Reproduction DEC 144-lamp indicator panels (was Re: RK11-C indicator panel inlays?)

[Ethan Dicks]

On Mon, Dec 6, 2021 at 9:42 AM David Bridgham via cctalk
<cctalk at classiccmp.org> wrote:
> The inlays are mostly not done with any tools I have.  I do the graphics
> with Inkscape.  Rod made up the blanks with silk screening.  Then I have
> the white printing done at a printshop I found who has a large, flatbed
> printer that can print white ink.  I do have some ideas about how I
> might try to make up blanks with a laser etcher I have access to but at
> the moment we have an ample supply.

Cool.

> Also, I've experimented with making my own bezels out of PVC board from
> Home Depot using a CNC router.  In the pictures below, the yellowed
> bezels are old DEC bezels while the white ones are ones I made.  I
> figured that if we ever get the QSIC shipping and people want indicator
> panels (I hope they'll want indicator panels), I'd rather not depend on
> them ripping apart old DEC bezels to make this work.

Yes.  I'd rather not demolish my only indicator panel.  I was planning
on demolishing a blank (I have a few short blanks, but most people do
not)

> Anyway, I'd be most happy to have another person with more tools to help
> build bits and pieces of this stuff.  I've noticed that as I gained
> access to different tools, I came up with different ideas about how to
> make things.  I didn't think the laser etcher was all that useful until
> I started using it.

I have a small 40W laser etcher that I essentially haven't used since
I have had access to large-format 80-120W laser cutters.

As for tools, I can rent a 4'x8' Shopbot router at our local
Makerspace that can turn out the light blocking bar or, from your
file, the frame.  We also have a local company (IC3D) that makes
cubic-meter 3D Printers and makes their own filament from pellets,
keeping costs down.  The founders are friends of mine and I've helped
repair sensors on their manufacturing line.  If I had an STL, I could
get a bid on what it would take to 3D print one.  It wouldn't be as
smooth as a machined PVC foam milled one, but it would be strong.
With a little post processing, a 3D Printed frame may give an adequate
look.  Just a possibility.  I haven't worked with PVC foam much but I
understand the principle.

>  Now I want to use it for everything.  Turns out it
> can't quite handle 3/8" Delrin; it just melts it and makes a mess.

That sounds like a power problem.  Normally, Delrin lasers quite
nicely, at least at 80W.  Thick stuff is hard in any printer because
of lenses, beam diffusion, etc.  We sometimes have problems with 1/2"
material of any kind in ours.  I've done some stuff in 2 passes, one
high, one low (refocusing/repositioning Z axis between job runs).  We
also have multiple lenses for different focal points.  One is only
good for etching/surface work, and one is good for cutting 3/8" and
thicker materials.  We usually use the middle one since 99% of what
goes into our laser is 3-6mm stock.

> Speaking of help, if anyone wants to review the QSIC design, I'd welcome
> that.  This is by far the most complex circuit board I've ever designed.

I could take a look at it, I have some background in making Qbus and
Unibus interfaces, but how useful I'd be depends on what kind of
feedback you are looking for.

> Back to indicator panels, here's a picture showing a bit of the
> evolution of my indicator panels...
>
> http://pdp10.froghouse.org/qsic/indicator-panel-stack.jpg
>
> ... The only real thing I'd like to
> change is the gloss.  Somehow, DEC's inlay is as flat as flat can be.

I did notice that.  I have no idea what to recommend.  AFAIK, DEC just
used an acrylic with a specific surface texture.  The only stuff I can
get is like what you have - smooth as window glass.

Cheers,

-ethan