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Relativity Space - Simulation engineering candidates' project

This readme contains a project that candidates can work on as a take-home project

Instructions:

  1. Solve the problems from this repo
    • You can use any simulation tool you want but ANSYS is recommended. If you don't have access to simulation software we can provide a machine that has Ansys and you can Remote Desktop into it from web browser. Ask your interviewer for access. The machine will be available to you for two days. Reach out to your interviewer if you need more time.
    • Depending on your time and level of enthusiasm about the problem you can choose to do only parts of the problem
  2. Once done, email the results requested back to your interviewer.

Open an issue on this repo if you have any questions about the problems.

Adding clarification and description as powerpoint, pdf, or readme file is welcomed if needed.

Project : Simulating FDM process

The goal of project is to simulate FDM process using laser as energy source. If you are not familiar with the FDM process read its Wikipedia page. The process involves a laser as energy source, a wire feed and build platform which is the same material as wire.

Directed Energy Deposition with laser

The deposition and the build platform moves under the laser and wire feed, as wire is pushed out and laser melts the wire and forms the part layer by layer. Alternatively laser and wire feed can move instead of the build plate.

Directed Energy Deposition with laser

Check out the video of the described process.

The goal is to simulate around three inches of straight deposition and capture maximum depth of molten material throughout the deposition.

Assumptions

  1. Diameter of the wire is 0.03 inches.
  2. Wire feed rate is 150 inches per minute.
  3. Speed of movement of the build plate with respect to laser and wire feed is 100 inches per minute.
  4. Laser spot size is circular with 0.1 inches in diameter.
  5. Total laser power absorbed is 800W
  6. Feel free to make reasonable assumptions about other details that are not mentioned here. Please include your assumptions when submitting the results
  7. You can use aluminum for material
  8. Assume subtrate and build plate is also aluminum
  9. The run will be a transient simulation running for 2 seconds
  10. You can assume there has been no prior deposits and this is the first layer
  11. Substrate is 1 inches thick and it is not actively being cooled. You can assume room temperature air around it.
  12. In reality there is a very fast stream of shield gas blowing on top of melt pool but for simplicity we don’t need to model it in this exercise.

Deliverables

  1. Capture and report maximum depth of molten material throughout the simulation for every time step.
  2. If your simulation software supports, an animation that shows liquid fraction of the cross section in the middle of the deposited material. For example see below:

Liquid fraction of the cross section