Comparison of 3D Printout Quality from FDM and MSLA Technology in Unit Production

Abstract

The paper presents research on the comparison of printouts from two different additive technologies: FDM and MSLA. Two printers were from the same producer. The paper describes the successive steps of the research and the final results. The study was carried out to determine the strengths and weaknesses of the FDM and MSLA technologies, as well as their suitability for use in unit and hobby production. The research consists of the following steps: conceptualization and design of 3D models (in Autodesk Fusion 360 2.0.12670 software), development of the survey questionnaire, expert selection, setting the printing parameters for two printers, printing process, evaluation of the printouts, and finally calculating and analyzing surveys results. The authors designed eight models; therefore, they get sixteen printouts that were the subject of comparison for experts. All cube-based models were symmetric about point, axis, and plane. The research included ten experts who were chosen on the basis of specific criteria. The research was referring to unit production. The symmetrical layout of each model on the 3D printer worktable was to verify the operation of the nozzle of this machine in relation to all axes. Moreover, the symmetry of the models made it possible to check the quality of the printouts on each side in three planes. The sum of all collected data from the surveys was 2400.

1. Introduction

According to the broader technology radar [1], five key technologies stand out due to their wide applications and impact in many countries, industries, and value chain steps. These five technologies—the Internet of Things (IoT), 3D printing, artificial intelligence (AI), wearables, and advanced robotics—have increased competition within production systems. They force companies to reorganize their work and attitude. Disruptive technologies [1], such as 3D printing, robotics, and augmented reality, have captured the imagination with groundbreaking applications demonstrated in all sectors. However, the level of application and development of these technologies depend on the given country, its economy, the development of technology, and the general standard of living in a given country and region. Some of the technologies, such as 3D printing and advanced robotics, have a long industrial history and are about to become mainstream adoption [1]. Other items such as artificial intelligence and wearables are in an initial stage but are very promising. Virtual reality also has great potential to become more useful and practically applied [2].

3D printing, also referred to as additive manufacturing, is a process of making three-dimensional solid objects from a digital file. The creation of a 3D printed object is achieved using additive processes. In an additive process, an object is created by laying down successive layers of material until the object is created. Each of these layers can be seen as a thinly sliced cross section of the object. The manufacturing process begins with a 3D model, usually created by computer-aided design (CAD) software [3]. To obtain models, it is also possible to scan an existing artifact into program [4]. Specialized software slices the model into cross-sectional layers, creating a file that is sent to the 3D printer. Then, the printer creates the object by forming each layer by selectively placing the material [3]. Various materials can be used for 3-D printing. They include ABS (Acrylonitrile butadiene styene) plastic, PLA (Polylactic acid), glass filled polyamide, polyamide, stereo lithography materials, steel, silver, titanium, photopolymers, wax, and polycarbonate [4]. In the reference to input materials for 3D printers, the topic is potentially endless. In other words, the range of materials is constantly expanding. There are 3D printing technologies for chocolate printouts [5,6,7]. The chocolate 3D printing is similar to pushing chocolate through a syringe by a chef. Its advantage over the manual process is repeatability and accuracy in precision of detailing. It is possible to get any shape that the recipient wants [7]. Other original input materials are sand [8,9], sugar [10,11], food gum [12], concrete [13,14], and many more. Moreover, there have been studies conducted on other flexible, stretchable, and lightweight soft 3D printed objects [15]. Initially, additive manufacturing was referred to as rapid prototyping [3]. Applications for additive manufacturing processes are being improved [16]. It should also be emphasized that with the increasing availability of 3D printers and design programs, the issues of copyright protection within this area become vital [17]. 3D printers are used for professional purposes, e.g., medicine, modeling, as well as for domestic purposes by individual users.

The main goal of the research presented in this paper was to compare 3D printouts from FDM (Fused Deposition Modeling) and MSLA (Masked Stereolithography) 3D printing technologies. Based on the analyzed literature [18,19,20,21,22,23,24,25,26], a research gap was found, which inspired the authors to conduct the research. The research gap can be described as a lack of direct comparison between the printouts from the FDM and Masked SLA 3D printing technologies in order to determine their strengths and weaknesses, as well as suitability for use in unit and hobby production.

