Belt-Driven Open Source Circuit Mill Using Low-Cost 3-D Printer Components

Abstract

Barriers to inventing electronic devices involve challenges of iterating electronic designs due to long lead times for professional circuit board milling or high-costs of commercial milling machines. To overcome these barriers this study provides open source (OS) designs for a low-cost circuit milling machine. First, design modifications for mechanical and electrical sub-systems of the OS D3D Robotics prototyping system are provided. Next, Copper Carve, an OS custom graphical user interface, is developed to enable circuit board milling by implementing backlash and substrate distortion compensation. The performance of the OS D3D circuit mill is then quantified and validated for: positional accuracy, cut quality, feature accuracy and distortion compensation. Finally, the return on investment is calculated for inventors using it. The results show by properly compensating for motion inaccuracies with Copper Carve, the machine achieves a motion resolution of 10 microns, which is more than adequate for most circuit designs. The mill is at least five times less expensive than all commercial alternatives and the material costs of the D3D mill are repaid from fabricating 20-43 boards. The results show that the OS circuit mill is of high-enough quality to enable rapid invention and distributed manufacturing of complex products containing custom electronics.were economically viable even when used for only fabricating hard plastic toys [35] or flexible products from relatively-expensive specialty 3-D printing filament [36]. However, currently DM has matured primarily in mechanical products and components because of widespread cost declines due to the open sourcing of 3-D printing [37]. Open source electronics has created many successful companies, because various open hardware business models work well with hobbyist electronics [38], however, DM of electronics is not as mature. For example, the fabrication stations at Home Depot [18] and the U.S. Postal service [19] only include mechanical prototyping, but do not offer electronics prototyping. The lack of maturity in DM of open source electronics is a limiting factor in the complexity of products. There are two primary reasons for the slow adoption of DM circuit boards. First, there is a lack of unified sources for pre-designed projects, equivalent to sources for 3-D printable models like MyMiniFactory [39], Thingiverse [40], and YouMagine [41] or the search engine Yeggi [42]. There are some sources of FOSH circuitry such as Open Circuit Institute [43] and Open Circuits [44], though they have not been widely adopted. Most importantly, there are no widely recognized low-price FOSH circuit milling machines equivalent to the RepRap 3-D printers that can be built by consumers or purchased from companies like Lulzbot [45], re:3D [46] and Ultimaker [47]. The existing mills on the market are either prohibitively expensive [48], or lack proper documentation and are difficult to tune due to reliance on closed source designs [49]. The current traditional methods of circuit board procu...