Journal Club!

I've been thinking that we don't pay much attention to the published literature. So I hereby start ... The RepRap Joural Club!

Here is one book and two articles about RP which people may find interesting.

Forrest's thoughts on them:
[3dreplicators.com]
Please email me at penguin at supermeta dot com if you want me to email you a copy of one or both articles. I'd attach them as files, but there's a note from the publisher asking that I not do that.

The second article, "Conceptual framework for the thermal process modelling of
fused deposition", is from the bibliography of this book:
"Rapid Prototyping: Laser-Based and Other Technologies"
by Patri K. Venuvinod and Weiyin Ma
[www.amazon.com]

abebooks has it for USD$16.52
[www.abebooks.com]

**
[pep.metapress.com]
Three-dimensional finite element analysis simulations of the fused deposition
modelling process
Journal Proceedings of the Institution of Mechanical Engineers, Part B:
Journal of Engineering Manufacture
Publisher Professional Engineering Publishing
ISSN 0954-4054
Issue Volume 220, Number 10 / 2006
DOI 10.1243/09544054JEM572
Pages 1663-1671

Authors
Y Zhang1, Y K Chou1

1Mechanical Engineering Department, The University of Alabama, Tuscaloosa,
Alabama, USA
Abstract

Fused deposition modelling (FDM) is a layer-manufacturing technology that has
been widely used for rapid prototyping applications in product design and
development. Owing to the intensive energy, rapid cooling, and phase changes,
parts made by FDM and other layer-manufacturing processes deviate from the
designed geometry, and some require laborious post-processing. Most severe
form inaccuracies such as curl, warping, and delamination are attributed to
the residual stress accumulations during prototype fabrications.

This study investigates the FDM process, which consists of complicated heat
and mass transfer phenomena coupled with mechanical loading and phase
changes. A finite element analysis model using element activations has been
developed to simulate the mechanical and thermal phenomena in FDM and further
used for residual stress and part distortion simulations. The model has also
been used to study the tool-path effects on the FDM process. Tool-path
patterns affect the residual stresses in not only the magnitude but also the
distribution which shows stress concentrations aligned with the primary
direction of the tool path. Measured prototypes from the experiment show that
the part distortion centre shifts distinctly owing to different tool-path
patterns, which is consistent with the residual stress characteristics in the
simulations. From the simulations, it is also shown that the short-raster
tool path results in higher residual stresses, and thus possibly larger
distortions, than the long-raster and alternate-raster patterns, both having
similar stress distributions and distortion features.

Keywords
fused deposition modelling, finite element analysis, layer manufacturing, part
distortion, residual stress
References

References secured to subscribers.

**
[www.emeraldinsight.com]
Title: Conceptual framework for the thermal process modelling of fused
deposition
Author(s): M. Atif Yardimci, Sel

Hmm... Slightly off the topic, but your writeup suggests, to me, interlacing as a possible component in getting the shrinkage issue under control.

I ordered the book and am trying to get the articles through the college.

Sean, on that off topic topic I found this:

"""
The mechanical effects of deposition patterns in welding-bflsed layered manufacturing
Mughal, M.P. (Faculty of Mechanical Engineering, GIK Institute of Engineering Sciences and Technology, NWFP); Mufti, R.A.; Fawad, H. Source: Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, v 221, n 10, 2007, p 1499-1509
ISSN: 0954-4054 CODEN: PIBMEU
Publisher: Professional Engineering Publishing Ltd.

Abstract: This paper presents a finite element (FE)-based three-dimensional analysis to study the structural effects of deposition patterns in welding-based layered manufacturing (LM). A commercial finite element software ANSYS is used to simulate the deposition incorporating a double ellipsoidal heat source, material addition, and temperature-dependent material properties. Simulations carried out with various deposition sequences revealed that the thermal and structural effects on the workpiece are different for different patterns. The sequence starting from outside and ending at the centre is identified as the one which produces minimum warpage.
"""

Of note is that last sentence in the abstract.

Demented

> Of note is that last sentence in the abstract.

And surprising, I was planning to try starting at the inside and spiraling out as intuitively that would seem better. Each new turn of the spiral has a solid core to resist its shrinkage inwards.

---

[www.hydraraptor.blogspot.com]

LOL! Tried that. Its right that each new loop around the object shrinks against the extant print. It's also true that the shrinkage-induced stress tends to pop the middle right off the foamboard after a while and make a little mountain of it in the middle of the print. I've got some pics of that happening somewhere around here.

Might work better with PP base board instead of foam board.

Have you tried building from the outside in?

---

[www.hydraraptor.blogspot.com]

Yup. I don't recall exactly what went wrong, but it didn't work right. It wasn't until I started stopped trying to make objects 100% solid on the inside that things started going well. 50-60% fill was about the best.