Tag Archives: openscad

One Simple Trick Can Save You 30 Minutes…

Posted on by
2

After mentioning long render times on my machine, @raster suggested switching to the manifold 3D rendering backend.  Depending on your OpenSCAD version, you might need to poke around to find how to enable this option.  It’s absolutely worth your time and should really be enabled by default.

If you dig into this option a little, and you’re a 3D printing old timer, you might recognize the creator of this library as none other than Emmett Lalish!!!  Emmett was an early 3D printing adopter, from back in the MakerBot Thing-O-Matic days, creator of the original heart gears, and just all around incredible engineer. 1 2

Emmett’s manifold library dropped the render time for one of my designs from 300 seconds to… under 8 seconds.  I literally used to avoid hitting F5 on more complex designs or avoid cranking up the facets so I didn’t have to wait for long renders.  A single comment from a friend, telling me about an option written by another friend, has completely and permanently changed how quickly I’m able to iterate and design objects forever.

Here’s how you can instantly save tons of time with your OpenSCAD designs:

"Manifold (new/fast)"

“Manifold (new/fast)”

#OpenSCADClub
  1. OpenSCAD 3D Printed Spring
  2. OpenSCADClub Week 2: Directional Pad
  3. OpenSCAD Render Times
  4. One Simple Trick Can Save You 30 Minutes…
  1. Emmett even wrote a guest post on this very blog about… 14 years ago?!?!  Time flies, I guess? [↩]
  2. Special thanks to my honorary editor Andrew for catching a typo… [↩]

OpenSCAD Render Times

Posted on by
Reply

Thanks to @raster, I’m going to do a side-by-side taste test of several different flavors of OpenSCAD.1 To give each one a similar test, I’m trying out my D-Pad design from … uh, earlier this morning.2

Version Release F5 Preview F6 Render Notes
2021.01 Stable 09:50.220 2.302 Best place to start
2024.01.13 Current 04:37.763 0.948 I’ve been running this one for a while
2025.04.04 Latest 04:36.593 0.483 Latest snapshot

Obviously, the good folks working on OpenSCAD have dramatically improved preview/render times over the last four years.  The speed boost in using a later snapshot is pretty significant if you’re doing any kind of complex designs.  They must be using some kind of cache system to make the render times so fast.

The speed differential between 2024.01.13 and the latest snapshot is so slight, I’m not going to switch things up unless I bump into a design that struggles with rendering some complex feature.

#OpenSCADClub
  1. OpenSCAD 3D Printed Spring
  2. OpenSCADClub Week 2: Directional Pad
  3. OpenSCAD Render Times
  4. One Simple Trick Can Save You 30 Minutes…

 

 

  1. *I’m not avoiding work!* YOU’RE avoiding work! [↩]
  2. Like, way earlier…  midnight or so… [↩]

OpenSCADClub Week 2: Directional Pad

Posted on by
Reply

This week’s topic related to @deshipu’s directional keypad designs.  The directional pad is clearly the most complicated part of the design.  The four buttons are basically just cylinders that can be created in several different ways.

@deshipu's D Pad Design

@deshipu’s D Pad Design

Brian published his designs to Github.

@beerriot's designs

@beerriot’s designs

After staring at the design a little longer, I changed from my original design idea to creating a 2D cross, extruding that, subtracting out the curved area described by a sphere (a homebrew hack I’ll describe below), using the minkowski function to surround the entire surface with a small sphere to give it a rounded look, then cutting the bottom off to ensure it is flat.  I didn’t include a flat cylinder as in the original design above, but that’s a trivial addition.  The downside?  This is a 5 minute render on my machine, largely due to the minkowski function.

