Additively
Manufactured
Composite
Tooling

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High-performance
thermoplastics offer
efficiencies and design
flexibility

2Additively Manufactured
Composite Tooling

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The advanced composites industry has acontinual need for innovative tooling solutions.
Conventional tooling is typically heavy, costly
and time-consuming to produce. New
applications, product improvements and thedemand for faster, lower-cost tool creation
challenge composite product manufacturers
to innovate and remain competitive.

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Additively Manufactured
Composite Tooling
FDM™ (fused deposition modeling) technology
is an additive manufacturing process using
high-performance thermoplastics. The FDM
process builds objects layer by layer throughthe deposition of material, using informationfrom a digital model. The process is typically fasterand less expensive than traditional
manufacturing technologies.
The combination of additive technology and FDM
material capability offers a much more effective
way to produce composite tooling. This includes
both high-temperature (>180 °C), low-volume
lay-up and repair tooling as well as moderatetemperature (<121 °C) sacrificial (washout) tooling.
Compared with traditional materials and methods,
FDM technology offers significant advantages interms of lead time, cost, and simplification of tool
design and fabrication, while enabling increased
functionality and geometric complexity.
This paper forms an abridged version of the “FDM
for Composite Tooling” design guide (referredto herein as “design guide”) and provides an
overview of the best practices associated with 3D
printed composite tooling. It also provides relevant
performance data and examples of effective tools
designs. More detailed information can be found in
the full version, available at:
http://www.stratasys.com/solutions/additivemanufacturing/tooling/composite-tooling.

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Background and Purpose
Traditional manufacturing methods for highperformance fiber-reinforced polymer matrix(FRP) composite structures require the use of
hard tooling for the mold or mandrel that dictates
the shape of the final part. The mold or mandrel
is most commonly made of metallic materials(aluminum, steel, or Invar alloys), although non-metallic materials are also utilized (specializedcomposite tooling materials, high-temperature
tooling board, etc.). Regardless of material, tool
fabrication typically requires significant labor andmachining, leading to high costs, material waste,and long lead times, consisting of many weeks
for even relatively simple part shapes and many
months for more complex tools. The use of additive
manufacturing (or “3D printing”), and specifically
FDM, for composite tooling has demonstrated
considerable cost and lead time reductions whileproviding numerous other advantages such as
immense design freedom and rapid iteration, nearly
regardless of part complexity.
Stratasys FDM technology has been successfully
utilized for low-volume composite lay-up and repair
tooling applications for years, but was limitedby the lack of materials capable of withstanding
the 180 °C cure temperature frequently required
for aerospace and similar high-performance
structures, as well as a lack of design knowledge
and guidance. FDM materials ABS (and ASA), PC,
and ULTEM™ 9085 resin have been demonstrated
to be effective to temperatures up to 85 °C, 135°C, and 150 °C, respectively. With the introductionof ULTEM 1010 resin, FDM technology has
demonstrated numerous advantages for fabricationof composite structures cured at temperatures inexcess of 180 °C and pressures of 0.7 MPa.
Scope and Contents
The purpose of the design guide is to provide
engineers, designers, and manufacturers ofcomposite structures with the information andknowledge to effectively design, produce, anduse FDM composite tooling, regardless ofprior experience with or exposure to additive
manufacturing. This paper provides a subset

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Additively Manufactured
Composite Toolingof the contents of the “FDM for Composite
Tooling” design guide and is intended to inform
readers regarding the general capabilities andkey considerations for FDM composite tooling,although it will not contain the depth or detailed
design aspects provided in the design guide itself.

tooling for small quantities of prototype parts vs.
production tooling). All of these factors influence
final design and construction of an FDM tool andare addressed in detail in the design guide and at ahigh level in the following information.

Tool Design,
Production, And Use

The cure temperature of the composite structure
primarily influences material selection. FDM
materials are capable of covering a broad rangeof cure temperatures, as displayed in Figure 1.
As shown, ULTEM 1010 resin has the highest
temperature capability of relevant FDM materials
and also has the lowest CTE (refer to Section 2.2of the design guide), making it the preferred andrecommended choice for the majority of composite
tooling applications. Thus, while tools made fromPC and ULTEM 9085 resin can withstand thecure cycle for a 125 °C-cure material system forexample, ULTEM 1010 resin is likely still the mostappropriate choice to minimize expansion impacts.

