As a continuation to the first part of this series (click on the picture below for link), the second article of the series is focused on presenting the framework of risk based design process by taking an example of the safety framework of an ocean going ship. Also get to know, how the design decision making is limited to the initial concept design stage and the economic advantages to making most of the decision changes at the initial concept design stages.
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LSD
Article By: Soumya Chakraborty
Author's Note: This article is different from the first one, as in it gives you and insight as to how the risk scenarios are actually framed in the design process and analyzed accordingly. Thank You for reading. In case of any doubts or queries please comment. You may also write to learnshipdesign@gmail.com
3D printing is a technology which makes it possible to build real
objects from virtual 3D objects. This is done by “cutting” the virtual object
in 2D slices and printing the real object slice by slice. Slices are printed on
top of each other and since each slice has a given thickness, (e.g. 0.5mm), the
real object gains some volume every time a slice is added.
The technique builds a solid object from a series of layers
- each one printed directly on top of the previous one. The machines’ operating
software cuts the CAD model of the work piece into slices, whose thickness
depends on the type of material used
Objects that are manufactured this way can be used anytime
throughout the product life phase, from industry scale production in addition
to applications and customization.
The term Additive
manufacturing is also used to refer to methods that create or
manufacture objects through progressive or uniform layering. [1]
Subtractive
Manufacturing refers to the existing industrial techniques
which rely on processes involving removal of unwanted material by milling,
grinding, drilling, filing etc.
Our paper calls for its mainstream application in the Maritime
Industry with a scaled up perspective.
We shall discuss the industrial manufacturing techniques to create
functional and durable ships with reductions in costs and limitations of
machining parts. Together with such high degrees of freedom in design and rapid progress in material sciences, a day is not far when we shall see
such novel technologies become a reality.
BEGINNINGS AND MODERN DAY TECHNOLOGY
Several different 3D printing processes have been invented since
the late 1970s. The printers were originally large, expensive, and highly
limited in what they could produce. It was not until the early 2010s that the
printers became widely available commercially. The first working 3D
printer was created in 1984 by Chuck Hull of 3D Systems Corp. [1]
First technology according to Mr Hull is Stereolithography Since the
start of the 21st century there has been a large growth in the sales of these
machines, and their price has dropped substantially. [2]
Fused deposition modelling (FDM) was developed by S. Scott Crump in the
late 1980s and was commercialized in 1990 by Stratasys.
As potential future techniques,only some of the following sound promising to us they are:
EXTRUSION DEPOSITION:
(FUSED DEPOSITION MODELING)
In this form of modelling the object is produced by casting out
small globules of material which harden immediately to form layers. A metal
wire that is wound on a coil is uncoiled to supply material to an extrusion nozzle
head. The nozzle head heats the material and turns the flow on and off.
Typically stepper motors or servo motors are
employed to move the extrusion head and adjust the flow and the head can be
moved in both horizontal and vertical directions. Control of this mechanism is
typically done by a computer-aided manufacturing (CAM)
software package running on a microcontroller.
FDM has some restrictions on the shapes that may be made-up. For
example, FDM usually cannot produce stalactite-like structures, since they
would be unsupported during the build. These have to be avoided or a thin
support may be designed into the structure which can be broken away during
finishing.
An example of a FDM manufactured part
using complex geometry
ADVANTAGES:
·High Strength.
·Cost Effective.
·Water Proof.
PGRANULAR MATERIALS
BINDING:
Another 3D printing approach is the selective fusing of materials
in a granular bed. The technique fuses parts of the layer, and then moves the
working area downwards, adding another layer of granules and repeating the
process until the piece has built up. This process uses the unfused media to
support overhangs and thin walls in the part being produced, which reduces the
need for temporary auxiliary supports for the piece. A laser is typically used
to sinter the media into solid.
DIRECT METAL LASER SINTERING:
It is a process that sinters (diffuses atoms at temperatures below
melting point) layers of powdered metal in a chamber of inert gas. When a layer
is finished, the powder bed moves down, and an automated roller adds a new
layer of material which is sintered to form the next section of the model.
Repeating this process builds up the object one layer at a time. DMLS is a
metal additive manufacturing technique the, DMLS refers specifically to metal
sintering and is not used for plastics. The physical process is different
from Selective Laser Melting (SLM) in
that it only sinters the powder as opposed to achieving a full melt.
ADVANTAGES:
·Excellent levels of purity and homogeneity in
base material.
·High strength materials can be fabricated.
