1. Introduction
Additive manufacturing (AM) technologies offer the opportunity to fundamentally rethink design approaches for final products, thus creating added value for customers and companies, e.g. by an increase in product functionality (Reference Tüzün, Roth and KreimeyerTüzün et al., 2023). However, creating added value for AM stakeholders in industries means that these manufacturing technologies must unfold their potential beyond laboratory conditions by being integrated into industrial product development processes. Although it has been recognised that the industrial application of AM also requires a rethinking of product development processes (Reference Roscoe, Cousins and HandfieldRoscoe et al., 2023), research still does not adequately cover complete development processes, but rather addresses only certain aspects of development methodology for AM (Reference Jemghili, Ait Taleb and MansouriJemghili et al., 2023). As a consequence, the application of AM for final products cannot keep pace with the rapid increase in technology readiness (Reference Lianos, Koutsoukos, Bikas and StavropoulosLianos et al., 2020). Adding to this difficulty is the tendency for existing development approaches not to be designed collaboratively from the ground up together with industry stakeholders but to be deployed in a prescriptive manner with the aim of validation according to their promised added value. The authors of this paper argue that the lack of collaborative foundational research together with industrial stakeholders leads to overlooked challenges, making the developed frameworks for product development processes unsuitable for industrial applications of AM. For this reason, this paper aims to contribute to the identification and understanding of current challenges within product development processes for additively manufactured products. A thematic scope for AM product development frameworks is presented, which maps unresolved challenges AM stakeholders face in current industrial practice, along an AM-specific development process. The proposed thematic scope is based on an interview study on product development processes for additively manufactured products in which 11 engineers from 11 different German companies participated in 2024.
2. Background
Since the industrialization of additive manufacturing processes, the original focus on prototyping (Rapid Prototyping) has been shifting toward the production of final products (Direct Manufacturing) (Reference Thompson, Moroni, Vaneker, Fadel, Campbell, Gibson, Bernard, Schulz, Graf, Ahuja and MartinaThompson et al., 2016). This shift creates a demand for AM specific development methodology, as Direct Manufacturing has to cope with additional requirements and constraints beyond prototyping applications (Reference Gibson, Rosen, Stucker and KhorasaniGibson et al., 2021). This demand has already been recognized in the academic literature, and addressed with various Design for AM (DfAM) approaches for the concept phase (e.g. Laverne et al., Reference Laverne, Segonds, Anwer and Le2015; Renjith et al., Reference Renjith, Park and Okudan2020) as well as approaches for complete development processes based on generic models (e.g. Kumke, Reference Kumke2018; Omidvarkarjan et al., Reference Omidvarkarjan, Cipriano, Rosenbauer, Biedermann and Meboldt2020), strategies for redesigning existing components (e.g. Dalpadulo et al., Reference Dalpadulo, Pini and Leali2020; Wiberg et al., Reference Wiberg and Persson2019) and dedicated development processes to address specific AM-related aspects such as minimization of support structures (e.g. Diegel et al., Reference Diegel, Schutte, Ferreira and Chan2020). In addition to academic literature, the ISO ASTM 52910 (2022) industry standard offers a general design strategy that illustrates the development of an optimized AM component as a step-by-step process model as well as descriptions for the included process elements such as the identification of general AM potential or DfAM methods like function integration for example. The process model presented in ISO ASTM 52910 (2022) can also be interpreted as a multi-phase product development process that maps the path of a component starting from defining the task, through the design phases, to its detailed documentation. This model, however, is thematically oriented towards mechanical, structural and shape optimization of AM components, which does not cover all industrial use cases of AM. For this reason, a more generic model (Fig. 1) based on the ISO ASTM 52910 (2022) is used as the theoretical basis for the present study, as explained in Chapter 3.2. This work aims at clarifying which themes should be addressed by development frameworks for AM to provide companies with an approach to efficient product development for AM. The following research question thus needs to be answered: What challenges should a development framework for additive manufacturing address to support efficient product development?
Figure 1. A product development process for AM at phase level based on ISO ASTM 52910 (2022)
This work provides a thematic scope for the development and implementation of AM-specific product development processes in industrial applications and is therefore based on current issues AM stakeholders face in industrial practice.
3. Methodology
Semi-structured guided interviews were used as the method for the interview study on which this article is based. The systematic development of the interview guide was carried out according to the five-phase framework by Kallio et al. (Reference Kallio, Pietilä, Johnson and Kangasniemi2016) and the transcribed interviews were subjected to thematic analysis following Braun and Clarke (Reference Braun and Clarke2006). To ensure transparency and reliability, a detailed description of the research methodology is provided in the following chapters, from the determination of the applicability of semi-structured interviews in Phase I to the presentation of the complete interview guide in Phase V.
3.1. Phase I - applicability
The prerequisite for the appropriate applicability of semi-structured interviews is given insofar as the study placed particular emphasis on depicting different perspectives of stakeholders in additive manufacturing across the industry. Due to the variety of the participants job profiles, different areas of interest within the product development processes for additively manufactured components exist. Therefore it is necessary to ask individual follow-up questions as the participants’ perception and understanding of the topic varies - for which semi-structured interviews are particularly suitable (Reference Adams, Newcomer, Hatry and WholeyAdams, 2015).
3.2. Phase II - theoretical context
To accommodate a wide range of use cases in addition to part optimization, the process step representation of the design strategy from ISO ASTM 52910 (2022) is generalized to phase level in accordance with generic phase models. The resulting model (Figure 1) thus represents a development process, albeit with the inclusion of four elements that are specific for additively manufactured products and derived based on the ISO ASTM 52910 (2022), namely the Assessment of Additive Manufacturing Potential, the Additive Manufacturing Process Selection, an AM-related Decision Process and Design for Additive Manufacturing. These four elements represent the AM-specific share of a generic development process for AM and are therefore used to structure the proposed thematic scope. The coding guide used for the analysis of the interviews aims to assign interview passages to the corresponding phases of this development process. The use of an industry standard for structuring the results follows the argument of Günther and Koch (Reference Günther and Koch2024) that DfAM methodology should be based on uniform sources of knowledge to avoid contributing to further fragmentation of this research field.
3.3. Phase III and IV - pre-tests and iterations
The preliminary interview guideline formulated in Phase III was subjected to collaborative pilot testing by both research institutes. As the scope of this publication is limited, only the finalized interview guide following the pilot tests is presented in Phase V.
3.4. Phase V final interview guide
The final interview guide containing 10 questions is presented Table 1. All questions are open-ended and allow individual aspects to be explored in greater depth through follow-up questions. The follow-up questions are not included in the interview guide. Before the interview, the participants are given a brief introduction on product development theory and the industrial standard ISO ASTM 52910 (2022).
Table 1. Interview guide for the semi-structured interviews
3.5. Interview analysis
The analysis of the transcribed interviews was based on both qualitative content analysis (Reference Mayring, Fenzl, Baur and BlasiusMayring & Fenzl, 2019) and thematic analysis (Reference Braun and ClarkeBraun & Clarke, 2006). A deductive coding guide was used to assign interview passages to the corresponding development phases. Drawing from Braun and Clarke’s (Reference Braun and Clarke2006) thematic analysis method, further codes are derived inductively from the interview material, which are used to form, compare and summarize overarching thematic concepts into themes, that are presented in Chapter 4. Since the themes that were formed are linked to the text passages coded along the development phases, they can also be assigned to the corresponding development phases. This procedure is shown in Figure 2 using an example. The resulting framework thus displays the results of the thematic analysis (i.e., the themes) mapped by development phases.
Figure 2. Analysis procedure. Interview excerpts are assigned to development phases following a coding guide. Emerging themes are also mapped onto the development phases and arranged according to the frequency of their occurrence within the four development phases
3.6. Participant characteristics
The interview participants are engineers (4 process engineers or specialists for AM, 3 development engineers, 4 head engineers or technical managers) with levels of professional experience with AM ranging from 1 to 34 years (median, 4 years), from 11 different companies (3 automotive, 2 manufacturing service providers, 2 aerospace, 4 mechanical engineering). Broken down by company size, one company has less than 100 employees, two between 101 and 500, one between 501 and 1000, two between 1001 and 3000, one between 3001 and 10,000, three between 10,001 and 20,000 and one over 20,000. All data collected during the interviews is presented anonymously.
4. Themes
This chapter presents the results of the thematic analysis, i.e. the themes. In Figure 3, the themes are assigned to the relevant development phases according to the procedure described in Chapter 3.5. Since the focus of the thematic analysis is on identifying challenges, the terms theme and challenge are used interchangeably. The themes are described and supplemented with illustrative quotations below.
