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.