Cure Temperature

Just as design and construction aspects oftraditional composite tooling vary depending on
the material of construction (e.g., Invar vs. carbon/
epoxy), there are factors and key considerations
that are critical to the effective design and useof FDM composite tooling. In particular, in thecontext of the design and development of themold or mandrel, it is important to understandand consider the processing parameters (e.g.,cure temperature, vacuum bagging scheme, andpressure) for the composite structure, coefficientof thermal expansion (CTE), tool/part tolerances,and the intended use or application (e.g.,

Material

AMBIENT

180°F (82°C)

250°F (121°C)

350°F (176°C)

ABS or ASA
FDM Sacrificial Materials
PC
ULTEM 9085 resin
ULTEM 1010 resin

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FDM Master +Tooling Prepreg
FDM Master +High Temp Wash-Out
Figure 1 – Temperature capabilities of FDM materials.

ST-130ULTEM S1

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Additively Manufactured
Composite Tooling
Coefficient of Thermal Expansion (CTE)
CTE is an important consideration for nearly allcomposite lay-up tooling. The CTE was determinedusing thermomechanical analysis (TMA) per ASTM
E831 for relevant FDM materials and can be seenin Table 1, along with that of common conventional
tooling materials for comparison.

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As a result of the relatively high CTE of FDM
materials, it is an important consideration during
tool design. Tool designs can and typicallyshould be compensated for resulting dimensionalchanges. Detailed examples of such adjustments
are provided in the design guide. In addition togeometric compensation, CTE differences between
the tool and final part materials are also factorsthat impact tool type (male vs. female tools) andpotential complexity. For male tools, sizing themto compensate for growth will frequently beadequate. And for some applications, such as
mandrels for winding / wrapping, the CTE can beused advantageously to improve ply compaction
and simplify mandrel removal. For female tools,
particularly those with steep contours and deepdrafts, additional care is required to ensure parts
can be safely demolded without inducing tool orpart damage.

FDM Materialsµm / (m•C°)µin / (in•F°)

ABS / ASA

88

49

PC

79

45

ST-130(sacrificial tooling)

106

59

ULTEM 1010 Support (sacrificial
tooling)

58

32

ULTEM 9085 Resin

65

37

ULTEM 1010 Resin

47

26

Conventional Tooling Materialsµm / (m•C°)
36 – 72µin / (in•F°)
20 – 40

Aluminum alloy(AL 6061-T6)

25

14

Tool Steel

12

6.5

Carbon/epoxy

8

4.5

Invar

1.2

0.7

Tooling Boards

Table 1. CTE for FDM materials and common traditional toolingmaterials.

Accuracy / Tolerances
FDM is capable of producing parts (tools) withaccuracies of ± 0.09 mm (0.0035 inch) or ±0.04 mm / mm (0.0015 inch / inch), whichever isgreater. It should be noted that all accuracies aregeometry dependent (primarily due to the thermal
nature of the process). Additional information onmachine accuracy can be found on the Stratasys
website (including a white paper on the topic).
For development of the design guide, accuracy
data was compiled for various representative toolgeometries, both before and after thermal cycling– refer to Sections 3.1 and 4.1 of the design guidefor additional details.
For composite parts that require greater accuracy
than what can be achieved directly from the FDM

6Additively Manufactured
Composite Toolingmachine, production of “near-net” shape tools,
combined with skim-coat machining is a viableoption. Additional development work is underway
on this topic and will be provided in subsequentversions of the design guide.
Process Parameters and Tool Design
Fabrication process and cure cycle parameters,
particularly cure pressure and vacuum bagging
method, impact the design of FDM composite
tools and specifically the “style” of the tool. FDM
composite tools are primarily classified as “shell”
style or “sparse” style (cellular) tools. The basic
differences are as shown in Figure 2.

Shell style tools are effective for most applications,can withstand autoclave pressures exceeding
0.7 MPa, and are conducive to both surface andenvelope vacuum bagging methods. And for many
tool geometries, they are the most cost-efficientdesign as they minimize material usage and build
time. Sparse style tools tend to have greater
overall rigidity and stability and some geometries
dictate the use of such a construction, as isdemonstrated in more detail in the design guide.
Sparse style tools can also be either surface (edge)
or envelope bagged. When envelope bagging isused, additional guidelines regarding construction
parameters (e.g., sparse-fill spacing) should be
followed to avoid damaging the tool. Generalguidance for envelope-bagged, sparse-style tools
is shown in Table 2, although results will vary
somewhat based on geometry.

