NISTIR 7858
 

A Review of Test Artifacts for Additive 

Manufacturing 

Shawn Moylan 

April Cooke 

Kevin Jurrens 

John Slotwinski 

M. Alkan Donmez 

http://dx.doi.org/10.6028/NIST.IR.7858 
 

 

 

NISTIR 7858 

A Review of Test Artifacts for Additive 

Manufacturing 

Shawn Moylan 

April Cooke 

Kevin Jurrens 

John Slotwinski 

M. Alkan Donmez 

National Institute of Standards and Technology 

Engineering Laboratory 

Gaithersburg, MD 20899 

http://dx.doi.org/10.6028/NIST.IR.7858 

May 2012 

U.S. Department of Commerce 

John E. Bryson, Secretary 

National Institute of Standards and Technology 

Patrick D. Gallagher, Under Secretary of Commerce for Standards and Technology and Director 
 

Abstract 

A standardized test part can be used to quantitatively evaluate the performance of a machine or process. 

This document reviews existing test artifacts used to characterize additive manufacturing processes that 

are reported in the literature. Several aspects of the test artifacts and their use for performance 

characterization are discussed, including the purposes of the studies, important features found in various 

test pieces, and characteristics that are desirable in test pieces. The works were divided into four 

categories: test artifacts for comparing processes for decision making, test artifacts for evaluating 

individual processes, test artifacts for evaluating metal-based processes, and test artifacts for other uses. 

Many of the test parts have similar characteristics because research typically builds upon the findings of 

previous research, and many researchers may have been influenced by “rules” put forth in earlier works. 

Most of the test artifact designs have various “real” features atop a square or rectangular base. The main 

alternative to the square-base, multiple-feature artifacts appears to be a smaller, simpler artifact that is 

built at multiple positions and/or multiple orientations throughout the work volume. The proposed test 

parts were as large as 240 mm x 240 mm in lateral dimensions and contained features as small as 0.2 mm 

in dimension. 

Table of Contents 

1. Introduction............................................................................................................................................ 1 

2. Machining Artifact................................................................................................................................. 2 

3. Additive Manufacturing Test Artifacts .................................................................................................. 3 

3.1 Test Artifacts for Comparing Processes for Decision Making ............................................................ 3 

3.2 Test Artifacts for Evaluating Individual Processes .............................................................................. 4 

3.3 Test Artifacts for Evaluating Metal-based Processes ........................................................................... 5 

3.4 Test Artifacts for Other Uses ............................................................................................................... 6 

4. “Rules” for Test Artifacts ...................................................................................................................... 6 

5. Summary of Part Designs ...................................................................................................................... 7 

6. Next Steps for NIST............................................................................................................................... 8 

7. Acknowledgements ................................................................................................................................ 9 

8. References.............................................................................................................................................. 9 
 

1. Introduction 

Additive manufacturing (AM)—also known as additive fabrication, additive processes, additive 

techniques, additive layer manufacturing, layer manufacturing, and freeform fabrication—is defined as 

the process of joining materials to make objects from three-dimensional (3D) model data, usually layer 

upon layer, as opposed to subtractive manufacturing methodologies such as machining [1]. Additive 

manufacturing of functional components has grown from the initial capabilities for rapid prototyping 

(RP), where the resulting part, usually manufactured layer upon layer, was used for form, fit, and/or 

functional testing. Additive manufacturing processes demonstrate significant potential for a 

revolutionary, rapid art-to-part capability for making high-value, complex, and individually-customized 

parts. Additive processes promise the ability to manufacture parts that are difficult or impossible to make 

with conventional manufacturing techniques, e.g., parts with complex geometries, engineered porosity, or 

lattice structures. However, widespread adoption of additive processes is currently held back by 

deficiencies in part accuracy, surface finish, materials and material properties, process speed, and 

standards. 

The goal of the AM projects at the National Institute of Standards and Technology (NIST)1

 is to facilitate 

the widespread adoption of metal-based additive processes. The work focuses on metal-based processes 

because parts produced by these processes are likely to be used as functional components, have a higher 

inherent value than other materials, and require further improvements before widespread acceptance can 

be achieved. The projects address measurement and standards for the characterization of AM processes 

and equipment, as well as characterization of the materials used in and resulting from AM processes. 

