2013 03-12-masterclass-biomedical-applications-of-am sirris-ad_dtechnic

Masterclass:
Biomedical applications of
Additive Manufacturing

Part 03 : Technical aspects

Magnien Julien

 Context sensitization
 Additive Manufacturing principle
 Description of the different AM technologies
 Technologies comparison
 Well suited applications cases
 Conclusions

Masterclass: Biomedical applications of Additive Manufacturing Organized by SIRRIS the 12th of March 2013
2

The traditional ways to manufacture parts are :
 Machining : remove material from a bloc larger than the part itself. This is
a « subtractive » way.

 Injection/molding : build a mold and place a melted material inside
which will solidify.

3

MACHINING INJECTION / MOLDING

 Very high precision  High production rate
o Long time and higher price o 1 mold = 1 part model
needed if complex part o Long test period to find good
o Need to replace tool when worn parameters
o Geometrical restriction due to o Complex fluid dynamic
tool access (shrinkage, solidification rate,…)
o A lot of waste material o An error at the early beginning
o Sometimes several steps to have have a very expensive impact
the final part o Strong geometrical limitations
o Single material parts o Single material parts

4

AM try to solution these problems since 1990 :

 Only the required material is used.
 To increase the geometrical complexity, a layer-by-layer building fashion
is chosen.
 No tools are used.
 The complexity doesn’t increase the cost.
 Very different parts (size, complexity,... even color !) can be built together
in a same job, and even be added during processing.
 Some technologies allow multi-materials parts in one shot.
 Functionalities can be added (hinges, spring, gears,…)
 The delay is usually a week, compared to several months with the
traditional ways
 Customization can be used at its highest level
 Weight reduction is far more easy than before (lattice)
 Texturing, conformal cooling, internal cavities,…

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- Is it just perfect ? – Almost :

 Part size limitation : 250 x 250 x 300 mm as mean vol (max 2000 mm).
 Minimum wall thickness : 0,3 -> 1,5 mm
 Surface quality : Ra ~10 – 20 µm
 Anisotropy of mechanical properties due to layer-by-layer
 The raw material (usually powder) is surrounding the part after the
process. Inside and outside… So It could be hard to remove it from a very
narrow and long channel.
 With metal powder or liquid photosensitive polymer, supports are
required. They are built in the same time than the part and act as an
anchorage. They will keep the part in place. They have to be removed
after the process and damage a bit the surface quality in the contact zone
=> small post-machining often required.

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- But how does it work ? What means “layer-by-layer” ?
Everything starts from the CAD file of the part (.iges, .stp) which is
converted in the .stl format, proper to AM technologies. This file is
virtually placed in the building chamber of the process :

7

The “layers” of the job (all the virtual parts into the building chamber) are
then automatically generated vertically and the resulting slices of the
part are stored in another file proper to each technology manufacturer.

8

Now the goal is to convert this virtual slices in a stack of real slices into solid
material and to combine them together to have the desired part :

Virtual world Real world

AM machine

9

To convert a virtual slice to a real one, the machine simply spreads a thin
layer of raw material (let’s say in powder form) over all the bottom of the
working chamber. Then the machine analyze the first slice to
“materialize” and reproduce it on the layer spread in 2D. It agglomerates
the raw material in the area described on the virtual slice.

Agglomeration of Completed slice
the specified
Top view of the
areas
virtual slice, areas
to agglomerate
Fresh new layer
of powder
10

LBM process description : Laser beam

Main tank

Melted
zones
Argon Recoater

Previous layers
Spread powder

Initial plate
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Let’s begin with the simplest one, the 3D printing of plaster powder with
color functionalities.
1. The powder is spread over the workplate by a roller
roller

powder

Work plate
2. The printing head deposit a binder on the areas specified by the slices,
and color on contours
Printing head
Printing head

Binder droplets

layer
Zone without binder Zone with binder
Powder grain

12

These are the kind of parts produced with 3D printer from Z Corporation :

13

It is possible to print metal (e.g. stainless steel) in 3D with a binder but the
parts have to be post processed to replace the binder by a low melting
temperature metal, such as bronze.
The processed green parts are placed in a oven and, by increasing the
temperature, the bronze melt and the binder is degraded, leaving
porosity in part which filled by the bronze by capillarity.
“green part” “brown part”
Structure of
the final part
As built Curing Debinding Infiltration

14

Some part produce by Prometal 3D printing process (60% stainless steel,
40% bronze) :

= > Can you make such parts with traditional
technologies… in one or two week maximum ?


15

The small problem with the previous technology is the multi-material
characteristic of the final part (glue or other metal). How can we have a
part made of only one material ? So they replace the printing head by a
laser driven by a set of lens and mirrors which melt the powder, exactly
like welding. This is the LBM process :

16

When the raw material in a polymer (ABS, polyamide, PVC,…) this is quite
easy and you can but part wherever you want in the volume of the work
chamber, the powder itself is enough to support the part.

Magics software from Materialise
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Here are some parts made of polymer with LBM technology :

18

With metal powder in LBM, there are more barriers to produce parts :
 Due to stronger thermal stresses that occurs during welding, the parts
tend to be deformed.
 The higher laser power induce higher heat input and the powder doesn’t
take it away as efficiently as bulk material
For those reasons, supports have to be added to the CAD file of the part to
prevent deformation and drive the heat away. To ensure this anchorage,
supports of the part are directly welded on the thick removable working
plate :

19

Supports are a necessary evil in LBM but :
 If there are in hard-to-reach zone, it’s very complicated to remove them after the
process.
 If they support a very thin structure, this latter can be distorted during removing.
 The surface contact between supports and part has a worse surface quality which will
required post machining.

 They consume the silicone wiper of the recoater quicker than “part” area. So more
supports you have, worse is the flatness of the last layers.
 This is an additional material cost.

Some design and positioning rules can reduce the amount of supports
needed.

20

Some parts made of metal with LBM technology :

21

Another technology use the same principle but with an electron beam. So it
works under vacuum conditions and the work plate is heated at high
temperature (~600°C) which reduce the thermal stresses and, so,
supports are less (not) needed :

22

In every previous technologies, a recoater is needed to spread the powder
over the flat workplate. But it is also possible to add features (coating,
local repair, additional geometry,… ) on a non-flat surface with another
principle : replace the drill of a CNC machine with a material deposition
nozzle. Powder is blown through a laser beam thanks to that nozzle and
this allow 5-axis welding. The superposition of tracks can make 3D shapes
Laser +
central gaz
(coaxial)
Shape Gas

Carrier gas
+ powder

Motion direction
Meltpool
Track
Substrate
Heat Affected Zone
23

This process is called Laser Metal Deposition. Thank to multiple axis, it is
possible to bring the material wherever on a surface and locally increase
mechanical properties, repair a damage area or reload a wearing part :

Fraunhofer center
for surface and
laser processing
ICE Pototyping (LENS)

IWS fraunhofer

IRIS

24

The oldest system is working from liquid a photosensitive raw material. The
principle is the same as LBM. The drilled workplate is gradually plunged
in a tank of resin. The liquid surface is leveled by a wiper between each
downward movement and a UV laser polymerize the resin in the
specified areas. This process need a UV curing to finish polymerization

part
supports
wiper Liquid
displacements

workplate

Liquid polymer

25

Here are some examples made in Stereolithography :

26

 3D Objet printing : mix between 3D printing and stereolithography. The
printing head deposits à photosensitive resin in specified areas. The
deposition is directly followed by a polymerization with a UV laser
mounted on the same support than the printing head.

27

It is also possible to build in ceramics parts. This is a combination of SLM
and stereolithography technologies. There isn’t a spreading of powder
but a paste made of ceramic powder and a photosensitive polymer, like
in SLM, but the laser doesn’t melt any material, it polymerizes the resine,
like in stereolithography. After processing the parts, they are removed
from the paste, cleaned and placed in a oven for sintering the ceramic
and remove the polymer. Here are some examples :

Recoater

Parts

Laser processing

Slurry
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 Fused Deposition Modeling : A wire of solid polymer is push through a 3-
axis heated nozzle which cause slightly melting. The solidification occurs
by air cooling just after extrusion/deposition.

29

 Small summary of technologies :

3DP Z-Corp 3DP Objet 3DP Prometal 3DP Optoform

LBM EOS Stereolithography LBM SLM Solution EBM Arcam

FDM Makerbot LMD

30

 Metal technologies :
LBM EBM LMD 3DP
Size (mm) 250 x 250 x 350 210 x 210 x 350 900 x 980 x 500 1000 x 500 x 250

Layer thickness (µm) 30 - 60 50 130 - 600 70 - 170

Min wall thickness (mm) 0.2 0.3 0.6 0.75

Accuracy (mm) +/- 0.2 or 0.1% +/- 0.13 – 0.2 N.A. 0.2 - 0.3

Build rate (cm³/h) 5 - 20 10 – 40 (lattices 80) 2 - 30 Up to 120

Surface roughness (µm) 5 - 15 15 - 35 15 - 20 20 - 30

Geometry limitations Supports needed Very few supports but No powder bed. Same No support. Almost no
everywhere (thermal, rest of the powder no limitations as 5 axes limitation.
anchorage) more fluid but pre- milling.
sintered as a “cake”
materials Stainless steel, tool Only conductive Every powdered SS 316L or 420 + bronze
steel, titanium, materials (Ti6Al4V, materials. (standard)
aluminum,… CrCo,…)

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size (mm³)
 Metal technologies : 10

8

6
Best surface roughness (µm) layer thickness (µm)
4

2 SLM
EBM
0 LMD
3DP

Build rate (cm³/h) min wall thickness (mm)

Best accuracy (mm)

32


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 Polymer technologies :
LBM (EOS) 3DP (Z-corp) STL 3DP FDM
(Viper Si2) (Connex 500) (Makerbot)
Size (mm) 350 x 350 x 630 250 x 350 x 200 250 x 250 x 250 500 x 400 x 200 225 x 145 x 150
(P390) (Makerbot)
Layer thickness (µm) 100 - 150 100 25 - 150 16 - 30 100 - 300

Min wall thickness 0.6 – 0.7 2-3 0.2 – 0.3 0.5 – 0.6 2
(mm)
Accuracy (mm) 0.2 - 0.2% > 100 mm 1-2 +-0.1 +-0.1 - Positioning : 11 µm

Geometry limitations Almost non Almost non Removing Removing supports
supports in in closed volume
closed volume
materials PA, PA+Al, PA+C Plaster powder Acrylate-based Acrylate-based ABS, PLA
resins resins

36

 Polymer technologies : size (mm³)
10
9
8
7
6
5
4
3 LBM EOS P390
2
3DP Z-Corp
1
Best accuracy (mm) 0 layer thickness (µm) STL Viper Si2
3DP Connex 500
FDM Makerbot

min wall thickness (mm)

37


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Summary :
 Z-corp : attractive demonstrators, cheap prototype, architecture, trendy
reasons. (color, powder, no support)
 3DP Prometal : Stainless steel part with complex internal geometry and
“foundry” surface quality. (No heat input, powder, no support)
 3DP Objet : Mutli-material polymer parts with high resolution and bending
functionalities. (multi-material nozzle, resin, supports needed)
 3DP Optoform : Ceramic parts (HA, TCP, Zr,…) for bone implants mainly
(paste, supports needed, high shrinkage)
 LBM EOS : Polyamide parts for every applications (Powder, no support)
 Stereolithography : Transparent resins for every applications (Resin, supports
needed)
 FDM : Cheapest technology, medium quality (wire, supports needed)
 LBM SLM Solution : Most effective with thin metal parts. (powder, supports
needed)
 EBM Arcam : high build rate, well suited for massive parts (Powder, ~no
support)
 LMD : repair, local coating, graded material on non flat surface (powder,
limited 3D complexity)
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 Design simplification :

From 12 components to only one with better efficiency :

Sirris

41

 Medical prothesis :

Every patient is unique and needs, of course, a specific shape. Material
properties have to be adapted to the bone to preserve it :

42

 Complex piping :

Sirris – compolight project

43

 Articulated parts without assembly :

Objet 3D

EOS

Oak Ridge National Laboratory

Barosens (Morris technology)
Objet 3D
Materialise

44

 Lightweight parts :

EADS

Within Technology

EOS

Sirris – compolight project Laser Cusing

45

 Jewelry:

Shapeways

46

 Customization :

Materialise

Sirris (YAMM)

Sirris (Driessen & Verstappen) Olaf Diegel

47

 Conformal cooling :

Before AM Part to produce by With AM
injection

• Conventional cycle time: 38s

• CCC cycle time: 32s

• Reducing cycle time: 16%

• Profit for the 1st year: 222.000
€ (6.000.000 units/year)

48

 You can have a part within a week.
 A lot of different materials are available.
 AM let you make quickly a first prototype to validate a concept and avoid
future mistake.
 A lot of functionalities can be added to your part (hinges, spring,
lightweight, conformal cooling, local coating, multi-material,…)
 The complexity doesn’t increase the price.
 Highest degree of customization.

 Don’t forget that supports are sometimes required.
 Parts are surrounded by powder /resin/paste which has to be removed.
 Post machining or polishing is often required after the process.

=> Thank you for you attention !
Magnien Julien
49

2013 03-12-masterclass-biomedical-applications-of-am sirris-ad_dtechnic

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