Working with Acrylic or Molding Plastic

[TheEdge]

Does anyone have any experience with this? I am building a rather small case and would like the 4 sides and top to be one seamless piece either by expoxying acrylic together or using some product that can be molded to form the 8" cube shape I am looking for. I would like its finish to be a high gloass as well.

I have contructed an 7.5" cube out of 1/16" angle aluminium and rivets. I would like to be able to slide this case into the exterior enclosure and secure it from the bottom so all screws are hidden.

I have selected a mini-ITX board with a slot style DVD-RW ad notebook HDDs. Backpanel outputs will only include 3 LAN ports, VGA, 2xUSB and a serial port.

Case components:

http://www.michaelbellini.com/frame_parts.jpg

contructed Case:

http://www.michaelbellini.com/frame.jpg

Desired finished look:

http://www.michaelbellini.com/mod_cube.gif

If anyone has any input on how to acheive this finished look I would like to hear what you have to say.

Thanks.

[tybrenis]

Hello,

I guess you could say that I "specialize" in plastics. I have experience with injection molding, vacuum forming, casting, extrusion, and most aspects of plastics and thermoforming.

For that nice, high gloss look, I recomend using acrylic (polymethylmethacrylate, to be specific).

You can purchase 1/8" acrylic at home depot or lowes. However, for a computer case, I would normally recomend thicker acrylic (like 1/4"), but since your frame is so small you could probably pull it off.

I would buy a sheet of 1/8" acrylic in the size that you need. Home depot won't cut your acrylic for you, just to let you know. They don't do plastic. Use a table saw to cut the pieces to length and size.

Once the acrylic is all cut properly, you should spray paint the back side of it. Put the unpainted side out, and this will give you an automatic glossy look. Krylon makes a brand of paint specifically for plastics, known as Krylon "Fusion" paints. Look for those. Otherwise, with a little bit of sanding with say a 400-600 grit sandpaper before painting should work fine for you.

To cut out holes and shapes in acrylic, a router mounted on a table is what I would recomend the most. However, you can also use a bandsaw or scroll saw with a fine toothed metal blade.

If you need any help with any type of plastics or any of this feel free to ask, I love to help people with their plastics problems. I have even done a few custom acrylic enclosures for people before, so if you need a part or something I'll do my best.

[TheEdge]

Just the feedback I was hoping for.

I made the cube frame 7.5" to allow for 1/4" acrylic, so I will go with that. I would like the corners mitred, I was hoping to have all four sides and the top joined as one piece, how hard would this be to accomplish, and will there be a trade off in overall strength doing it this way?

Does vacuum forming offer any advantages to accomplising my goal? Are there places that will vacuum form plastic to a certain spec that won't require a bulk order?

[tybrenis]

There aren't a whole lot of places that will vacuum form to a small order like this, and besides, vacuum forming is NOT what you want in an object with square corners and everything. I recomend purchasing some solvent glue and a syringe for the gluing of the pieces together.

This method actually strengthens the pieces structural integrity, as opposed to weakening it.

Also, you won't want to glue every piece in, you'll need to remove stuff some day!

[TheEdge]

What abotu blades for cutting, what should I be looking for there?

Also, I have found some companies that sell solid color acrylic in 1/4" x 24" x 48" sheets, would you recommend using a colored acrylic or painting the back of the acrylic?

[gobygoby]

I also specialize in working with acrylic.

If you want to cut acrylic on a table saw use an 80 tooth or higher blade to get the best cut, it will be "ok" to go straight to welding, but for near perfect edges they should be cleaned up on a router.

Also, mitred edges on acrylic is pretty tough, but since your only dealing with smaller pieces it may turn out ok. I would suggest using a jointer/planer to get the 45 degree edge. I have done this and it works rather well. Just set the fence at 45 and make a couple of passes.

I would recommend using weld on 3-4 as the solvent. no real need to go with anything higher

[tybrenis]

If you can afford/find colored acrylic sheet, I say go for it. Before gluing, you could do goby's router method, but I always just scrape my edges first, using an edge scraper or just a sharp square of something like steel or cobalt.

If you need to polish any edges, you'll want to scrape them as well before sanding or flame polishing them to a nice finish.

Try and find a local plastics shop. They will be happy to sell and cut all of this for you and save you the trouble.

Now, I don't know your budget, and I don't know how much you plan on working in plastics later on. However, if you want the best solution for cutting acrylic, you'll need a table saw with a blade with carbide tips, in the "triple chip" format. This is the perfect blade for acrylic, however, it'll be fairly expensive.

Weld-on is a great commercial solution for gluing acrylic. But you can also glue it with methylene chloride, or using a mix of acetone and methyl ethyl ketone.

[TheEdge]

I will look into a shop to make the cuts and do the welding, but if I have to do it myself I would invest in the proper blade.

I found this site who sells colored Acrylic:

http://www.usplastic.com/catalog/variant.asp?catalog%5Fname=USPlastic&category%5Fname=21314&product%5Fid=9841&variant%5Fid=44750

And this site that sells welding supplies:

http://www.delviesplastics.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=DP&Category_Code=Acrylc_cement

Thanks for al the good tips. I will post my updates of the custruction as I go.

[tybrenis]

Both of those web sites are great resources and sell both the supplies you need.

http://www.usplastic.com/catalog/category.asp?catalog_name=USPlastic&Category_Name=24840&Page=1&clickid=leftnav

[Nox]

Just a warning if using MEK (Methyl Ethyl Ketone) - DO NOT get that **** on you!
It is highly absorbent throught the skin and respiratory sytems and when absorbed into the body in large quantities, can cause blindness as the toxins in MEK go straight to the optic nerves. Ask any numer of retired car parts guys, they used MEK to clean car parts without using gloves, and thats why they can see for **** any more.
There are also several other dangers in working with MEK: See this link -

http://www.inchem.org/documents/icsc/icsc/eics0179.htm

[tybrenis]

There are many dangers involved when working with ANY solvent or thinner. You should ALLWAYS look up safety precautions before using any chemicals.