TANK3 Preview!

Here's a preview of a tread-based robot that I've been working on.  More details of the build to come!

3D Printing: E-Bike Miniature Frame Joints

I miniaturized the joint design to build a straw mockup of the frame.  Nothing beats the touchy-feely aspect of a physical mockup!

Being able to hold it in my hands gave me a new direction on the front-end design of the frame.  The new design moves the lower connection to the fork tube closer to the wheel.

Also, received my order of XTC-3D brush-on coating for 3D printed parts.  It's supposed to self-level as it cures so it should cut down finishing time by quite a bit.  I'll do some tests this weekend and report back what I find.

3D Printing: E-Bike Frame Joint

I'm using these joints to build the PVC frame of the E-Bike. They'll most likely be solid urethane resin casts for a couple of reasons.

The primary reason being that these joints take about 4-5 hours to print with a 50% infill.  An OOMOO 30 silicon mold would require roughly 6 hours to cure, but each Smoothcast 320 resin part has a demold time of only 10 minutes.

I need about 16 of these.

Another reason is that the cast joints would be solid and therefore stronger.  ABS has stronger material properties than Smoothcast 320, but the nature of the FDM (FFF) process makes the part prone to delamination under stress.

Here's a quick comparison between the two materials:

• Smoothcast 320:  (datasheet)
• Tensil strength: 3,000 psi
• Compression strength: 3,650 psi
• ABS: (datasheet)
• Tensil strength: 5,532 max psi (based on Makerbot filament)
• Compression strength: 7100 max psi (based on Makerbot filament)

As you can guess from the pictures below, I now split tricky parts in half when printing.  They're merged either with ABS glue, super glue, or JB Kwik Weld.

I used to split the parts directly in Solidworks, but for 2015, I'm trying to ween off commercial software and rely on open source tools wherever I can.  

This part was:

• designed in FreeCAD
• split in Netfabb Basic
• arranged in MeshMixer
• sliced in ReplicatorG 0040 r28 (Sailfish)
• printed on a FlashForge Creator Pro

The toolchain becomes much longer when going the open source route.  However, with the exception of the 3D printer itself, everything is free and available for Windows, OSX, and Linux.  More to come!

3d Printing: Plastic Thrust Bearing

As a personal challenge for 2015,  I'm trying to ween myself off of commercial software and focus on using open source software.  This was modeled in FreeCAD, a wonderful open source parametric modeler available for Windows, OSX, and Linux.

This is a test for a thrust bearing design as part of a work-in-progress all-plastic electric bike.

3D Printing: Heat Shields for Larger Prints

Not 100% sure where I read it first, but the idea of using a heat shield (technically a "draft" shield) really does work! Usually on my Replicator, a part that spans across the entire build platform will curl up on both ends.

However, using a 0.8mm thick heat shield (single 0.4mm shell all around), this client part came out perfectly straight. Also helped with the start and stop filament gapping that occurs with accelerated printing.

The New D.I.Y: Design-It-Yourself

I've had the Makerbot Replicator for a little over a year and a half now and I've come to realize just how much a 3D printer has changed my life.  I love making things, both in the real world and in the computer.  My two worlds collided the day I got my printer up and running smoothly.

DIY projects used to require that I peruse the aisles of hardware stores and dollar stores for the required bits and pieces to kitbash.  I still love looking at dollar stores and supply stores, but now it's more for "raw materials".  

For example, I can get 3 button cells for $1 at Dollar Tree, and it comes with free LED circuit and reed switch.  It was also cheaper for me to buy a $17.99 sheet metal rack from IKEA than to pay nearly $100.00 for the sheet metal needed on the Quad-Quad MK1 blades.

Since the Makerbot: Replicator came into my life, things that used to exist only in the computer can now have corporeal form.  Things that had to be shaped through blood, sweat, and tears, can now be designed in the computer!

Well, actually, it starts on paper.  The first thing I do when I have a random idea for a "DIY" project is to doodle out concepts on a piece of throw away paper.  Usually the first few sketches are brain dumps, and the idea that I'm drawing on scratch paper helps quite a bit with my paralyzing 'blank page' syndrome.

From there, the next generation of sketches make it in to my current sketchbook.  The sketchbooks include anything from sketches to dimensions on parts that I have at hand.  I have a library of sketchbooks for myself to recall information that has, or definitely will, skip my mind.  My girlfriend can attest to the fact that I have the memory of a goldfish, and getting worse by the years.  

Then I bring it into 3D (Solidworks or Maya) and begin the modeling process.  I start with modeling out the physical items I already have at hand.  Battery packs, PCBs, buttons, etc.  I measure the dimensions with a set of metal calipers from Harbor Freight ($8.99 on sale) and try to get these as close as possible to the real world counterparts.

After that, I model out the project parts with close attention to matching the real world part dimensions.  I take into account the print tolerance of my Replicator when building parts that need precise fitting. Note, screw holes can be drilled or bored out post-print.

When in doubt, I print out a sample and test.

Nothing's more satisfying than holding a physical piece of your digital creation in your hands after a successful print.  Even more "awesome-er" is when everything fits and works the way it was meant to.  Even if it does, there's always a way to make it better!

"D.I.Y" projects for me are no longer hand-made "Do-It-Yourself" projects of yore.  They're now "Design-It-Yourself" projects.