The research refers to unit production. These printers are often used for unit–element production in the home environment. To realize the goal, the authors conceptualized and designed eight different 3D cube-based models, which were the objects of analysis (16 printouts). The scope of the research was also the included development of the survey questionnaire, which included criteria on the comparison and selection of experts who evaluated the printouts. The important part of the study was the printing process and the setting of the printing parameters for two printers. After evaluation, the final stage was the calculation and analysis of the results for the surveys. In the study, the following research question was asked: Q1: “Which of the following 3D printing technologies: FDM or MSLA, is more suitable for unit production in terms of printout quality”? The paper is divided into five sections. Section 2 describes the Materials and Methods. Section 3 presents the Results of the research. Section 4 includes a Discussion and Section 5 ends the paper with Conclusions.

2. Materials and Methods

2.1. Materials

2.1.1. Models Designing

The conducted research concerns the issue of FDM and MSLA 3D printing technologies. The authors presented successive steps of the research that aimed at comparing printouts of two 3D printing technologies. Those technologies were applied in the unit production. The models were designed in the Autodesk Fusion 360 software. Fusion 360 is a cloud-based 3D, CAD, CAM, and PCB modeling software platform for product design and manufacturing [27]. As part of the research, eight cube-based models were designed. The models differed slightly from each other. The differences were as follows:

• Wall filling;
• Patterns on the walls;
• Surface roughness;
• The sharpness of edges;
• The sharpness of corners;
• Additional irregular tabs (that were possible to print without supports in the case of FDM technology);
• Weight.

The common feature for all models was symmetry about point, axis, and plane.

2.1.2. 3D Printing Technologies, Materials and Parameters

In the research, two 3D printing technologies were used. The first was FDM (Fusion Deposition Modeling). The FDM technology is based on the deposition of molten material. It consists of the alternate application of the model and support material through the nozzle embedded in the printing head according to the following cross sections of the designed model [28,29]. The most frequently used basic materials in FDM technology are the following polymers: ABS (acrylonitrile–butadiene–styrene), PLA (polylactide acid), and PET-G (polyethylene terephthalate) [30,31,32]. The other technology that was used in the conducted research is MSLA (Masked Stereolithography). This technology uses light to cross-link chemical monomers and oligomers. The result of this process is the formation of polymers that form a three-dimensional body [33]. The most commonly used material by this technology are mixtures called “resins” [34]. They are thermosetting polymers [35]. The printer used for the purpose of the article uses MSLA. technology with an LCD panel.

The models in this article were printed from PLA (FDM technology) filament and UV light-hardened polymer resin (MSLA technology). The diameter of the filament used in FDM technology was 1.75 mm. The filament was manufactured by DevilDesign [36]. The

Table 1. Filament parameters.

Parameter	Value
Diameter of filament	1.75 mm/2.85 mm
Dimensional tolerance of filament	±0.05 mm
Roundness of filament	±0.02 mm
Surface of the material	Gloss
Shrinkage of the material	Very low
Product weight	1.0 kg net, 1.36 kg gross
Spool material	Transparent polycarbonate
Packaging	Printed cardboard
Package size	~205 × 205 × 80 mm
Vacuum packaging	Yes
Moisture absorber	Yes
Hotend suggested temperature	200–235 °C
Build plate suggested temperature	50–60 °C
Recommendation of cooling the printout	Recommended
Density	1.24 g/cm3
Elongation at Break	160%
Spencer impact	2.5 joules
Softening temperature	~50 °C

Source: [36].

contains information on the technical parameters of the filament. This specification was taken from the PLA filament product card, which is available on the manufacturer’s website [36] (Table 1).

After designing and rendering each model, the slicer parameters were set. The key print settings for an FDM printer are presented below (

Table 2. Key printing parameters for FDM printing technology [authors’ own study].

Parameter	Value
Layer height	0.1 mm
Wall thickness	0.8 mm
Wall line count	2
Top and bottom thickness	0.8 mm
Top layers	8
Bottom Layers	8
Infill density	20%
Infill pattern	Grid
Printing temperature	200 °C
Build plate temperature	60 °C
Print speed	40 mm/s
Retraction	Enabled
Fan Speed	100%
Supports	No supports
Build plate adhesion type	Skirt

Source: Authors’ own work based on parameters available in CURA 4.13.1 (The Nederlands).

