Swamp Castle

OnShape: Shapes up great!

2015-08-07T22:56:00.000-05:00

Eureka! I have found treasure, and its name is Onshape!
Edit: I now use Fusion 360 for my home projects.

My CAD wish list:

Free (or very low cost)*. I need a copy for five family members, and their friends.
Open source*. My previous favorite app was sold and absorbed into a more expensive product.
Importable/Exportable. Can't bear to leave a design locked in a proprietary format.
True CAD. Associative, sketches, precision, all the good stuff. Written by someone who "gets it".
Collaborative. Need to share those designs and keep up with the latest version.

I ran across Onshape in a trade article somewhere. Didn't want to get my hopes up too much, so I've put it to the test. Tonight I have completed my first test, and this looks like the real deal! It only lacks being open-source, but given the philosophy and business model of this vibrant new company, it seems like a pretty safe bet*.

My test subject:

Harmonic Transformer

The models have been exported from Alibre, and successfully imported into Onshape. I had to rebuild the dome because of errors during export. Happily, I was able to piece-part out the original model as a collection of extrudes, and then perform Boolean operations to reassemble and re-cut the dome. I did have to redraw a couple of parts, which was fairly easy.

The final dome is possibly better than the original! And the best part? Even though it is no longer a sketch-based model, in Onshape, it is live geometry! I can snap to it, project curves, move faces, and add details. Now my lovely harmonic transformer is free!

Guess what else? I've made it public in Onshape, and you can go make your own copy and play with it too! Grab that little handle, and take it for a spin! Woooooo! :) You'll need to sign in first, and it will take a minute to load in: harmonic transformer

Onshape. My new favorite tool. Go there now. Sign in. Make stuff!

*May have spoken too soon. They just changed the terms for "free" accounts, reducing the amount of storage space. While models can be exported, it is unclear to me whether an Onshape format model can be removed from "the cloud", and then restored to it without loss of functionality. The "pro" plan is costly for a recreational maker, especially for a multi-user family. So when you run out of space, there may be a big problem.

Toasty Fingers

2014-05-16T18:21:00.002-05:00

For all those out there with frozen fingers, I offer this solution: the humble heating pad, already available at any drug store or Wal Mart. Keep those fingers toasty!

My office is freezing, no matter what temperature it is outside. The AC blows constantly, and my fingers get cold and stiff. This makes it uncomfortable to type and use the mouse. My employer has banned space heaters, as a cost-saving measure. I have no control over the AC (I even taped up the vents). They won't turn it down/off, because other offices need it. I end up sitting on my hands to warm them. Arguably not the best solution, since that tends to affect my productivity oh, just a tad.

This has finally gone on too long. I tried gloves, jackets, and wrist warmers, to no avail. Between the convection flowing across the backs of my hands and conduction to the cold desk, mouse, and keyboard surfaces, my fingers don't have a chance. Then I thought of a solution. Buy a cheap heating pad, and put it under my mouse and keyboard. Hurrah! Not a perfect fix, but so so so much better. I also turned my computer backwards, so that the fan exhaust blows towards me. That helps a little too.

Solving this problem did not result in a nifty design, and in fact does not seem very interesting at all. However, I've mentioned it to several other people who have commented on how cold their offices are, and they have all been surprised by this simple solution. That made it seem worthy of posting. I have since covered it with a cheap "backpack" from a trade show, and put a mouse pad on it.

Note: This was actually about 1 1/2 years ago, and I still really love it. The keyboard warms up too and keeps my left hand warm as well.

FreeCAD still in development

2014-03-15T11:31:00.002-05:00

I gave FreeCAD a test drive, and built this model in the process.

FreeCAD seems to be in the midst of a major overhaul. In their forums, the developers discuss this excellent presentation from the makers of Solid Edge, and have taken it to heart. Once they digest the very sound advice on making robust CAD models, and roll out the new release, FreeCAD will be worth another look. They are an active and enthusiastic community, and could use more manpower to achieve their goals. However, since my current goal is to create models, I'm going to look elsewhere for now, and give FreeCAD some time to mature.

Update: Go try Onshape!

Conclusion: I'll give FreeCAD a try

2014-02-20T23:25:00.003-06:00

My Model-Creation App Criteria:

Models to be used for manufacture via CNC mill, laser cutter, or extruder 3d printer.
Primarily for mechanism type designs, with artistic/sculptural features to enhance aesthetics.
Models to be shared with online communities, students, and family members.
Low-cost in the short term and long term.
Accessible to students, family.

CAD fits the bill for design needs. CAD models are solid, avoiding most 3d print errors. They are dimensionally driven (parametric); once you have a feel for how much clearance is needed between a "peg" and a "hole" on your 3d printed parts, that clearance can be used in all future designs. Most CAD apps include at least a modest tool set for aesthetic features.

A separate polygonal app with compatible import/export formats will allow for additional aesthetic flexibility. Also many of the 3d printer models available online are in stl format, which is polygonal and does not import well into CAD.

For fancy formulaic shapes, a scripting app would come in handy.

Open source apps are perfect for low cost and accessibility by all. Also consider that a model format which is not open source, it can be unexpectedly purchased, application prices can go up, or the format might be discontinued. If that happens, you may find yourself locked out of the apps and unable to work in the native format of your designs.

My selections:

FreeCAD: hopefully this can fill the traditional CAD tool set

Blender: a polygonal app

OpenSCAD: scripted modeler

I'll be sharing my FreeCAD experiences in future posts. The FreeCAD community appears lively and enthusiastic, but the app itself is definitely a work in progress.

UPDATE: FreeCAD still in development
Update: Go try Onshape!

The Best App for Creating 3d Models

2014-02-19T20:42:00.002-06:00

Have you wondered how to choose between all the many different 3d modeling applications? What makes them different from each other? Here is some info about what is out there, and what their models are used for.

Rendered models:
Think Pixar movies. These are large polygonal models for rendered animations, using bones, shaders, nurbs and many many polygons. They will be rendered with fancy lighting and effects that can take a long time to compute. Computational time is not an issue here, though, within reason.

Some Apps: 3dStudioMax, Lightwave, Maya, Blender

Real-time models:
Think flight simulators and games. These are also polygonal models. This model type is made to look great but render fast, to be used in interactive simulations. They are streamlined for most efficient rendering; the modeler tends to know each polygon so well that they have individual names and hand-made, lovingly applied textures. The driving criteria for efficiency change with the power of the hardware, but always are a balance between efficient use of polygons and textures, a well laid-out hierarchy, and good levels of detail so the model fidelity will change with viewing distance. The model is a bundle of tricks used to make them look more detailed than they really are.

App: Creator

CAD models:
Think blueprints for houses or rockets. This is a precision model, and is not made of polygons. A circle is defined by a formula, and is round no matter how far you zoom in on it. The models are solid, or "air tight". Dimensions and constraints control the shapes of the objects. Models are used to make manufacturing drawings and are sent to a shop to make, or the models are used to create CAM routines so automated machinery can produce hardware directly.

Some Apps: ProEngineer/Creo, Autodesk Inventor, Solid Edge, Rhino, FreeCAD, Alibre
Update: Go try Onshape!

There is, of course, crossover. 3d printers use polygonal model formats to produce parts. The models must be closed in order to print correctly. They can be produced from CAD or from polygonal applications. Apps like Open SCAD produce solid models through scripts, rather than visually. Programmers find this more accessible, and there is capability for making some very exotic formulaic shapes that can't be done with conventional CAD tools. Sketchup produces models by visually manipulating geometry, making numerical input optional. The models are more CAD-like, although they are not required to be "air tight" solids, and they are not numerically driven like CAD.

Apps: Sketchup, OpenSCAD,

Sketchup model

3d print of parametric openscad models

Direct Modeling is a new CAD movement appearing from all the major CAD apps, and also the Finite Element Analysis (FEA) crowd is joining in. It appears very much like Sketchup for CAD models, regardless of the native model format. Direct Modeling reads in the files, and frees the user from the hierarchy. It is handy for modifying models that someone else made. Time will tell if it can replace traditional Parametric CAD. For now, Direct Modeling is marketed as an additional app in a suite including Parametric.

