## 4 Results
### Technical Feasibility  
The greatest technical concerns according to Table 2 were that the number of commercially and readily available materials for AM was low (3.31 out of 5), the accuracy levels and tolerances could not be fulfilled (3.2 out of 5), and the AM build chamber volume (3 out of 5) was too small. [PERSON] and [PERSON] indicate that the null hypothesis is not fulfilled (results are not normally distributed). The Mann-Whitney testing (Appendix A, Figure A1) points out that the limited 3D-printing build chamber volume is a significantly larger challenge for large (\(p\) = 0.044, mean 3.67) and medium-sized (\(p\) = 0.047, mean 3.71) companies than for micro companies (mean 2.53). Another observation is related to the IT system needed to realize the DSP concept: Large companies (\(p\) = 0.019, mean 3.38) consider this aspect to be a greater challenge than very large companies (mean 1.5). An explanation for these results could arise from the demand from large- and medium-sized companies for larger components and higher batch sizes in general. Costs per part are decreasing by fitting as many parts as possible into a single print. Thus, enlarged build chambers are advantageous, if a company produces large numbers of components. Moreover, very large companies do not seem to be troubled by the IT-system related obstacles of the realization of the DSP concept, because larger and better equipped IT resources could be available. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Technical Barrier** & **Mean** & **CI** & **Median** & **SD** & **SW (BD)** & **SW (Number)** & \(\chi^{2}\) (GD)** & \(\chi^{2}\) (**Number** \\  & & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\ \hline  & & & & & & & & \\  &  
To analyze if the concern regarding the low number of commercially usable materials in AM can be confirmed, results of Question 12 (Appendix A, Table A1) are shown in Figure 2. Participants were asked to rank (1 to 5) applied spare part materials in descending order. The material rank is inverted and normalized, determining weighting factors for all ranks (rank 1: 0.438; rank 2: 0.219; rank 3: 0.146; rank 4: 0.110; rank 5: 0.088). Consequently, materials are grouped in categories and their absolute shares (%) are calculated. According to Figure 2, 49% of applied spare part materials are classified as metallic materials and 51% as non-metallic materials. Most metal materials belong to the group of ferrous materials (32%), a smaller share (17%), is listed as non-ferrous metallic materials. Ferrous materials were further divided into steels (25%) and cast irons (7%). Non-metallic materials are mainly represented by organic plastics (49%), especially by polyamides. SS316L (16%), ASi10 Mg (6%), PA6 (13%), PAxx (8%), and ABS (7%) describe single materials with the largest share used as spare part materials. The \"xx\" or \"xxx\" in addition to the material name indicates that the specific material type is not mentioned (e.g., PAxx or Sxxx) and hence not considered to be commercially 3D printable. The share of applied metals and plastics is distributed almost evenly (49% versus 51%) and steels and plastics represent the main subgroups. Regarding the printability of materials mentioned in Figure 2, the following aspects need to be considered:  
* The majority of listed materials are available as 3D printing materials (i.e., for SS316L, AlSi10 Mg, Ti, PLA, etc. ), but not necessarily offered by 3D printing service providers. * Some materials can directly be traced back to materials of 3D printing service suppliers (PA2200, PA3200 GF, Visijet SL Impact, and Ultem 9085), representing a share of 5%. * The euivalent in 3D printing can differ slightly from the original material (e.g., ABS-like resins in Stereolithography), which often results in modified and/or inferior material properties. * Cast irons (e.g., EN-GJS-500), special alloys (e.g., Al 7075-T6), specific plastics (e.g., Teflon), and inorganic materials such as glass-fibers are not available as materials for 3D printing.