Thread: How to: Duplicating a radio bezel.

Here's a few pictures of how the LCD I'm planning on using might look when situated in my WRX's dash:

8.4" LCD in WRX dash.

Since the LCD takes up so much space, I'm going to want to mount it securely to the dash instead of the bezel, so in order to do that, I'm going to have to make some brackets.

As you can see in the pictures, the red lines indicate where the brackets would need to fill to support the LCD.

Instead of trying to bend metal into shape, I'm going to make an exact-fit part, using 2-part molding putty (pic attached) to capture the exact shape and size of the area.

To use the putty, you take equal parts of the blue and purple putty, knead them together, and push the putty into place. The now-activated putty will then cure in about 5 minutes, and you can then pull it out with an exact impression.


But you can't make a bracket out of rubber, right?

No - instead, what you'll have is a positive mold, or what the actual part would look like, but made out of rubber.

In order to duplicate that rubber blank, you would then have to mix more silicone molding rubber, and pour it on top of the rubber blank.


But what happens when you pour rubber on top of rubber? It fuses together! Uh-oh!

The solution to avoiding that is to coat the rubber blank in what's called a mold release - normally this is something like talcum powder, but there are other things you can use with silicone rubber as a mold release:

• Talcum Powder
• Lacquer Primer Spray Paint

The added benefit of using the Lacquer Primer is that it doesn't stick to the rubber - so if you spray the inside of your finished mold and let it dry, when you pour your resin, it cures inside the mold against the primer, and bonds to the primer for a pre-primed part out of the mold, ready for painting.

I made two right-angle pieces of foamboard, and used them to form the molding putty up against the upper radio mount points on the WRX console.

The picture shows the two rubberized moldings - the part on the left is actually the piece for the right side of the opening, and the part on the right is the one for the left side of the opening.

The sides of the foamboard that face "up" are in the center.


As you can see, the left piece (the "right" piece) turned out fairly well.. I may re-mold the other piece.

The pieces will be trimmed and re-shaped to fit better, and may be shortened to properly support the LCD in the right position.

Could you explain why the box has to be so much larger than the original part?

It looks like there will be a lot of space around the area that needs casting, but I'm sure there must be a reason for that, is it just strength of the mould?

Originally Posted by mp3oplecarrier

Could you explain why the box has to be so much larger than the original part?

It looks like there will be a lot of space around the area that needs casting, but I'm sure there must be a reason for that, is it just strength of the mould?

Absolutely, I welcome any and all questions... this thread would be kind of one-sided if it were just me posting here.


This box has extra room around the sides so I can leave room for the pouring and venting channels, but normally it's reasonable to have an extra 1/2" to 1" of room around the sides.

In this particular case, I have left plenty of space above the part because I am expecting to rebuild and extend the duplicated part by about 2 inches in height.


The finished extended part will be placed back in the original mold, and the sections of rubber that lay under the extended sections of the part will be cut out and new rubber will be poured into the cut-out sections.

In this way, the original mold can be modified and extended, without having to re-pour an entirely new mold.


And to a certain extent, the box itself lends some strength to the finished mold, though in most cases the box is cut apart to remove the mold.

I'm nearly done trimming and shaping the rubber blank for the part that will be the right-side LCD mounting bracket.

The piece snaps in perfectly and fits so well, I may not even need to use screws to secure it!

With two of these pieces in place, and an LCD or a mounting plate screwed to the front of it, the lugs on the side of the bracket will keep the whole assembly in place.

I've cut some extra pieces of 1/2" foamboard to fill up some of the space around and under the bezel, so as to reduce the amount of rubber I will need to pour.

The addition of the 1/2" foamboard reduces the cubic inches by about 45 CI, reducing the amount of rubber needed by about 2 pounds. And for rubber, a single-pound of rubber can cost you about $15-30, so it all adds up.

The first picture shows the box with the extra pieces of foamboard in place, and the holes where the bezel's pegs sit.

With the bezel in place, the vertical gap between the board and the bezel is about 1/4", which is easy to fill with modeling putty.


The second picture shows how the pouring and venting channels will be laid out.

Normally, for larger (thicker) pieces, you can just have a wide opening at the top, and pour the resin in there, with enough room for the air to escape the mold.

However, for something thin like this, you need to create seperate pouring and venting channels so the resin can get in, and the air can get out.


The second picture shows the pouring channels in Red, and the venting channels in Blue.

Now you may be asking, why are the pouring channels looping down to the bottom of the piece?

That is because if you pour the plastic resin in this fashion, the resin actually pushes the air out of the mold out through the top, resulting in a perfect pour with less air bubbles in the finished piece.


The pouring/venting channels will be sculpted onto the posterboard with modeling clay, and will actually be molded into the rubber when it is poured.

Man, this is one hell of a job... very nice ... stickyyyyyyyyyy a must.

Originally Posted by MatrixPC

Man, this is one hell of a job... very nice ... stickyyyyyyyyyy a must.

Thanks!

And I'm not even half done.. this thread is just on how to duplicate the bezel, but I'm also going to modify and extend the duplicate part in the process.

Right now, I'm waiting on my shipment of silicone RTV molding rubber to arrive in the mail before I can really continue.


I used to (and still will, when I have time) build anime models, and sold hobby supplies through a web store (I don't anymore), so I've become quite experienced with casting, modeling, and generally making things.

I've made resin copies of super-small parts before, about 1" long, with fine detail - it takes a little bit of thought and design, but in most cases you get good results.