Choosing an app depends heavily on your budget and what kind of models you want to make. The price is as low as free, and goes up to the thousands with additional yearly fees for support and upgrades. There are certainly many apps that I did not include, and I'm sure there are quite a few niche apps that I don't really touch on; hopefully this will be helpful as a starting place for your search. I will be posting more articles about the direction I am going. FreeCAD looks promising.

UPDATE: Conclusion: I'll give FreeCAD a try.

UPDATE: FreeCAD still in development

Tipi pole and hat system

2013-11-21T23:38:00.002-06:00

Here is my first follow-up on my tipi post. As I said in that first post, I decided to make a traditional tipi cover, based on instructions in the book "The Indian Tipi", but replace the traditional 17 wooden pole system with a single aluminum center pole to carry the weight of the tipi cover, and 1" nylon webbing serving as guy wires and "poles" for the tipi cover. In the spirit of being pack-able in a car, the pole is made of 2' sections, each having an additional 6" taper for slipping them together. In the photos below, you can see the black webbing "poles" and the sectioned 16' aluminum sch 40 pole.

The above views are looking up through the smoke flaps, which allow venting of smoke from a fire inside the tipi. We did try an open fire inside, but it was unfortunately smokey, and we were worried about CO poisoning. We now have a battery-powered CO detector. That also puts a portable wood-burning stove, preferably rocket-mass-heater style, onto our list of things to explore.

The other thing you may notice is that the smoke flaps allow rain to fall into the tipi. The smoke flaps can be manipulated at angles that will block most of the rain. However, the center, where the pole goes through, is not protected. For that, I made a "hat" with a "crown" of dowels that both keep the hat open in a cone shape, and give the aesthetic hinting at real tipi poles extending above the tipi.

Above is the canvas pattern for the tipi hat. I need to look again at the one I made, and write some instructions on how to sew it. I used a Pfaff sewing machine, because it is capable of sewing through 4-5 layers of canvas. Below is a CAD screenshot of my custom-designed, 3d printed parts for assembling the hat and webbing "poles" to the top of the 16' aluminum pole. The parts are available for download at Thingiverse.

The webbing goes through the green "pole cap", which has a conical shape. I plan to rework this part, because the straps end up cracking the vertical features. There are five straps in all, creating ten "poles". The "cone" sits on the top of the rain hat. The "plug" is underneath, and the two are bolted together, sandwiching the canvas in between. The "cone" holds the dowels, which go into pockets in the canvas.

Below is a view inside the rain hat, showing three bungees feeding through the canvas around the "plug". They stretch down and hook into the holes in the part labeled "pipe", and hold the rain hat in place. In the above photo, you can see the knotted end of the bungee, as it feeds through the cone.

I made an "accessory ring" that locks into the groove where the aluminum poles join. It is useful for hanging things from. The ring clamp is in two sections, and locks in place when the accessory ring slides over the top of them.

Harmonic Transformer Design Process

2013-11-18T01:00:00.000-06:00

Here is a very brief snapshot of the design process for my Ideal Harmonic Transformer. The images are pulled from my various blog posts, where more detail is provided. I hope this gives you insight into the process of developing a design. Time, patience, and iteration are required.

Harmonic Transformer for the Classroom

2013-11-17T23:26:00.003-06:00

Treat yourself and your classroom to a machine that shows you how Sine and Cosine relate to angles. Get the stl model files Here, or check them out in Onshape, where you can make mods, if you want.

How to use:
Use the knob to rotate the arm to an angle. Read the value on the Sine and Cosine scales. Sine and Cosine values are given for a circle with a radius of 1, which is also called a "unit" circle. To obtain lengths for a circle with a radius other than one, multiply the reading from the machine by the desired radius.

