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Production Engineering

, Volume 13, Issue 6, pp 675–684 | Cite as

Reusable unit process life cycle inventory for manufacturing: stereolithography

  • Timothy Simon
  • Yiran Yang
  • Wo Jae Lee
  • Jing Zhao
  • Lin Li
  • Fu ZhaoEmail author
Production Process
  • 55 Downloads

Abstract

Additive manufacturing technologies have been implemented in a variety of industries such as aerospace, automotive, healthcare, and military. The increasing application is owing to the unique capability of AM for fabricating parts layer by layer. Compared to traditional manufacturing processes, AM can achieve enhanced design and manufacturing complexity. In addition, it has been argued that AM could also reduce the environmental footprint of a product. However, recent studies reveal that AM processes may cause environmental consequences. Characterization of manufacturing processes for their environmental performance can be achieved by evaluating input and output material and energy flows. The unit process life cycle inventory methodology is a promising approach to develop reusable models and tools to calculate these flows. The unit process life cycle inventory models can be connected to estimate the total material/energy consumption of and emissions from product manufacturing based on a process plan. In this paper, we develop a unit process life cycle inventory model for one of the most widely used additive manufacturing processes i.e., Stereolithography, which fabricates parts by using ultraviolet light to solidify the photosensitive liquid resin in a matter of seconds layer by layer. The model is constructed with the knowledge of physical and chemical principles and is based on production information and equipment specifications. A case study is provided to demonstrate how to use the unit process life cyle inventory model on Stereolithography.

Keywords

Stereolithography Mask image projection Additive manufacturing Unit process life cycle inventory 

Abbreviations

AM

Additive manufacturing

UPLCI

Unit process life cycle inventory

SLA

Stereolithography

UV

Ultraviolet

LCI

Life cycle inventory

List of symbols

\(E_{total}\)

Total energy consumption (Wh)

\(E_{projector}\)

Projector total energy consumption (Wh)

\(E_{motor}\)

Energy of motor (Wh)

\(E_{computer}\)

Total energy consumption of the computer (Wh)

\(E_{board}\)

Total energy consumption of the computer (Wh)

Ecuring

Projector curing stage energy consumption (Wh)

\(E_{idle,p}\)

Projector idle stage energy consumption (Wh)

\(P_{computer}\)

Computer rated power (W)

\(P_{board}\)

Control board rated power (W)

\(P_{curing}\)

Curing power (W)

\(P_{idle}\)

Projector idle stage power (W)

\(P_{motor}\)

Power requirement of motor (W)

\(N_{bottom}\)

Total number of bottom layers (#)

\(N\)

Total number of layers (#)

\(d\)

Layer thickness (mm)

\(T_{printing}\)

Printing time (s)

\(T_{LS}\)

Layer lift and sequence time (s)

\(T_{curing,b}\)

Curing time for each bottom layers (s)

\(T_{curing}\)

Curing time for each layer (s)

\(T_{idle}\)

Total idle time (s)

\(T_{post}\)

Post-processing time (s)

\(T_{pre}\)

Pre-processing time (s)

\(ER\left( t \right)_{volatilization}\)

VOC emission due to the volatilization process (g/s)

\(S_{part}\)

Surface area of printed part (cm3)

\(V_{part}\)

Volume of printed part (m3)

\(m_{input}\)

Mass of input raw materials, liquid (g)

\(m_{part}\)

Mass of finished part, solid (g)

\(m_{waste,g}\)

Mass of gaseous VOC emission (g)

\(m_{waste,l}\)

Liquid waste percentage (g)

\(m_{waste}\)

Total material waste (g)

\(v_{z}\)

Air flow speed (cm/s)

\(\alpha\)

Liquid resin coating thickness (cm)

\(\rho_{a}\)

Air density (kg/m3)

\(\rho_{part}\)

Solid part density (kg/m3)

\(\rho_{resin}\)

Resin density (kg/m3)

\(\rho_{v}\)

Vapor pressure of liquid (atm)

\(\Delta z\)

Length of air–liquid interface in the direction of flow (cm)

\(D\)

Air diffusivity (cm/s)

\(K\)

Mass transfer coefficient (cm/s)

\(M\)

Molecular weight of resin (g/g mole)

\(P\)

Ambient air pressure (atm)

\(Q\)

Mass transfer rate (g mole/cm3 s)

\(R\)

Universal gas constant (cm3/kPa/g mole K)

\(S\)

Surface area (cm2)

\(Sc\)

The Schmidt number (cm)

\(T\)

Absolute temperature (K)

\(\mu\)

Air viscosity (g/cm/s)

Notes

Acknowledgements

This work is supported by the National Science Foundation under Grant no. 1605472. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. This work is also supported by the U.S. National Science Foundation under Grant number 1604825.

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Copyright information

© German Academic Society for Production Engineering (WGP) 2019

Authors and Affiliations

  • Timothy Simon
    • 1
  • Yiran Yang
    • 2
  • Wo Jae Lee
    • 1
  • Jing Zhao
    • 3
  • Lin Li
    • 3
  • Fu Zhao
    • 1
    Email author
  1. 1.Purdue UniversityWest LafayetteUSA
  2. 2.Department of Industrial, Manufacturing, & Systems EngineeringUniversity of Texas at ArlingtonArlingtonUSA
  3. 3.Department of Mechanical and Industrial EngineeringUniversity of Illinois at ChicagoChicagoUSA

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