Figure 3. Distribution of the identified themes along the four phases of the product development process for additively manufactured products. The vertical arrangement reflects whether a theme concerns a particular phase or several phases
Inefficient Utilization of available Resources
This theme includes text passages which address how a lack of or a late utilization of available resources, in this case mainly employees, leads to inefficiencies within the four process elements considered. Situations were described in which the AM experts did not have the opportunity to provide their input, which can lead to inefficient processes of potential assessment, process selection, decision-making for or against AM, as well as the actual design of components. This is attributed to time pressure in product development projects, which, for example, tempts design engineers to rush into design without consulting AM process engineers:
“But the biggest factor that comes into play again and again is the timeline that colleagues are exposed to, mostly, actually always too short, which is why they simply design something. We are not consulted, we are only consulted when the part is actually to be printed (…) where we then say, we’re sorry, we can’t print it like that (…).” (Process Engineer AM)
In this context, process engineers also point out the importance of being involved in the design process as early as possible, since otherwise potential for AM development can already be lost at early stages.
“If we have not tackled the issue and have not set the right tone to encourage them to lead the corresponding designs in an additive direction in the first place, this will not happen.” (Process Engineer AM)
Furthermore, situations were described in which the lack of or unclear responsibilities within development processes made it difficult to involve the relevant key employees, as the following two quotations in the context of decision-making and process selection respectively show:
“This [decision to design a part for AM] is actually almost always decided at a point at which we, as a specialist department, cannot intervene directly because, in most cases, from our experience, it is a mental leap or a small, individual, lost thought that the designer has at his desk before he starts designing.” (Process Engineer AM)
“We purchased a few [printers] in our department, and somehow, they fell to me. Others bought them, but then they just stood around forever and I didn’t think it made sense, so I inherited them. I’m not saying that they fell from the sky, but I wasn’t involved in the process.” (Process Specialist AM)
Fostering Additive Mindset
The topic of conventional versus additive mindset, especially in relation to design, has been discussed since the industrialization of AM (e.g. Abdelall et al., Reference Abdelall, Frank and Stone2018; Blösch-Paidosh & Shea, Reference Blösch-Paidosh and Shea2022) and, has been frequently addressed in the interviews. For example, participants articulated that many design engineers “approach additive components in the same way as [conventional] components”, which leads to “possibilities [being] not fully exploited” and therefore inhibiting the development of an understanding for problems that would favour an additive solution. Consideration should also be given to the following statement by a process engineer, who describes how identifying problems for which an AM solution is appropriate represents the biggest challenge for his company:
“3D printing (…) only works economically when a (…) real problem, is solved with it and not just to print a component that used to be manufactured conventionally. The biggest challenge is (…) the understanding of when a problem can be solved with 3D printing, that is the biggest challenge.” (Process Engineer AM)
In product development, problem solving is intrinsically linked to early development phases, where solution principles are defined. For this reason, companies are trying to foster an additive mindset and thus support the finding of AM-compatible solutions in early development phases, i.e. when new products are being developed.
Realizing AM Value Potential
The coded text passages assigned to this theme describe new products that meet the definition of a new development in the sense of a design that went through the design phases conception, drafting and elaboration (Reference Ehrlenspiel and MeerkammEhrlenspiel & Meerkamm, 2017). Participants were generally convinced that newly developed products for AM provide the greatest added value. In contrast to this, conventional products, for which the manufacturing process is changed to AM either without or with only minor adjustments to the design are believed to be at least non-economical if not infeasible. However, new developments for AM are also associated with risks that could deter companies from investing in manufacturing equipment to solely produce products developed for AM.
“And then we have real added value, but then it is also a completely newly developed product.” (Process Engineer AM)
“So new developments naturally have the greatest potential in the sense that you can really design the part from scratch. However, I also see the effort as being the greatest. That means the risk is also the greatest.” (Development Engineer AM)
Hesitation towards metal-based AM
During the interviews, a clear hesitation towards metal-based AM was observed. This hesitation was articulated directly, but also indirectly through the attitude of some interview participants towards polymer AM, which was significantly more positive compared to metal AM. The aspects addressed as problematic in the context of metal AM included material properties and complex post-processing, but also aspects of the development methodology itself. These methodological aspects range from the inability to identify suitable applications in their own company to the belief that a viable application of metal AM requires a completely new development process, as described by the following quotations:
“We have been trying for several years to produce components for our [product] using metal processes. (…) So far, we have not found a component where we can use metal printing that really makes sense.” (Head Engineer AM)
“But if we were to go about it naturally and provide complex structures from the very beginning of the design, then we could actually print cooling channels and so on in the structure, then 3D printed parts can also be profitable for metal printing parts. But that is really a completely new development process, which we are not yet familiar with, it has to be said quite clearly, we are still at the beginning.” (Head Engineer AM)
Uninformed Decision-Making
It has been shown that the decision-making processes involved in product development for AM are more complex than for conventional manufacturing and require special consideration of new information flows (Reference Hajali, Mallalieu, Brahma, Panarotto, Isaksson, Stålberg and MalmqvistHajali et al., 2023). This study found that such decisions, for example, whether a component should be manufactured additively, are often made uninformed and based on naive assumptions. This theme shares parallels with the additive mindset, which manifests itself, for example, in decisions that are justified with phrases “like yeah, we don’t do it that way”. The following quote also shows how, from the perspective of a technology service provider, most customers arrive at the decision to have components additively manufactured not so much methodically but rather opportunistically.