).

The print parameters in FDM technology, and in particular, the layer thickness, have been selected to enable direct comparison of the quality of the printouts made with the use of both technologies. It is known that MSLA technology is characterized by a much higher “resolution” of a printout due to the thickness of the layers reaching 150 microns [37]. Hence, the layer thickness of the FDM printouts is relatively small. The same process was carried out with the preparation of printouts for the MSLA printer. Photon Workshop software version 2.1.21 was used as a slicer.

Table 3. Key printing parameters for MSLA printing technology [authors’ own study].

Parameter	Value
Layer thickness	0.050 mm
Normal exposure time	8 s
Off time	1 s
Bottom exposure time	60 s
Bottom layers	3
Z lift distance	6 mm
Z lift speed	3 mm/s
Z retract speed	3 mm/s
Anti-alias	8
LCD screen resolution	1440 × 2560 pixels
XY-Pixel size	47.250 μm
X size	65 mm
Y size	115 mm
Z size	165 mm
Supports	Yes

Source: Authors’ own work based on parameters available in Photon Workshop software version 2.1.21.

shows the parameters for MSLA printing technology.

For the purpose of the study, a 3D printer using the LCD screen was used. The parameters of the printer from the manufacturer’s website [38] used for the experiment are presented below (

Table 4. Parameters of resin 3D printer used for the study.

Parameter	Value
Printing Technology	LCD-based SLA 3D Printer
Light-source	UV integrated light wavelength 405 nm
XY DPI	47 um (2560 × 1440)
Y axis resolution	1.25 um
Layer resolution	25~100 um
Printing speed	20 mm/h
Rated Power	50 W
Printer size: 230 mm × 200 mm × 400 mm	Printer size: 230 mm × 200 mm × 400 mm
Printing volume	115 mm × 65 mm × 165 mm (4.52″ × 2.56″ × 6.1″)
Printing material	405 nm photosensitive resin
Connectivity	USB Port

Source: [38].

).

2.2. Methods

2.2.1. Survey Questionnaire

As part of the experiment, a survey questionnaire was designed to assess the quality of printouts manufactured with FDM and MSLA 3D printing technology. The questionnaire included 15 criteria for evaluation. The criteria referred to the quality of the printout itself and the whole process, which was also partially observed by the experts. The experts provided answers on a five-point Likert scale, where 1 meant poor quality and 5 meant very good quality.

Table 5. Criteria for the evaluation of the printouts [authors’ own study].

Number of Criterion	Criteria for Evaluation of the Printouts	Scale
1.	The accuracy of surface	1–5
2.	The accuracy of grooves	1–5
3.	The accuracy of overhangs (that are possible to print without supports)	1–5
4.	The accuracy of edges	1–5
5.	Smoothness of surfaces	1–5
6.	Lack of visible flaws	1–5
7.	Lack of cracks	1–5
8.	Lack of melting	1–5
9.	Lack of rolled up layers	1–5
10.	Lack of delamination	1–5
11.	Lack of visible gaps between layers	1–5
12.	Lack of dents or gouges on the surface with a slight overhang	1–5
13.	Assessment of the noise of a working printer	1–5
14.	Assessment of the nuisance of the smell emitted by the printer	1–5
15.	Lack of visible asymmetry of the printout	1–5

Source: Authors’ own work.

presents the criteria for the evaluation of the printouts.

2.2.2. Experts’ Selection

To provide the evaluation of the printed elements, it was necessary to choose a group of experts who had special competences, experience, or knowledge on the topic of 3D printing technology, or who had other necessary features to be considered as an expert for the given research. At the same time, the experts were representatives from different fields. The characteristics of the experts were the following:

• Two people—graphic designers, who designed 3D models in programs such as CAD, Inventor, Fusion 360;
• Two people—businessmen who ran small companies on 3D printing;
• Two people—doctors in production engineering, conducting research on 3D printing technology;
• Two people—clients of a 3D element printing company;
• Two people—who were not in any of the above categories.

