FrankerFab D638 Tensile Tester 3D Printing Instruction Manual
- June 1, 2024
- FrankerFab
Table of Contents
Tensile Tester Instruction Manual
v1.0 11/27/2023
D638 Tensile Tester 3D Printing
Section 1: 3D Printing your Tensile Tester
Section 2: Final Assembly
Section 3: Performing a Tensile Test
Section 1: 3D Printing the Parts
Printing the Test Part
To ensure proper printer calibration for these parts it is highly recommended
that you start by printing the Fit Test.stl part first. This part is a small
section of the pivot arm with the 1/2” hole. Print this part with 100% infill
and then verify that you can tap the provided ½” shaft through the hole
without excessive force. It should be a light press fit (not a slip fit),
capable of being tapped through the printed part with a rubber mallet.
If adjustment is needed, most slicers have an XY size compensation setting
that you can adjust to get the proper fit.
Digital Files & Recommended Material
The provided zip folder will have all of the parts saved as a .STL format. For
anyone with a Prusa MK3 printer, Gcode files with our preferred settings have
been provided as well.
Your everyday basic PLA works very well for these parts. It’s very easy to
print with and has good dimensional consistency and excellent stiffness. The
design has been optimized around the strength of typical PLA and it should
serve you very well with this affordable material.
Recommended Print Settings
These parts have been designed to be relatively easy to print. We use a 0.2
layer height with the default settings for PLA (0.2mm Quality mode in the
Prusa slicer).
Four parts are the most highly stressed and should be printed at 100% infill.
Gear, Front Leg, Pivot Arm, Clevis
The remaining parts can be printed at 80% infill for a good balance of
strength and stiffness.
Following these settings, you should be able to print all the parts with
around 1.5 kg of filament. The four flat parts shown below can be printed with
minimal support material required. The other parts should be orientated as
shown with more support material required.
Note the orientation of the front leg and clevis is such that no support
material is required in the slot. These parts are shown grouped together, but I would highly recommend printing them all individually.
Section 2: Full Assembly
After all your 3D printed parts are done you are ready for the full assembly!
You will only need basic hand tools; specifically, a rubber mallet (or regular
hammer), socket set, and a small punch.
tep 1 – Clevis Bearings & Shaft
Press in the small clevis bearings so that they are roughly flush with the
outside face of the clevis. It’s helpful to slide the pivotarm between the
clevis for structural support while you tap thebearings in. Use a socket or
similar to press it flush. Next align the ½” hole with the pivot arm and tap
the shaft through until it is flush with the outside face. It should be a
light press fit.
Important! Note the correct orientation of the clevis features. Step 2 –
Pivot Support Bearings & Shaft
Similar to step 1, press in the bearings so that they are flush with the
outside face of the bore. It’s helpful to slide the pivot arm between the
support pivot for structural support while you tap the bearings in.
A 11/16” socket works well to tap the bearing into place, supported with a
larger socket on the back side against your work bench. With both bearings
pressed in you can now insert the ½” shaft.
The shaft will pass through the bearings and then be tapped into place witha
light press fit into the pivot arm. Supporting the part underneath with a
large socket while you tap the shaft into place until it is flush with the
bearing.
Important! Note the correct orientation of the pivot arm is with the gear
teeth on the longer side of the support >
Step 3 – Gear Support & Pivot Shaft
Again following a similar process as step 1, press the bearings into place,
flush with the bore face. Use the gear as structural support while tapping the
bearings in.
Next press the 5/8” shaft through the assembly until the dowel pin hole is
aligned.
Important! Match the orientation of the dowel pin hole as close as
possible before you press it in > Finish by tapping the provided dowel pin
through the two parts until it’s below the surface on both sides. The dowel
pin usually has one end with a larger taper. It works best to start with that
end as it will help align the parts.
Verify that all parts rotate smoothly. All shafts should be very easy to turn
by hand.
Step 5 – Fasteners and Wooden Base
Place the parts on the wood base, aligning the parts to the bolt holes. Drop
the bolts in, the larger 3/8” bolts all going in from the top, whereas the two
smaller 5/16” bolts for the center support are bottomup orientation.
Each bolt will be paired with a washer and nut (washer goes on the nut side).
Do not over tighten! Snug the bolts finger tight and then add a quarter turn
with a wrench.
Optional: Bench Mounting
With 3/8” cap head screws (not provided) you can bolt the tensile tester to
your bench for better support and control.
Section 3: Performing a Tensile Test
Note: YouTube video demonstration of a tensile test is available on our
website!
Step 1 – Print the ASTM Dog Bones
Using the provided STL file for the ASTM D638 dog bones, print the quantity
desired with your material and settings Step 2 – Load the Sample
Insert the dog bone sample into the tensile tester, aligning with the slot
profile. The sample should be an easy slip fit, but it is good practice to use
a screwdriver to make sure it is fully seated in both upper and lower slots.
Step 3 – Break the Sample Using a digital torque wrench (1/4 size works
best) set to peak hold mode, apply a slow and even rotation until the sample
fails.
Record the peak torque achieved for each sample and any observations on the
failure mode.
Note, the provided sample dog bone was printed from basic PLA and should
achieve roughly 45 MPa. Step 4 – Data Analysis
Using the provided Excel calculator tool, convert the measured torque into the
tensile strength of each sample.
Note, this calculator has been calibrated with force measurements so that it
correctly accounts for the gear tooth friction losses. Notes on Testing
Sample Sizes
Sample sizes of 6 is a good starting point to get a good measurement of your
mean strength and distribution. Sample to sample variation can be high,
especially with heat treating processes and may 0benefit from larger sample
sizes to capture this variation.
We hope you enjoy your FrankerFab tensile tester and use it to better
understand your 3D printed parts and materials!
Read User Manual Online (PDF format)
Read User Manual Online (PDF format) >>