Previously on I Heart Robotics the internet blog, we used the power of science to test wood screws as fasteners for 3D printed parts. Now that our plastic thread forming screws have arrived and we have a few moments, we will use the power of science to test these as well.
The primary problems we saw with using wood screws was that the flat head required a countersink and they have a tendency to split the screw boss at high torques. The plastic thread forming screws we have sourced are available with a pan head and Torx® drive. The Torx® drive allows for better torque transfer and less chance of stripping the screw head.
The screws used in this test are Camcar® PT® Thread-Forming Screws for Thermoplastic from Acument® Global Technologies. On the datasheet they are listed as K40-1.79x10TXP P/T or as part number 3BT-P8009-00.
In New York City, you can order them from Century Fasteners.
SetupFor each experiment two plastic parts were printed. One part had a series of square screw bosses and the other part was a plate with a series of holes. The assembled parts were placed in a vice and a Ryobi cordless drill model P205 with adjustable torque was used to tighten each screw until failure.
The torque settings on the drill produce an unknown torque and have an unknown error and unknown repeatability. However for the purpose of comparing the relative holding strength of each fastening method, these issues should not prevent a rough estimate from being made.
The parts were printed in ABS on a Stratasys FDM Machine with the holes oriented upwards. This is the same material as Shapeways Grey Robust.
As noted, some holes are printed at the desired size and some were printed as pilot holes and drilled to the required size.