Cutaway, Hollow Elements

by mrule, published

Cutaway, Hollow Elements by mrule Apr 27, 2011

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6121Views 2936Downloads Found in Math Art


A collection of pieces for building polyhedral shells. Derived from http://www.thingiverse.com/thing:5961.

The original pieces took a while to print. This version reduces plastic, and therefore print time. I've been using these pieces to print out lamp-shades ( with http://www.thingiverse.com/thing:7857 ). The thinner pieces might be a bit better for diffusing light.

The .scad file can be modified to produce different polygons, different sizes of hinge, and different depths of cutaway.

models.zip contains several pieces :
-- octagon, hexagon, pentagon, square, triangle
-- hollow and cutaway
-- a range of hinge sizes depending on shape size to adjust hinge strength

The good :
-- less plastic
-- faster prints
-- symmetric hinges
-- range of hinge sizes to balance strength and ease of assembly
-- fun with glow-in-the-dark ABS : https://lh6.googleusercontent.com/_KLnvj61OxTo/Tbh6JxKqlkI/AAAAAAAACqc/RJWNnHgdTYo/DSCF2997.gif

The bad :
-- fragile hinges ( depending on printer calibration )
-- overly tight hinges ( depending on printer calibration )
-- large force required to assemble larger hinges


I print on a heated build platform with no raft to keep the parts clean, at 235C for the first layers and then 220C extruder temperature for the rest of the print, and 123C for the heated build platform.

I also adjust the skeinforge profile until the hinges are double-walled with minimal infill. Properly calibrated oozebane ( or a stepper extruder ) is essential, as strings would make the hinges take forever to clean.

After printing, trim off the extra plastic that stabilizes the hinges.

After this, I 'loosen up' the hinges a bit by snapping two pieces together and bending them back and forth several times. This tends to dislodge most stray plastic, or at least make it clear where you need to trim.

The larger hinges are quite strong but hard to snap together. I use a pair of needle-nose pliers to add force. Some polyhedral shells are very difficult to assemble in the end, and pieces with smaller hinges might be easier to insert in this case.

When building lampshades with Element http://www.thingiverse.com/thing:7857, I leave the bulb socket holder for last, since it is more flexible and easier to insert.

note on hinge clearance : The hinges can sometimes be a little tight. Make sure the first layer isn't pressed too far into the build platform. A compressed first layer will propagate up and make part of the hinge wider, decreasing the clearance. These parts are designed to fit tightly and may require pliers to assemble. If all else fails, removing some of the pins on the hinges can make assembly easier.

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Printed it out on a MakerBot Replicator 2 with PLA. Pieces printed great. Can't fit them together.

Yes, this is a known issue. The pieces were designed to fit as tightly as possible using ABS. ABS is more elastic and so can tolerate more deformation of the hinges when snapping together. You will need to increase the hinge spacing, and decrease the elevation of the "nubs" on the hinges, in order to get something that will work with PLA.