Sine and cosine are trigonometric functions of an angle, defined by using right triangles. In the animation above and the figure below, a right triangle has been drawn on top of the Harmonic Transformer. The angle below is set to 30°. The hypotenuse is the radius of the circle, shown as a green line. The hypotenuse/radius is drawn from the arm's pivot center to the center of the knob, where the yoke pin is. The blue horizontal line is the "adjacent" side of the triangle, and the magenta vertical line is the "opposite" side. Notice that the blue side is the same length as the reading on the cosine scale. Similarly, the magenta side is the same length as the reading on the sine scale.

Assembly Instructions
Step 1
Print and clean up the five model files, shown below. These are sized to fit the print volume of the MAKERBOT® REPLICATOR 2®: 11.2L x 6.1W x 6H. The dome is optional, but adds character and protects the "key" nut. Note that the files with "-raft" in the name need to be printed with a support raft. The other model files do not require a raft.

Step 2

Slip the bezel ring screws (csink head) through the bezel ring, and loosely thread into the support base. Make sure the notch in the support base is oriented as shown in the figure.

Step 3

Piece together and slip Dome Capture Segments between the Support Base and Bezel Ring, as shown. The Support Base should fit into notches in the Dome Capture. Do not tighten the screws yet.

Step 4

Carefully turn the assembly over, and slip the Bezel sections under the Bezel Ring. The Bezel Ring will lock into the groove in the Bezel segments. Tighten all three screws until snug.

Step 5

Fit the Mount Extensions onto the Support Base, taking care to put the Sine and Cosine in the proper locations. Lock them together using the Support Bushings, as shown. Both Hi bushings go on one Extension, and Lo's on the other. Either way is fine. Make sure to use the correct length screw, and slip an angle roller under each screw. Slip a Scale Clip into place on each before tightening the screws. Leave the screws out or very loose on one side for now.

Step 6

Push Knob Bushing all the way into the knob until seated. A very small amount of the bushing should show through the bottom.

Push the Arm Pin all the way into the Arm. Push the Arm Bushing onto the part of the Arm Pin that extends through the bottom. The Arm Bushing should contact the bottom of the Arm.

Step 7

Insert the Yoke Pin into the Arm until flush. Insert the Arm Pin into the hole in the center of the support base. Push the Gear Blank onto the Arm Pin, then secure into place with the Key, either the Rounded or Heart version.

Step 8

Assemble Yokes, et all onto the Yoke Pin, as shown in the picture. The Angle Rollers create a v-track for the inside of the Scotch Yokes. Tighten the Acorn Nut.

Step 9

Slide the Zero Scales onto the Yoke arms, and secure each with a Zero screw, adjusting them to point exactly at the 1 and 0 when at the extents of travel. Lay the lower Yoke into the Low Bushings, and secure with Angle Rollers and Low Bushing Screws. The Rollers and Bushings create a v-track for the Yoke to slide in. Secure the higher Yoke in the same manner, on the High Bushings.

Step 10

Align the Dome notches with the assembly, slip it into the Dome Capture Ring, and rotate it clockwise until it stops. I found it helpful to line up the screw holes first, then look at the notch that lets it fit over the support base/mount extension frame. Then clock it to the other edge of that notch, carefully push the dome edge into the slot, and clock it back until the holes line up again. I found it to be tricky, and might try wetting the edge lightly with water next time, to slightly lube it. Insert the Dome Screw to secure the dome in place.

All Done! Now start reading the sines and cosines of those angles!

My Printer in Action

2013-11-17T18:30:00.001-06:00

I have one of the original Up! printers. Here are some photos, and notes on how I have it set up.

The print table has a bumpy surface (paint from the factory), and is covered with kapton tape. Prior to printing, I give the surface a quick wipe-down with acetone (fingernail polish remover) to clean the surface. This has been working well for me. The part clings to the table while printing, then peels off fairly easily with a spatula.

I made an enclosure out of an old cardboard box, tape, and a sheet of acrylic that slides across the front as a door. There is an opening in the top with an air conditioner filter covering it. The enclosure keeps the machine warm, which improves print quality. It also makes it quieter. The filter keeps down the aroma of melted PVC.

The door is off in the video below. It is very quiet when the door is on.

When the part breaks free from the table during the print, the results are pretty disastrous.

Convert Raster graphic into a Vector graphic for laser cutting with Retina Engrave

2013-07-07T23:08:00.001-05:00

Why I need a vector graphic: For laser cutting with my Full Spectrum Laser, the preferable way is to create a vector graphic. The most convenient way I have discovered so far is to work on the image with Inkscape before "printing" to the Retina Engrave "printer", which is the program that controls the laser cutter.

Here's how I got a raster image from Photoshop converted into an Inkscape vector graphic:

To make strong outline vectors, draw filled shapes in Photoshop. The vectors will be outlines of these shapes. Crisp up the edges by using Threshold or sharpen masks. Print to a PDF file via cute pdf. If layers are to be preserved, print each layer separately.
Open the first pdf in Inkscape. For multiple layers, import the other pdf's. Align them and move each to a separate layer.
For each layer, select the imported image, which is a single box on the screen. Right-click and select "ungroup". Repeat this until "ungroup" is no longer available, probably 3 times.
Select the image, then: Click Path > Trace Bitmap > Colors, Stack scans, Remove background > Update > Ok. To verify it worked, you can click Edit, and it should say "Undo: Trace Bitmap". If it doesn't say this, then you may not have "ungrouped" enough times.
Click to select the object, which will actually be the trace, and move it to a new layer. It will look the same as the original image. Hide the layer with the original. Click Shift+Ctrl+F to open the fill/stroke paint/stroke style menu. Select the trace object. Click the "Fill" tab, and click the "X" button. The graphic will disappear. Click the "Stroke paint" tab, and click the "flat color" button. Now you will see outlines. Select desired color. If "printing" to Retina Engrave for laser cutting, to prevent the vector from show up in the "raster" tab, click the "Stroke style" tab, and enter .1 pixel for the width.
"Ungroup" the object once again. Now there will be about seven copies, varied slightly in darkness and size. Delete all but the most desirable one. To do this, I drag one to the side, and delete. Repeat until dragging reveals that there are no others left, then undo the last move. Note: If the original image was not one solid color, these seven layers of lines will be contours around changes in colors. In that case, keep however many vectors you like. I kept two layers for the wheat graphic below.
Repeat for each separate layer. Color the layers a different color for each unique laser power/speed setting desired, choosing from the six main colors & complements: red, green, blue, cyan, magenta, yellow. Black may also be used, but is best reserved for raster images.
To make a raster image also, either fill a shape or outline with more than .1 pixel thickness. Make sure there is a raster dot (even a white one will do) at the upper left of the page, so that the raster image will align properly with the vector image in Retina Engrave. In Retina Engrave, checking "Ignore Raster" then printing from Inkscape will load in the vector data without updating the raster data. Works the same way with "Ignore All Vector". This gives nice control over what is in the raster and vector images.

Add any text or features desired, then "print" to Retina Engrave, and you're ready for some laser cutting! The settings in the photo below worked well for cardboard, if it lays flat on the table. If it curls up, the cut may not go all of the way through.

Photoshop image

Converted Photoshop layers, plus text and a graphic

Settings for laser cutting cardboard, test case before trying on wood. Cutting paths are color-coded and assigned an order, speed, and power. The Magenta speed was changed to 100 before cutting was started.

Burning the graphic. This scorched the top layer without actually cutting.

The laser actually caused an orange flame to briefly appear while cutting. The cardboard shifted midway through the cut, because of the vent fan. Next time I will tape it down before starting a cut.

The cardboard test cut being tried out. Now my measuring cup and spoon collection will stay put in the drawer.

Tipi, Teepee, Tepee

2012-08-01T00:33:00.001-05:00

Here's what I've been doing all spring and half the summer in my free time: making a tipi! My daughter in the back is eight years old, and is sitting on a deflated air mattress; the cloth in the foreground is the edge of the door opening.

