2.1

OpenSCAD

The optics designs evaluated here begin by being developed in OpenSCAD [52] (as shown in Figure 1) and the details are well documented [31, 52]. OpenSCAD is an open-source, script-based computer aided design software which is freely available for Linux/UNIX, MS Windows and Mac OS X. This application focus on CAD aspects rather than artistic 3-D modelling and is ideal for applications such as creating machine parts and 3-D objects of interest. OpenSCAD is a 3D-compiler that reads in a script file that describes the object and renders the 3-D model from this script file. This gives the designer full control over the modelling process and makes it easy to change any step in the modelling process or make designs that are defined by configurable parameters (e.g. they are parametric) [31, 53]. A detailed description on modeling using OpenSCAD is provided by the open source community [53]. The designs are made to be parametric by declaring variables and then using them throughout the code. This facilitates making changes in the designs such as diameter (in case of a lens holder as shown in Figure 2-3) rather than making complex changes in the code. Changing the relevant variable results in the entire design being scaled accordingly, and new design can then be exported as a 3-D model in the form of a .STL file. The files are then sliced using an open-source slicing program such as Slic3r [54], Cura [55] or MatterSlice [56]. These slicing programs take a CAD model, slice it into layers, and output the GCode required for each layer to be 3-D printed [57].

Figure 2.

3-D design for a lens holder in OpenSCAD 2013.06

Figure 3.

Lens holder 3D design opened in customizer [58, 59].

Figure 2 shows an example of an OpenSCAD design for a common lens holder [31]. As OpenSCAD is computer code (similar to C) and not all users are comfortable with it there is a Customizer app that intakes OpenSCAD code and outputs a relatively easily understood GUI. Figure 3 shows the customizer view of the same 3-D design.

2.2

Open-source 3-D Printing

The g-code generated as described in Figure 1 above is loaded onto the open-source printer controller such as or Franklin [60] or printrun [61]. The objects can either be printed using polylactic acid (PLA), acrylonitrile-butadiene styrene (ABS) or other low melting point thermoplastics on any type of RepRap such as a MOST-version of the open-source RepRap Delta, or the later version called the Athena [62]. The preferred print parameters are set during slicing in Cura, slic3r or other slicing program following the path outlined in Figure 1. Figure 4 showing Cura print parameters for the lens holder.

Figure 4.

Lens holder print parameters shown in Cura.

The Athena RepRap 3-D printer is the improved version of the MOST Delta Printer [62], keeping all of the features that have proven to be effective and adding some new. It has the same build volume, but uses metal GT2 pulleys and GT2 timing belts with approximately twice the positioning precision of the MOST Delta. All electronics (e.g. Melzi microcontroller and Beagle Bone Green) are tucked away under the build platform and wiring management is improved with the addition of built-in passages and anchor points in idler and motor ends. This makes it easy to handle and safely transport the printer unit. The design utilizes the improved extruder drive and the MOST Delta’s end effector fitted with quick release pneumatic couplers for simplified assembly and easier maintenance. The open top makes for better use of wood and removes a resonator, making the machine quieter and more flexible and even lighter to carry. Simply put, the Athena is: simpler to assemble, clean wire management, easier to maintain, offers greater flexibility, efficient use of materials, best fit for franklin and offers improved print quality [63].

3.1

Open-source 3-D Printable Optics Library

The global open-source optics library is continuously growing with new additions of customizable printed 3-D parts being added from designers all over the world. This paper presents a few selected open-source optics lab components and more comprehensive list of components are freely available at various online repositories. The collection of both open-source optics and science equipment including source files (OpenSCAD and .STL) are thoroughly documented on Thingiverse [64] and Appropedia.org [65]. Figure 5 shows the 3-D component designs for a parametric automated filter wheel changer in different rendering settings, and Figure 6a) shows the rendered image and, 6b) is the digital photograph of the parametric automated filter wheel changer with 8 filters and 6c) another example of the same filter wheel with changed number of filters.

Figure 5.

Parametric automated filter wheel 3-D rendered components [66].

Figure 6.

a) Rendered image of an 8 filter automated filter wheel and, b) digital photograph of the complete parametric automated filter wheel changer, and c) the same filter wheel rendered in OpenSCAD for 9 filters (d=290,x=9, z=100) [67].As this design is parametric by changing a few parameters the filter wheel can be radically changed with minimal effort. For example in Figure 6c shows the same filter wheel is shown rendered for 9 filters (d=290,x=9, z=100).

OpenSCAD designs and STL files for the entire open-source optics library [64, 65] are available on several digital design repository at no cost. Any researcher, scientist, or teacher, whether professional or amateur with access to a low-cost 3-D printer can utilize the designs to radically reduce the cost of optical support equipment as summarized in Table 2 [31]. As can be seen in Table 2 cost reductions over 99% are common with only some components representing only 5% of the current commercial investment. It should be noted that these values are even better economic savings than first reported by Zhang et al. [31] in 2013. The reason this method of fabricating physics optics equipment has improved economically is the cost of 3-D printing filament has dropped considerably in the last 4 years as desktop 3-D printers have become more common throughout the world.