Figure 2 – FDM tool construction styles.

Figure 3 – Cross-section of FDM tool paths for an example build layer
to illustrate the inherent occurrence of porosity (from Stratasys
Insight™ software).

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Consolidation Pressure

Recommended Sparse
Double Dense Spacing

Recommended
Hexagram Spacing

MetricVacuum only –0.3 MPa

US Customary
Vacuum only –40 psi

Metric13 mm

US Customary
0.5 inch

Metric25.4 mm

US Customary
1 inch

< 0.4 MPa

< 60 psi

6.5 mm0.25 inch

25.4 mm1 inch

0.55 – 0.7 MPa

80 – 100 psi

4 mm

0.15 inch

12.7 mm

0.5 inch

Table 2. Tool construction guidelines for envelope vacuum bagging.

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Composite Tooling
Tool Preparation (Post-Processing)
The FDM process inherently produces some levelof internal porosity due to physical limitations of the
extruded material beads, as can be seen in Figure
3, which shows the cross-section of tool paths(extruded material) for an example build layer. The
process also produces perceptible build layers,which vary based on the shape of the part andthe layer thickness. As a result, to ensure highquality surface finish and vacuum integrity, postprocessing of FDM tools is typically required.

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In preparation for use, tools are abraded to smoothout build lines, sealed, and then undergo a final
polish, resulting in surface finishes consistent
with typical industry requirements. Althoughrequirements do vary somewhat across industries,
typically a finish of 1.6 µm (64 µinches), Ra isconsidered acceptable. Using a standard processwith progressively finer abrasive papers, a finishsmoother than 0.4 µm (16 µinches), Ra can beconsistently achieved on FDM composite tools.
Sealing can be performed using a range ofmaterials depending on the specific application.
The most common materials used to date havebeen high-temperature, two-part epoxies. Epoxy
film adhesives and adhesive-backed FEP films(and similar consumable products) have also beenused successfully and have distinct advantages(e.g., ease of application), depending on therequirements of the specific application. Oncesealed, common mold release agents can beapplied in preparation for composite part lay-up(water-based released agents are recommended
for applications with long-term exposure).

Evaluation of the impact of post-processing(sanding and sealing) on the accuracy of FDM tools
was also performed and confirmed that minimal
dimensional change occurs. Additional data is
contained in the design guide and all accuracy
characterization data was measured on tools that
had been post-processed.
Tool LifeOne of the final key considerations for effective
design and use of FDM composite tooling is anunderstanding of the intended use or applicationof the tool. It is important to consider the intended
tool life, or the number of anticipated parts to befabricated. Tools intended for a few prototype
composite parts can be constructed in a manner
to minimize cost. Tools intended for a time-criticalcomposite repair can be optimized for build time.
And tools intended for longer-term production use
and higher part volumes require greater scrutiny
regarding nearly all aspects. Detailed examples areprovided in the design guide.
The majority of usage to-date for FDM composite
tools has been for relatively low part volumes (<25 parts). However, in development of the design
guide, tool life characterization testing was initiated;refer to Sections 3.3 and 4.3 of the complete
design guide for more details. The available data
indicates FDM composite tooling is capable ofmuch longer tool life – 100s of cycles – depending
on cure cycle process parameters of course.
Additional tool life evaluation is ongoing to further
characterize performance and will be provided insubsequent design guide releases.

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Additively Manufactured
Composite Tooling
Testing And Characterization
A subset of the testing and characterizationthat was performed during development of
the design guide is presented in the following
sections. Additional characterization work that was
performed, but deemed somewhat more routine
and is not presented herein, include outgassing(to verify a lack of potential contaminants), solvent
exposure (to verify compatibility with the mostcommon solvents used in composite fabrication
facilities – IPA, acetone, and MEK), and surface
roughness assessments before and after postprocessing (to demonstrate and quantify resulting
surface finishes). Details for these evaluations areprovided in the design guide. All testing presented
herein was performed on tools produced in ULTEM
1010 resin.
Accuracy and Thermal Stability

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To assess accuracy and stability of FDM composite
tools, multiple tools were evaluated both before
and after thermal cycling. Three different tool
designs were produced and build construction(shell vs. sparse build) and sizes were varied fora total of five variants. The tools were sent toan external inspection facility for precision 3D
scanning. A Platinum FaroArm (from FARO®
Technologies) with an SLP 300 laser head (fromLaser Design, Inc.) was used. The scan data wascompared to the CAD model for each variant
using PolyWorks View 3D metrology software (from
Innovmetric).
All composite tools used for this evaluation were
post-processed (abraded) prior to the initial 3D
imagery. This configuration was selected sincenearly all FDM composite tooling will undergo suchpreparation prior to use, making the accuracy ofa post-processed tool the most relevant data.

