4.1. Limitations of the Study
There are several limitations to this study. First, the utility of a given educational aid may vary widely in a given classroom and thus the limited selection of aids evaluated here may not be representative for all classrooms. Future work could address this by evaluating more designs but also doing field work to see how 3-D printers are being used in the classroom—specifically those purchased to fabricate educational aids. Another limitation is that not all schools have the initial capital to invest in a 3-D printer. The model used here retails for USD 2500 and is considered a mid-range fused filament fabrication (FFF)-based 3-D printer. Open-source FFF-based 3-D printers can be purchased for 10 times less, and even less if built in kit form. Previous work has shown that these lower cost 3-D printers would be expected to be capable of printing all of the designs evaluated [23
]. The major difference is the lower cost printers tend to have a smaller print bed and, for particularly large prints, the model would need to be divided into several parts and then assembled afterwards with tabs or some form of adhesive. In addition, it should be noted that because some of these lower cost 3-D printers do not have heated beds, the distributed manufacturing costs would be slightly lower. Another limitation of this study is that only one material—PLA—was evaluated. It is the one of the safest and best choices for filament, especially around young children; however, other choices of filament could be more durable (e.g., nylon) or more cost-effective and better for the environment (e.g., recycled materials [70
]), depending on the print. It should also be noted that with the nozzle and filament diameter size, a small amount of error occurs within the print, with the larger nozzles providing faster print times but cannot produce fine detail and vice versa. Another source of errors is when taking the Cura-estimated mass of the material. There could be slight error, as Cura rounds to the nearest gram. This could throw some of the calculations off when determining how much is being saved and how much filament is actually being used. Finally, this class of 3-D printer is not foolproof. If a print fails for any reason (e.g., nozzle clog, lack of bed adhesion, etc.), then filament is wasted. Previous studies estimated this failure rate for new printer users at 20% [23
], however, the modern self-bed leveling printers have errors far below this. The error rate will depend on the complexity of the print but can be estimated to be in the single digits when using guaranteed printable designs, as was done in this study. It should be noted, however, that the lowest cost 3-D printers that lack a heated bed can increase the probability of print failures from a lack of bed adhesion due to contraction as the part cools during printing. For some polymers, this can be a substantial problem (e.g., polypropylene should not be printed without a heated bed and best results are found with a heated chamber). For PLA, which was used in this study, printing on an unheated bed does not pose any substantial issues, particularly if a common glue stick is used to lay down a thin film before printing to ensure adhesion.
4.3. Teacher Training
Teachers will also need to be trained on how to use a 3-D printer [48
], as well as incorporate it into their classroom. The training process for the teachers can be formal, as in a full university course on additive manufacturing, or a 3-day workshop in which teachers learn how to build, maintain and use an open-source 3-D printer from scratch (i.e., [48
]). This level of detail, however, is unnecessary for basic use and maintenance. Creality, an open-source 3-D printer manufacturer, estimates that it takes 30 min of using free online videos for someone already familiar with 3-D printers to get their Ender 3 model (USD 170) up and running, but 2–3 h for a completely inexperienced person [76
]. As the cost of low-end 3-D printers has come down, more and more students are being exposed to them at home and could be deputized to help set up a classroom 3-D printer. This relatively low level of depth would only enable a teacher to print out pre-designed teaching aids. This is the assumption used in this study and provides access to thousands of learning aids. In order to go further and be able to modify existing designs that were not made parametric or create completely new designs, however, learning CAD (computer aided design) would be necessary. CAD education ranges from a full university course to a self-paced free tutorial (e.g., EduTech [77
] or FreeCAD [78
]) that could be accomplished over several intense hours or a more leisurely “learning weekend”. Fully mastering any of the open-source CAD packages would normally take several months of practice after learning the basics but, again, this is unnecessary to get started. Finally, with the skills to run the printers, teachers would also need to think about the best way to incorporate them into their own classrooms. So, for example, if students are getting distracted, prints can be run while they are at recess, at lunch or overnight/on the weekend. Future work is also needed to reduce the volume of printers during the printing process. It should also be pointed out here that at many schools and universities, the 3-D printing shops are run by an experienced technician. For example, a library might employee an expert 3-D printing employee to enable teachers with minimal training in CAD and additive manufacturing (AM) to obtain learning aids or the help they need to do it themselves without formal training.
