost. So I have made non-folding versions as well.

My sense is that with the non-folding version, you can approach +/-1mm in accuracy, and with the folding version +/-2mm.

Because the z-axis moves it makes the entire assembly awkward to use (too many moving parts) so I added detents every 5mm. When mapping something vertically you set a height (say at 10mm) and then measure the x-axis (and y if you want). Shift the z and repeat.

Even with the z-axis snapping into position the entire assembly was still super awkward because it wants to fall over so I added a snap-on and adjustable stand. The stand snaps onto the back of the z-axis and the legs can rotate forward to find an optimal position.

When using the caliper it is important to go slow and make sure you are finding the dimensions of anything you are measuring without stressing the caliper which would cause it to flex. Also, because of the folding components you need to carefully check that all the members are square when using the MAC. This means going slow and being methodical.

The thumbwheel is interesting. I originally tried to use a rack and pinion approach to move the x-axis but it was too cumbersome. In the end, I essentially mimicked the design on my digital caliper and while I am not sure why it works as well as it does – it works well. The thumbwheel is split and rides on either side of the x-axis. Pressing firmly while spinning it moves the x-slide.

Installing the thumbwheel involves inserting the arm on the thumbwheel assembly into the slot on the x-slide. A considerable amount of force is required to get it in as the arm is curved to prevent it from coming out after it snaps into place.

Interference in Slides: I have added some sprung interference into the slides. By doing this I was able to leave enough space in the slides to allow relatively smooth movement. The sprung interference tries to take up the slack so that the sliding element remains square to the frame. If this is too tight slide the sliding element back and forth a few times fast and it will effectively sand it down.

Folding vs. non-folding: As noted above, I have consciously traded a little accuracy to make the entire thing collapsible. Since I will use this infrequently, I want to be able to put it away somewhere until needed. But if you want the best this can be, print the non-folding parts.

Tolerances: Everything fits together pretty tight. So I recommend using my print settings as closely as you can. If the parts you print are loose then review your print settings and check you are not under-extruding. If the parts are too tight, try cleaning all the edges, and or sanding the tight areas.

Material: I recommend something stiff, like PLA or ABS. But I have printed this all in PETG. The flex of PETG does not lend itself well to the accuracy of measurement. But I had PETG loaded already and it does work.

My Setup: Nozzle = 0.4mm Layer height = 0.2mm Line width = 0.4mm Wall count = 4 (1.6mm) Infill = 40%

Support: Designed to print without additional support. All necessary support is designed in.

The thumbwheel has support that will be tight and therefore require needlenose pliers to remove. The tightness is intentional to make sure the gap in the thumbwheel mates with the edge of the x-axis.

During one print, I had the edge of the x-slide curl up from my print bed which is quite unusual with PETG. But because of that, I added a small pad at the end of the piece to help with bed adhesion and ensure the edge of the slide is straight. You can break that off after printing.

If anyone needs any size adjustments to this design to fit your printed let me know and I will do my best to make whatever is needed.

More details are available at... https://logicalplanet.com/