Team 2: 3D Printed Stirling Engine
Additive manufacturing of metals (AMM) is a relatively new process currently with an unknown value in today’s fabrication shop. As additive technology continues to develop, recent advances in AMM have caused interest among manufactures across the state. The Advanced Manufacturing Center at the University of Maine is one of many Maine manufactures interested in learning more about this technology. Our team has been tasked with manufacturing an operational Stirling engine to demonstrate the capability and practicality of AMM when compared to conventional subtractive manufacturing (SM). A Bound Metal Deposition (BMD) Desktop Metals Studio printer will be utilized to manufacture the majority of the engine. The engine will consist mostly of printed parts using the new printer, but one of the shafts that need to be very precise will be bought. Hardware will also be bought for assembly due to the low cost and easy access to hardware. This, along with welding and post-process-machining, will continue to demonstrate the wide range of uses of AM in fabrication, as well as the ability for our team to stay within our budget.
If you are looking to learn more about our groups project or how to make a tax deductible donation you can contact our team’s preferred point of contact, Kyle Rooney, at email@example.com.
The team has sent out the CAD model to various companies to get a quote for a subtractive manufactured engine and another AMM engine of a different process (selective laser sintering) to compare the cost to the engine printed on the Studio+ System. Maine Day is in 2 days and the team is getting everything finished that they can before presenting. The team hopes you can make it at 11am in Bennett 137 at the University of Maine on 5/1 to watch our presentation! Thank you to all of our sponsors and everyone else that has helped along the way the team really appreciates it.
The team is sending Kyle's dad up with the two flywheels and the last crankshaft that are sintered along with the last two parts (backplate/cylinder and base left) that still need sintering. The University has now received the Studio+ System from DM and someone should be here today to set it all up.
Unfortunately, the team didn't win anything at the Student Symposium but it was a great learning experience! As of now all but 5 parts need to be sintered and sent to the University. All other parts have been scanned and post-processed.
The team is up to date on scanning and post-processing the parts received by Desktop Metals and are currently awaiting to be sent more parts. Once again, the Student Symposium is in 2 days at the Cross Insurance Arena in Bangor ME, be sure to come check out our progress!
The University just received the system. APRIL FOOLS! The system is now expected to come at the end of April when the project should be finished. With the Student Symposium only 9 days away the team is diligently working on the poster that is due for it along with finishing up the other aspects of the project like process sheets, analytical model, etc.
The University is supposed to get the whole Studio+ System some time this week. The team will be presenting at the Student Symposium at the Cross Insurance Arena in Bangor ME, come stop by and check us out on April 10th!
Interim report 3 has now been completed and passed in. The team has been accepted into Nanotech 2019 which is going to be held June 17-19 in Boston where the team will show the completed additive manufactured Stirling engine. The abstract for this conference is due this Friday (3/15) so that will be the team's primary focus for the rest of the week as they are preparing to get parts from Desktop Metals. Desktop Metals now believes they should be able to sinter most, if not all of the parts before the engine is due on Maine Day (5/1).
The full drawing package has now been completed for "as-printed" and "as-machined" versions which were requested by the client. The analytical model has now been completed, including finding the lower heating value of the fuel tablets to ultimately determine the heat rate of the engine. Also thermal expansion has now been considered due to the high temperature of these tablets but expansion rates do not appear to be a problem for the team as the highest expansion was found to be about .001 in. The third interim report is due this upcoming Wednesday (3/13) so the team is working diligently to get that completed.
The team has now decided on Esbit fuel tablets as the heat source for the engine. Esbit fuel tablets have a high temperature of 1300 degrees Fahrenheit for a run time of about 12 minutes per each 14g tablet. All purchase request forms have been sent out for all purchased components. The teams next task is to finish the analytical model and to create a holder under the hot side of the cylinder for the fuel tablet.
The team has now nearly finished the entire design of the Beta Stirling engine. All of the parts have been sent to Desktop Metals as of now but they are afraid they won't be able to sinter all of the parts so the team is researching possible 3rd party furnaces that can handle the same process.
The team continues to finish the final design of the engine with the newfound tolerancing information given by desktop metals. The team hopes to send the first two parts out to be printed by the end of the week. Challenges include adding the University of Maine and the Center of Additive Manufacturing of Metals logo to the engine.