Although there is likely some variability in postprocessing between operators, the overall amountof material removed during abrasion was foundto be quite small (using standard “best practice”
procedures) and does not represent a significant
portion of overall dimensional variation.
As stated, tools were scanned before exposure toelevated temperatures and then sent for thermal
cycling. For cycling, the tools were vacuum bagged(envelope bagging scheme), heated to
180 °C, held at temperature for two hours(minimum) under full vacuum, and then ramped
back down to below 65 °C between cycles for a
total of 10 consecutive oven cycles.
Moisture Exposure
Many polymeric materials absorb moisture tosome extent over time at various rates. Per the
manufacturer (SABIC), ULTEM 1010 resin will
absorb 0.7% when saturated (23 °C / 50% RH).
Since moisture can be detrimental to composite
laminate quality, relatively rudimentary testing was
performed to ensure that such adverse effects canbe prevented with basic precautions.
To ensure saturation and a “worst case” exposure
scenario, two tools (one each shell style and sparsebuild constructions) were placed in a humidity
chamber at 60 °C / 90% RH for two weeks. After
conditioning, both tools were subsequently driedfor 4 hours at 125 °C. Eight-ply quasi-isotropic
carbon/epoxy laminates were then produced oneach tool. The laminates were visually inspected
after cure and then sectioned for microscopy toinspect for porosity, delamination, blistering, andother indications of moisture-induced effects. The
primary objective was to demonstrate that even in
the most severe climates, if moisture absorption
becomes a concern, oven drying of tools prior to9Additively Manufactured
Composite Toolinguse is sufficient to prevent adverse effects on cured
parts. In reality, most tools in a state of regularuse are likely to be stored in environments far lessharsh than those tested.
Tool Life
A thorough understanding of the potential usefullife of a non-metallic tool is critical, particularly
for production tooling consideration (or for any
substantial part volumes beyond prototyping).
It is also challenging information to obtain
experimentally due to the time and resources
involved. In working toward a preliminary
baseline, both practical (empirical) and analytical
data was gathered.

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For empirical testing, the basic approach outlined
for the accuracy and thermal stability testing
described in Section 3.1 of the design guide wasfollowed, but extended to higher numbers ofthermal cycles. A single tool geometry (UAV fan
blade), built in the two primary build constructions(i.e., shell and sparse build styles) was tested (thetools are as shown in Figure 2). Tools were cycled
for 30, 60, and 90 cycles (180 °C, full vacuum,oven only), followed by evaluation (inspection and
3D scanning) and laminate fabrication (eight-ply,
quasi-isotropic carbon/epoxy) with subsequent
inspection and dimensional evaluation.

viscoelastic behavior for a given temperature
can be superimposed on data for a different
temperature by shifting the curves along the time
/ frequency axis[1, 2]. It should be noted that the
majority of loading applied to molds and mandrels
is not flexural in nature, but rather compressive.
Thus, evaluating flexural properties represents
a “worst case” loading condition and ensuresresults are conservative, albeit slightly less directly
applicable. An evaluation of compressive creep
would be ideal, but such an apparatus was notavailable at the time of testing.
Results
Analysis of test and characterization data for
accuracy, thermal stability and moisture impacts
are provided in the design guide. Tool life evaluation
was still in progress at the time of publication. As aresult, preliminary results are provided herein. Data
included herein was selected to be representativeof and consistent with the broader results. As
stated, all data is for ULTEM 1010 resin tools.
Accuracy and Thermal Stability
3D scanning of example tool geometries was
performed both before and after thermal cycling,
as described in Section 3.1 of the design guide.

For the analytical portion, dynamic mechanicalanalysis (DMA) was used to evaluate creep in
flexural specimens (3-point bend configuration).
Isothermal testing was performed with a 0.7 MPa(100 psi) loading condition at multiple elevatedtemperatures (i.e., 180 °C, 195 °C, and 205 °C)
and then time-temperature superposition (TTS)
principles were used to form an understandingof long-term behavior. The basis for use of TTS
comes from the demonstrated principle that
Figure 4 – 3D scan data for a UAV fan blade (shell style) tool withcolor map comparison to the original CAD model (no thermal cycling).
Dimensions are in inches.