A part of a fuel injector made using DMLS Technique, these are at par with their conventional counterparts
ELECTRON BEAM MELTING:
As the name implies, EBM uses an electron beam to melt a titanium
powder. The additive fabrication processes builds parts on a layer-by-layer
basis. After melting and solidifying one layer of titanium powder, the process
is repeated for subsequent layers.
Within the electron beam gun, a tungsten filament incandesces and
"boils off" a cloud of electrons
When the high-speed electrons strike the metal powder, the kinetic
energy is instantly converted into thermal energy. Raising the temperature
above the melting point, the electron beam rapidly liquefies the titanium
powder.
ADVANTAGES:
A simple trial for effective strength of components made
from EBM Methods for dissimilar metals
Cycle time reductions of up to 40%.
Vacuum melt quality can yield high strength properties of the material.
Combinations of dissimilar metals.[5]
SELECTIVE LASER
MELTING
The process starts by slicing the 3D CAD file data into layers,
usually from 20 to 100 micrometres thick, creating a 2D image of each layer;
this file format is the industry standard .stl file
used on most layer-based 3D printing or stereolithography technologies. This
file is then loaded into a file preparation software package that assigns
parameters, values and physical supports that allow the file to be interpreted
and builtby different
types of additive manufacturing machines.
With SLM thin layers of atomized fine metal powder are evenly spread using a coating mechanism onto a substrate plate, usually metal, that is fastened to an indexing table that moves in the vertical axis.
ADVANTAGES:
·The complete freedom in defining the geometry
of the part.
·The reduction of the production cycle.
SLM Techniques combine CAD and high end prototyping
to give complete freedom to the designer
STEREOLITHOGRAPHY:
Stereolithography was patented in 1986 by Chuck Hull.
Stereolithography is an additive manufacturing process which
employs a cask of liquid ultraviolet curablephotopolymer "resin" and an ultraviolet laser to build parts' layers one
at a time. For each layer, the laser beam traces a cross-section of the part
pattern on the surface of the liquid resin. Exposure to the ultraviolet laser
light cures and solidifies the pattern traced on the resin and joins it to the
layer below.
After the pattern has been traced, the SLA's
elevator platform descends by a distance equal to the thickness of a single
layer, typically 0.05 mm to 0.15 mm. Then, a resin filled blade
sweeps across the cross section of the part, re-coating it with fresh material.
Stereo lithographic modelling of a car wheel rim
ANALYSIS
According to Mr Hull, the 3D Printing Market as a whole will be
worth around 4.5 Billion US Dollars by 2018. [2]
Because of the promising possibilities it is assumed that Rapid
Prototyping is going to spread out during the next years as it was the case
with the introduction of CAD years ago. Besides others like speed and cost
arguments we can see especially 2 reasons why naval architects should think
about extending their toolbox by 3-D printing techniques. Below the table gives
us an idea of costs
COMPARISON OF
COSTS AMONG SHIP TYPES USING NORMAL MANUFACTURING TECHNIQUES:
Ship Type
Average Light Ship
Cost [$US/1000 Ton]
Conventional Submarine
103 to 347
Nuclear Submarine
185 to 250
Destroyer
122 to 168
Frigate or Corvette
70.8 to 217
Aircraft carrier
69.8 to 67.0
Cruise ship
10.0
US built crude oil tanker
(medium)
6.93
Chemical product tanker
(small)
2.84
Container ship
3.10
Crude oil tanker (medium)
2.20
Oil product tanker
1.63
Bulk carrier (small/medium)
1.26/0.88
Source: John Birkler, ET. al., “Differences between Military and
Commercial Shipbuilding:
Implications for the United Kingdom’s Ministry of Defence, RAND Report MG-236 (Santa Monica: RAND Corporation,
2005), statistics taken from Table 3-1, available at http://www.rand.org/content/dam/rand/ pubs/monographs/2005/RAND_MG236.pdf.
The initial
cost savings of 3D printing come from the designs allowed by the layer-by-layer
process.Experts
predict 3D printing has the potential to completely revolutionize the manufacturing sector this
year.
3D printing
is on its way to becoming the next trillion dollar industry. It's all in the
numbers...Manufacturing
currently accounts for 17%, or $10.2 trillion of the $60 trillion global
economy. That being said, if 3D printing is able to “capture” at least 10% of
the manufacturing sector we'd easily have ourselves a $1 trillion (+) industry!