//  Settings
    fn = pow(2,5);
//  Measurements
    pad = [10,30,1,3];
    corner = 1;

dpad();

module dpad()
    {
    difference()
        {
        minkowski()
            {
            difference()
                {
                linear_extrude(height=pad[3], center=false)
                    offset(r=-corner/2, $fn=fn)
                    for (i=[0:1])
                        rotate([0,0,90*i])
                        square([pad[0],pad[1]], center=true);
                translate([0,0,pad[3]])
                    scale([pad[1]*1.03,pad[1]*1.03,pad[3]-pad[2]])
                        sphere(r=0.5, $fn=fn);
                }
            sphere(r=corner/2, $fn=pow(2,4));
            }
        mirror([0,0,1])
            cylinder(r=pad[1], h=pad[1], center=false);
        }
    }

Renders to:

MakerBlock's design

MakerBlock’s design

Hacks:

  1. You’ll notice I use “offset” to reduce the size of the directional pad, because I knew I was going to round it all with the minkowski function in a few lines.
  2. The directional pad is actually just a rectangle, run through a for loop once to rotated it by 90 degrees, before being extruded to the specified height.
  3. The last two lines of code are used to create a large cylinder, larger than what I knew the pad would be, then mirrored in the Z axis to cut everything below the XY plane.
  4. As in prior designs, I pre-define “fn” to be a “pow(2,5)” so that I can use a low exponent to iterate designs quickly, then crank it up for a detailed design.
  5. The hack I use the most often here, and the one I’m the most proud of, is where I make a sphere like “sphere(r=0.5)” and then scale it by whatever I need.  Since the sphere has a diameter of “0.5” mm, the actual sphere is 1mm in diameter – so when I scale it in the XY by 30 and in the Z by 2 (since the edges of the keypad are 3mm tall and the center is 1mm tall), the diameter is now 30mm and the height is 2mm.  This little trick, of being able to scale a sphere to the exact size I need has come in handy countless times.

I’m not the best programmer, not the best at OpenSCAD, but I’m kinda happy that I was able to build this in about 31 lines of code.  :)

#OpenSCADClub
  1. OpenSCAD 3D Printed Spring
  2. OpenSCADClub Week 2: Directional Pad
  3. OpenSCAD Render Times
  4. One Simple Trick Can Save You 30 Minutes…

OpenSCAD 3D Printed Spring

Posted on by
Reply
OpenSCAD spring design by @rasterweb

“I’m trying to come up with a good way of creating this in OpenSCAD… I have something using a bunch of hull’d cylinders but I’m wondering if there is a better/easier way to do it.” @rasterweb

A friend posted a design pondering whether there was a better way to design an object in OpenSCAD.  As so often happens when I approach a 3D design, one solution pops up in my head… and is immediately discarded as garbage.  That first thought was to create a negative of the interior of the spring, then iterate along the length of a stretched cube.

In the end, I opted for1 creating a flat version of a single “loop”, made from differenced hulled circles, repeated over the number of desired loops, then trimming alternating ends (so it wouldn’t look like a chain).

OpenSCAD spring by MakerBlock

OpenSCAD spring by MakerBlock

Here’s the OpenSCAD code to produce this spring:2

//  Settings
    $fn = pow(2,6);
//  Spring Dimensions
    springH     = 5;
    springOD    = 10;
    springW     = springOD*2;
    springOR    = springOD/2;
    springTh    = 2;
    springIR    = springOR-springTh;
    loops       = 8;

    spring();

module spring()
    {
    linear_extrude(height=springH, center=false)
    for (i=[0:loops])
        {
        translate([0,(springOD-springTh)*i,0])
            difference()
                {
                spring_loop();
                translate([-springOR+(springW+springOD)*(i%2),0,0]) 
                    square(springOD, center=true);
                }
        }
    }
    
module spring_loop()
    {
    difference()
        {
        hull()
            {
            circle(r=springOR);
            translate([springW,0,0])
                circle(r=springOR);
            }
        hull()
            {
            circle(r=springIR);
            translate([springW,0,0])
                circle(r=springIR);
            }
        }
    }

Some notes about my OpenSCAD style:

  • I like to use OD/ID/OR/IR to mean outer diameter, inner diameter, outer radius, inner radius.
  • I think the “spring_loop” module could be simplified slightly by calling another module which creates each hulled circle, but weighing the additional module code against just retyping a little code I opted for what got it done faster.
  • I like to specify the facets on circular objects right at the top of the file. This way, I can adjust the smoothness of the object by just changing just the exponent part of the $fn system variable.
  • Reasonably parametric. There’s some additional further optimization that could be done in the spring alternate end clipping.