In summary, the group of experts consisted of 10 people. Experts were present during the printing process, because the survey had also part referred to evaluation of some issues of the printing process itself. The selection of experts was motivated by the fact that this research refers to the usage of 3D printing technologies by unit production manufacturers, graphic designers, and to customers using their services and products, as well as by hobbyists and amateurs of 3D printing. This allows for reflection on the realities of using FDM and MSLA technologies by people who use them in the unit production process. The surveys were carried out using paper questionnaires. Each expert received the questionnaire individually and the experts did not communicate with each other to avoid biased research results.

The method that was used in the research was the Delphi method. The Delphi method belongs to the group of heuristic methods that use the knowledge, experience, and opinions of experts in a given field to make a decision. The results are obtained after conducting surveys. Then, for the results obtained, the appropriate calculation procedures should be applied [39]. The Delphi method has been shown to be suitable and effective in forecasting technology trends [40]. The success of this method is based on the competences of the experts and their commitment to research [41].

2.2.3. Unit Production

The research refers to unit production. 3D printing technology as an example of additive manufacturing technology is usually used for a small series or unit production. The nature of 3D printing technology does not allow for bench, mass, or continuous production. It is used for individual and original printouts. An example of wide usage is printing objects for medicine, which is mainly due to the increasing demand for custom-tailored and patient-specific medical products [42].

Unit production is characterized by manufacturing one or a few quantities of products designed and produced according to the customer’s specification. The distinguishing feature for this type of production is the low volume and high variety of products. Unit demands unique technological requirements, processing on machines in a certain sequence. This type of production can be characterized by the following [43,44]:

• High variety of products and low volume;
• Individualization of products;
• Use of general-purpose machines and facilities;
• Highly skilled operators;
• Large inventory of materials, tools, and parts;
• Variability of material demands;
• Detailed planning;
• High diversity of technological operations;
• High diversity of production times for a unit;
• Often retooling;
• An important role of customer service and management.

3D printing technology is used to meet individual needs and has excellent practical application. 3D printers have become more common and affordable for use by individuals. Users can use 3D printing technology for printing any objects they need. In the case of missing some element, the user can print it. Will 3D printers be as popular as regular printers? The increasing interest in 3D printing technology inspired authors of [45] to carry out research determining whether FDM or MSLA 3D printing technologies were more suitable for unit production.

2.2.4. Methodology

Summing up the information above, the research consisted of the main seven stages. They are presented in Figure 1. The first stage was conceptualization and design of 3D models. The authors designed eight different cube-based models. The models were designed in the Autodesk Fusion 360 software. Then, the important part of the research was the development of the survey questionnaire. The next stage was the selection of experts. Subsequently, the printing parameters were set for two types, from a 3D printer for the same producer to start printing in the next step. The final stage was the evaluation of the printouts. The research was conducted in the first quarter of 2022.

3. Results

3.1. Models Designing Effects and Printing Preparation

The effects of the first stage of the research were eight 3D cube-based models, designed in Autodesk Fusion 360 software. Figure 2 presents the designed eight different models. The eight models differed slightly from each other. The common feature for all of the models was symmetry. All cube-based models were symmetric about point, axis, and plane.

The symmetric layout for each model on the 3D printer worktable was to verify the operation of the nozzle of this machine in relation to all axes (Figure 3). Moreover, the symmetry of the models made it possible to check the quality of printouts on each side in three planes. In addition, all models were 50 mm × 50 mm × 50 mm.

The figures below (Figure 4 and Figure 5) show the placement of two of the eight designed models in the slicing software. The size of the models, which was 50 mm × 50 mm × 50 mm, was chosen because of the dimensions of the MSLA printer build plate. Models for the FDM and MSLA technology were printed in the same sizes.

3.2. Printouts

The designed objects were successively printed separately. Eight objects were printed using FDM 3D printing technology, and another eight objects—using MSLA 3D printing technology. The average printing time for printouts for FDM technology was 9.0 h, while it was 4.6 h for MSLA technology.

Table 6. Printing times for each printout [authors’ own study].