4.4. Values and Costs
The benefits of centralized large-scale manufacturing are well established in the literature and historically have included reduced costs due to the economies of scale, from: (i) bulk purchasing of materials, supplies and components through large and long-term contracts; (ii) technological advantages of returns to scale in the production function, such as lower embodied energy during manufacturing of a given product because of scale (e.g., injection molding plastic products); (iii) favorable financing in terms of interest, access to capital and a variety of financial instruments; (iv) centralized marketing and (v) increased specialization of employees and managers [79
]. These advantages of mass-scale centralized manufacturing have created a general trend towards large-scale manufacturing in low-labor cost countries, especially for inexpensive plastic products [81
]. As the results of this study show, the centralized paradigm is no longer economically competitive because of the advances in distributed manufacturing technology for some products (e.g., learning aids manufactured from plastic). Although this has been pointed out in the literature for other products as detailed in the introduction, the new and rigorously detailed results shown in this study are still somewhat surprising.
Critics will point out that this study is equating the costs of production with the costs of retailing and may argue that it is not a fair comparison. From the teacher’s perspective, however, the cost to obtain a learning aid is the full cost that matters to their supplies budget and the value is only what they acquire in the classroom. To clarify the economic position and provide some insight into why it is less costly to manufacture a learning aid in the classroom than buy a mass-manufactured product, Table 5
shows the costs and values from the teacher’s perspective for (1) the typical mass-manufactured proprietary product and (2) the distributed self-fabricated open-source products. Each item making up the cost will then be discussed in turn. In Table 5
, the green symbols represent a benefit and the red symbols represent a disadvantage for the consumer (e.g., teacher) and the check marks indicate that the item is present while the X indicates that it is not. Thus, the ideal system would have all green marks (X for costs and checks for values).
As can be seen in Table 5
, the self-fabricated open-source approach has nearly all of the advantages seen but considerably fewer disadvantages than the mass-manufactured model. This explains in large part why the results of this study found that distributed manufacturing would result in considerable savings for teachers (consumers).
The cost of the research and development (R&D) in the standard model is borne by the company to create the design that benefits the consumer. In the open-source model, however, this same benefit is gained at no cost because the learning aid is open source and developed by someone else. In addition, considerable costs are shouldered by the traditional company for intellectual property (IP) protection, which has no direct benefit to the consumer for a given product. For example, even companies like Apple, that are known for innovation, spend more on lawyers than engineers [83
]. On the other hand, there is no IP cost for the open-source self-fabrication model.
The conventional mass-manufacturing company has a substantial advantage in the cost of materials because of bulk purchasing. Assuming identical materials (i.e., plastic) the self-fabricated cost for the materials will be greater (e.g., USD 20/kg for retail 3-D printing filament vs. USD 1–5/kg for bulk plastic) and the value will be the same. Similarly, to fabricate the product, in both cases, the consumer benefits from the product produced and there is a cost associated with the making. This cost is generally divided into labor, energy and equipment costs. The labor costs for the traditional manufacturer is higher as it is essentially free to self-fabricate a pre-designed product on a 3-D printer. On the other hand, the energy cost would be expected to be larger for the self-fabricator because of the economy of scale advantage for the mass manufacturer. Similarly, the mass manufacturer, although using larger and more expensive equipment (e.g., an injection molding machine), would produce far more copies, thus the machine cost per product would be expected to be lower for mass manufacturing. 3-D printers and the cost in electricity to operate them is so small [23
] that neither of these advantages for mass-manufacturing play a major role in the cost of a product.
Next, there are several costs that must be included in a mass-manufactured product that offer the consumer no advantage, which are unnecessary with the open-source approach, including: packaging, shipping, retail (e.g., store costs, online or brick and mortar), advertising, management, financing and profit for the company. Some of these costs can be quite substantial and others represent a disadvantage for the consumer. First, not only are packaging costs eliminated for self-fabricated products, but the consumer also saves time in unpacking items. Packaging waste and difficulty in opening some products are a source of frustration for consumers [84
]. Second, shipping costs are not only eliminated (assuming 3-D printing feed stock is on hand because it can be purchased ahead of time) but, in general, the print time for a learning aid will be less than the order/ship time for a mass-manufactured product (e.g., the print times for the products here are in the order of hours, while shipping is normally in the order of days). This, again, saves the consumer time, which is a value. The costs associated with the overhead and profit of retail establishments are also all completely eliminated. This is true of the online retailers that need to pay for servers, programmers, etc., but even more so for brick and mortar stores. It is estimated that the markups for retailers were 10% for Costco, 15% for Amazon, 32% for Walmart and 46% for Target [86
]. The costs for advertising and marketing are completely eliminated for the self-fabrication model, while advertising represents a time cost and source of frustration for consumers who attempt to protect their time [87
] (e.g., some of the most popular plugins for both Firefox [88
] and Chrome Internet browsers [89
] are for ad blocking software, which have been downloaded tens of millions of times and have saved consumers enormous amounts of time and money by conserving energy to run their computers to service ads [90
]). The management costs to run large corporations have swollen [91
] even when the company is failing [93
] and, again, these are not needed in the distributed model. Similarly, financing and profit only add costs to the mass-manufactured model, while they are not needed in the distributed model.