Can’t wait to see what @rasterweb makes with a 3D printed spring!

#OpenSCADClub
  1. OpenSCAD 3D Printed Spring
  2. OpenSCADClub Week 2: Directional Pad
  3. OpenSCAD Render Times
  4. One Simple Trick Can Save You 30 Minutes…
  1. And, please forgive the inside-baseball / OpenSCAD-speak [↩]
  2. To display the code above I had to use the WordPress block editor. 🤮 [↩]

Building a Travel Ukulele: Back to Basics

Posted on by

My experiment with a multi-piece turn around didn’t work.  The idea was for a multi-segment turn around where each string could be tightened and that portion of the turn around would be able to rotate as needed independent of the other pieces.  I simply did not account for the kinds of stresses the pieces would be under through normal use and string tension.  Each segment deformed, resulting in none of them being able to rotate and the slightly less rigid turn around bowing slightly under the pressure.  I couldn’t get a great picture of the deformed parts, but perhaps this will give some idea.

In the end, the best result for my ukulele has been a 3D printed turn around, finely sanded smooth, unadorned by paint, with a small amount of lubricant (I’ve used machine oil) over the metal bridge and across the turn around.  These simple elements have, hands down, beat the over engineered / over designed pieces above.  If they were printed out of a more rigid material, milled or turned from solid metal, created by using a system of washers, or made using a full length bolt, I’m sure it would have worked better.

The design of my turn around uses captive nuts in the plastic core, secured by bolts on either side.  This ends up being dramatically easier and cheaper than trying to source very long Chicago bolts and posts – but has a minor downside in that the two bolts don’t actually connect.  As long as the material between the two bolt ends is strong enough to withstand the continued forces of four strings under tension, there shouldn’t be a problem.  However, even printing the turn around with the best orientation for printing strength in PLA didn’t result in a part that could withstand these forces for a long time. 1  One of my ideas for this part involved using bolts that were possible slightly longer or of different lengths so they would both tighten slightly into the same captive nut, resulting in one “continuous” piece of metal for the turn around core, then using washers to ensure / assist in minor distance adjustments.

Here’s how it looks today:

I don’t plan on any more improvements for this particular ukulele.  I’ve deeply enjoyed playing it since it became “finished enough” to be playable in August of 2022.  That said, I’ve been thinking about how I would create another one.

  1. CNC Cut Wood.  I spent the vast majority of the time on this project just rough cutting the wood to size using a combination of hacksaw and coping saw blades.  I spent a ton more time shaving wood off the neck using rough files.  Starting with a piece of wood that was already the approximate dimensions and only needed finishing would feel like starting at the 90% mark.
  2. Different Wood.  I went with mahogany for a variety of reasons – but cost was one of the biggest and dumbest of these.  The difference between a plank of mahogany for $10 and the most expensive wood from Rockler at maybe $30 is a rounding error when the project took more than 100 hours of my time.  I’ve suggest that wenge, zebrawood, ironwood, or walnut would be my choice for another attempt.  Of these, I am leaning towards walnut for a deep brown, possibly gray finish.
  3. Strap Attachments.  The strap was not quite an afterthought.  I had always planned on using nylon webbing / seat belt material for the strap and had designed printed strap buttons for hooking the strap onto the ukulele, but in the end I just couldn’t bring myself to drill holes in the finished uke.  This was just as well since I had wanted to try using some paracord in a project for a while.  After using a flame to seal the ends of the paracord and webbing, the result was way too thick to use in my sewing machine and had to be hand stitched.  I’m not great at hand sewing, but it is functional.  Given the dark colors of the thread, paracord, and webbing, the haphazard stitching isn’t very noticeable.  If I really took my time with it I might be able to do a better job.  If it came to that I might want to use some silver or light gray thread to add a little pop.
  4. Acoustic Improvements.  I’ve noticed a dramatic change in the quality of the ukulele sound when I place a book, empty box, or large piece of rigid cardboard between the uke and myself while I’m playing it.  I’ve thought about how this could be incorporated into a new design by creating a system for bolting, attaching, or otherwise connecting a larger section to the ukulele.  Another incredibly interesting option is the plastic sheet used by TitchTheClown.  He used thumbtacks to secure a sheet of plastic from a soda bottle against the ukulele, then a heat gun to tighten it into something like a drum surface.
  5. Other prior improvements per a prior post.

