Espresso Distribution Tool WDT - Easy Print (Loose Tolerance)

thingiverse

## Overview This design is largely based on the geometry of [ 9 Prong Espresso Distribution Tool WDT](https://www.thingiverse.com/thing:4819617), but the CAD models were created from scratch. I used [Hestya 10 Pack 0.4 mm Drill Bits for 3D Printer Nozzle Cleaning Kit Stainless Steel Nozzle Cleaning Tool Kit](https://www.amazon.com/dp/B078HXTLX8?psc=1&ref=ppx_yo2_dt_b_product_details) needles, but there are probably cheaper options available. * 0.3mm diameter needle (any size should work) * 1.27mm diameter handle * 30mm handle length * 105mm total length I redesigned this espresso distribution tool with the goal of making a tool that could be easy to print (i.e., loose tolerances) while still being functional. My goal was to solve two main issues: 1. Small holes may come out undersized and be filled in (i.e., needles can't be inserted) 2. Screw threads may bind if parts come out over or undersized (i.e., handle can't be attached) To address these issues I made couple design changes: * Maximize needle hole diameters * Upper limit is based on handle size of needles (~1.3mm) * Convert circular holes to circumscribed triangles which can be printed more precisely * See [HydraRaptor: Polyholes](https://hydraraptor.blogspot.com/2011/02/polyholes.html) * ~~Convert threaded connection to snap fit connection~~ * Discontinuous annular snap joint * Cantilever design with 0.8mm to 0.4mm taper * See [Snap-Fit Joints for Plastics](http://fab.cba.mit.edu/classes/S62.12/people/vernelle.noel/Plastic_Snap_fit_design.pdf) * Increase clearance on threaded connection ## Outcome * Successfully printed design Printrbot Simple Maker 1405 (a printer made of wood and zip-ties) so you likely won't have any issues ## Updates * 2022-02-12 * Replaced snap connection with threaded connection (M16x2 6H with additional 0.15mm clearance offset on all thread flanks) * Snap tabs were brittle (probably because tensile from bending where perpendicular to print layers)