Since I haven't taken the time to write even one blog entry on it, I'll try and capture the story now, starting with this post. It all started when we were wanting to plan a camping trip for the summer. Our tent is more complicated to set up than we would like, and is nothing special. We found a Tentipi online, and thought it was really nice; well, until we found out that they don't sell them in the USA, and besides that they're very expensive. The main thing about them seems that they are a tipi made with a single center pole, rather than the 17 or so poles of a traditional tipi, and the outer shell goes up very quickly. Clearly the next best option was to try to build our own.

That put us on the path of researching tipis. It just so happens that tipis are fascinating. There's a lot more to them than it seems at first glance. There's the inner wall, that insulates them. You can light a fire inside, something that was never possible in any tent I have owned. They have big smoke flaps with poles to maneuver them around and control the air flow vs rain. And they are stitched together up the front with those nice wooden stitch pins.

In the end, I would be happy with nothing less than a traditional tipi cover and inner wall design, but I had to convert it to use a single, collapsible pole so it will fit in the car. This required a special design that made my 3d printer and Alibre modeling tool just the thing I needed to achieve it with. It's standing in my back yard right now, waiting to be packed up and taken to a campground in a weekend or two. It did not cost less than the Tentipi in the end, but I sewed every bit of it, made it be just how I wanted it, and I also have a new sewing machine. It is also very pleasant to sit in. :)

Note: while technically the single-pole design makes this more of a "bell tent", the canvas is a traditional tipi design, and would work equally well attached to a traditional 17 pole tipi structure. Also, the black nylon webbing straps running from the top of the pole to the ground act like poles, although not as rigid. I continue to think of it as a tipi, and choose to refer to it as such.

Garland attached to Brick

2012-01-25T20:52:00.000-06:00

This post isn't exactly timely, but you'll have plenty of time to prepare for next Christmas. :) I bought garlands to hang on the doorway Christmas-before-last. Then I looked for hangars to let me hang it on my brick home. Guess what? I couldn't find anything!

I needed something:

Easy to use
Not damaging to the brick
Attractive or subtle enough to look ok when the garland wasn't up

Here is what I came up with:
3D print a set of clips (file is here on thingiverse, and on Shapeways), paint them black, stick them to the brick with sugru, and use paracord to tie the garland to the brick. It works like a charm!

To attach with sugru, sofen up a piece and work it into the grooves in the clip base, making sure it comes through the holes also. Push onto the brick, making sure it gets a good bond. Also work some sugru over the lip on the top edge of the clip base.

To attach shock cord, tie a simple knot in both ends of the cord. Slip one end through the large hole, then push into the slot. Pull on the cord until the knot bumps against the clip. Loop the cord around the garland, then wind the cord around the clip and into any available clip groove, or even into two.


Grooves on the base of the clip grip the sugru for a good strong bond.

Holes through the clip give even more hold for the sugru. The clip's shape is both fancy and practical, giving multiple ways to attach the shock cord securely, even without seeing what you're doing.

A clip attached to the brick with sugru.

Several clips sugrued to the face of the brick arch on our front porch.

Paracord, looped through the clip, like it would be when holding the garland.

Garland attached to the house with shock cord, sugru, and my clip.

Dropper Caps for Extract Bottles

2011-12-30T22:08:00.000-06:00

Two of the four droppers I bought from KAF

I got a four-pack of dropper lids for my citrus oils, because they are so strong you measure them in drops. Unfortunately, they only fit on the amber bottles, like the butterscotch bottle in the photo below.

Not being in a mood to be denied, I decided to pull the dropper out of the original cap, and make a cap to fit the clear, small mouth bottles. Using Alibre and calipers, it was easier than I had hoped, and also fit the McCormic bottles from the grocery store! Hurrah!

Orange oil with dropper, and three more caps I printed.

I went back and added some texture details to make the cap easier to turn, and more attractive. I decided to offer the model for free at Thingiverse, and the caps for sale on Shapeways at my store's kitchen section. They are more expensive than I would like, but perhaps worth a splurge if you frequently use extracts or oils in this kind of bottle. Either way, you'll need to purchase the droppers.