Default Series Title

  1. I’d say it took about six months for the deformations to become noticeable [↩]

Loudest Whistle on Thingiverse… The Answer Might Surprise You!

Posted on by

You'll need a pair of these earplugs

You’ll need a pair of these

Whistles have been a staple on Thingiverse for years, probably because they’re such a small, simple, and impactful way to demonstrate the usefulness of a 3D printer. 1 I don’t know how many there are, but there are a LOT of whistles on Thingiverse.  I’ve been curious about which whistles on Thingiverse are the loudest and conducted a semi-scientific experiment to figure this out.

Six whistles

Six whistles

I say “semi-scientific” because I don’t have a decibel meter.2 My methodology was to have my family at one end of the house while I went to the other side, closed the door, put in my earplugs, and wailed away on six whistles as hard as I could.  In any case, here’s my findings:

NameThingiverse IDMass (grams)PricePrint Time (minutes)RankDecibels
Extremely loud and compact emergency whistle [v1]29330213.9$0.12221TBD
2 chamber whistle (LOUD) [w5]26165128.1$0.24492TBD
Extremely loud and compact emergency whistle [v2]29330213.7$0.11183TBD
v29 (Over 118 db!)117916013.9$0.42904TBD
Emergency Whistle with Solidworks 2014 source4951721.2$0.0475TBD
Whistle Ring Modified [v2]20271151.6$0.0596TBD

I added a few columns that may (or may not) be of interest to you.  I indicated the weight of each whistle, because sometimes I want to know how many whistles I could produce off a single spool of plastic.3  Sometimes I want to produce the loudest whistle for the time I have to produce a whistle.4  I showed the cost per model5 , because it brings me so much joy to know I can make my daughter’s classroom louder than a jet engine for less than the cost of a pack of gum.

I know there are a number of important variables are are simply not addressed in this test.  Different frequencies sound louder or might be easier to hear through the door.  I tried to blow each whistle the same amount, but some whistles are louder with less forceful or more forceful blows.  Once that decibel meter shows up, I’ll be sure to post another update.

Loudest 3D Printed Whistle

  1. MOAR WHISTLES
  2. Loudest Whistle on Thingiverse… The Answer Might Surprise You!
  3. Loud 3D Printed Whistle Test, Take 2
  4. Loudest 3D Printed Whistle – now with 100% more science

  1. Photo by mosambers [↩]
  2. Yet.  At <$20 on Amazon, you can be sure I’ll be adding actual readings soon [↩]
  3. With careful design, approximately 2,500 whistles per kilogram of plastic [↩]
  4. The v2 of this whistle is the clear winner [↩]
  5. Assuming a spool costs about $30, shipped [↩]

Printable Prosthetics: Brainstorming

Posted on by

An illustrative hand

An illustrative hand

My overall designs for a printable parametric hand are still far from done.  And, yet, I’ve come a long long way since jumping headfirst into the realm of open source prosthetics a little more than 30 days ago.12

Forgive the digression, dear reader, before I return you to considerations of prosthetics. After visiting the Asian Art Museum today with the family, I am feeling particularly inspired to discuss dualities.3 I find I am an often-inspired person. This is a very charitable way to describe myself by what would otherwise colloquially and clinically be considered ADHD. When I am inspired by a new topic, I tend to jump right into it – reading voraciously and trying to learn as much about it as I can. When this happens, I also tend to set aside whatever thing I was most recently working on. This means that recently I’ve done little work on drawing robots (big and small) and a multitude of other small projects that would otherwise be just amazing. However, such inspirations/distractions are not only external to a project – but can also be very much internal to a project. Consider, for instance, feature creep – the adding of ever more features to a project, usually at a faster rate than which features are resolved and refined. In order to combat this aspect of my nature, the wanting to add more and better features, I have developed a coping mechanism. To prevent myself from falling down the rabbit hole of features and improvements, I jot them down someplace – either in a blog post4 , in an email to myself, or in a notebook.5 I find that once I’ve externalized and memorialized an idea, I can continue working on a project unfettered and undistracted these other ideas.