NIST’s expertise and established presence in metrology methods and standards for traditional metalcutting processes offers a unique perspective to the AM community. 

In manufacturing metrology, two primary ways exist to evaluate the performance of a machine and/or a 

process: (1) through a series of direct measurements of machine and process characteristics, and (2) 

through measurements of manufactured test pieces. Manufacturing a test piece enables a composite test 

since most errors present in the machine and the process contribute to errors in the part. The 

disadvantage of composite tests is that linking specific part errors to specific machine or process error 

sources is often difficult. However, the advantages of test pieces are that producing parts is directly 

aligned with the actual purpose of the machine and specialized measuring equipment is typically not 

necessary since the required equipment is common for discrete part manufacturing. 

A standardized test part can be used to quantitatively evaluate the performance of a machine or process. 

The clear benefit of a standardized part is that different machines or processes that produce the same 

standardized part can be easily compared. Additionally, if designed properly, the standard test part can 

test the limitations of the machine or process. The standardized test part can serve as a method for 

performance verification between users and vendors, as well as provide a platform for vendors to 

demonstrate improvements in their product. 

This document reviews existing test artifacts used to characterize additive manufacturing processes that 

are reported in the literature. Several aspects of the test artifacts and their use for performance 

characterization are discussed, including the purposes of the studies, important features found in various 

test pieces, and characteristics that are desirable in test pieces. But first, an example of using a welldesigned test artifact to benefit an industry is discussed. 

1 http://www.nist.gov/el/isd/sbm/matstandaddmanu.cfm; http://www.nist.gov/el/isd/sbm/fundmeasursci.cfm 

1 
 

2. Machining Artifacts 

The use of test artifacts for performance characterization is not unique to AM, and in fact, several 

standard artifacts are used to characterize machining processes (see, for example, Ref. [2] and Ref. [3]). 

One example of a test artifact that benefits U.S. manufacturers is the standard machining test artifact 

known colloquially as the circle-diamond-square test piece. This test piece is described in Ref. [2] and 

Ref. [3] (see Fig. 1), but is well established in the machining community, having been originally defined 

in 1969 in Ref. [4]. 

Figure 1. Test artifact, commonly known as the “circle-diamond-square,” 

for machining centers defined in Ref. [2] and Ref. [3]. 

The strength of the circle-diamond-square artifact lies in its simplicity. Each feature of this artifact tests 

a specific aspect of the machining center used to produce it. The outside square tests the straightness of 

the individual axis used to cut the respective side of the square and the squareness between the two axes. 

The diamond feature tests the ability of the controller to execute linear interpolation of two axes. The 

large circle feature tests the ability of the controller to execute circular interpolation of two axes. The 

four pairs of concentric circles are measured for true position and characterize the machine’s linear 

positioning accuracy. The small angle cuts test the machine’s smallest actionable step. The drilled hole 

in the center tests the performance of the machining center’s main spindle. As such, errors observed in a 

specific feature can often be attributed to a specific aspect of the machining center’s performance. 

Additionally, the test part is easy to design in computer aided design (CAD) or computer aided 

manufacturing (CAM) software, and machining process parameters are suggested within the standard 

that defines the part. The test part is easy to measure, and several measurement options exist, in addition 

to measurement with a coordinate measuring machine (CMM). 

An interesting aspect of this test part, as defined in ISO 10791-7, is that tolerances are associated with the 

part. These tolerances are established by the standards committee through the consensus of 

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representatives from machine builders, machine users, government institutes, and academia. The 

tolerance values are intended to be met or exceeded by a relatively modest (not high-end) machine. It is 

noteworthy that the current standard tolerance levels for machining of this test part are on the order of 

0.020 mm, likely tighter than even high-end metal-based AM machine capabilities. By setting a baseline 

for machine performance, machine builders can often demonstrate quantitatively the extent to which their 

machines exceed standard specifications. 

One consideration in the design of the machining test artifact is that metal cutting machines were well 

established when the standard test artifact was developed. Most metal cutting machines (especially 

three-axis machine tools) have a similar design of stacked linear stages. Since most machine 

configurations are similar, the observed errors and limitations are similar. As such, it is easier to design a 

standardized test part with features that highlight these common errors and limitations and to make it 

possible to compare the performance characteristics of various machines. 

Additive manufacturing processes and systems are far less mature and several different machine 

configurations exist to correspond with different types of processes. These differences have led to a 

number of proposed AM test artifacts to-date, many of which have very different features and designs. 

3. Additive Manufacturing Test Artifacts 

Based on a substantial review of the available literature, the following sub-sections briefly discuss many 

of the different test artifacts used to characterize different aspects of the performance of additive 

processes. The resulting works are described in four categories: test artifacts for comparing processes for 

decision making, test artifacts for evaluating individual processes, test artifacts for evaluating metalbased processes, and test artifacts for other uses. This discussion is by no means exhaustive, nor is it 

unique. 

3.1 Test Artifacts for Comparing Processes for Decision Making 

Additive manufacturing gained prominence in the late 1980s and early 1990s as layer manufacturing or 

rapid prototyping (RP). Stereolithography (SLA) was the first additive RP process, followed closely by 

fused deposition modeling (FDM), laminated object manufacturing (LOM), and selective laser sintering 

(SLS). As AM matured, many more processes, such as three-dimensional printing (3DP) and polyjet, 

entered the market. Users wanting to benefit from the advantages of RP had to choose which of the 

processes best fit their application. 

Many researchers proposed the use of test artifacts, often called benchmarking parts, to quantitatively 

compare the capabilities of the various processes [5-18]. Kruth was the first to mention a test artifact for 

comparing AM processes, citing a study done by two Dutch companies using a U-shaped artifact with 

various geometric features such as circular holes (in various orientations), circular bosses, square holes, 

and angled surfaces [5]. Other researchers built upon these results, adding more and/or different features, 

including overhangs and freeform objects, to demonstrate some of the advantages of additive processes 

(see Fig. 2) [7, 15]. Still more researchers followed, investigating the surface roughness of test parts in 

addition to geometric accuracy as a means to compare AM processes [9, 10]. As additional AM 

processes gained prominence, researchers added these to the comparative studies. For example, Byun 

added 3DP [12] and Kim added polyjet [17]. Ultimately, specific AM processes gained sufficient 

capability and acceptance to support multiple machine platforms and manufacturers, leading to 

3 
comparative studies of systems within a process family, e.g., seven types of 3DP machines produced by 

six different manufacturers [13, 14]. 

Figure 2. Solid model of the test piece used by Mahesh [15]. 

3.2 Test Artifacts for Evaluating Individual Processes 

Artifacts are also used to evaluate individual processes, either when a new process or material emerges in 

the market [19-26] or when process improvement/optimization is the goal of the study [27, 28]. The socalled “user part” is one of the first test pieces designed to quantitatively assess the accuracy of 

stereolithography systems (see Fig. 3) [19]. This part was designed in 1990 by an SLA user group and 

focuses on assessing the machine accuracy in the x-y plane. This same part or slight variations of it have 

been used by many other studies to characterize other additive processes, including evaluation of SLS for 

indirect manufacturing of metallic components (i.e., using SLS to create an intermediate, “green” part 

that must undergo subsequent post processing to become fully dense) [21]. Additionally, when new 

material options are introduced into an established process, it is important to quantify the accuracy of 

parts made with this new material [24, 26]. 

Figure 3. Solid model of the “user part.” 

Development of new materials led to the first test artifacts dedicated to process improvement and 

optimization. During SLA’s first years, newer, stronger materials were being quickly developed and 

introduced into user systems. The “windowpane” and “Christmas tree” test artifacts were used at this 

4 
time to quantify the effects of changing various process settings, leading to iterative optimization of 

process design [27]. 

