Hello, Jan--
Thank you for your thoughtful comments-- I have added a few responses,
not as criticism
but as further attempts to apply bounds to the problem (>).
On 7/16/2014 11:41 PM, Jan Kok jan.kok.5y@... [Homebrew_PCBs] wrote:
> I've used hobby-type 3D printers and also used HP pen plotters (for
> their normal purposes, not for producing PC boards). Based on that
> experience, I suspect that using using something like an Ultra Sharpie
> pen (but with still finer tip) to draw resist on a board would give
> better results than trying to lay down plastic resist with a 3D
> printer. The problems with laying down plastic resist are:
>
> Hard to control the height of the nozzle above the board with
> sufficient accuracy, thus the traces would be wider in some parts of
> the board than others.
> Trace-width variability might not be a problem for low-density,
discrete-component layouts. For
surface-mount designs, fat and lumpy resist would cause problems.
> How would you mount the board to the table perfectly flat?
>Double-sided-sticky tape between the copperclad and the table? Drilled
and tapped holes
in the table and washers overlapping the blank board's edges? Screws
through the washers
and into the mounting holes would clamp the board to the table.
> Even a slight bend in the board could cause lots of problems.
>Agreed.
> Some copper clad also has a surface texture due to the fiberglass
> weave in the substrate.
>Does this depend on the cladding's thickness? It might be needed to
specify 1-ounce copper cladding.
> That could lead to variable trace widths.
>Agreed.
> In contrast, the pen tip can contact the board with light spring
> pressure, thus the trace widths should be more consistent.
>Would pen-point life be a problem? Flare due to breakdown under spring
pressure
would cause thicker traces.
>
> There _may_ be problems with getting traces to start and stop exactly
> where you want. The way to stop a trace is to stop pushing plastic
> through the heated nozzle, while continuing to move in X or Y. In fact
> the extruder motor is usually reversed a bit to avoid continued
> extrusion due to compression of the plastic fiber into the nozzle.
> Then when you want to start a new trace, you have to run the extruder
> forward by about the same amount before the plastic starts to extrude
> again. I suspect that tuning that process could be time consuming, and
> the process might not be stable (depending on nozzle temperature and
> other factors).
>Ah-- I was unaware of that as it's not covered in the ads<g>. Could
the extruder nozzle be raised (Z axis)
as the motor gets reversed? That might leave a vertical lump at the
trace's end.
>
> I think a 3D printer would be a great platform for experimenting with
> pen-plotting resist onto copper clad. Just replace the extruder nozzle
> with a pen holder. Or possibly an ink jet cartridge.
>That's an excellent point. Flat-bed pen plotters are essentially 2-D
printers, with a binary
Z axis (pen up or down), and finer control might be an an improvement.
If someone out there has a 3-D printer and PC board design software,
perhaps he or she
could actually try a sample layout? That would yield some definitive
results, or point out
showstopping flaws.
Thanks again, Jan, and 73--
Brad AA1IP
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