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From: Don Y <blockedofcourse@foo.invalid>
Newsgroups: sci.electronics.design
Subject: Re: poor man's decal
Date: Wed, 2 Apr 2025 09:25:31 -0700
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On 4/2/2025 7:57 AM, Liz Tuddenham wrote:
> Don Y <blockedofcourse@foo.invalid> wrote:
> 
>> On 4/2/2025 4:23 AM, Liz Tuddenham wrote:
>>> Don Y <blockedofcourse@foo.invalid> wrote:
>>>
>>>> I need a full-color, durable decal to label a front panel.
>>>> The panel is ~8x17".  I'm only looking for prototype quantities
>>>> (someone else can deal with production quantities and "revised
>>>> artwork").
>>>>
>>>> I think I can just color print the image, 1:1, laminate it
>>>> and use a spray adhesive to affix it to the actual panel.
>>>
>>> For prototypes or one-offs, I print in mirror-image on an overhead
>>> projector acetate sheet using a laser printer.  The print side is then
>>> spray-painted white (several very thin coats, allowed to dry between
>>> coats, so as not to dissolve the printing) and stuck to the panel with
>>> double-sided sticky tape.
>>
>> Do you cover the entire surface with tape?  Or, just the edges?
> 
> Usually the entire surface and a bit beyond, then trim off the excess.

Doesn't that make it hard to remove?  Or, are yours "small(er)"?
(Note my smallest is 8x17 and they quickly get larger)  I was
assuming I would need a low tack adhesive -- almost like Post-It
notes...

>> Most of the double-sided tape I've used would have too much tack
>> if used to completely cover it; removing the decal would be tedious.
> 
> My experience has been that the weakest bond is between the print and
> the acetate sheet.  Pulling the acetate sheet from a corner leaves a lot
> of the paint and print on the sticky tape; some of the tape can be
> removed mechanically and the rest comes off with solvent.

I'm hoping that having the front AND BACK sides be a single sheet
(i.e., the laminating film) would allow it to come off cleanly.
If the adhesive can be low enough tack that it gives up the
ghost easily...

>> [I just want the decal to stick to the surface, now cling for dear life!]
> 
> On double-sided sticky tape it will - your biggest problem will be
> getting it lined up before it sticks in the wrong place.  I have two
> methods:
> 
> 1) Put the tape on the panel, then use a soldering iron and/or file to
> clear the tape from the holes where the control shafts and switches will
> be.  By shining a light through the holes I can then line-up some +
> marks on the print, which correspond to the hole centres, while I bring
> the decal onto the sticky surface in exactly the right place.
> 
> 2)  Put the tape on the panel etc as before. then line up one long edge
> of the decal on the edge of the panel and let it touch.  The decal can
> then be swung down, using that edge as a hinge, and carefull pressed
> onto the panel starting from the hinge edge.

I was planning on making a form onto which the label could be
positioned "upside down".  Then, mate the label-carrying form
to the panel surface.

With the decal being thick (consider:  two layers of 7 mil laminate
plus the "print stock" within), I am hoping to avoid the electrostaic
cling that tends to cause flimsier materials to "jump" to the other
surface, unbidden.

> Once it has stuck, any attempt to reposition it or remove any air
> bubbles will probably finish up tearing the print off the back.
> 
>>> The unprinted acetate surface is fairly durable and the print side is
>>> towards the panel, so it can't be scuffed off.
>>
>> Yes, I took that approach with a digitizer overlay.  But, that's a pretty
>> gentle environment; you're never poking at it with anything that may
>> have an edge.
> 
> True, but i have known these acetate labels to survive nearly 5 years
> outdoors on a south-facing wall (in English weather, which is not the
> severest of UV tests).

Yes, but no one is likely *poking* at it.

>>> If you need to change it, the sticky residue from the tape can be
>>> removed with white spirit or petrol.
>>
>> I was hoping to eliminate the use of solvents.
>>
>> Many products, here, bear "printed labels".  Historically, these have
>> been paper; removing them is a chore as the label needs to absorb a
>> solvent to facilitate its removal (I use water, alcohol, mineral
>> spirits and, rarely, acetone -- as it often attacks the surface to
>> which the label is adhered).
> 
> The acetate sheet can be ripped off, so the solvent attacks the sticky
> stuff fairly directly.

I can try it.  I will try a spray adhesive instead of double-sided tape
as that seems like it would be easier to address a large surface.
E.g., when you reinstall a headliner, that's the approach taken.

>> But, there are also similar labels printed on a plastic/nylon
>> sheet.  These can be removed "intact" -- with patience -- just
>> by getting a corner "started".  The adhesive used is weak enough
>> (and the label material strong enough) that it doesn't tear the
>> label as it is removed.  And, the printed content is well-bonded
>> to the substrate such that it doesn't require any additional
>> coating (or, that coating is applied in the process of making
>> the label).
>>
>> So, I'll either print on paper and use a laminating *pouch* (so
>> both sides of the paper are coated in plastic instead of having
>> paper on one side) OR try mylar (or acetate) and hope the printed
>> material doesn't "linger" after the adhesive is released.
> 
> The acetate sheets are so cheap that it doesn't matter if you destroy
> one when you remove it.  If they are not too big, you can also print
> 3-up or 4-up on an A4 sheet, so you can easily keep a few spares.

I consider the label to be discardable.  I just want to make it
easy to remove and replace so there isn't much labor (time)
involved as that sort of repair would have to be done /in situ/;
the more time a "service man" has to spend at a site, the more
costly the repair would be.  (this is why I prefer replacement
for most items -- carry the "failed" unit back to the depot
for analysis/repair but get the customer back up and running
quickly.

>> As I said in my post, it's just to get through prototypes so it
>> looks "professional" to VCs and is as *functional* as the real
>> decal would be ("How do you service this?  It seems awfully
>> costly to adopt a replace-as-FRU policy")
> 
> You can see a picture of the sort of results I have managed to obtain
> at:
> http://www.poppyrecords.co.uk/other/DistortionMeter/Manual.pdf

Do you precut the openings?  Or, as you mentioned above, "burn"
through the acetate once the label is affixed (less of an alignment
problem, there)?