Metal
Injection Moulding market has grown from $ 382 million USD in 2004 to $985
million USD in 2009. Further the market is estimated to be about $1.5 billion
USD in 2012. [BBC
Research]
APPLICATIONS:
Additive
manufacturing's earliest applications have been on the tool room end of
the manufacturing spectrum. For example, rapid prototyping was one of the earliest additive variants,
and its mission was to reduce the lead time and
cost of developing prototypes of new parts and devices, which was earlier only
done with subtractive tool room methods.
With technological advances in
additive manufacturing, however, and the dissemination of those advances into
the business world, additive methods are moving ever further into the
production end of manufacturing in creative and sometimes unexpected ways. Parts
that were formerly the sole province of subtractive methods can now in some
cases be made more profitably via additive ones.
Example of a jet propeller made using Stereo lithographic techniques at 3D Systems, something that may be extended to propellers in ships
APPLICATIONS OF 3D PRINTING IN NAVAL ARCHITECTURE:
One of the
most immediate ways 3D printing will impact the shipping industry is through
the design and construction of ships, submarines, aircraft, and everything
carried on board. This is due largely to the economic benefits derived from the
technology.
If the
“build volume” is large enough, a manufacturer can print a component as a
whole, forgoing the need for further assembly. This means it can go without the
brackets, flanges, and surfaces required for handling, bolting, or welding
pieces of the component together—thereby saving material and weight. It also means
internal systems such as ducting and piping can be designed to maximize
fluid-flow efficiency from more rounded shapes,simultaneously
eliminating unnecessary system volume and making it lighter still.
Additive
manufacturing’s second cost savings come from the materials used in the
process. The traditional production technique, subtractive manufacturing,
starts with a “billet” of fill and whittles it down to the desired product,
wasting up to 90 percent of the material. When working with the rare and expensive
top-grade materials that the military demands in high-performance aircraft and
precision weapons, the waste is all the dearer.[5]
Researchers
at EADS, a major European aerospace company, found that a type of 3D printing
using titanium powder could create parts just as strong as traditionally
produced items using only 10 percent of the titanium. The production lines and
shipyards of the future could be, in effect, enormous 3D printers that would
maximize the economies derived from the additive manufacturing process.
Augmenting shipboard supply departments with 3D printers can alleviate the need
to carry large stocks of pre-manufactured stores. Instead of spending weeks
trying to track down a repair part or seldom-used consumable, a repair-parts
petty officer could scan the discarded part labelled with a barcode quick
response (QR) code, or some other embedded identifier that, once scanned, sends
the item’s schematics to queue at the nearest printer.
Some ship parts like the bulbous bow (see our article on bulbs) may be easier to manufacture using these techniques
This simple
scenario illustrates many potential benefits.
The most obvious is the speed
with which a ship could secure a replacement part. This is especially true of
rare components or those with low-failure rates not typically carried on board
vessels or not in large numbers. “An individual ship has hundreds of thousands
of parts,” “supply can’t stock all of them.
Advances in
printing and robotics indicate how shipboard additive manufacturing may be
useful beyond simple repair parts. Already researchers at the University of
Southampton have successfully printed an entire working unmanned aerial
vehicle, except for the engine.
Meanwhile,
this year scientists at the Naval Research Laboratory will start testing on the
ex-USS Shadwell of the Autonomous Shipboard Humanoid (ASH) fire fighting
robot, meant to be able to “walk in any direction, keep its balance at sea, and
go through narrow passageways and up ladders”. The Navy has also funded a
similar project at the Georgia Institute of Technology for a “MacGyver Bot”
that can solve complex problems and assist in dangerous situations by using
whatever it finds nearby. If these trends are a clue, the future could hold the
ability to print completereplacements of the robotic
crew members, weapon systems, and remotely piloted or autonomous vehicles that
fight the ship and project power.
3D printing
can enable the creation of complex geometries which are very difficult,
expensive, or impossible to be manufactured using conventional production
methods. It will provide a boost to the art industry.It would
also be possible to build individual intricate artistic designs never
before possible while giving the architects freedom of design without
sacrificing structural rigidity or safety of workers.This technology can also help engineers to rebuild and restore old
heritage designs quickly yet accurately.
Instrument makers are using
3D printed parts when crafting instruments.
CONCLUSION
The research comes to the conclusion that there is not one single
system best suitable for all existing tasks in naval architecture. Each of the
systems has some advantages but also drawbacks.
As creating moulds is possible in very less time often in a
few hours, we can take complete advantage in designing ships keeping this in
mind. The profile of the ships now shouldn’t matter as it used to be because of
bending limitations in steel. Naval Architects can now concentrate on
hydrodynamics and aesthetics during the design stage making it more efficient
and green.
