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

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 subsystems of the OS Distributed 3-D (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.

Attachment 32065

To view the project's page on Appropedia, use the following link:
https://www.appropedia.org/Belt-Driv...ter_Components

Follow the link below to see the academic paper:
https://www.academia.edu/37347133/Be...ter_Components

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Interesting post. 10 microns is a good result for such a machine. My son has left me with a 3D printer sans printing head and I have often thought about turning it into a dedicated PCB mill. However, I have a full size mill (Bridgeport) and so as my needs for PCBs are limited there is no motivation to use the 3D printer. It just seems overkill whenever I used the BP for a small circuit board.

I note in the linked description a claim that 2 mm warpage of the base boards is not uncommon as justification for using height compensation. I have never seen anything approaching that except for an overall bow, which is easily fixed with a vacuum chuck or even edge clamping. Here is a post on a small one that I made. More recently I had cause to make a larger one and with only 0.1 mm DOC there has never been uneven depth.
https://www.homemadetools.net/forum/...589#post128299
I use the G-code straight out of FlatCam without any compensation for warp.

I note also the very slow feed rates used, is that necessary because of the limitations of a machine based on a 3D printer, or is the spindle speed less than optimum? I use feed rates around 10 x those mentioned, with a 24,000 rpm spindle.

Here is a pic of a recent board Attachment 32215 Click for full size.

a quick look at the web site linked didn’t turn up much info on the spindle. That is key to any decent PCB routing as runout must be tightly controlled.

also resolution is just a number, what I would like to see is repeatability! Well that and positioning precision.


in any event I think the professors or students here have misplaced priorities. If one is to build a machine (router or mill) to aid in the invention of electronics you might a well make it robust enough to handle a wide array of electronic production needs. For example have enough rigidity and performance to machine your device chassis / panel. I realize this is likely a project to meet a programs requirements and in that regard it is pretty neat.

Quote:

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Originally Posted by tonyfoale

Interesting post. 10 microns is a good result for such a machine. My son has left me with a 3D printer sans printing head and I have often thought about turning it into a dedicated PCB mill. However, I have a full size mill (Bridgeport) and so as my needs for PCBs are limited there is no motivation to use the 3D printer. It just seems overkill whenever I used the BP for a small circuit board.

I note in the linked description a claim that 2 mm warpage of the base boards is not uncommon as justification for using height compensation. I have never seen anything approaching that except for an overall bow, which is easily fixed with a vacuum chuck or even edge clamping. Here is a post on a small one that I made. More recently I had cause to make a larger one and with only 0.1 mm DOC there has never been uneven depth.
https://www.homemadetools.net/forum/...589#post128299
I use the G-code straight out of FlatCam without any compensation for warp.

I note also the very slow feed rates used, is that necessary because of the limitations of a machine based on a 3D printer, or is the spindle speed less than optimum? I use feed rates around 10 x those mentioned, with a 24,000 rpm spindle.

Here is a pic of a recent board Attachment 32215 Click for full size.

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