This week the team used the Cura software to optimize our models and prepare initial prototypes. Additionally, the use of alternate production methods was examined.
We examined multiple alternatives to FDM production of the beer faucet and attachments. For one, the use of either material jetting or binder jetting processes to make molds and cores for casting was discussed. We believe that this could be a feasible option, assuming that the necessary equipment for metal casting was available. As the initial beer faucet is made from cast metal, many of the downsides encountered with FDM production (e.g. watertightness or food safety) would be eliminated in the final part. The use of AM techniques to produce tooling for metal casting is a proven process, as well. Binder jetting and material jetting would allow for accurate creation of fine details such as threads or other features in the part, with better resolution than FDM. However, since this method requires metal casting capabilities as well as material/binder jetting processes, it is far less accessible to our group than FDM.
Another alternative examined by the group was an SLS process. While there are some advantages, notably the resolution available for fine features and the lack of internal support required to produce the hollow parts needed for a beer faucet, there are some concerns. We determined that residual powder left behind after post-processing may pose a food safety issue, and the cost of purchasing food-safe plastic powder would be a significant cost barrier. Finally, any porosity produced in the SLS process could be a concern from a food safety and watertightness standpoint.
To start the tap optimization process we first imported it into the software. The first thing we modified was the orientation of the part on the build platform. The main consideration we had in orientation was where the support material would be needed, and how to minimize the amount used. The orientation the part was printed can be seen below.
Next we looked at the parameters for the build and noted ones we felt were important to our part. Since it needs to be water tight wall thicknesses are very important. For the first build we set them to one millimeter. Layer height is important to part quality but it is also important to optimize build time. For the initial part we went with .1 millimeters. All in all our build time started around 8 hours and we got it down to 3.5 hours. It produced a pretty good quality part, but water tightness still has to be tested.
For the “pinwheel” attachment, as the part will experience far lower pressure flows and thus water tightness is less of a concern, our primary focus for optimization is for build time. A lot of the progress here is reducing the amount of support material required, to accomplish this the parts are printed in the configuration shown below:
Using the default settings, print time was reported as slightly over 2.5 hours. Halving the wall thickness resulted in a time savings of only 20 minutes, while increasing layer height to 0.2 mm cut an hour from print time. In future tests we will examine the suitability of the larger layer size. We attempted to produce one test part using the default settings, however the computer crashed after one hour and the extruder nozzle crashed into the part after reboot. The failed print is shown below:
Future prints will be done with more active supervision of the process. Warpage and one broken part are issues that will have to be fixed. One possible adjustment is to move from an axle that is a part of the pinwheel to a separate metal axle. This would eliminate the need for any support structure on the wheel and probably eliminate warpage, as well as fix the breakage problem.