While Shapeways says that the plastic is not food safe, the cap doesn't touch the extracts. The black rubber on the dropper acts as a gasket/seal, and serves as a barrier between the cap and the bottle. If this makes you uncomfortable, then I suggest not getting them. Personally, I am comfortable that it is safe.

Variety of bottles with and without droppers.

McCormic bottle with and without dropper.

Filament Guide

2011-12-30T21:38:00.000-06:00

The feed motor on my Up! printer failed a while back, and I have been living with a duck tape repair. Catching my breath after Christmas festivities, I decided it was high time to make a proper fix.

The feed motor is not needed, as the nozzle feed is strong enough to pull the filament from the spool unassisted. After first trying to modify someone else's model in Sketchup, and getting frustrated with the lack of associativity, I used Alibre instead. I sure wish I could find a way to import an stl for free, so I could trace off of the existing model, but instead I grabbed my calipers and started measuring.

It's pretty simple. Slip the filament in through the end, no need to pull it out of the nozzle, and the guide keeps the filament in check as it comes off the spool. While lacking frills, it works and looks better than tape. Model available at Thingiverse.

Harmonic paint job

2011-07-22T22:44:00.000-05:00

Ah, finally! After base coats, sanding, and feeling afraid of messing up, the paint job is complete! Thanks go to my husband for helping, and for the photography.

Here's how it looks from the back.

And here it is back-lit by a lamp, to illuminate the layers. It's hard to capture the details in a single photo.

Scale matters

2011-07-22T22:33:00.000-05:00

Also for Father's Day, my hubby wanted a work bench on casters. So obviously I made him one. I discovered that I could print these tiny casters with axle and wheel all at once. Some careful knife work, and the support material comes out, leaving free-turning wheels. Then just push the caster pegs into the table, and there you have it! The wheels turned out unfortunately not really round, but that didn't seem like a big deal.

He was surprised with his work bench; I think he wanted a larger one. So we'll go get a bigger one later at the store. One of the casters fell out and was lost. On the re-print, the wheel wouldn't break free and spin. I think it may be because I didn't pre-heat the platform. That was unexpected; I didn't think it would matter on such a small part.

Terrible Trio

2011-07-22T22:22:00.000-05:00

What could be better than a greeting card for Dad on Father's Day? How about home-made, 3d printed Minecraft monsters, hand-painted by the kids? I thought it would also be a nice way to start the kids on their 3d modeling ventures. They look perfect to me. :)

Why decorate the back?

2011-06-13T00:59:00.000-05:00

It seems odd to put decorative details on the back of a printed part.

The bezel has patterns all over it. While I do think it looks cool that way, there was a more practical reason.

Large, flat parts printed on my machine tend to weld themselves to the support structure in at least a couple of spots. This results in a long, frustrating cleanup process, and usually several gouges in the part. I found that adding 1/32" x 45° v-grooves in the bottom, and chamfers around the edges, makes the process easier. If it does stick, it's usually only between one pair of grooves, and is more easily dealt with.

I've also discovered that the support material separates more easily during marathon printing sessions. The only explanation I have is the heat. I will take more care in the future to heat my printing platform before printing large parts.

Make!

2011-06-11T09:00:00.000-05:00

Make Magazine

Awesome! I made the cut on Make!

Fastener Improvement

2011-06-10T01:36:00.000-05:00

My first set of fasteners had a high failure rate. About half had their head pop off while either removing them from the support material, or with only mild torque while using them. I had been using standard print settings, and found that they worked better when printed at highest fill and print quality. But many still sheared off more easily than I found acceptable. I've found a solution.

The gray bolts are the original style; the gold are new and improved. Notice that the gold countersink head has a continuous slope, where the gray one is disjointed. On the button head bolts, the gold has an undercut at the head interface, while the gray head is flat and just "stuck on top".

Here's why this makes a difference. In the sketch labeled "flat", you can see what the printer does at the transition from head to shaft. It makes an outline around the head, then fills it solid. The shaft outline will then be laid donw in the middle of the fill surface, and proceed to print the rest of the bolt. There is not much structure, poor adhesion, between the layers.