To this end, and in the spirit of open source ideals, I will jot down some ideas while I have them:

  • How large and how small are prosthetic designs typically scaled?
    • I wanted to have a range of sizes for which my designs were optimized.  My guess would be no smaller than 85% and not much more than 160% of the size of the existing  Cyborg Beast.  Jorge Zuniga was, again, patient enough to discuss this with me.  His estimate of a range would be between about 105 – 150%.
  • What is the diameter of the Chicago Screws typically used in the creation of a Cyborg Beast?
    • From the retailer’s website, it appears the “barrel” diameter is 0.2 inches, or 5.08mm.  I’ll need to make some adjustments to holes for the Chicago Screws in the designs.
  • How important is hyperextension of these fingers?
    • The designs of the Cyborg Beast include fingers that can bend “backwards” very slightly.  Each finger joint includes a “stop” at the back of the joint.  While certainly useful, I question their necessity.  I previously designed a connection system for printable snap-fit parts ((For use in an equally noble project)) that connect very tightly and/or bend with a user specified degree of movement.  The point with me mentioning these parts is that the “stop” used at the back of each knuckle and joint in the Cyborg Beast may not be necessary at all.
  • How necessary are metal Chicago Screws to strength and durability of the hand and fingers?  
    • Before you laugh, consider this question – what is the weakest point of any given finger which uses a metal Chicago Screw when having to deal with lateral forces?  I would postulate the weakest points would be those thin plastic parts surrounding the Chicago Screws themselves.  Thus, even though the hand incorporates metal pins, I have to wonder just how much strength they are providing to the overall device.  It would be easy to conceive of a plastic prosthetic hand that was so small that there wasn’t a lot of plastic around each metal screw6.  In such a case, the weakest points would be plastic surrounding the metal parts.  Extending this conjecture, of what use are metal fasteners to a design that is primarily plastic?  The best guess I can offer is that they allow reliable and smooth operation.
  • Work on proportional fingers
    • In designing the fingers, I worked to be able to make them customizable in several different ways.  The user may specify whether the fingers have the “star grip” pads, whether the finger should be slightly shorter or longer, and scale the finger up or down – without distortion to the hardware and cord channels.
    • I need to add at least three additional options to these parametric designs.  The designs should include the option to add “mouse ears” and easily removable support structures.  Additionally, the design should also allow the user to change the diameter of the finger.  I did implement this, somewhat, in part of the design.  Without implementation throughout the entire design, these partial attempts aren’t helpful.
    • In creating the fingers shown above, I adjusted their lengths to conform to the measurements of my own hand.7 Next time, I think I would also measure finger diameters.
    • I think I should create a way to prevent finger parts from being mixed up accidentally while printing.  A possible solution is to include “mouse ears” with each finger – but embed an identifying mark in each mouse ear to label the parts.
  • Ideas on making a better parametric palm
    • The palm should be redesigned so that the fingers, at the appropriate lengths, would fit into it.  I designed the fingers quite a while since working on the palm.  I haven’t had a chance to ensure the parts would mesh well without adjustment to the scale.
    • On an entirely different note, I have an idea to redesign the entire palm.  By carefully placing deformed spheres, I was able to design a palm.  Using a similar process, I subtracted out a void for the user’s hand.  The result is a palm with an uneven thickness throughout.  Uniform thickness isn’t necessarily an interesting or useful goal.  That said, it could lead to a reduction in unnecessary plastic.  If I were to redesign the palm, I could design the internal area first8 – and then use the “Minkowski” function to create a uniformly thick shell around the internal form.  The bottom would have to be sliced off and the original internal area would need to be subtracted from it.
  • Ideas on making a more realistic hand
    • My designs so far are based primarily on the Cyborg Beast, with some minor changes.  The “Flexy-Hand” appears to be very organic and realistic.  It also features flexible printed connections between each finger segment.  Additionally, each finger is comprised of three segments – rather than two like the Cyborg Beast.  Interestingly, since the flexible connections between segments allows the hand to return to an “open” position, the hand only requires five tension cords – rather than five tension cords and five elastic cords.  The fingers appear to not have any “stops” behind each joint.  I have to wonder how having three segments to each finger impacts the function.  Does it allow the hand to better grip things?  Does it make the hand less sturdy?
  • Masculine/Feminine hands
    • One well-intentioned comment to my latest designs is that they are “pretty.”9 While I accept the compliment with the spirit in which it was given, it immediately made me wonder – is the hand I designed “feminine?”  Then it occurred to me that with more design effort, I could make “feminine” and “masculine” version of these hands.  I think the primary differences would be two-fold – thinner fingers and a less “hefty” palm for a more feminine version and a thicker and perhaps more “blocky” palm for a more masculine hand.
  • New developments
    • There have been a number of interesting and new developments and experiments of late.10 In no particular order, these ideas are:
  • Discussions with a 7-year-old
    • A few days ago my daughter and I were jotting down some ideas in my sketchbook.  As we did so, she saw some of the notes from the e-NABLE meeting on 3/21/2014 – including several sketches.  We discussed the problem – affordable, customized, and comfortable prosthetics.  We talked about amniotic band syndrome, how fibrous amniotic bands affect fetuses, and the different ways in which these bands can cause11 deformities to single fingers, whole hands, and a range of changes in between.  I explained how Mr. Jose Delgado Jr. had a $42,000.00 myoelectric prosthetic, the problems he has with that prosthetic, how and why he prefers his $50.00 printed replacement, and how for the price of his one prosthetic people could make 840 more prosthetics.12 She asked, “Why can’t someone use a stump to operate a hand?” I replied that this was exactly how these prosthetics worked – and I drew a few simplified sketches of the Cyborg Beast.  Her next question was, “Why can’t it move side to side?”  I said that Mr. David Ogreman had designed such a prosthetic.