“[Referencing the design strategy from ISO ASTM 52910] (…) only two of our customers actually follow it, and they use the possibilities of design freedom and component integration and more. But at the moment, only two of our customers actually do that. All the others follow the path of, we’ve heard that’s trendy, we’ve heard that you have to have it, and we want that now.” (Technical Management)
Illusory Expectations towards AM
Unrealistic expectations regarding the capabilities of additive manufacturing can lead to problems both within companies and in the collaboration between manufacturing service providers and customers. For example, AM process engineers receive components that are not suitable for AM from designers who, due to the assumed shape complexity capabilities, expect that AM can produce virtually anything. Although the achievable shape complexity with AM undoubtedly exceeds that of conventional manufacturing, understanding what AM-compatible structures are is often counterintuitive for designers without AM expertise. This can lead to AM being dismissed as a manufacturing option, as described in the following situation:
“We are confronted with this exact situation where we are given [a part] that we are supposed to print exactly as it is […] and we then say that we’re sorry, we can’t print it like that, it won’t even come out close to the dimensions from any machine we have available here. And then there isn’t any understanding and that’s the end of it.” (Process Engineer)
Lack of Tools
Companies are currently facing a changing tool landscape in the context of development processes for digital manufacturing technologies such as AM. In this study, a lack of tool support in the evaluation and selection of many possible constructive solutions for AM was emphasized.
“(…) the variety of solutions that can arise from [Design for AM] are very high and this is what’s fundamental for 3D printing. [Appropriate tools are] exactly what we often lack.” (Process Engineer)
Furthermore, the demand for computer aided design (CAD) tools that also help designers with little AM experience in the design process according to additive principles was expressed.
“We would like the CAD system to also support these older senior designers, because we can’t wait for the next generation, my children, who have absorbed additive manufacturing with their mother’s milk.” (Technical Management)
Optimization of AM Solutions
Some of the interview partners believe that the optimization of components, whether through bionic structures or functional integration for example, is a prerequisite for a viable application of AM. Stakeholders may find this perspective confirmed by the ISO ASTM 52910 (2022), in which the result of a general design strategy for AM is a component optimized for AM. However, it was also stated that in industrial practice, most AM applications are not optimally designed for AM, yet they may still be profitable.
“However, we also say “this is not an optimal AM design, but it can be done”. We have maybe 20-25 percent of the parts that have an actual AM design.” (Head Engineer)
Unclear Timing of Decision
The study found that the development processes described by the participants differ in terms of the point at which the decision is made as to whether a component will be designed for AM and whether the component will then also be used in (or as) the final product. The tendency to have several decision points in the development process is also reflected in the process described in ISO ASTM 52910 (2022). However, it is also described that in practice it is “difficult to say at what point you really say whether you are manufacturing it additively”, implying uncertainty regarding the timing of these decisions.
“Whether a component is actually used can always be decided during development. If you realize that it doesn’t work, you can switch back to the conventional option, or you can do so at the very end if you realize that it is becoming too expensive.” (Process Specialist AM)
Desire for simple Processes
Participants expressed interest in development and in particular decision-making processes that (allegedly) support the high iteration capability of AM technologies by keeping processes leading up to manufacturing short and the number of decision-makers involved low. The following situation, for example, describes how a company deliberately does not have a decision-making process for deciding whether a component should be additively manufactured and instead prefers to simply print on a trial basis.
“We haven’t set up a process here because we’re trying to keep it as low level as possible, few processes, few decision-makers, but rather, the colleague comes, hey, can you print this for me, and we print it – done.” (Process Engineer)
Figure 4 shows the solution approaches mentioned in the interviews for the issues identified along the development phases. Note that individual approaches may have been mentioned by several of the respondents. A breakdown has been omitted in order not to imply any value judgement of the approaches.
