joshdoeExperiment Design and Decision Making:
1.) Filament-
Raptor PLA from MakerGeeks.com was chosen based on affordability, accessibility (USA), and advertised heat resistant properties. High temperature PLAs seemingly rival much more expensive polycarbonate and composite filaments in high temperature applications, though, information is limited to intuitive YouTube videos showing limited samples being exposed to near-boiling water under no load. While this experiment is still intuitive (lacking a controlled weight-bearing setup), relating actual temperature readings to visual deformation should still benefit those designing parts for use within specific temperature ranges.
Raptor PLA is quoted to have "NO DEFORMATION UP TO 125C (250F)". This is essentially the maximum annealing temperature, where the part won't deform under its own weight. Here, a general/intuitive understanding of this plastic's ability to function in various temperatures will be created in order to assess the viability of using the plastic to support loads upwards of kilograms at these temperatures. This isn't exactly a real scientific experiment, but can provide answers not readily available online.
2.) Temperature Control-
A version of this Arduino-powered sous vide cooker is used: https://learn.adafruit.com/sous-vide-powered-by-arduino-the-sous-viduino/sous-vide
Raptor PLA is made with "FDA Compliant" resins, all food cooked with this tool is separated from the water bath by a vacuum sealed bag, and submerging the parts in near-boiling water is part of the suggested annealing process, so, this sous vide cooker was determined as an appropriate heat source.
This particular sous vide cooker uses an under-powered hotplate, an over-sized steam table pan, and doesn't have an active cooling feature, so, the PID controller struggles to keep a precise temperature but always stays within a couple degrees of the set point and creates restaurant quality food, sufficient for this experiment.
3.) Deformation Testing-
A proper load-bearing setup will not be made due to time restrictions. Simple twisting, squeezing, and pulling of heated parts with pliers will be used to determine deformation limits. This experiment is being done to determine the temperatures at which this plastic can perform very reliably. A Pass/Fail determination will be made, rather than testing various loads at various temperatures, in order to find the maximum service temperature of the plastic relative to the design of a heated build chamber.
4.) Test Prints-
A geometry will be used that contains both thick and thin parts to increase available "data" witnessed, allow determination of relationship between deformation and part thickness if available. Two samples will be tested for each temperature setting to create "repeatable" results.
5.) Experiment-
A target of 90°C is set, as this is the heated build chamber temperature required to print ABS warp free.
The Raptor PLA packaging recommends a nozzle temperature of 245°C and a heated bed temperature of 0-60°C. A nozzle temperature of 245°C and a heated bed temperature of 60°C will be used. A 1.0 mm diameter nozzle and a layer thickness of 0.65 mm will be used, which practically anneals parts during printing with most filaments.
All test parts will be printed at the same time with identical settings.
The recommended annealing process requires heating the parts "for 5-10min or so around 100c (212f)".
A starting point of 40°C is chosen, a temperature which should not show any deformation under moderate strain. Parts will be heated in the water bath for 15 minutes to ensure heat absorption. After 15 minutes, the parts will immediately be tested by inducing rotational and compressive forces using pliers and monitoring irreversible damage.
The temperature will be increased by 10 degree increments and the parts retested. This will be repeated up to 100°C or further, depending on performance. A Pass or Fail grade will be applied for each temperature setting.
*NOTE: This plastic is not necessarily expected to perform at 90°C, but if it can perform slightly below this temperature it can still prove useful in supporting more heat resistant materials in the heated build chamber design. This would retain design freedom and lower part costs considerably. The heated build chamber design mentioned is an attempt to isolate the build volume from electronics and structural components rather than enclosing the entire printer. This requires moving parts and custom designs, something a 3D printer could easily solve with the right filament.