Simple Tensile Strength Tester

Introduction

This is a simple and cheap tensile strength tester for measuring relative tensile strength from filament samples.  It's used to test the layer adhesion strength across various filaments or settings.  Does increasing the temperature on your favorite filament create stronger parts?  Does high speed printing create weaker parts?  This mini tester is designed to answer these questions.  

Design Concept

The tester is very simple to build and requires only a few 3d printed parts and a few cheap parts that can be bought on Amazon or elsewhere (links below).  The best part is everything can be printed from standard PLA, as long as you print with appropriate settings.  The machine maxes out at around 100 pounds of force (roughly 45kg), so samples need to be relatively weak.  But it will give you a relative idea on which filaments and settings are stronger.  The whole thing can be built for around $100 and uses minimal fasteners and requires no electronics experience and any soldering is absolutely minimal and optional.  No programming or motor drivers are needed.

Bill of Materials

Here is a list of everything you will need.

• 1x 500mm 3030 Aluminum Extrusion
• 1x Linear Actuator (50mm stroke, 200+ pound rating)
• 1x Momentary Polarity Reverse Switch
• 1x Luggage/Hanging Scale
• PLA Filament
• 2x 5x20mm Steel Dowel Pin
• 1x DC Barrel Jack (optional)
• 1x 12VDC ~50W Power Supply (or bench supply or existing wall-wart)
• 10x Sliding T Nut (3030 series, M5, 8mm wide)
• 9x M5x12mm Button Head Screw (or 10-32 ½")
• 7x M5x25mm Button Head Screw (or 10-32 1")
• Various Fender Washers (optional)

Print Settings

These parts will be under fairly high stress, so it's important they are printed in the correct orientation and have the correct settings.  PLA will work just fine for this as long as you follow the following settings.  Print all parts in the orientation shown in the picture at the top, and where noted on the files.

• 0.2mm layer height is fine (with 0.4mm nozzle)
• standard PLA settings should work (just use default settings for your filament)
• Increase perimeters to 5
• Make sure you have 5 solid shells top and bottom
• Use at least 30% gyroid in-fill.  You can go higher, but anything over 70% starts to cause more problems I've found.  30% should work for most filament, but 50-60% might be needed for particularly weak filament. 
• You could print all parts in the above settings except for the two ‘sacrificial’ parts that carry most of the load, and print those with much higher in-fill or even perimeters. 

Assembly and Design Video