I considered many different ideas:-
1) A full sheet of perspex on the front of my enclosure. Great finish but expensive and difficult to seal as fully transparent.
2) A small piece of perspex over a cut hole in the enclosure. Cheaper but not so nice finish, showing the full LCD through and any rough enclosure cutting.
3) Looking for access to a laser cutter to make a profiled perspex window that sits through the enclosure hole to sit flush with surface. Difficult tolerances and no depth control with a laser.
4) Asking a local workshop to make a profiled perspex window on CNC milling machines. Cost more than using a full perspex sheet.
So, eventually I tried something else and ended up with what I think is a nice professional finish that is easy to do, cheap, and results in an iPhone type black glass frame style, with a clear window exactly the right size to show the display properly. It can also be easily adapted to any other type or size of display.
Step 1: Create and Print a Template
Since I've been getting more proficient with CADSoft Eagle, I simply used a blank BRD file with mm grid to create my drawing and print at scale on to some card.
You could use any package that allows you to create accurate drawings at a 1:1 scale. You need it to come out in print to the correct scale.
I took the original dimensions of the 16x2 LCD display I had and drew it up, including the stand-off holes. I then added an additional 5mm surround to give my bezel additional strength around the fixing holes, and also to make it look better since the holes wouldn't be right on the edge.
Print the template off and then use a sharp knife (craft knife, trimming knife, scalpel), or scissors, to cut out the outline and the inside border.
I used plain card for this, but a bit of extra time to make a plastic/acrylic template might be better if you intend to make a lot of these.
Step 2: Use Template to Mark Out on a Piece of Perspex
A fine tip permanent pen like a Sharpie or Write-4-All works well on the acrylic. I used 1.5mm clear acrylic sheet for a glass-like finish. You could use different colour acrylic or thicker/thinner to suit your requirements.
You can cut the acrylic by hand with a hacksaw or use a machine like a jigsaw or fretsaw very carefully.
The ideal way of cutting these would be using a Laser Cutter for the perfect finish.
If you, like most of us, don't have access to a Laser Cutter, then use a file to get the edges straight and smooth afterwards.
Step 3: Mask Up the Window Area
For the 16x2 LCD the display area is approx 15mm x 65mm. I made my window 14mm x 64mm so there is a slight overlap to the display so no edges can be seen.
To do this we simply want a piece of tape stuck to this area so that it does not get painted. I used electrical insulation tape as it cuts and peels easily and leaves no residue.
Lay a piece of tape long ways across the centre of the acrylic piece.
Lay the template back over the top, lining it up with the acrylic edges.
Use a sharp knife to score lightly along the inside edges of the window area. Pay careful attention to meeting up in the corners so that our tape has a continuous rectangular cut.
Remove the template and then peel the outer area of tape away and this will leave a nice clean cut 14mm x 64mm piece where our display will eventually show through.
Step 4: Drill the Mounting Holes
These correspond exactly to the stand-off holes in the LCD PCB. This means we can use a single metal or plastic bolt to mount both our bezel and the LCD when finished.
NOTE : Always drill a pilot hole first. This means you can be more accurate with positioning, and also means you don't make a large hole in the template.
Lay the piece on top of a scrap piece of timber. I used a bit of 1/4" ply. I also put a piece of the protective film underneath to stop the acrylic picking up any dust and fibres as much as possible.
Place the template back over the piece, taking care to align with the acrylic edges.
Drill the center of the stand-off holes with as small a drill bit as you can. I used a 1mm drill bit.
Remove the template and then re-drill with the correct sized drill bit. I used a 3.5mm bit to give me a slight play to offset any error due to manual drilling.
Make sure the piece is always flat, with the timber behind, and that you drill SLOWLY. This will ensure an accurate drill with minimum of swarf, rough edges and chances of cracking.
Step 5: Spray Paint the Piece
The key here is preparation and patience. The longer you take the better the finish will be.
Use some of the insulation tape doubled back on itself to act as double sided tape and mount the acrylic piece to some backing paper or card. The masking tape applied already should be FACE UP.
Mounting the piece is to make sure it doesn't get blown around by the force of the spray can, as we don't want overspray onto the other side of the acrylic.
EDIT: On making one for a 64x128 1.8" TFT display it occurred to me that we can simply mask the back side of the acrylic completely. This ensures 100% that you don't get any overspray on what will become the top face. When everything is dry just peel off the masking on the other side too.
Make sure the upper surface around the masking taped area is clean and free of grease and dirt so that a good coverage of paint is achieved.
Take the piece into a well ventilated area before spraying. Outdoors is best, or a garage with open door. The paint has quite an odour until fully dry.
Apply a generous coating of spray paint from a distance of 15-25cm minimum. DO light coats and repeat as necessary. Take care to also paint the acrylic edges if you want this, although these will appear coloured anyway.
Let the piece dry THOROUGHLY before handling.
Step 6: Remove the Masking
Be VERY careful when picking at the edge of the tape as you don't want to scratch the painted acrylic.
Once you have an edge then slowly peel the tape away from the acrylic and you will be left with a nice sharp and clean edge between painted and non-painted area.
Now, turn the piece over, so that the paint is on the bottom.
You now have clear acrylic top face with a painted underside. The top is nice and shiny and the coloured finish cannot be marked or worn away as it will be face down on your enclosure.
I found that black paint gave a finish that looked like a black glass bezel with window.
Step 7: Finished Bezel
If you need weather/water proofing then simply apply a thin layer of sealant under the black border outside of the stand-off hole line. When this dries in place it will form a watertight seal that can't be seen.
The finished article looks quite nice.
A better finish could be made if you have access to a Laser Cutter and/or Milling Machine, but hand made can look very good.
This same technique could be used for any size display that needs a custom bezel/window making.
I hope this helps a few people achieve a nice finish to their project.
This is the first instructable I have made so please take a moment to leave feedback on anything you think could be improved, or if this helped you in any way.