## 4 Discussion
### Cost Analysis
\begin{table}
\begin{tabular}{l c c} \hline \hline \multicolumn{1}{c}{**Commercial Proprietary Product**} & **Cost (USS)** & **Cost Savings for OS Nutating Mixer (\%)** \\ \hline Labnet GyroMini Nutating Mixer [49] & 291.65 & 87.3 \\ Benchmark BlotBoy 3-Dimensional Rockers [50] & 381.65 & 90.3 \\ Benchmark Scientific B3D1008 Mini [51] & 322.15 & 88.5 \\ Boekel 201100 Mini Orbitron [52] & 491.00 & 92.4 \\ Globe Nutating Mixer [53] & 443.03 & 91.6 \\ Globe Scientific 522-230 Nutating Mixer II [54] & 420.60 & 91.2 \\ Benchmark Mini BioMixer 3-D Shakers [55] & 313.65 & 88.2 \\ Chemglass CLS-4029-100 3D Nutating Mixer [56] & 325.00 & 88.6 \\ Average & 373.59 & 90.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Commercial nutating mixers cost and cost saving percent for the use of the open source nutating mixer. of disciplines). However, it would appear challenging for those with no experience in 3-D printing. For those with experience and access to a basic RepRap or similar the time investment for setting up a print again is trivial. For example, although only the two flexible components were printed out on a Lulzbot Mini here, all of the components could have been. The first five components can be printed on any such hard plastic FFF 3-D printer using default settings, or the settings recommended here. There are hundreds of thousands of these 3-D printers deployed globally, which are thus readily accessible to most labs. A tuned DIY RepRap or a commercial self-bed leveling 3-D printer can be left unattended after the file has been sent to print just as long as 2-D print jobs can be left to print without the printer being monitored by a user. Thus, although the actual 3-D print time is much longer, the time that labor is focused only on printing is less than half an hour. The two flexible 3-D prints must be made on an advanced (or upgraded) 3-D printer (e.g., the Lulzbot Mini with the Flexystruder) and may not be available even in every workshop with a 3-D printer. In these cases, the local FabLab [59; 60], makerspaces [61], hackerspaces [62], and even public libraries [63] often have 3-D printing services available either for free, or for the cost of materials. Most universities now have at least basic 3-D printing capabilities somewhere on campus. For researchers wishing to fabricate the open source desktop nutating mixer with no access to 3-D printers locally, an on demand quasi-local 3-D print service can be used, such as MakeXYZ [64]. The costs for a 3-D printing service will be more than the costs of the materials alone, but in general reasonable, because of the high degree of competition, quotes are available immediately for users in any given area. Lastly, once all of the components are gathered they must be assembled. Having designed the system, the researchers in this study could build the device in about 10 min. To remain conservative, it is estimated that for a novice builder the build time would be under 30 min. (with the assembly instructions in this paper). Thus, the overall cost in labor to source, print, and assemble a 3-D printable open source desktop nutating mixer is about 1 h. This indicates that it is profitable for an organization to use the open source version if their labor costs are under $250/h, even for the least expensive commercial equivalent (or under $330/h for the average commercial system). Finally, a point should be made about the life cycle cost advantages of the open source mixer. As all of the files are shared and the BOM is known, regardless of the failure mode of the device it is easily repaired from readily available components (e.g., reprint a broken plastic component or replace the DC motor). This ease of repair and upgrading is simply not available for all of the commercial systems, which would demand the purchasing of a replacement device. Thus, the value of the open source tool can be considered higher than the commercial functional equivalent, even though the open source tool costs less money to build upfront.