Table 2.

Material and energy costs associated with open-source optics component fabrication compared to commercial prices and percent savings. The data was adapted from Zhang, et al. [31] with updated cost figures.

a

The price of 3 mm ABS filament is $0.01/gram [3D Printer Stuff. Available:

http://www.3dprinterstuff.com/shop/page/4?shop_param=Accessed_2017_Apr_25.].

b

The national average cost of electricity is 11.53 cents/kWh [US Energy Information Administration. Available:

http://www.eia.gov/beta/enerdat/#/topic/7?agg=0,1&geo=g&endsec=vg&freq=A&start=2008&end=2011&charted=1 Accessed 2017 Apr 25.] and the electricity cost was derived from multimeter is 0.006925 kWh/gram (using 3 mm ABS) assuming a Prusa RepRap 3-D printer.

c

Commercial prices were derived from website data from various vendors including: Edmund Optics, Thorlabs, McMaster-Carr, AutoMate Scientific, and Pasco.

3.2

Other Open-source 3-D Printable Science Equipment

This section discusses other open-source 3D printable science equipment in addition to optics related components details of which is documented in ref [64, 65]. The inventory for the open-source lab ranges from hardware to automation software. Examples are shown in Figure 7 below include 7a) an automated open-source four-point probe for making sheet resistance measurements on thin films over large areas [68] and 7b) an open-source 3-D printed microscope slide holder to ease moving samples around the lab [69]. There are now literally hundreds of such tools for every area of science already available on the Internet with more being posted routinely on websites like the NIH’s 3-D Print Exchange (70).

Figure 7.

Examples of open-source 3-D printable science hardware showing a). Open-source four-point probe [68] and b). Open-source 3-D printed microscope slide holder [69].

Generally most of the 3-D printed optical components are less attractive in appearance and in precision than commercial versions. However, experimental setups particularly for high schools contain overly engineered expensive components with limited flexibility. Most of the open-source tools provide more flexibility through both customizability and the ease at which different experimental setups can be reconfigured. A clear example is eliminating an optics table in exchange for using magnetic bases and re-purposing an existing steel case desk for use in optics classes and hence reducing the setup costs while enabling far more flexibility and ease of reconfiguring an optical experimental setup [31]. The open-source optics library enables both teachers and lab technicians to design and conduct a variety of educational experiments much less expensively and easier than with conventional equipment. According to Zhang et al, [31] it would cost less than $500 using the open-source optics approach to outfit an undergraduate teaching laboratory with 30 optics setups including 1 m optical tracks, optical lens, adjustable lens holder, ray optical kit, and viewing screen, the as compared to $15,000 for commercial versions, resulting in over $14,500 in savings. Today as shown above in Table it could be done for even less thereby saving even more. In addition to economic savings offered by the use of open-source 3-D printing, the ability to customize and locally fabricate high quality science equipment for all Science subjects (Physics, Chemistry and Biology) for all levels from elementary school through middle, high school and college education can dramatically change the way sciences are taught in schools located in resource constrained communities around the world. Empowering schools, teachers and communities with the ability to fabricate their own basic science equipment help motivate teachers and enable them to undertake effective planning for their classes.

Another interesting aspect presented here, by having the open-source optics library is that many middle school, high school and college-level experiments can be performed using designs directly downloaded from the library. An added advantage is that students within the classes and their teachers could get the opportunity to learn and used the 3-D printers to fabricate some of their own optics (or other scientific) equipment and even make or improve existing designs to suit their requirements. Ideally these students and teachers would share their designs following the open source licenses back on the web for the entire global scientific community to enjoy. This hands-on experience on designing and construction help nurture student’s practical abilities and introduces them to useful engineering skills such as geometry, CAD and additive layer manufacturing as well as the open-source philosophy at an early stage in their school lives. Having scientists from all over the world download their work is also empowering and can build self-esteem [71]. These skills will be vital and can help map their future careers. Finally, the use of solar powered 3-D printers will also further expose both students and teachers to environmental friendly sources of energy such as solar energy and help off-grid communities to print their own basics science and research equipment [71]. Finally, to reduce the cost of the equipment even further recyclebots can also be used to turn post-consumer thermoplastic containers into 3-D printer filament [72, 73]. The resource poor communities could benefit greatly from 3-D printing by having the means to obtain much less costly filament, which in turn reduces 3-D printed product costs. For example recyclebots can be used to make filament from commercial PLA pellets costing approximately $5/kg [74]. This will further increase the cost savings and also ensure sustainability by ensuring that there is enough filament in the local market and therefore reducing the reliance on imported filament.

3.3

Limitations of 3D printed Equipment

There are several merits for using 3-D printed equipment for optics and basic science in general presented in this paper. However, open-source 3-D printing using low cost printers has a number of limitations. The most notable one also include the following: