Multitouch Display: a plexiglas case for the LCD FTIR multitouch (part one)

As you surely remember, three weeks ago I posted about my first test with an LCD panel for multitouch applications. I saw that it had enough chances to work out but I was so scared about the fact that the bare LCD panel is extremely delicate. So, as I was saying at the end of the post, I started to think, then work, to a case for this multitouch display.

Of course I thought about a case that should also look nicely, what's better than a plexiglas one?

So, after some weekends of work, this is how the case is looking today:

I designed it trying to keep its size as small as possible, so I went for a cut pyramid shape. The pyramid is (or better, it should) be deep enough to hold the webcam in a position that, using the wide angle optics, is far enough to capture the entire screen view.

I can honestly say that probably I choose a very complex shape to build, infact it took me several days to bring it to this stage. For this reason I'll talk about how I proceed and I think that this will fill at least 2-3 posts. Let's start!

First of all, reading also several modding forums, I undestood that plexiglas is quite difficult to work so I choose a similar material, the transparent polystyrene. It seems more tollerant to mistakes even if it is more easy to melt while working with electrical tools like drill or saw.

Anyway, all begins with a good drawing scheme of the whole case and the pieces that needs to be cut. I paid big attention in this trying to consider every factor like angles because there are very few square angles in my design, and exact polystyrene sheet thickness.

In addition, there are some bends in my design and I was not knowing how much material the bend was taking, so, basically, I was abounding with measures (3-5 millimeters more) impacted by bends and I considered to cut again the parts after bending them.

I used the electric hacksaw for cutting the polystyrene sheet but, keep in mind that it tend to melt very easily. So, to avoid that, I used a dimmer to regulate at very low speed the saw. Let's say a 2 saw movements per second under load. This useful also to be very accurate in cutting following a straight line.

I know, every single sencond that you spend working this kind of material you are tempted to take away the protective film but, I can say that it is very important to keep it on until the very end. In bad cases keep it in place with adhesive tape but don't remove it!


Then I cut some pieces of wood to use as mold for bending the pieces of polystyrene. Then I used those pieces to build a complete mold for every piece. It was a little bit of work more but absolutely essential to have a precise bent shape.


Once I had the molds, I started to heat the polystyrene. I used a heat gun, one of that tools that are useful to remove the paint. Basically it is a sorta like of hairdryer with a high temperature airflow.

I used it very gently, moving it very often, slowly but constantly to avoid any break in the plastic sheet. Despite this, one of the pieces broke and it was the last one (of course)!

The polystirene sheet that I used was 5 millimeters thick and it took about 2-3 minutes with the heat gun to soften enough.



When it was ready I gently pressed it on the mold and I used other wood sheet and small morsel to keep it in place. The polystyrene needs another 3-5 minutes to cool down enough to be hard again and, with the morsels it could take all the time it needs.


I paid particular attention to the angles. In order to have clear ones I used pieces of wood to press the polystyrend exactly on the edge.

I can say that the more you heat up evenly the polystyrene sheet, the best bending results you will have.


The last step that I will show in this post is regarding the piece for the back and bottom of the case. It was the most difficult one because it had two bends. Of course I had to create an ad-hoc mold just for it.

I'll continue to illustrate the case building process in the next posts, stay tuned!