Cups for Water Vapor Permeability test (ASTM E96)

prusaprinters

These are cups designed to test the properties of polymer plastic films. I use it to test the moisture barrier performance of biofilms. The cups are filled with either water (or dessicant), and the sample loaded in between the gaskets and held tight with the convenient screw lid. The evaporation (or absorption if using dessicant) of water in the cup (measured on a scale) over time determines the "Water Vapor Permeability" compliant with the ASTM E96 calculated as shown in here: https://www.youtube.com/watch?v=wulHes6Dm9E. The 50 mm diameter cup features ridges every 5 mm from the surface that makes it easy to fill the water to the correct level. 2-3 ridges down (10-15 mm) is the preferred level. The gaskets can be cut from a sheet of rubber, neoprene or similar hydrophobic material. (OD 68mm / ID 50mm). Or simply print two gaskets here in TPU or other flex. The screw lid features M70 x 1.5 threads that keep the sample film tightly in place, and requires no additional screws. NOTE: I will test these cups over the next few days and determine if it needs further modifications. For now though, I am quite pleased with the outcome. Print Settings Printer Brand: Ultimaker Printer: Ultimaker 2 Rafts: Doesn't Matter Supports: No Resolution: 0.12 mm Infill: 30% Filament: Generic ASA or ABS for cup/lid and TPU for gasket White Notes: Print cups and lid in your material of choice with 4 perimeters. Note that different plastics absorb different amounts of water - something which is undesirable and can lead to inaccuracies in the measurements. If possible use "Enable Ironing" in Cura, to smooth over the last layers. This will give a flatter surface, making it easier to have it water tight. Total print time was approximately 5½ hours for cup and 2 hours for the lid with the settings. I used a layer height of 0.12 which gave me fitting enough resolutions on the screw thread, but I assume that you could go slightly higher which would speed things up. The enabled ironing added more than 1½ of print time, so if you are confident about your printer tolerances you could disable this. Category: Engineering