Strength Test Facility for Open Source Appropriate Technology (OSAT) 3D Printing

A Test Bed and sample Test Pieces for strength / stiffness testing of 3D Printed parts

(See attached Word document for a detailed description)

I am recording my development process and experiments in more detail on my blog: http://julianh72.blogspot.com/ I will continue to post relevant files here on Thingiverse, but I will have more space for discussion and debate on my blog. The first entry is here: http://julianh72.blogspot.com/2011/11/testing-strength-of-reprap-printed.html but there will be more discussion on later posts.

EDIT 02 December 2011 - Modified parts (Mk II) uploaded, to make the test assembly more stable.

The strength and stiffness of components manufactured using RepRap and other 3D Printing technologies are affected by a number of independent and inter-dependent parameters, including:
a) the generic stock material used (e.g. PLA, ABS, PE, etc)
b) the actual source and condition of the stock material; e.g. it has been reported that PLA filament will absorb atmospheric humidity over time, and this affects its condition when placed using RepRap-type fabrication; it has also been reported that different coloured batches of otherwise nominally identical filament from the same source can exhibit significantly different fabrication properties, and therefore presumably different mechanical properties
c) the tool-path and build parameters which are used to fabricate the component (e.g. filament diameter, layer thickness, number of layers in the surface “shell”, % solid fill vs. % voids used in the core fill, etc)
d) the orientation of the part during printing (filaments parallel or perpendicular to the main load paths, etc)
e) the attributes of the actual printer (print head speed, precision / repeatability of placing the print head, backlash, etc)
When manufacturing components which are intended to have mechanical strength and function, it is necessary to be able to measure the actual strength of materials which can be printed with a particular machine, using a particular set of printing parameters, so that the strength and service life of the component can be predicted, and to assist in the design of new components which will be subjected to loads whose magnitude can be predicted or estimated.
This project came about partly because I am an engineer, and I “need to know” these sorts of things, but was also spurred on by reading an paper on “3-D Printing of Open Source Appropriate Technologies for Self-Directed Sustainable Development” by Pearce, Blair, Laciak, Andrews, Nosrat & Zelenika-Zovko.
[Ref: www.ccsenet.org/jsd “Journal of Sustainable Development” Vol. 3, No. 4; December 2010 http://www.ccsenet.org/journal/index.php/jsd/article/view/6984/6385 ]