Or, to tie this in with an Arduino, instead of just reading the voltage on a multimeter:
Here I've just added in an Arduino Nano (I used one of these generic versions) to read the sensor voltage.
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).
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.
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’.
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
V1-V5 files can be found here: Printables | Thingiverse
Shortening the leafs made the two small 'stages' to be far too stiff.
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.
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.
Ummm, yeah....I think this one looks cool as hell!...but it doesn't fit on the Panavise 🤦♂️
This one from Adam Savage is a fun look at both a fractal vise, and the general joy that they bring hardware nerds:
https://youtu.be/NUhrF0xkhhc?si=YvwaEeE7oxlwUBhj
Really nice restoration video
https://youtu.be/QBeOgGt_oWU?si=QO1tu4-0Jl_mqmxz
A really nice 3d printable option:
https://youtu.be/eCfw9fd0mHg?si=knRpBk3tQjuHg-MT
Like the bucket of assorted fasteners on that bottom shelf, this category is for stuff that I didn't know how to group...oh, and speaking of those fasteners, check out the little sortin fella!
2020 Aluminum Extrusion Hardware |
Quick Bolt Sorter |
During the good financial decision-making times of Covid lockdowns, etc. I decided it was a good idea to buy a license for the Fusion360 Generative Design extension...Good news, I did finally pay that off :) I had worked around, and been somewhat involved in a handful of Topology Optimization/Generative Design projects through my work, and I've found the tech super interesting for some time. So after the free trial, and feeling like I was just starting to gain some level of competence in Fusion360's tool....I done did it, and bought the year. Ok, now that I'm done justifying that to myself...I mean you...
<engineering/design> What I really like about Generative Design is that it forces the designer to think about the thing they are trying to design from it's core requirements: Forces, Interfaces, and Keep Outs. I think it's far from perfect, especially given the still very primitive Design For Manufacture capabilities these tools have (among other shortcomings, but this one is certainly a big one to me.)
<precision engineering> One last also (for now), but ALSO, what I find exciting about these tools from a precision engineering perspective, is that the above-mentioned focus on forces and interfaces, these tools are extremely well-suited to kinematic/exact constraint designs! I think every one of the Generative Design projects below features at least some aspects of kinematic constraint (I say, "I think" because I may or may not be writing this before I go through my files and remind myself what all I actually made vs what I just thought about making ¯\_(ツ)_/¯ )
A lot of projects I work on/have worked on seem to involve the controlled movement of fluids. Below is a bit of a history of my builds involving attempts at obtaining this controlled movement for incompressible fluids. I haven’t done much myself with making custom solutions for the compressible stuff, but if you’re interested in such things, I thoroughly enjoy Major Hardware’s “Fan Showdown” series :)
This article/section is by no means intended as a thorough overview on the design and operation of pumps. While I will try to give some overview on operating principles and design considerations as I go, this is mainly just going to be a wander through my personal builds and experiences.
I’m sure there are innumerable sources online for (much better) detailed discussions of the workings of peristaltic pumps. So I’m just going to hit the highlights, and I’ll try to remember to find some promising links and add them below, should a deep dive seem intriguing to ya.
The fluid being pumped is carried into the pump in a compliant tubing. This tube is routed around some portion of a circular/cylindrical path around the axis of the pump and then exits the pump. This is one interesting/attractive aspect of peristaltic pumps, the fluid never has to leave the tube that it is in, making these pumps well-suited to situations where contamination and/or leaks are highly undesirable. The housing that features the cylindrical wall that the tubing is being routed along can be considered the Stator, and that is generally the nomenclature that I tend to use.
So if there’s a Stator, there must be a Rotor…? Yup, the rotor includes some set of features that extend out to some defined gap between this feature and the Stator wall. These features, which in many peristaltic pumps are rolling element bearings, pinch the tubing to the point of sealing (ideally) the tube. As the rotor turns, this contact point proceeds around the circumference. Because the pinched point of the tube is sealed, the volume of fluid in the tube ‘ahead’ of the pinch point are, as a result, pushed forward. So, keep rotating, keep pushing….pretty much as simple as that!
Pros:
Cons:
A couple of years back, I had a concept for an in-line-mixing hydroponics system. The idea being that the supplies to the system would be just pure water and nutrient concentrates, and a series of pumps and valves would allow precise dosing mixes to each target plant in a system (I refer to this concept as Rail Yard Hydro, since it moves the fluids around the tubing network quite like rail cars are moved around a rail system. I’m planning to add a separate page diving into that one a bit deeper since it is the design scheme I am using in my current projects.)
Well, to facilitate this plan, I wanted to find an option for a dosing pump that I could integrate in to my control system (aka Arduinos and Raspberry Pi’s :)). Unfortunately, I quickly found that a servo-driven peristaltic pump could easily set me back north of $100….so I set out to spend many multiples of that making my own!
Actually, when I saw the pricing, I decided I should see if I could make myself a cheapo, manual version that I could use to just test out some basic questions on the Rail Hydro idea (mainly verifying that I could induce good material mixing in-line and that there was no cross-contamination between fluid reservoirs.) And so, ‘twas this endeavor that resulted in the pump I’m apparently referring to as “Test Build 1”
She ain't pretty (especially after a good while of getting knocked around), but the pic above shows the dual pump setup I rigged up for my testing needs. I was VERY pleasantly surprised that, other than a tweak to the hand wheel, these things worked pretty damn well!
I decided upfront that I was going to go with a resin printed build, because I thought the high stiffness and good surface finish throughout the 'pinch region' would give me a better chance. Since I was already going to have the good surface roughness, I might as well also integrate the main bearing into the printed parts.
In the image of the model, below, the Stator is the part shown in green, and the Rotor is shown in blue(ish.) Riding on the rotor are roller skate bearings to provide the contact with the tube. Race 1 has v-grooves on both sides of the race, providing the main constraint for locating the rotor, and Race 2 has a v-groove on the Stator, but only a single plane of contact on the Rotor side. This keeps from over-constraining the bearing.
The absurdly overkill bolt running through the center is a real showcase of "using what I had on hand" :) in that these were the only bolt/nut sets I had on hand with the length I was looking for.