Details: Parent Category: Just Playin and Concept Demo Projects; Category: Flexure Fun; Last Updated: 16 January 2024

Overview

I, like pretty much every engineer I know, was absolutely enamored with the idea of fractal vises from the first time I encountered one.

At some point along the way I finally gave in, and decided I wanted to try my hand at making one for myself. But while I do have some basic machining equipment, I don’t want one of these quite badly enough to go that route, so I wanted to find a viable option for a 3d printed, or mostly 3d printed variant.

I tinkered with some concept designs for print-in-place versions, and other printable variants of the same general concept for the classic flavors. But then it occurred to me that the bearings/bearing surfaces could possibly be replaced with flexures that create a virtual pivot along that same line. Below are my attempts to date in testing this out.

All of these jaws are designed to fit onto my Panavise 350 jaws (see below GIF).

If you aren't familiar with fractal vises, I’d recommend watching one of the awesome videos folks have made (a handful of ones I’ve enjoyed personally are below).

Versions

Models for V5 and V6 can be found on OnShape here. I'd need to find where I did 1-4, but if you're interested, just let me know and I can dig em up.

V6

Printables | Thingiverse

This rev is essentially just a slightly beefed up V5. I thickened up the jaws themselves (the V5s were intentionally a bit thinner than desired to speed iteration), and also thickened the 2nd and 3rd order flexures, counting the jaw flexures as layer 1.

I also significantly thickened the out of plane thickness as it gets closer to the jaw. This was primarily aimed at increasing the torsional stiffness overall as well as to allow the jaws to rest on the Panavise bracket instead of ‘floating’.

Printables | Thingiverse

V6 "Booties" - by @aoty

Printables

A user on Printables came up with these awesome little 'booties' for the vise jaws...I must admit, since I originally was calling this "Flexure Fractal Fingers" (to noone but myself, of course), I can't stop callin these 'fingertips'. But I think @aoty's 'booties' moniker is better.

They're intended to be printed in TPU and to give the jaw teeth some better grip. I printed some in both TPU and resin, which I thought was 3dMaterials SuperElastic, but based on the parts, I think Past Bubs may have put some SirayaTech Fast Smoky Black (my 'daily driver' resin of choice) into the 3dMaterials container. It does seem to have some elastic material in the mix, but it's far too stiff to be the SuperElastic...plus it's smoky black....so there's that.

I think these little things are great! One of those, "wish I'd thought of this" things for sure. They give a nice bit of extra grab on parts, and given that I've had more than one part come flying out of what is essentially a springloaded vise, so these are damn-near a safety requirement now for me

The resin parts look great (IMHO), but the TPU wins hands down for performance. So naturally I'll be leaving the resin ones on

V5

V1-V5 files can be found here: Printables | Thingiverse

V4

Shortening the leafs made the two small 'stages' to be far too stiff.

V3

This has been the best performing of the four bar designs thus far, but turns out that final pivot for the full jaw is important. Without it, the jaws can't accommodate an overall wedge.

V2

Worked ok, but I think the lever arm between the contact point and the pivot point is too small. As a result the clamp force has to be quite high to drive deflection into the flexures.