Examining the literature for use of test artifacts to evaluate individual processes may lead to the incorrect 

conclusion that using a test artifact to optimize process parameters is uncommon. In reality, most AM 

system manufacturers and users working on process development typically have their own internal test 

pieces for this purpose, though their designs remain proprietary. 

3.3 Test Artifacts for Evaluating Metal-Based Processes 

In recent years, the capabilities of metal-based AM processes have grown tremendously and these 

systems have emerged as viable methods for the direct manufacturing of metallic parts (i.e., using an 

energy source to melt and bond metal raw materials, creating a fully-dense part without the need for 

substantial post-processing). Numerous studies have concentrated on benchmark parts to evaluate metalbased AM processes [29-36]. The various processes that have been studied include selective laser 

sintering (SLS), selective laser melting (SLM), direct metal laser sintering (DMLS), electron beam 

melting (EBM), and micro-welding technologies. Kruth took a traditional approach by creating a test 

artifact with characteristic features to determine and analyze geometric errors and surface roughness (see 

Fig. 4). Additionally, this artifact included features to be extracted for mechanical testing to provide 

information about mechanical properties. The study used other features of the artifact to determine the 

capabilities and limitations of the different AM processes used for fabrication [29]. Castillo provided a 

similar comparison, though with an innovative test artifact that characterized the system’s accuracy and 

capability to build at various angles using an “open book” feature (see Fig. 5) [30]. Ning investigated the 

process characteristics of DMLS using test artifacts to highlight the effects of part shrinkage during the 

build process, which is minimized through a shrinkage compensation function [31]. Ghany used a “realworld” test part as the reference (instead of fabricating an arbitrary design) and compared the visual 

appearance, mechanical properties, chemical composition, microstructure, and processing costs of the 

components made by different metal-based AM processes [32]. Hanumaiah manufactured numerous 

benchmark parts to assess geometric errors of the various features incorporated in the designs [33]. 

Similarly, Pessard created a test part used to evaluate the dimensional accuracy of embedded features 

[34]. Delgado followed with another test part used to assess geometric accuracy, but this part was 

fabricated many times to evaluate the accuracy and repeatability of position [35]. Finally, Cooke used a 

common machining test artifact to assess the geometric accuracy of its features when built using two 

different metal-based additive processes [36]. Differences in the process parameters, however, prevented 

comparative conclusions from being drawn. 

5 
Figure 4. Approximate re-creation of the test piece used by Kruth [29]. 

Figure 5. Approximate re-creation of the test piece used by Castillo [30]. 

3.4 Test Artifacts for Other Uses 

The primary purpose of most test pieces previously mentioned was to characterize the accuracy of the 

machines and/or processes under test. Other researchers have used test artifacts to examine different 

aspects of additive processes. The layer-upon-layer nature of AM typically leads to stair-stepping on 

sloped and freeform structures based on the layer thickness. Accordingly, several research efforts have 

focused on the surface roughness of various additive processes [11, 37, 38]. Similarly, the layer-uponlayer nature of AM can lead to unique and often anisotropic mechanical properties of materials, 

triggering further investigations of these properties through producing test artifacts. [39, 40]. 

4. “Rules” for Test Artifacts 

Early in the development of SLA, Richter and Jacobs saw the need for a standard accuracy test to help 

provide quantitative results and noted the qualities of an “ideal accuracy test part” [41]. Paraphrasing, 

the standard test artifact would: 

 be large enough to test the performance of the machine near the extremes of the platform as well 

as near the center, 

 have a substantial number of small, medium, and large features, 

 have both holes and bosses to aid in verifying beam width compensation, 

 not take too long to build, 

 not consume a large quantity of material, 

 be easy to measure, and 

 have many features of a “real” part (i.e., thin walls, flat surfaces, holes, etc.). 

6 
Other researchers [28] have followed these criteria/rules closely. Byun referenced these rules, but added 

that the test part should include features along all axes and should include features used to determine the 

minimum feature size attainable [12]. 

