How to: Duplicating a radio bezel. - Page 3

imprezive one · 01-03-2005, 07:25 PM

I *heart* this thread

imprezive one · 01-03-2005, 10:06 PM

Quote: Originally Posted by Giuliano

Here's an obviously photoshopped image of what I expect the modified and finished bezel to look like.

I'll probably end up painting it a pretty blue color to match the car..

I've got some specialized hobby paints that will do the job nicely - they're acrylic lacquers, so they go on real smooth and are real durable.

Just wondering. How will this fit into the stock bezel mount location? It looks to be much taller to accomodate the bigger screen. Are you going to modify/get rid of the cupholder/blank peice to accept this? I assume so.

Giuliano · 01-03-2005, 10:50 PM

Quote: Originally Posted by imprezive one

Just wondering. How will this fit into the stock bezel mount location? It looks to be much taller to accomodate the bigger screen. Are you going to modify/get rid of the cupholder/blank piece to accept this? I assume so.

Yes, I'm getting rid of the cupholder/blank section (already have) to make it fit.

See this thread for pictures:

http://www.mp3car.com/vbulletin/showthread.php?t=39131

I've been cross-posting various threads for this project, depending on the subject at the time.

In this LCD thread, I mentioned an 8.4" LCD that had a native resolution of 1024x768, which is outstanding.

Unfortunately, that LCD is another 2cm too tall, or 4cm compared to the original bezel, to fit in the dash as-is, or even with the cupholder/blank removed.

The only option would have been to remove the A/C controls for space, and replace them with a servo/relay computer-controlled system.

THAT is a project for "Version 2" of the car computer system, far in the future, or next year, which ever comes first. ;-)

I'm already brainstorming on it... computer controlled with custom software designed to look like the WRX's A/C controls.. but with a small control box/panel for manual control.

It's a hefty project in itself, nevermind adding it on to an already big project like this.

Optikal · 01-04-2005, 12:49 AM

Can't you just order a replacement bezel from the Subaru dealer? I know you can for Acura's (and you can get a cheaper bezel from SoundDomain specifically for the RSX).

Giuliano · 01-04-2005, 09:59 AM

Quote: Originally Posted by Optikal

Can't you just order a replacement bezel from the Subaru dealer? I know you can for Acura's (and you can get a cheaper bezel from SoundDomain specifically for the RSX).

Absolutely, I could, and it would cost me about $50 plus shipping for the part.

However, the part itself is made out of a very hard plastic called ABS (Acrylonitrile Butadiene Styrene), a form of "normal" plastic (styrene).

As a result, it is rather difficult to cut, modify, and shape - it tends to shred instead of cut smoothly.

Polyurethane resin plastic, which is what I'm going to be using for this, is a lot like epoxy glue/putty in nature, and is quite a bit easier to work with.

It also has the useful property of being immune to strong solvents, such as lacquer thinner.

So yes, in this case, I am spending a lot more to create a mold and duplicate the part in resin.

The upshot is that if I was working on the modified part, and I somehow screw it up.. I can just pour another cast, and start again.

Marsupial · 01-04-2005, 02:29 PM

Also, I think it is easier to make a bigger and to cut from it then making an actual factory made part bigger then it was intended to...

Giuliano · 01-04-2005, 02:44 PM

Quote: Originally Posted by Marsupial

Also, I think it is easier to make a bigger and to cut from it then making an actual factory made part bigger then it was intended to...

If you meant that it is easier to make a copy and cut it, than it is to cut the original, then yes.

The resin is a softer plastic, and is easier to sculpt/cut/carve.

Not that it has to be soft - there are resins that have plastic fiber fillers and aluminum fillers, and can be milled, turned, tapped, etc..

If you modify a part, and then cast a duplicate of it, the new copy would be stronger than the original modified part, because it is cast as one whole piece.

Marsupial · 01-05-2005, 08:44 AM

Well, if you take the original part, manage to cut it, you're stucked to putty it bigger and paint it for a (IMHO) ****ty result, compared to having a whole new part with your technique...