“By building
durable concept models, prototypes, tooling and low-volume end-use parts
in-house, engineers and designers can work more iteratively, test more thoroughly
and move confidently into production.”-Stratasys
The Economist claims this to be the "Third Industrial Revoultion".
“As
manufacturing goes digital, a third great change is now gathering pace.It
will allow
things to be made economically inmuch smaller numbers, moreflexibly
and with a
much lower input of labour, thanks to new materials, completely
new processes such as 3D printing,
easy-to-use robots and new
collaborative manufacturing services available online. The wheel is almost coming full circle, turning away
from mass manufacturing and towards
much more individualised production.”-The Economist
“Three-dimensional
printing makes it as cheap to create single items as it is to produce thousands
and thus undermines economies of scale. It may have as profound an impact on
the world as the coming of the factory did... Just as nobody could have
predicted the impact of the steam engine in 1750 — or the printing press in
1450, or the transistor in 1950 — it is impossible to foresee the long-term
impact of 3D printing. But the technology is coming, and it is likely to
disrupt every field it touches”.
- TheEconomist
Some food for thought, if you think 3D Printing is the new frontier think again and see this video.
LIMITATIONS:
The most capable machines, such as those that can print
titanium alloy objects, are quite expensive and quite large and increasing the
speed of printers is “daunting.” However, the competitive effects should drive
down both costs and printing time. Printers will continue to get faster and
faster,” moving ever-closer to providing true “object on-demand” capabilities.
The costs of fill materials can be similarly prohibitive. This has been due in
large part to the proprietary nature of the fill materials and requirements for
interfaces with the machines. Printers can’t yet build with every material. A
list of to be accomplished are: “Flexible plastics, polymers, rubbers, wax,
translucent materials, and different types of metals.
Objects created layer by layer rather than through a traditional
casting or moulding process are different at the molecular level. This allows
designers to develop intricate internal structures that yield
stronger-than-normal materials and equipment. But it also leaves some of the
cheaper products, like those made with plastics, weaker, because they were not
created as individual pieces. This need not remain the case, but it is so now.
It introduces new security challenges in efforts to prevent
proliferation. In late June 2012, a Wisconsin engineer made headlines when he
used a 3D printer to fashion a working receiver assembly for a firearm modelled
on the AR-15. Although it was only a portion of the weapon, the project to
create a complete gun continues with new supporters. It is not difficult to
imagine the attraction of such a capability for some not-so-nice state and
non-state actors. As the Navy introduces 3D printers into the fleet, it will
need to secure them against cyber threats as it does other information systems.
Unique vulnerabilities exist from the same 3D printers that are opportunities
for our own cyber efforts. For example, a printer could be hijacked to create a
self-destructing weapon or an infiltrating robot. Exploitable, unnoticeable design
flaws could be introduced, or a crucial supply capability could simply be shut
down.
It will take years, likely decades, to overcome all these
challenges. But they will not stop the development and evolving opportunities
afforded by 3D printers. One of the biggest tasks will be to evaluate each new
breakthrough’s impact on the shifting economic calculus of consigning any one
of the thousands of shipboard parts to print-on-demand status. Better
understanding of the link between printer developments and new capabilities
will allow to focus research the resources to achieve them. The potential cost
and capability benefits are enormous. Let the great experiment begin.LSD
REFERENCES
[1] http://en.wikipedia.org/wiki/3D_printing
[2] CNN interviews Chuck Hull: 'The night
I invented 3D printing'
[3]Rapid Manufacturing with Electron Beam Melting(EBM) – A manufacturing revolution?-
·Ulf Lindhe, M.Sc., Manager of Marketing, Sales and
Service, Arcam AB
·Morgan Larsson, Technical Manager, Arcam AB
·Ola Harrysson, Ph.D., Assistant Professor, Industrial
Engineering Department, North Carolina State University
[4] Aerospace Case
Studies http://www.stratasys.com/resources/case-studies/aerospace
[5] Print Me A Cruiserhttp://www.usni.org/magazines/proceedings/2013-04/print-me-cruiser
Article By: Sudripto Khasnabis
Vishal Kumar Jha
Sake Avi Kunal
Author's Note:This article is adapted from a paper titled "PRINTING SHIPS: A REALITY" presented by the authors at the "Samudra Manthan",the Annual Technical Meet of IIT Kharagpur's OENA Department.The paper discussed the potential of 3D Printing as a future manufacturing technique.Views expressed here are purely that are held by the authors themselves.The pictures do not belong to LSD, and full credit for the same goes to their respective owners. If you have any queries or doubts,do not forget to write to us at learnshipdesign@gmail.com
