Homebrew PCBs

Rick,

You can also try etching aluminum using lye.

 

I understand you desire to try new and different procedures but at the same
time what are your goals and tradeoffs?  To me, the accuracy of a functional
(not decorative) scale is the most important requirement, then readability,
and I guess finally appearance.

 

Wrapping an artwork around a cylinder looks to me as an instant tradeoff in
accuracy.

 

Also to make initial testing easier, try your etching procedures on a piece
of flat metal and then afterwards progress to the cylinder.

Good luck and keep us up-to-date.

Bertho

 

From:  Rick Sparber  Sent: Monday, March 25, 2013 17:22



I am not ready to abandon contact printing.

On my first attempt, I plan to take some large diameter thin walled copper
pipe and slice off a 1/2" long piece. This will be heated so it expands and
then put down around a piece of steel round stock. As it cools, I will get a
thermal fit. That copper will not come off. Then I will machine the piece
true and face the end. A center hole will be drilled. 

I next plan to coat the copper with photo resist and used a laser printed
mask to expose. Then I'll use ferric chloride for the etching and see how
deep I can get. This will prove out the concept of contact printing and
etching a cylinder.

If this works, I will play with electo etching with salt water directly on
steel. I know this process is much slower and tends to tear up the mask but
sure would be great if it works.

Rick

-----Original Message-----
From: Homebrew_PCBs@yahoogroups.com <mailto:Homebrew_PCBs%40yahoogroups.com>
[mailto:Homebrew_PCBs@yahoogroups.com
<mailto:Homebrew_PCBs%40yahoogroups.com> ]
On Behalf Of KalleP
Sent: Monday, March 25, 2013 7:45 AM
To: Homebrew_PCBs@yahoogroups.com <mailto:Homebrew_PCBs%40yahoogroups.com> 
Subject: [Homebrew_PCBs] Re: etching the OD of a cylinder to create a
graduated dial

This will not work as is for a cylinder but for a conical scale it might
work.

Instead of projecting a line and then indexing the dial you could look at
some of the long wave UV photo cure polymers that are used for 3D stereo
lithography. You would dip the scale in the resin, pull it out and project
an image with a UV modified DLP video projector, no need to dry the resist
as you would be hardening it in-situ with the UV image. Have to keep the
projector as far as convenient to maximise the focus depth if you have a
conical scale (long focus lens) but you could have arbitrary complexity of
the artwork that could be changed on every scale.

You would rinse and post cure the resin and then try out various etching
methods to get a good bite. You could paint fill and then strip the resin
off with a suitable solvent.

This method might have some value in making DIY PCBs as well, I know there
are very (very) expensive industrial machines that do just this and have
many of these projectors and expose a 50mmx50mm square (or whatever) and
scan across the material and have the image track the material motion to get
a continuous scan while having a largish projection area (instead of a
single laser spot or scan line that is too slow). Imagine a video projector
and a simple jig to position a pcb in 50mm grid, you could manually project,
move, project and expose arbitrary image. Using the 3D printing resins
might be a way to do a wet photo resist at home but I have not tried it.
The materials are still a bit expensive but the layer required for etch
resist should be fairly affordable.

A Google search found these two interesting hits, the second is just an
abstract unless you pay or are a member of some secret cabal.

http://maskless.com/High_Speed_MLI_TechPaper.pdf

http://www.researchgate.net/publication/24261077_Direct_projection_on_dry-fi
lm_photoresist_%28DP%282%29%29_do-it-yourself_three-dimensional_polymer_micr
ofluidics

Regards

Kalle





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