Number of a Model	FDM	MSLA
1	524	275
2	314	275
3	459	275
4	602	275
5	542	275
6	490	275
7	977	275
8	414	275
Sum (minutes)	4322	2200
Averages (minutes)	540	275
Sum (hours)	72.0	36.7
Averages (hours)	9.0	4.6

Source: Authors’ own work.

shows the printing times for each printout.

During the printing process, there were no issues such as filament jams, objects falling off, or detaching of the printed objects from the build plate. For the MSLA printing process, it was necessary to carry out additional activities aimed at cleaning the printouts and hardening the resin from which the models were made. The time for these activities was not included in the printing times for individual objects in the study. The printouts were cleaned with concentrated alcohol. For this purpose, technical isopropanol was used. To harden the printouts, ultraviolet light-emitting diodes were used. Figure 6 shows the process of rinsing and hardening the objects. The origin of the presented equipment can be found in [38]. Figure 7 shows the first pair of printouts ready for evaluation by exerts.

3.3. Results and Analysis of Printouts Assessment

Sixteen printed objects were given to experts for evaluation. Ten experts evaluated printouts according to fourteen criteria. Experts were comparing the pairs of cube-based objects—because every model was printed on two different printers. They compared eight pairs of objects. Every expert evaluated every object, which consequently resulted in the gathering of 240 data from one expert. Therefore, the sum of the collected data was 2400. After conducting survey research, the authors collected the data and performed the analysis. They prepared tables for every evaluated model. Then, they calculated the average values of the assessment for every model for FDM and MSLA 3D printing technologies, as well as the overall average value for every technology. Figure 8 shows the view of the data sheet with the table of the collected for model number 1.

After analyzing all 2400 data, it was calculated and concluded that the overall average value for FDM technology was 4.48 and for MSLA technology was 4.69. MSLA 3D printing technology got better results according to almost every criterion. The average results according to the 15 criteria are presented in Figure 9. The MSLA technology was evaluated worse than the FDM technology according to only two criteria—the accuracy of the edges and the nuisance of the smell emitted by the printer. For both technologies, the best evaluation was for criterion 7 (lack of cracks), 9 (lack of rolled up layers), 10 (lack of delamination), and 15 (lack of visible asymmetry of the printout)—they were rated higher or equal to 4.98. The MSLA technology achieved an average of 5.0 according to the following criteria: 8 (lack of melting), 9 (lack of rolled up layers), 10 (lack of delamination), 11 (lack of visible gaps between layers), and 15 (lack of visible asymmetry of the printout). In turn, FDM technology was rated 5.0 according to three criteria, which were 7 (lack of cracks), 9 (lack of rolled up layers), and 14 (assessment of the nuisance of the smell emitted by the printer). In the case of FDM technology, the lowest values were in accordance with criterion number 13 (assessment of the noise of working printer)—3.8 points. The MSLA technology obtained the lowest evaluation according to criterion number 14 (the nuisance of the smell)—2.9 points. It was the lowest value of all the average values.

The data were also analyzed in the context of the model of the evaluation of the given object’s model. Figure 10 shows the average values for every printed object depending on the designed model for both printing technologies. The highest value for both technologies was achieved for model number 8 (4.63 points for FDM technology and 4.74 points for MSLA printing technology). The lowest value got model 5 (4.35 points for FDM technology and 4.64 points for MSLA printing technology). These values can be explained by the complexity of the designed models. Thus, the highest value was in the case of the regular cube, the lowest value—the most complicated model, which translated into loss of quality for the final printout. All the objects were evaluated quite well, which means that two 3D printing technologies are characterized by the high quality for such unit manufacturing. It shows that those technologies can be used by unit production manufacturers, graphic designers and to customers using their services and products, as well as by hobbyists and amateurs of 3D printing.

