“I have made a promise to publish the new version in fall in the original version. Well, here it is, the now “Universal” Tensile Testing Machine Version 2! I might publish it on Thingiverse as well (though I’m not certain).
I am a 9th grade student at Arizona College Prep Erie Campus. The project to make a tensile testing machine started all the way back in 8th grade when my friend and I wanted to make science fair projects on the tensile strengths of 3D printed testing specimens. We successfully designed a fully functional tensile testing machine in Tinkercad and used it for our Science Fair projects.
Earlier this year, I published the original version as my first instructable. It had detailed design and build instructions and was featured on the home page. I promised that a newer version will be published on Thingiverse within 2 months, but there were some major delays due to shipping. I apologize for the extended delays. Nevertheless, now the new version is published.
The project presented in this instructable is an improved remake of the original tensile testing machine through Fusion 360. Combined with past experience and lessons, this version is much more powerful than the older one (see list below).
I will be carrying on the tradition of explaining every step of the design; this includes every bit of detail from the design process all the way to the assembly of the machine (excluding few hard-to-explain parts). This makes it so that the user understands every step made to achieve the end result.
What is a universal tensile testing machine and how does it work?
Tensile testing machines are variants of universal testing machines made specifically to test tensile strength of testing specimens. It applies a tensile force to a specimen (stretches it) until it breaks, and measures the forces applied while doing so. Although this specific machine is built with mainly tensile testing in mind, this version is now able to perform compression tests as well.
This tensile testing machine has mainly five parts: the stationary fixture, moving fixture, load cell (and its mount), and the motor (a geared NEMA 17 stepper motor). The moving fixture is attached to a load cell and controlled by the motor via a lead screw. After the specimen is loaded and a tensile test had begun, the motor rotates the lead screw. The lead screw translates rotations into linear motion, causing the the load cell to be pulled back, but the specimen resists the pulling force by exerting an equal and opposite reaction, which is then measured by the load cell. This process continues until the specimen fractures. The same process is used for compression tests, except the specimens will be loaded in the opposite direction.
Do I need advanced electronics knowledge to build this?
Depends, but usually no. You will need basic intermediate knowledge to solder the components onto the PCB. Most of the components are through-hole, and those that are SMD are not strictly required. By following the build instructions, you should be able to replicate the machine without much experience in electronics, but if you plan on customizing some features, then you need to be familiar with the required skills.
Benefits From The Original
This is a list of improvements that are made from the original version.
Ability to perform compression tests
Much less fixture deflection due to reinforcements
Much stronger grips
Shaft collars instead of flanged nuts to save space
Higher torque transfer
Designed in Fusion 360
More detailed build guide
More clearance in mounting holes
Custom PCB for a more permanent electronics solution
Buttons and OLED display for testing without computer
Emergency Stop/Reset All button
Many more testing modes, including speed selection and modulus testing.
Support for PLX-DAQ data acquisition
Dedicated ATTiny85 for separate stepper motor controls
Easy to configure Arduino code
From my testing, this new version is able to handle at least 1kN of load.
Table of Contents
This is a table of contents for the different sections of this instructable:
Steps 1-66: Design Process - This is where I explain design process of this tensile testing machine.
Steps 67-68: Design Assembly - This is where I give the design files and explain how to print them.
Steps 69-79: Component Selection - This is where I explain the component selection process of this machine.
Steps 80-89: Physical Assembly - This is where I cover the physical assembly steps
Steps 90-96: Electronics Assembly - This is where I cover the assembly steps for the electronics.
Step 97: Video - a video.
Step 98: Conclusion - Brief thank you to Maker Hub Club and supporters.
I would estimate the cost to build this machine from scratch be around $180-200. If you’re planning on upgrading from the ORIGINAL version, then it will cost around $75-$90 to upgrade.
1x 550mm 2060 Eurpoean Standard Aluminum Extrusion
2x MGN12H Carriages
1x MGNR12 300mmm Rail
1x 400mm T12 Lead Screw, 7mm Lead, 4 Starts
1x T12 Flanged Nut
2x/1 Set 7201 Single Row Angular Contact Ball Bearings
1x 6001 -zz/-2rs Deep Groove Ball Bearings
2x 12mm Shaft Collars
1x D25 L40 8mm to 12mm Rigid Coupler
1x S-Shaped Load Cell Rated for 500kg/1T
1x Custom PCB
1x Arduino Nano (and cable)
1x 12/24V Power Supply (and wires)
1x HX711 Board (either XFW or the red type)
1x StepStick Stepper Motor Driver (A4988/DRV8825)
1x Planetary Geared NEMA 17 Stepper Motor (51:1 to 100:1)
1x SSD1306 128x64 OLED Display
1x LM7805 (need heatsink) or Equivalent Package Buck Converter (noisy but no heatsink)
6x B3F-4000 Push Buttons
A Lot of Male and Female 2.54 Pin Headers
Screws/Bolts and Nuts:
20x M5x14mm Button Head Screws
20x M3x8 Socket Head Screws
4x M12x50mm External Hexagon Screws
4x M3x22 Socket Head Screws
4x M3x8 Low Profile Screws
4x M3x8 Nuts (preferably nyloc)
2x M5x50mm Button Head Screws
2x M16x25 Screws (or what fits the load cell)
20x M5 T Nuts (2020 extrusion type)
20x M3 T Nuts (2020 extrusion type)”