The team traveled to Desktop Metal's headquarters in Burlington MA. The team toured the facility and learned a great deal of knowledge about the BMD process and equipment. The printer is now scheduled to arrive at the University in late March so Desktop Metals has agreed to print the engine at their facility and ship them to us given there's enough time with Maine Day quickly approaching! Picture link: https://www.unispace.com/projects/desktop-metal
Through the holiday the team was able to continue work on the early stages of prototype development. This has allowed the localization of points of interest within our mechanical design helping the team implement practical changes.
Although the claimed tolerance of the printer is 0.009 inches, the test artifact received from Desktop Metals had a maximum deviation of .0189 inches from the CAD model. Post processing will likely be needed for the cylinder interior and piston skirt.
Physical measuring devices and a Faro arm were used to scan and measure printed test artifacts. These scans have yet to be compared to CAD models for numerical precision. Background: Kyle Rooney is pictured above operating the Faro arm.
The design of the engine has been changing rapidly as new information is found. An early stage CAD model of our Stirling cycle engine using SoloidWorks is shown above.
We wish all of our sponsors and friends a Happy Thanksgiving as our team takes a recess. Background: Art, trinkets, and test pieces produced by various AM processes.
Today the team received word that the test specimens printed for us by Desktop Metals had delamination issues due to sharp edges. The team has fixed this change and resent the files for the test to be reprinted. The team moves forward with solution concepts and research. The background image is of a topology optimized beam. Through topology optimization our team is able to minimize material usage while maintaining the required strength and stiffness.
Desktop Metal Studio's Fleet containing the metal printer, de-binder, and sintering furnace required for the BMD process (left to right). This photo was taken from DesktopMetal.com home page.
The Center for Additive Manufacturing of Metals (CAMM), housed at the University of Maine’s Advanced Manufacturing Center (AMC), recently purchased a Desktop Metals Studio . The Desktop Metals Studio printer uses Bound Metal Deposition to sequentially extrude layers of a metal-binder composite in a layer-by-layer fashion to construct 3D metal artifacts. CAMM has proposed that the printer be used to “strengthen Maine’s precision manufacturing technology sector through industry driven support, applied research, workforce development, and dissemination of information involving Additive Manufacturing of Metals (AMM).” Success of this proposal will use enhanced part functionality, reduced lead times, and eventually reduced costs to bring economic growth to Maine’s manufacturers.
A Beta Stirling engine was chosen as a test platform for the Desktop Metals printer due manufacturing complexity of these engines. AMM’s anticipated challenges include but are not limited to:
- Minimization of build time and mass via topology optimization while retaining both rigidity and strength.
- To maximizing surface area in order to optimize heat transfer between the heat source and engine as well as between the engine and the working fluid.
- Determining post process requirements feasibility.
- Provide physical properties of the printed medium such as tensile strength, fatigue, coefficient of thermal expansion, porosity, and permeability in order to compare these results to the expected values.
- Measure the precision, accuracy, and repeatability of the printer.
- Investigate the microstructure of the manufactured build to analyse any anisotropic material properties.
- Compute an analytical model for both the thermodynamic processes and the mechanical properties such as combined loads (e.g., hoop and axial stress), abrasion at wear surfaces and anisotropic thermal expansion
The team would like to give a special thanks to:
For his help in locating test methods for various properties.
For his help in the thermodynamics of the engine.
For his knowledge and experience in 3D manufacturing.
For his help in setting up our website
Quinn is from Saco, ME. He got his start with 3D printing and engineering during his junior year of high school where he took part in a vocational drafting class. This lead to two summer internships where he worked primarily with CAD and design. During Quinn’s junior year of college he worked part time during the school year as an undergraduate research assistant at the Advanced Structures and Composites Center, where he helped with research and the application of FDM 3D printing. Currently, Quinn is the president of the 3D Printing Club here at the University. His preferred method of contact is through email at Quinn.Campbell@maine.edu.
Mike is a 4th year Mechanical Engineering Technology student from Hampton, NH. He has been involved with mechanical engineering most of his childhood with a keen interest in cars and motorcycles. Following graduation, Mike will be working at Woehner LLC as a junior design engineer. Mike can be reached through email at firstname.lastname@example.org.
Kyle is from Amesbury, MA. He is a senior in the MET program here at the University and is expected to graduate in Fall of 2019, along with a minor in Mathematics. He is currently employed as an undergraduate research assistant at the University researching combined heat and power systems. He has not yet set his mind on Graduate school or the work force upon graduation, but he’s open to a variety of opportunities. You can contact Kyle at Kyle.Rooney@maine.edu