Finally, the mass manufactured products undergo usability, durability and safety testing that enables companies to provide some form of warranty. This has value for the consumer, which is not captured in the self-fabricated approach. This is the one area that may prevent a given product from providing an equivalent value to a mass-manufactured item. This area is most important for products that are likely to fail due to complexity or have a long lifespan. For the products evaluated here made out of plastic and often lacking moving parts, this is unlikely to be a major concern (e.g., would a teacher rather pay less than one USD for a spirograph set he or she can make in class on his or her 3-D printer or pay over USD 15 to buy one from Amazon even if it comes with a warranty?). Future work is needed to determine the value for the consumer for the explicit or implicit warranties (e.g., Amazon returns) for mass-manufactured products.
Overall, it is clear that although mass manufacturing enjoys advantages in material and energy costs compared to the self-fabrication model, it is not enough to overcome all of the other cost disadvantages, which is why the cost to the consumer (e.g., teacher) was found to be so much lower than the retail cost for the teaching and learning aids investigated here.
4.5. Overall Economics and Advanced Applications
Despite both this study’s limitations and those of the concept of distributed manufacturing in schools with 3-D printers in general, it is clear that fabricating learning aids in the classroom is economic. Even for the relatively expensive 3-D printer used, printing even 100 aids on average would pay for itself. This could easily be accomplished in the “first 100 days” of class. Further, with each teaching aid, on average, that is 3-D printed, the school saves the cost of an entire roll of filament. These savings are clearly substantial and, as seen from Table 4
, the technique appears to be already being used throughout the world by teachers or other educators trying to help their students understand concepts. It is quite remarkable that, on average, a given open-source educational aid is saving well over ten thousand U.S. dollars per year for the educational community. This value uses the assumption that for each download, one item is printed, following [94
]. It does not take, in general, USD 10,000 worth of engineering time to produce a learning aid. This thus provides a return on investment (ROI) for investors hoping to improve education, on average, of more than 100% [95
]. The ROI is so high that it could be justified even in a single school that uses any substantial number of copies of a learning aid. Particularly if these are for more advanced science classes, like optomechanical systems [96
], micropumping [97
], bioadhesion [98
] or bioreactors [99
]. The savings that, on average, are 86% for learning aids would go a long way at a school that makes use of learning aids, but perhaps more importantly, with the costs being accessible, more teachers would be likely to use them and the teaching at a school would be improved. This needs further study and is left for future work.
In addition, 3-D printing enables economic access to the ability for schools to integrate special education students using advanced applications. For example, there are open-source parametric 3-D printable designs for Braille patterns developed in OpenSCAD [100
]. This script-based computer-aided design is extremely effective at teaching students both to code and the value of math [48
], but in this context, it can be used to have students directly help their blind peers learn. This could be a powerful learning motivation and means to better integrate blind and visually impaired students into classrooms. There are already many ways 3-D printers can be used to help blind and visually impaired students, including tactile maps, illustrations for books, learning games and artwork [101
]. Fabricating learning aids and even assistive aids for blind and visually impaired students with 3-D printers can make economic learning aids for art teaching [102
], but can also get quite functionally sophisticated. For example, a low-cost, open source ultrasound-based navigational support system in the form of a 3-D printable wearable bracelet has been demonstrated to allow people with vision loss to navigate, orient themselves in their surroundings and avoid obstacles when moving. Similarly, research has already shown the efficacy of 3-D printing to create orally disintegrating printlets (ODPs), suitable for patients with visual impairment, with Braille and Moon patterns on their surface, enabling patients to identify medications when taken out of their original packaging [103
]. Students may start printing learning aids and Braille labels for peers, but as they become more technically sophisticated, fabricating ultrasound-based navigational aids from open-source plans or ODPs is possible and no longer economically inaccessible. Future work is needed to look closely at this area on both technical and economic grounds.
3-D printers in the classroom can have other ancillary benefits. The opportunity to print objects now can give students something to look forward to when coming to school [48
]. They can become more interested in the STEM field [44
]. Additionally, students could design their own objects that can be made for classrooms or younger children to help proactive learners. In general, students that are first exposed to 3-D printers love to watch the printer work its magic and make objects. Young students ask questions about the printer, such as “How hot does it get to melt the plastic?” and “How does it know how to print what we want?”. Students are curious about the machine itself and would touch the print bed or the filament. 3-D printers (or even using them) could be used as prizes or awards for good student behavior or achievements. Finally, it could lead students who have already graduated to give back to the schools they grew up in following the open-source model [27
]. This equipment in the classroom gives the school a higher sense of technology. This may ultimately boost educational quality (e.g., ratings), attracting more students (e.g., funding).