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Additively Manufactured
Composite Toolingshowed 90 cycles, resulted in little deviation for the
printed geometry, Figure 6. The localized maximum
deviation measured was 0.145 mm (0.0057 inch)with an average deviation of less than 0.051 mm(0.0020 inch).

Figure 5 – 3D scan data for a UAV fan blade (shell style) tool after 10
thermal cycles with color map comparison to the 3D scan data forthe same tool prior to cycling. Dimensions are in inches.

An example set of data can be seen in Figure 4
for the resulting comparison between the printed
sparse style, UAV fan blade tool and the original
CAD model data (no thermal cycling). As displayed,
the scan data shows the tool has areas that varyfrom the model by as much as approximately 0.48
mm (0.019 inch). For reference, the subject tool
is roughly 355 x 256 x 100 mm (14.5 x 10.5 x 4inches) in size. Figure 5 shows the scan data forthe same tool after 10 thermal cycles. As can beseen, there is very little dimensional change andthe inherent variability and accuracy limits of the 3D
metrology system itself certainly come into play as
a likely source of the observed variation.
Moisture Exposure

As previously described, DMA was performed
to evaluate creep resulting from flexural loading(0.7 MPa) at 180 °C, 195 °C, and 205 °C. TTS
was then used to project long-term behavior. The
resulting relationship is shown in Figure 7. Again,
it is important to note that this data was obtained
under flexural loading conditions and is expected
to be a significantly harsher loading condition
than the actual cyclic compressive loading thatcomposite tooling experiences in reality. Thatsaid, the results support that an ULTEM 1010
resin composite tool is capable of performing wellFigure 6 – 90 thermal cycles before vs. after dimensional
comparison.

As expected, moisture exposure testing
demonstrated that tools dried (4 hours at 125°C) prior to use produce laminates of acceptable
quality (no significant porosity or otherobvious issues).

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Tool LifeThe empirical portion of tool life characterization(as described in Section 3.3 of the design guide)

Figure 7. Flexural creep data for ULTEM 1010 resin test coupons
shifted to 180 °C using TTS.

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Additively Manufactured
Composite Toolingbeyond the requirements of prototyping volumes.
The flexural strain at failure for ULTEM 1010 resin
was determined to be 3.5% (tested per ASTM
D790)[3]. Even a very low strain of 0.1% is notpredicted to occur until 80+ hours of exposure at
180 °C and 0.7 MPa. Refer to Section 5 of thedesign guide for additional information.
Conclusions
Stratasys FDM technology has been successfully
utilized for low-volume composite lay-up and repair
tooling applications for years. More recently, theintroduction of ULTEM 1010 resin has enabled
expansion of the technology into tooling for hightemperature-cure (180 °C) composite structures. A
comprehensive design guide has been developed
to provide the information and knowledge to assistin unlocking the potential value of FDM composite
tooling. A sub-set of the information assembled forthe design guide was presented herein, including
an introduction to the key considerations for
FDM tooling, as well as some importantcharacterization data.
Of particular importance, the tool life
characterization work performed to date wasfound to be very encouraging. Given that theflexural strain at failure is 3.5% and even using
a much lower threshold for acceptance, ULTEM

1010 resin demonstrates the ability to perform
under harsher loading conditions (flex) for theequivalent of dozens of high-temperature, highpressure autoclave cycles, perhaps even 100+
cycles (refer to Figure 7). And of course, use oflower pressure (and/or lower temperature) cure
cycles will only extend the usable life. This dataalso suggests that for use with the relatively low
loading produced in vacuum-bag only cycles,
tool life is not a significant concern for typicalaerospace industry part volumes (at least from theperspective of creep-induced tool deformation).
Further testing is necessary to confirm anddevelop a more comprehensive understanding andadditional tool life characterization continues to be
point of emphasis. Future development data will
be included in subsequent versions of the design
guide.
References
1. TA Instruments. “Application of TimeTemperature Superposition Principles to DMA.”
Thermal Analysis Application Brief, number TA-144.
29 January 2016. www.tainstruments.com.
2. A.V. Tobolsky. Properties and Structures ofPolymers. Wiley, New York, 1960.
3. Stratasys, Inc. “ULTEM 1010 Resin Spec Sheet.”
29 January 2016. www.stratasys.com.

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