need help and advice on cutting this shape in a project enclosure

Discussion in 'Off-Topic' started by count_volta, Nov 10, 2010.

  1. count_volta

    Thread Starter Active Member

    Feb 4, 2009
    435
    24
    Hey, I'm working on a little binary clock for fun. My clock requires a custom led matrix made from square led's. I have the led's and have superglued them together already. I got a radio shack project enclosure. Now I need to cut a hole to put the led matrix in.

    Here is the shape.

    [​IMG]

    I have tried to do a practice box using the dremel. It sorta sucks. LOL. Here take a look.

    [​IMG]

    This just won't do. I need to try something else. What can I use? Xacto knife? Drill press saw? What else?

    How about one of these babies?

    http://www.harborfreight.com/electric-body-saw-65766.html

    I can cut the shape in a piece of plexiglass and then cut a square into the project enclosure and glue the plexi into the enclosure, but what do I use to cut the shape in the plexi?

    I'm sure you guys have plenty of experience with stuff like this. Help me out please. :D





    [​IMG]
     
  2. Otaku

    Active Member

    Nov 19, 2008
    128
    2
    Got a buddy with a Bridgeport mill? If not, you can drill small holes at the corners of the pattern. Use a Dremel hand tool to "connect the dots". Use the rigid fiber cutting wheel to make the cuts, and use the slowest speed practical. ABS will easily melt if you go too fast. Secure the box so it can't vibrate, and use guides when you can. Take your time. The edges may not be perfect, but if you're using a bezel, it may not matter. If you just can't get what you need using hand tool methods, you could try a Tap Plastics store if you have one in your area - they do plastic fabrication work. A laser-cutting shop would be a good place to look, but the melting issue may come up again.
     
  3. count_volta

    Thread Starter Active Member

    Feb 4, 2009
    435
    24
    I used the rigid fiber cutting wheel in the photo above. You see the result. LOL. Drilling holes in the corners might actually be a good idea. I can try. I don't have a Bridgeport mill, but we have one in my university. I have also considered laser cutting. There is a pretty cheap service I found online that does it.

    More suggestions are welcome.
     
  4. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    It helps to have sculpting experience. Dremel is the way I do it. Slowly, softly catche monkey.
     
  5. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Laser cutting black plastic is a good way to go.

    Black absorbs the most energy which results in lower cost for laser cutting.

    It is also pretty exact.

    I would go that route if it is available.
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    You could also use a sharp exacto blade, it is slow but if you take your time, sure. A fine metal file (but not too small) is also good for fine work and corners.

    It becomes obvious why everyone likes home made milling machines now, doesn't it?
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,694
    904
    Look for a mortise cutter or a nibbler. There are lots of ways to get the basic shape, but you will have to contend with making round corners square. Even a mill with a very small bit will leave a little rounding. Is a little rounding bad?

    The mortise cutter can be used as a square punch in a drill press. You can also do it by hand. Nibblers are available in powered and hand versions. The hand versions are not too expensive. The nibbler is a square punch and die in one tool. It does just like the name suggests.

    Files, knives, etc. can also be used to square corners. Of course, a CNC laser or plasma cutter is probably the best way, but you probably don't have one in the kitchen cabinet.

    If you want a nice finish, I would not use heat. Some other advice is to lay out the pattern carefully on the plastic. Since the plastic is black, you will need a contrasting color. Silver, fine-tipped Sharpies are available. Alternatively, I print out a pattern and attach it with repositional adhesive.

    If I were doing it, I would attach a paper pattern to the back (as described). Protect the front with paper masking tape too. Drill a 1/4" hole somewhere, and cut the pattern to rough shape on a slow speed scroll saw. I would then finish the edges and corners with files or a modeling knife (XActo-type). Unless I had a good square punch of the exact right size, I would probably not use it. Even then, getting it positioned precisely is difficult.

    John
     
  8. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,789
    945
    Drill out various size holes for all that you can and use Xacto blade type tools AND wood working files to smooth out the ridges.

    If you had a router table, I would suggest a 1/8 inch side milling bit and Xacto for corner cleaning.

    Check out Micromark.com for a small mill(I own one myself). If you feel you can spare the $500 then you WILL find lots of uses for it in prototype building.

    With the proper bit and a well squared up machine you can mill away the copper on a circuit board, just .002 inch thick and not cut away the fiberglass board underneath. :)

    Beats the etchant tanks for a small one off board, like a SMT LED array. Lot of copper and just a few straight line isolation runs and you have plenty of copper for heatsinking and can solder the devices straight to the board over the channels you mill into it. You'll find lots of other uses as well. Templates and small bits in a router work about as well.
     
  9. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    Drill, compass saw, and a file or dremmel to do the touch-up . Use the drill in every corner to create space for the compass saw blade. Be patient and work slow the sawing. Do not cut exact on the line. But save some material for the file to work on, in order to do the touch-up .
     
  10. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Shoot, you get the basic shape right a simple pocket knife will square corners, this part isn't rocket science.
     
  11. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
    304
  12. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
  13. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Problem is, the jaws of a nibbler tend to leave major marks. I've used them since day one, they work but I'm not a fan.

    The best results I've ever gotten bar none is a bridgeport milling machine with a digital readout. That was sweet.
     
Loading...