Default Series Title

  1. My first concrete step was going to an e-NABLE meeting in San Francisco on 3/21/2014. [↩]
  2. The above picture is slightly misleading.  I haven’t confirmed that the fingers I’ve designed will properly fit into the palm that I’ve designed – or that the thumb would work at all.  Thus, the picture is partially a parlor trick and partially an indication of where I hope to take this design. [↩]
  3. Many of the gods and goddesses in Eastern religions embody dual natures – creation/destruction, life/death, etc [↩]
  4. In one of my several different blogs. Besides, what could be more ADHD than having 3+ blogs?!? [↩]
  5. You may not find this as amusing as I do – but I probably have about four different sketch/notebooks. [↩]
  6. Say, only 1mm [↩]
  7. From pinky finger to thumb, the non-scientific measurements from knuckle to finger/thumb tip were 77mm, 102mm, 106mm, 92mm, and 72mm [↩]
  8. Using the deformed spheres and hull trick [↩]
  9. Thanks Erik! [↩]
  10. I don’t even know why I’m saying “of late” when I’ve really only been involved a little over 30 days.  I guess becuase these developments are new to me? [↩]
  11. Please forgive my lack of a more politically correct term.  If you’ve got a better or more sensitive phrase, please let me know as I will gladly adopt it [↩]
  12. She wanted to know if he could get a refund! [↩]

Printable Parametric Prosthetics: Design Features

Posted on by

Parametric fingers - different lengths, same scale, with no distortion to hardware

Parametric fingers – different lengths, same scale, with no distortion to hardware

I’m not ashamed to admit it – I’m proud of these parametric designs like few of my other designs.  I’ve worked to make this design as customizable and organic as possible.  The two modules that define each finger can be customized in two important ways – they can be lengthened1 as well as scaled up or down – without any distortion or change in the size of the holes for the hardware, elastic cords, or tension cords.