I always wanted to try plastic molding, but never knew where to start from... thanks to you I might get to try soon...

Giuliano · 01-07-2005, 06:00 PM

My eagerly-awaited silicone RTV molding rubber arrived today! Huzzah!

The rubber consists of two parts - the base material, and a curing agent.

By themselves, they'll sit in their containers and do nothing.

But mixed together, the chemicals in the materials generate heat, causing the rubber to cure, or vulcanize, and become solid. Hence the RTV, room temperature vulcanizing.

The big bucket is a 1-gallon pail, filled with about 8-9 pounds of base rubber, in a liquid form - it can be poured, but it's thick.

The bottle on top contains the curing agent.

When the base rubber and the curing agent are mixed together in a 10:1 ratio by weight (base rubber:curing agent), the rubber starts the curing process, which takes 16-24 hours to complete.

For this version, once you mix the two parts, you have 60 minutes to work the rubber, and it cures in 16 hours at 77 degrees F. But for best results, leave the mold alone for 24 hours or more.

This rubber is measured by weight, so it helps to have a good scale - and for a 10:1 ratio, one that measures in grams or kilograms makes it easier.

I got mine direct from Polytek by mail order. The prices shown on the web site include the cost of shipping via UPS Ground, so the price may change.

When I ordered my 9 pound bucket, it was $116 - but there's a secret they don't tell you until you order, and that is new customers get their ordered product at a special discount price - basically free shipping, so it cost me around $96., or around $10 per pound.

Of course, I need a lot of rubber for this mold, so a full 9 pounds is necessary.

I'll be finishing up the molding box tonight, and will start the pour tomorrow. De-molding will probably be on Sunday.

imprezive one · 01-07-2005, 06:06 PM

w00t w00t!

Just wanted to ask, are there any cheaper alternatives out there that could be used? I had no idea it was so costly.

Giuliano · 01-07-2005, 06:46 PM

Quote: Originally Posted by imprezive one

w00t w00t!

Just wanted to ask, are there any cheaper alternatives out there that could be used? I had no idea it was so costly.

Yes, and no, of sorts.

There is a less expensive rubber type, polyurethane RTV instead of silicone RTV rubber.

http://www.polytek.com/products/poly_mold.html

The average price is about $60 for 6 pounds, or $160 for 24 pounds.

Polyurethane RTV rubber is normally used for casting plaster or wax, but you can use it to cast plastic with the use of a release agent, otherwise the polyurethane plastic will stick to the polyurethane mold.

I chose silicone RTV for specifically for this reason, as polyurethane resin won't stick to silicone (silicone is non-stick), and you don't need a release agent.

You can still use polyurethane RTV for casting, it just takes a little additional work.

Silicone RTV is easier to use, and is more easily found at local hobby stores.

Also, all mold rubbers will deteriorate with use and time, but silicone rubbers work best for polyurethane or epoxy plastic.

Giuliano · 01-08-2005, 05:31 PM

Now that my silicone RTV rubber has arrived, I can put the master part in the box, and seal its edges with modeling putty.

You have to seal the edges of the piece (unless it is perfectly flat, and even then I would still use clay), otherwise the poured rubber will flow underneath the piece, and you don't want that to happen for a 2-part mold.

In this case, I am using an oil-based modeling clay from Van Aken, that never dries out, and is compatable with silicone rubber.

That last part is important - the clay must not contain sulphur, because sulphur can interfere with the silicone rubber's curing process.

The stuff I got is pigmented (colored), and in retrospect I should have gotten pigment-less clay, as the pigments leave a mess on my hands, and the oil-base is a bit of a pain to wash off.

There was also wax-based clays available, but they didn't explicitly say "silicone compatable", so I passed.

The picture shows the master part mostly sealed.

I've applied a 1/4"-1/2" snake of putty to the edges, pressed it in to seal, and trimmed it with a special modeling razor blade.

The blade that I used was a Flexible PolyBlade from AMACO (American Art Clay Co), made of super-flexible stainless steel 6" long, and can shave off slices of clay super thin.