Figure 4. Approaches to solving the identified challenges as articulated by the interviewees
5. Discussion
As can be seen in Figure 3, some of the challenges in product development processes for additively manufactured components have implications for several development phases. Therefore, it is critical for companies to understand that certain challenges should be addressed holistically across different phases within their development processes, and that different solutions are needed depending on the phase (see Figure 4 for solutions already being pursued by the surveyed companies). This applies in particular to the challenges “Fostering of Additive Mindset”, the “Hesitation towards metal-based AM” as well as the “Inefficient Utilization of available Resources”, as these affect all four phases of the development process (see Figure 3). Although the companies surveyed are mostly aware of the challenges, operational solutions are lacking for fundamental challenges within product development, such as deciding when a “real problem is solved” by developing a product for AM. Implemented solutions with operational character have been found to mainly address the challenge of fostering an additive mindset within the workforce. Process engineers for AM tend to see themselves as “service providers” for the development department, whose task is not “to actively design the components [to be manufactured]”, but to support the designers by taking preventive measures such as training and developing design guidelines for AM. One process engineer described how documenting positive examples of AM applications and “feeding this information back to the designers in the form of a best practice newsletter” has proven to be the most beneficial measure to foster an additive mindset amongst the designers. The study’s data also revealed a particular need for action in decision-making, since all the identified challenges are related to the decision-making process (see Figure 3). Of all the process elements examined, decision-making has been found to be noticeably unmethodically implemented by the companies surveyed. This can, for example, be seen from quotations on the theme of “Inefficient Utilization of available Resources”. The situation described in Chapter 4 does not reflect a methodical decision-making process, but rather an unmethodical process started by a “small, individual, lost thought [of] the designer” by only one decision-maker, isolated from other employees “at his desk”. Additional evidence is provided by the fact that the theme “Desire for simple Processes” only occurred in the decision-making phase of the development process (see Figure 3). This circumstance can be attributed to the observation that companies which operate low-threshold polymer AM tend to prefer to exploit the rapid iteration capability (“we put relatively little effort into [decision-making], because often we simply print the parts, test them, print again, and test again”) given the relative ease of usability before investing too much effort in a decision-making process as to whether a component should be additively manufactured. However, we argue that once such opportunistic decision-making regarding the use of AM has been entrenched in a company, it could cause issues in terms of expanding capacities to metal printing, since the increased effort involved in handling the material and the more complex post-processing mean, that ease of use is no longer given. A latent and possibly causal connection may be postulated between this issue and the observed hesitation towards metal AM. Many companies start their AM journey with polymer systems that allow for relatively low-threshold use “if it is acceptable that the part is made of plastic, my first thought is whether the part can be printed” (Process Engineer AM). This allows them to accumulate technology-related expertise but does not necessarily promote the implementation of a development methodology for AM products, since their applications are usually not final parts or products (direct manufacturing). The lack of development methodology becomes evident as companies seek to expand their AM capacities to include metal AM and are for example no longer able “to find a component where [they] can use metal printing that really makes sense” (Head Engineer), preventing them from benefitting from their existing know-how. This study found that most of the companies surveyed have significant know-how on AM, but based on the limited decision-making ability discussed here, a comparatively underdeveloped know-why ability is apparent. Development frameworks for AM should therefore place particular emphasis on supporting the informed decision-making of all stakeholders involved, based on their existing know-how. To conclude, the following statements are made to answer the proposed research question. A development framework to support companies in the efficient development of products for additive manufacturing should:
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Acknowledge the phase specificity of challenges and solutions as context and stakeholders change over development phases. Companies need support in identifying relevant stakeholders along their development process and incorporating them into problem solving.
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Incorporate operational solutions . Some articulated solutions (Figure 4) are too high-level to support efficient AM operational development processes, such as the approach of developing new products for AM to exploit its full potential. Although the idea behind the approach is sound, the solution itself is considered a challenge by the participants. By contrast, the solutions for fostering an additive mindset among the workforce are more operational and should serve as a guide for mitigating the other challenges.
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Acknowledge the importance of informed decision-making by all stakeholders. To support the extension of prototyping applications to final products, which often equates to an extension to metal printing, the ability to make informed decisions (know-why) at every step of the development process is a prerequisite for efficient product development for AM.
6. Conclusion and further research
The aim of this study was to identify and contribute to the understanding of unresolved challenges in the development of products for additive manufacturing. By mapping these challenges to AM-specific development phases, a thematic scope for development frameworks for additively manufactured products is presented. The key finding of this study is that AM stakeholders in industry are less concerned with a lack of know-how with AM applications than with a lack of know-why, i.e. decision-making ability within product development. Since the thematic scope for AM development frameworks was jointly defined with industry stakeholders in this work, the next study will focus on completing the phase-specific solution approaches and evaluating them for specific development cases.
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