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Additive Manufacturing Research

Introduction

One of the main challenges when printing on fused filament fabrication (FFF) systems with ABS plastic is that the material warps upward due to the inconsistent cooling of the material. Our research aims to test the effects of reducing temperature variance within an ABS part during printing using forced convection, as a potential solution to part warping. The part warps due to the layers cooling to different temperatures at different rates, causing internal stresses. Using forced convection, the effect of steady-state temperature uniformity can be investigated.

Background

  • I've always found additive manufacturing to be incredibly interesting and in middle and high school, I was fortunate enough to be able to tinker with some 3D printers and see what I could do.

  • In my junior year at CMU, I took a graduate-level course on additive manufacturing which only fueled that passion.

  • After this course, I decided that I wanted to do some research in the field.

Applying for Grants

  • I found a classmate and friend who was interested in working with me on a project as well and we brainstormed about possible areas we could work in. 

  • We decided to test if we could reduce residual stress an FFF-produced ABS part by spraying it with a heated fluid, probably water or water-vapor since FFF parts are porous.

    • We chose ABS because it is well understood in conventional manufacturing and has advantageous material properties but is rarely used in FFF 3D printing because it warps very easily and frequently.​

  • Once we had a few ideas, we met with professor Chen to discuss our idea and ask if he could mentor us so we could apply for undergraduate research funding.

  • While our discussion with professor Chen was productive, especially because he was doing research into making polymers with high thermal conductivity. Unfortunately, he was taking a leave of absence next semester and could not mentor us.

  • We reached out to professor Malen, who agreed to mentor us.

  • We set to work and wrote up an application for undergraduate research. It would include the following

    • A full timeline

    • A method to measure warpage in a part

    • A full budget

    • Simulated results

    • 3 Test configurations - Control, spraying the part with water, and immersing the part in a heated water bath.

Trials and Tribulations

  • This was a very ambitious project and unfortunately, it proved too much for two full-time students.

  • But we still wanted to do research so we discussed viable alternatives that would still be significant in terms of research.

  • We pivoted our research to focus on heated airflow over the part instead of a fluid. This was much easier to set up but would yield similar data.

  • We discovered that the parts we were printing would not only curl but also crack in the middle, so we adapted our measurement of warpage to accommodate these cracks.

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  • We developed 4 test configurations and simulated data for each

    • Control​

    • Unheated fan blowing at 1 m/s

    • Heated fan blowing at 1 m/s

    • Heated fan blowing at 2 m/s

  • These would show the effect of both free and forced convection on the part as well as a higher convection coefficient. 

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We printed over 40 test pieces, quantified the curling in each, performed our analysis, and wrote up our report on the matter.

©2019 by Gordon Robertson.

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