Flexify (REV 2) - Template for Flexi Joints

Revision 2

After working on print-in-place flexible fabric, I have updated my templates to include expanding joints in addition to alternate orientations.  Style A uses a female socket in the middle, and Style B uses a male connector in the middle.

You can find an up-to-date list of Flexify designs here: https://www.printables.com/@FlyingGyroscope/collections/3017828.

Just Another Flexi?

Nope, this is not just another flexi.  This is a group of templates to help you make your own custom flexi prints in minutes with simple copy and paste methods.  It transforms solid, flat shapes by creating print-in-place hinges.

Templates define the negative space (or air gap) that separates pieces in a flexible joint.  Start with a solid piece and use the template to cut away material, leaving behind two interlocking pieces.  Use templates to cut "holes" with combine/boolean operations in CAD, or with negative volume modifiers in your slicer.

Templates are bundled into zip files that include step files, and the measurement in the filename is height/thickness.  Single, double, and triple versions alter the number of interlocking sections.  Double and triple versions are stronger and more stable than single versions.

If you want to skip the tutorial further below, you can jump straight to a test print.  Note that test prints are not an exact copy of the example in the tutorial.

Features

Yes, I admit that FlexiDinos are fun prints.  And yes, NASA chainmail has cool articulation.  However, Flexify joints are better in some scenarios.

• Easy to use.  Beginners can use the template in a slicer.  Pros can import step files into CAD, or make custom templates.

• Easy to print.  Interlocking parts use tightly controlled overhangs without bridges.

• Strong.  There are no isolated, vertical parts with small cross-sections.  This also greatly reduces retractions.

• Smooth.  No bridges and reduced retractions help create a smooth joint.

• Thin.  Flexify joints can be as thin as 5-6mm.  However, thicker joints create stronger prints.

New features

• Expanding joints.  Yo Dawg, I heard to you like flexi so I put flexi in your flexi so you can flex while you flex.

• Alternate orientation.  See Styles A and B in the drawing above.

Make it Flex (with PrusaSlicer)

PrusaSlicer, or similar modern slicer, is the best option for beginners looking to create a flexible print.  You can recreate the following tutorial with files inside the Example folder, and you can see a finished example with MK4S_Example_Snug.3mf or CoreOne_Example_Snug.3mf.  Pay attention to red callout arrows in the screenshots.  

1. Select a template that matches the height of your starting design.  It is important to match heights as closely as possible.  If your design is inbetween two template sizes, round down to the nearest one.  If your design is more than 2mm taller than the template, it will not work.  If none of the heights work for your design, trim your starting design or make a custom template (described in Advanced Users).

Be careful with scaling.  In PrusaSlicer, the template will automatically receive the same scaling as the starting object, but it should not get any scaling to work as intended.  Do not use non-uniform scaling.  You can use uniform scaling with the same caveats as other print-in-place designs.  Enlarging the scale increases clearance between parts, and decreasing the scale reduces clearance between parts.  

2. Load the starting design into PrusaSlicer and select the filename in the side bar to highlight the design.  Look at the Object manipulation section (located near the bottom right, just above the Slice now button) and ensure the X and Y positions are centered on the print bed.  Starting with the part centered simplifies the process of aligning the template later.  

3. Right-click on the filename to bring up the options menu.  Select Add negative volume and then Load to choose the downloaded template.  The template will then appear as a transparent shadow on the printbed.

4. Click on the template to select it, and rotate if needed.  Press R to rotate with the mouse, or rotate around the Z axis with the Part manipulation section.  Just like in step 2, check that the X and Y position values match the center of the printbed.  This ensures a precise, repeatable starting place.

5. Press M to slide the template around the bed with the mouse, or edit values in Part manipulation for finer control.  The example print places joints in 14mm increments along the Y axis.

6. Click Slice now to see a preview and inspect the joint.

7. Repeat steps 3, 4, and 5 for each flexible joint.  Remember to leave adequate space between joints to avoid creating thin walls.  The example uses a triple joint in the center, double joints at +/- 14mm, and single joints at +/- 28mm.

Advanced Users

Expert designers can import step files directly into their favorite CAD program, or edit the template to make custom sizes.  I am not giving CAD lessons at the moment, but I will share the Fusion360 design file that generated these templates.  Below is a double joint in Style B, but the same values apply to all styles.  (The variable socket_travel only applies to expanding joints, obviously.)

Thanks for visiting, and enjoy!