On the other hand, when the shaft of the undercut bolt starts to print, three outlines are printed, with two fill areas. This makes the print have more structure, and better adhesion. When I tried breaking a "flat" bolt, the head popped off easily. When I tried breaking an undercut bolt, it was considerably more difficult, and it snapped where the threads start, rather than at the head. In the photo above, you can see the sheared head of a "flat" bolt, and a nice set of "undercut" bolts. Looking closely, you can see the slight groove on the head, where the undercut is printed.

And thank you, TeamTeamUSA, for your suggestion to print them at a 10° angle. As you said, this causes the printer to "outline" the entire skin of the bolts, covering all the fill. Perfect! :)

Ideal Harmonic Transformer Evolution

2011-06-08T17:10:00.000-05:00

Discarded Parts

First print of complete butterfly dome

2011-06-08T15:37:00.000-05:00

Here it is, right off the printer table. It's filled with support material, a necessary evil for my machine.

After some patient cleanup work, here's the finished dome. Happy! :)

Not a great photo, but here it is on the partially-assembled Ideal Harmonic Transformer.

Ideal Harmonic Transformer prototypes

2011-06-08T14:04:00.000-05:00

These are my first two working prototypes for the Ideal Harmonic Transformer. I learned a lot from them, including how to make a fit with friction, snug but sliding, and loose. Also played with techniques for making parts that separate more easily from the print base structure. On the Up!, it's the same as the print material. It's very disappointing to spend 30 min to separate an intricate part before getting to use it, and having a marred surface for all of your care.

These prototypes use #6 machine screws. I had reasoned that they are already designed, readily available, and quite strong, so no need to reinvent. However, I could not find any off-the-shelf hardware that let me do what I wanted with the arm pin and yoke pin. After spending too much time in front of the fasteners at Lowes and Home Depot, I decided maybe it was possible to make plastic screws after all.

Once I got the hang of it, I converted all of the screws to home-printed rather than OTS. This let me eliminate all the nuts, by "tapping" the holes, which made the whole design cleaner. It also let me decorate the heads to go with the overall look, not to mention saving me the frustration of sorting through the store's wares.

One limitation, at least with my printer, is that threads must be printed vertically in order to work. The down side is that a print is basically a bunch of laminated heat-welded layers. I think this gives a certain grain to the finished material, and is contributing to the failures I'm experiencing. Some of my bolts snap off at the head right as I'm taking them off of the machine. Others turn out fairly strong. Setting the Up! print settings to fill=solid and quality=fine helps, but does not eliminate, this problem.

Introducing the Ideal Harmonic Transformer

2011-06-08T07:15:00.000-05:00

I needed a simple project to use while getting more familiar with Alibre. My husband suggested I make a simple sin-cosine machine. We were inspired by a documentary of a mechanical fire control computer for a ship that we had recently seen posted on Boing-Boing. Simple. I keep thinking about that word. But all designers know that simple is not easy. I will eventually post more of the intermediate steps of this design's evolution.

First, I made one that I thought would work. It sort of did, but lead to a series of improvements until it worked nicely. Then I got thinking how pretty that bracket was, and how cool this simple design could look if I added a few aesthetic features. Well, here it is. The dome is printing right now. I have the bezel assembled, with the central arm in place. There may be a few minor issues that I'll need to address, but I'm ready to call this done!

I don't think it's simple any more, but I like it. :)

Parts for making Ideal Harmonic Transformer

2011-06-08T07:00:00.000-05:00

What is it?
Ideal Harmonic Transformer
AKA Analog Sine/Cosine Calculating Machine
It is a thing to hold, enjoy turning the crank, and look at. If you can't find your calculator, and need to know the sine or cosine of an angle real quick, you can dial in the angle and read off of the Scotch Yokes. It also works in reverse.

Assembly Instructions:
Assembly instructions are here.

Print Plates:
Here is a screenshot of each stl file for 3d-printing my Ideal Harmonic Transformer.
Don't have a printer? You can order the parts from here.