While many of these qualities are indeed important considerations in designing a test artifact, an ideal 

artifact would not only highlight most errors and limitations of a machine or process, but it would also 

correlate those errors and limitations with specific aspects of the machine or process. Kruth moved in 

this direction, noting that a test artifact should not only evaluate process limitations, but should also 

include features to allow iterative process optimization [29]. Scarvetti took this idea a step further, 

stating that the qualification procedure must make it possible to identify and quantify defects, but also 

determine the sources of the defects [42]. In order to do this, the test artifact should: 

 have simple geometrical shapes, allowing perfect definition and easy control of the geometry, 

 require no post-treatment or manual intervention (e.g., there should be no support structures), and 

 allow measurement of repeatability [42]. 

In addition, several researchers state or imply the need for a test artifact to include multiples of the same 

feature to allow measurement of repeatability. However, including multiples of the same feature merely 

tests the machine or process capability to produce that same feature at different places within the work 

volume; it does not test the repeatability of the machine or process [43]. Various conditions may result in 

different systematic errors existing at different locations in the work volume, leading to differences in the 

shapes of the features produced in these positions. However, if multiple artifacts were produced, every 

feature produced in the same position in the work volume would be ideally the same. 

5. Summary of Part Designs 

While all of the AM test artifacts mentioned in this report are different, many commonalities exist. 

Common aspects are to be expected because much of the research builds upon the findings of previous 

work, and many researchers were influenced by the “rules” put forth by Richter and Jacobs [41]. Most of 

the test artifact designs have various “real” features atop a square or rectangular base (see Fig. 2, Fig. 3, 

Fig. 4, Fig. 5). The various features observed are: 

 rectangular holes, bosses, and tubes (in multiple directions), 

 round holes, bosses, and tubes (in multiple directions), 

 spherical holes and bosses, 

 conical bosses, 

 L-shaped bosses, 

 ramps, 

 overhangs, 

 angles, 

 side notches, 

 thin walls and fine features, 

 freeform structures, and 

 towers. 

The sizes of the test artifacts varied, but the largest observed dimensions of the square base were 240 mm 

by 240 mm. The smallest features observed were 0.25 mm thin walls (for both polymer-based and metal7 
 

based AM processes), 0.2 mm holes and bosses in polymer-based AM processes, and 0.5 mm holes and 

bosses in metal-based AM processes. 

One alternative to the square-base, multiple-feature test artifact is the use of a smaller, simpler test 

artifact that is built at multiple positions and/or multiple orientations throughout the work volume (see 

Fig. 6). A second alternative approach is the use of a standard library of 3D objects or part features (e.g., 

spheres, cylinders, prisms, cones, etc.), rather than a single test artifact, to evaluate AM system 

performance. Smith proposes a library of twelve objects to benchmark AM systems, with each object 

designed to demonstrate and evaluate at least one important feature of the resulting parts [44]. Jurrens 

suggests use of a standard library of 3D features that would be built and measured in a standard way [45]. 

The standardized features would be built in a variety of sizes, locations, and orientations, and potentially 

would be supplemented with selected “real-world” parts. 

Figure 6. Approximate re-creation of Delgado’s simple artifact in various 

orientations on an AM build platform [35]. 

6. Next Steps 

This review was a first step toward the development of an industry-accepted, standardized test artifact for 

AM. With knowledge of the work already documented in the literature, the next step is to determine the 

characteristics of a “good” test part. A candidate standard test artifact will be designed that incorporates 

as many of the characteristics of a good test part as possible, and then tested by building the candidate 

artifact on the existing DMLS machine at NIST. Lessons learned while building the first test pieces will 

certainly lead to improvements over the original proposed design. Concurrent to these efforts, the 

feasibility for using one standardized test artifact for all types of additive processes will be assessed. 

Proper performance characterization may require different test piece designs. The final design of the 

candidate test artifact(s) evaluated using the DMLS system, along with an assessment of other AM 

processes for which the test artifact(s) are also relevant, will be the focus of a future NIST report. 

8 
7. Acknowledgements 

The authors would like to thank Regina Avila of the NIST Information Services Office for her assistance 

in compiling the articles referenced in this report. 

8. References 

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