4. Discussion

The results for the research presented in the comparison of two 3D printing technologies may indicate the advantage of MSLA technology with the use of LCD displays over FDM technology. This is confirmed by the research presented in the article [19]. It is worth paying attention to the longer printing times indicated by the author of the quoted publication. The results obtained in the experiment described in this paper are different—the time is shorter. This is because Masked SLA technology makes the printing time dependent on the height (number of layers) of the printed object. In this study, all objects were the same height. This fact can be considered as the first research limitation in the conducted research. The disadvantage in the use of MSLA technology, confirmed in many publications [19,34,46], is a more complicated printing process. The necessity to use post-processes consisting of washing the printouts and their final hardening with UV light makes this method more difficult and time consuming for the average user in terms of unit production. Another aspect is the toxicity of thermo and light-hardening polymer resins [47]. The research presented in this paper shows the potential for a reduction in the levels of toxins contained in UV-curable resins. This issue also applies to the natural environment. With the development of both technologies discussed in the article and their dissemination, their use will have an increasing effect on the natural environment [48]. The article by Maines et al. [48] presents the important issue of developing a biodegradable material that could replace the toxic light-hardening polymer resins currently used in 3D printing in MSLA technology. From the point of view of sustainable development, it is also important to properly label and educate micro-entrepreneurs on the proper handling of waste generated during production using both FDM and MSLA technologies. One such element is the design of the product taking into account the appropriate environmental labeling [49]. An additional disadvantage of MSLA technology over FDM technology is the higher cost of light-hardening resins over PLA or ABS filaments. This was described in the publication “Product Development and its Comparative Analysis by SLA, SLS, and FDM Rapid Prototyping Processes” [50].

Paying attention to the comparison of both technologies in the context of individual production, it is difficult to indicate which one would be more appropriate for the application under given conditions. No comparison of the two technologies for unit production was found. The articles quoted highlight the aspects related to the specific application of 3D printing, not the overall quality and characteristics of the two technologies that could make the one specifically suitable for the given application be identified.

The research gap, which was pointed out in this article, is important from the point of view of small entrepreneurs, graphic designers, prototype designers, architects, and hobbyists interested in these two technologies. However, the article has some research limitations. Apart from the first limitation, which has been already mentioned, the next one is the hardware itself. The test was carried out on two FDM and MSLA LCD 3D printers from the same manufacturer [38]. The quality of the printouts could differ depending on the class of equipment and manufacturer. On the other hand, the approach presented in the article may reflect a situation in which the equipment is used by a designer or graphic artist who prints models or prototypes on request. The difference between these technologies is quite noticeable, and thus it is important to also conduct research in the field of comparing the general application of these technologies. However, attention should be paid to the basic research limitation resulting from the comparison by experts of the quality assessment of the finished printouts. This approach does not fully take into account all the differences between technologies. It should also be considered that the technology parameters that have been set for printing are different for FDM and MSLA technologies. This is a fundamental difference that makes these devices work in a different way, and they only belong to the group of additive technologies. Nevertheless, it is important to compare the prints made with the use of both technologies and indicate their usefulness in various areas and fields of production. Another research limitation is the optimization of printing parameters, which for the purposes of this article was carried out in such a way as to enable the closest possible approximation of the quality of prints made with the use of the two compared technologies. In practice, the layer thickness in FDM technology is usually set higher, which reduces the printing time and saves filament at the expense of quality. Optimizing FDM printing parameters in this way could become the basis for new research comparing the two technologies in practice.

It is worth mentioning the implications that were formulated based on the experts’ conclusions and presented in the Section 5.

5. Conclusions

The results for this research on the quality of two 3D printing technologies for use in unit production showed significant differences between the usefulness of the application of these two technologies. It should be noted that the FDM technology is well suited for the manufacturing of objects with sharp edges, both perpendicular and oblique. Additionally, the process of 3D printing in FDM technology, despite the fact that it was declared more acoustically burdensome for experts, was assessed as practically odorless in the case of the use of the PLA material. The MSLA technology was rated higher in the other categories. The attention of experts was drawn to the smoothness of the edges and the precision with which they were made. The elements that had to be printed “in the air” were also more precisely made and free from defects. They were called “overhangs” in the article. Another element that showed the advantage of MSLA printing over FDM in terms of 3D printouts was the lack of a visible seam, as well as the lack of shifts in relation to the X and Y axis (which is connected to the movements of the worktable during printing). The reason for this is the very small thickness of the layer, which was set to 0.050 μm for the purposes of the experiment. Consequently, the curved surfaces do not have visible sharpening when changing the angle of the surface. For comparison, it should be noted that the thickness of a single layer in the case of the FDM technology was 0.1 mm.