I got it from Michael's arts and crafts for about $5, well worth it. I also use it shave off thin slices of posterboard, but I wouldn't use it for heavy cutting.

The rest of the part will be sealed off, and the casting and venting channels will be created out of more modeling clay, to be cast into the rubber as channels.

Giuliano · 01-08-2005, 08:51 PM

I used about 1/4 pound of the modeling clay to create the pouring and venting channels in the box.

Rather, the clay will form the impression of the channels into the molding rubber.

When this side of the mold cures, those channels will be filled up again with molding clay, and the other side will be poured.

The result will be hollow channels in the mold, ready for resin to flow.

The channels were rolled out of 1/4" molding clay snakes, pressed to the posterboard, and trimmed down with the shaping blade.

The venting channels up top were made thin and narrow on purpose, as air doesn't need a lot of room to escape, and narrow channels mean less resin to take up space.

The pouring channels on the bottom were made a little wider, because the resin is thicker than water, and needs a little space to flow.

I picked up a few cheap supplies from the local Dollar Store for mixing the molding rubber, basically consisting of a large plastic bowl, a scraper spatula, and a cheap tupperware-like container for mixing the resin.

The large plastic bowl will be for mixing the molding rubber, and the spatula is for mixing and scraping the sides to get all the rubber out. The silicone rubber when cured won't stick to the plastic bowl, so you can just peel off any leftovers.

The resin, however, will stick to the regular plastic bowl, so the tupperware-like container will be used for the resin.

The tupperware-like container I believe is made out of polyethelene, and the resin shouldn't stick to that.
Any leftover resin should pop out, but in case it doesn't, it's not a big loss.

The stuff cost me like $3, so it's cheap.

I'll be mixing and pouring the molding rubber tonight, so more pics will be posted later.

Giuliano · 01-09-2005, 10:35 AM

The first half of the mold is complete, and I've taken it out of the box to air out.

The silicone RTV produces alcohol while it cures, so you should let it air out for 24 hours before using it.

There's a lot of pictures here, and they're all hosted from my cable connection, so please bear with the load times.

First, I modified the box some more to reduce the amount of rubber I would need to pour. The fact that it isn't a square anymore doesn't matter.

In order to measure out the rubber, the mixing bowl was placed on the scale, and the scale was re-set to 0, to ensure an accurate measurement.

I measured out 3 pounds of rubber to start, and measured 0.3 pounds of catalyst on the digital scale on the left.
Actually, I used Google to convert 0.3 pounds to grams, and measured it out in grams, as it's a bit more accurate that way.

Here's what the base materials look like:

And mixed:

As you can see, 3 pounds wasn't quite enough to cover the piece. Not a problem, as I had 60 minutes to work with, so I mixed another 1 pound.. then another.. and finally another, making 6 pounds total to cover.

About 8 hours later, and the rubber has cured enough to de-mold the part.

But first I have to get it out of the box - and the easiest way to do that is to cut the box apart at the seams.
Easy enough to do, and the box can be glued back together for the second pour, or a new box constructed.

Some of the excess rubber was trimmed off the edges, and the mold peeled right off of the posterboard.

The blanks on the back of the bezel were popped off, and the part was re-inserted into the mold face down. I also sliced the modeling clay venting channels off the posterboard, and re-inserted them back into the rubber.

All of the blue sections you see above will be later sprayed with a lacquer-based primer (without the part installed), the box will be reassembled with the mold face down (as shown), and the second half of the mold will be poured.

The lacquer primer will prevent the two halves of the mold from sticking together, and is called a barrier coat.

I don't have too much rubber left in the bucket, but I won't need that much, as the rubber doesn't need to cover too much of the back side of the mold.

imprezive one · 01-09-2005, 10:48 AM

rock and roll! that's so sweet. I have a feeling your experience and the wisdom that you're sharing with us is going to come in handy for me in the future. A lot of those things I would never have found out any other way but hard way. awesome.