Parametric fingers - with grippy bits

Parametric fingers – with grippy bits

Being able to lengthen2 the finger segments is important because it allows the user to create fingers of different lengths, as normal fingers are of different lengths, all without having to actually scale the fingers to different sizes and without causing a change in each finger’s diameter.

As I’ve discussed in earlier posts, being able to scale the parts up and down without distortion to the hardware holes is important because it allows users to use standard hardware throughout different designs.

For now, it’s back to work on the parametric palm to ensure a proper fit with these parts.

Default Series Title

  1. Or shortened [↩]
  2. Or shorten [↩]

Printable Parametric Prosthetics and OpenSCAD: Parametric Optimization

Posted on by

Picking parametric fingers

Picking parametric fingers

This post is intended as a set of “guidelines” to creating a parametric design in OpenSCAD.

Last Sunday afternoon was spent working out a parametric design for printable prosthetic fingers.  Using the OpenSCAD function “hull” it’s relatively easy to crank out a nifty organic appearing design.  Admittedly, you have to have a working knowledge the basic union/difference/intersection function first.  However, once you do it’s really quite easy.

The feature of the design I’m most proud of is the “nail” part of the finger tip.  I designed the “nail” by using the OpenSCAD function “intersection()” on two cylinders.  The little “nubs”1 consist of a small cube, rotated so a corner is pointed straight up combined, with an identically situated cube rotated slightly.

When I’m designing something to be parametric, I usually don’t really start out designing it that way.  I first strive to create a form in OpenSCAD that resembles closely the thing I wish to design.  Then, I poke through the design code looking for those elements that are related to the design aspects I’m interested in changing based on parameters.  Once located, I replace those parts of the design code with variables that can be specified when the module is called.  I realize this is kind of a “high level” description of my design process for parametric things, but it’s still the best description.

Since last Sunday I’ve really done a lot with the design.  Some simplifying and a lot of improvements.  In the next post I’ll go over these features.  I’m really excited to show these off.  :)

Default Series Title

Default Series Title

  1. Meant to give the finger grip and texture [↩]

Printable Prosthetics Fingers and OpenSCAD Design Tips

Posted on by

Solid finger tip for Cyborg Beast

Solid finger tip for Cyborg Beast

Above is my first attempt at designing a “solid” finger for the Cyborg Beast DIY printable prosthetic in OpenSCAD.1 The reason this is a “solid” finger is that I haven’t subtracted out any material to allow this partial finger to connect with anything else.

The problem with scaling (up or down) any design that requires fasteners and hardware is that when you do, the holes for the hardware are similarly scaled.  This leads to more post-printing work drilling holes to widen them or to find larger fasteners that won’t rattle around in too-large holes.

Thus, if the hardware consists of 3mm screws, the holes for the hardware should be 3mm no matter how much the parts are scaled up or down.  To make matters more interesting, not all holes in the model should be excepted from scaling.  The above finger tip has a plastic end that is supposed to fit into a mid-finger piece – and those parts should be scaled up or down according to the size of the overall hand.  Thus, some voids should be scaled2 and others not at all.3

I’m rather happy with how this finger has turned out so far.  It has most of what I understand to be the essential features of the Cyborg Beast fingertips, including little nubs along the finger pad to allow for gripping.  I intend to make this an option, in case a user would rather use something like Plasti-Dip to make grippy finger pads, rather than relying on printed plastic bumps.

However, converting a decent design into a parametric design requires a little more work.  The way I go about designing a parametric model is to first design one instance of the thing, in this case the finger tip.  My next step is to poke through the OpenSCAD code to locate those aspects parts that contribute to the models’ essential features – length of the finger tip, for instance.  Once I’ve found these bits, I then try to modify them so that I can insert different variables and arrive at sane variations on the model.

Wish me luck!4

Default Series Title

  1. If this is your first time tuning in, check out the prior posts in this series using the links at the bottom of this post [↩]
  2. Where parts meet [↩]
  3. Such as holes for hardware [↩]
  4. See, this is a post about finger tips and design tips!  Oh, man, I crack myself up! [↩]