Tuesday, 27 May, 2008 § 2 Comments
Since this project is based on an FTIR setup, the sides of the acrylic sheet need to polished as to allow TIR. However since most factory cut acrylic sheets are cut using a saw the they are really rough…
The Osyris Digital IO prototype consists of an acrylic sheet which will be mounted in a frame. Having tried to maintain a (4:3) aspect ratio. The The Acrylic Sheet is 24″ x 32″ = 60cm x 80cm of size and 3/8″ = 0.921cm thick. However the actual projection area is 58cm x 78 cm.
The acrylic sheet was purchased from Laird Plastics Toronto (Mississauga) for $55 CAD, it came in a traditional paper protective layer.
Below is the process of how to i polished my acrylic sheet.
– Fine hand file
– (Dry) sandpaper of the following grit sizes:
– (Wet) sandpaper of the following grit sizes:
– Old cloth
– Some old newspapers
– A bucket of water
– And finally a lot of patience!
General hint:After obtaining my acrylic sheet i found out that many suppliers polish the edges for you, i suggest this would be the best way to go, it will save you a good couple of hours of manual labour as well as a tired arm.
Polishing step by step
Depending on the state of the edges you should decide how many different types of sandpaper and/or the type of hand file you want to use.
In my case I rather than using sandpaper first i started off with a fine hand file. Mainly because as you can see from the picture, my acrylic sheet was very rough. Continue filing all 4 edges until no deep scratches of the cutting saw are visible anymore. After using a fine hand file the it should look a bit like this:
As you can see the acrylic at this point is still very rough, however it now has a an even surface which can be polished with sandpaper.
In my case I started with the P100 grit sandpaper. Sanding all 4 edges, resulted in all the scratches from the file disappearing. After a quick 30min of polishing with P100 it should look a bit like this:
Next i continued polishing all the sides with 200 grit sandpaper… followed that with using P400 wet sand paper. Note: when using Wet (black) sandpaper its best that you wet the sandpaper and then use it as it produces better results and lasts longer. After 400 grit sandpaper the majority all the scratches were eliminated but the surface still remained dull as can be seen from the picture below:
If (almost) no scratches are visible, continue using P600:
The Acrylic Sheet at this point is very clear it doesn’t appear to be so in the picture… but trust me it’s crystal clear… Just as a last final measure, use brasso and an old rag and buff out the edges to give that fine polished look.
Congratulations!! you now have a polished acrylic sheet.
At this point you if you are still able to move your hand pat your self on the back, sit back enjoy pull out a a good cigar, lean back on your chair and admire your creation… making it to this state i assure you your arm will be tired and most probably be hurting as well …
take a break and see you next time.