Analyzing the average time for all printouts, it was found to be 540 min (9 h) for FDM technology and 275 min (4.6 h) for MSLA technology. A significant extension of these times for FDM technology is also the result of the specificity of optimization selected for the experiment and compared to the actual work environment and the use of this technology; this time is overestimated. After optimizing the print parameters for daily and job printing, this time would be significantly reduced at the expense of print quality. MSLA technology determines the printing time dependent on the height of the printed object (Z axis). Its dimensions in relation to the X and Y axes do not affect the printing time. The printout quality also depends on the display resolution and the anti-aliasing parameter. In the case of a printer used in the research, this parameter had a particular influence on the smoothness of the edges and the absence of visible sharp edges of the layers. It should be noted that printouts from both printing technology were rated very high according to the symmetry criterion.

However, it should be noted that the printouts from the MSLA technology are not fully ready after being removed from the printer. They require two additional activities:

• Washing in highly concentrated alcohol; for the purpose of the research, technical isopropanol was used;
• Irradiation with an ultraviolet lamp or exposure to sunlight; for the purposes of the study, ultraviolet diodes were used. The time spent on these activities was not included in the printing time in the case of the conducted research.

A summary of the advantages and disadvantages of these two technologies is presented in the table (

Table 7. Comparison of FDM and MSLA 3D printing technologies [authors’ own study].

FDM	MSLA
The worse overall accuracy of surfaces.	The better overall accuracy of surfaces.
Visible overhang microdefects.	No visible overhang imperfections.
Higher edges accuracy.	The sharpness of the edges is not perfect.
Imperfections and fine lines visible on some surfaces.	The surfaces appear to be perfectly smooth.
Imperfections as points may occur in points where the nozzle starts layers.	No seam and no points in points where the nozzle starts successive layers.
Rolling up layers may occur. In the research, this problem did not occur.	No detachment of the first layer from the build plate (better adhesion).
Melting can occur.	No melting. There is no heating of the resin.
Delamination may occur.	The layers are very fine, there is no visible delamination.
Louder operation. The printer emits noise during the printing process.	Quieter operation. The printer emits noise during the printing process.
Emission of slight smell.	The unpleasant smell of polymer resin.
Possibility to use biodegradable and the environment- and user-friendly filaments.	Low availability/lack of substitutes for toxic polymer resins.
Lack of visible asymmetry of the printout	Lack visible asymmetry of the printout

Source: Authors’ own work.

).

The table above presents individual issues concerning the strengths and weaknesses of the technologies compared with each other. Based on them and the experience of the authors, the following conclusions have been drawn:

• FDM printers are better suited for producing items with sharp edges or surfaces with sharp patterns. Examples of such surfaces are threads or threaded holes. Purely technical elements, such as models of gears, will also be printed exactly by the FDM technology printer;
• MSLA printers are much better at dealing with curved shapes. Therefore, they can be much better suited for the manufacturing of rounded elements such as body parts or character models;
• FDM printers do not require any post-printing activities, such as additional rinsing of printouts or their hardening. The filaments are non-toxic and do not emit unpleasant odors. This makes them well suited for use in less spacious, poorly ventilated rooms, such as in homes (by hobbyists, amateurs), and for 3D designers who also provide 3D printing services;
• The polymer resin used for MSLA printing is highly pungent and toxic. It requires well-ventilated rooms, so it may not be suitable for hobby use and unit production, e.g., by graphic designers or architects and designers who want to use this technology in the form of a desktop printer in their design office.

The use of both technologies may therefore turn out to be effective for hobbyists, amateurs, and people running their own businesses—custom production and unit/individual production. For technicians and people who want to produce mechanical prototypes and objects in similar areas, a better solution will be the FDM technology, while modelers, artists, and architects will be satisfied with the MSLA technology. MSLA technology gives more realistic plastic curves without visible layers and a better aesthetic effect on the printouts. The disadvantages are the toxicity and smell of polymer resins, as well as the need for additional treatment after the end of the printing process.