Tactile Discouragement Knobs

Also known as "Ow Trees," “Hedgehog Handles” or “Knopes”, these knobs were designed for maximum discomfort in their use; to discourage use of any cabinet or drawer they are fitted to that may contain irresistible or forbidden items such as chocolate, knives, chemicals, trans fats etc. (or all of these.)

Features

• Sharp backward-facing spines offer a disincentive to access contents, or as stimulation to wake the user up in the morning when opening their underpants drawer
• Flat front face allows pushing and closing as well as firm adhesion to print bed
• Slippery forward angles make grasping other points of contact difficult
• Detail angles modelled to be easy to print with no extreme overhangs
• Uncomfortable to install and handle, as well as annoying to store and challenging to convince people to use - so all in all, fun
• Spine features can also be used as a stringing test at time of printing (see photo)

Model and Slicer info

Knob 1 is a smooth type with rounded spines while knob 2 is angular with a wider base. Type 2 seems to have a little more “Ouch Factor.”

3MF files

• Four of each knob type, in two sizes (around 43mm and 53mm in width)
• Each size includes adjustable cut-outs (negative volumes) for fitting with:
  • 4mm wood screw (40mm length should be good)
  • M4 machine screw (includes pause for inserting a captive M4 nutof approx. 7mm across flats and 3 ~ 3.2mm height)
• Custom slicer settings included

Blank STL files: One of each design which omit the fitting hole for more direct customisation.

Notes on wood screw type:  3 perimeters should be used to give extra strength and enough material for the screw thread to bite into. If it's very tight then try warming the screw with a lighter or hot heat gun to seat the thread nicely with less risk of causing breakage.

Notes on M4 type:  Please check the settings and nut heights etc. to make sure your particular parts will fit when made. The PrusaSlicer setting “Infill before perimeters” is useful to keep ticked so that the overhanging perimeter over the captive screw is has something to hold onto (see screengrab with the blue ring as example)

Material: I have used PLA in my tests of these which works well - as it won't string as much as PETG and its very hard finish seems a good choice for the spiny points. These would be even better if used to make metal castings, as the points could be sharpened even more.