Pourable acrylic for casting computer housing? Other clear materials to cast?

[greymatterfan]

Hi all -

For some reason I can't stand to throw away that oceanic prodigy hockey-puck computer that still works perfectly well despite the plastic housing which is showing wear / cracks on the threads. Several cracks are developing where the back piece (threaded ring about 2.5" in diameter) threads into the acrylic housing and I'd like to repair before it fails one of these days.

I've decided it's worth a shot to make a mold of the housing using Smooth-On OOMOO 30 silicone rubber, and that part has turned out well and it's been fun learning about mold-making techniques.

But now I'm running into a little trouble finding the right clear acrylic-type material that I can cast into the mold to make a perfect, rigid plastic, salt-water and UV / temperature resistant replica of the original part.

I've tried castin' craft epoxy, which is nice and clear, but it turns out it becomes rubbery when exposed to mild high temps (like sitting in a hot car or running under hot water).

Next idea is to try alumilite crystal clear or alumilite clear, but I wanted to see if anyone has played around with casting parts / DIY dive stuff using "household" grade resins that don't require pressurized or vacuum degassing?

Any ideas?

 

[Couv]

Hello Greymatterfan,

Unfortunately, I can not help you with your acrylic question, but have you considered using an old Oceanic Data Max depth gauge housing. I do not know if it will fit, but it might be a better solution if it does. I have restored a couple of the old Data Max gauges, so list the dimensions of the unit you have and I'll take some measurements.

Also, I would like to hear about your experiences doing the mold making etc. Could something like this be used to make mouthpieces and the like? Probably worth starting another thread to address this.

Cheers,

Couv

 

[halocline]

There's an acrylic adhesive called weldon#40 that you might have some luck with for repairing the cracks in your housing. It's a 2 part catalytic adhesive specifically for acrylic, and when it cures it's basically indistinguishable from the acrylic it adheres to. I used to use it all the time in repairing and building acrylic aquarium filters/devices. You'll probably have to mail order it, you can try a place called plastix (I think) in albuquerque.

 

[greymatterfan]

Hey Couv & Mattboy -

Thanks for the info.. I'll measure & document the mold making experiments I've tried so far and post up when I get a chance.. I actually realized there are better ways to make the 2pc mold after reading some info on Alumilite's Web site.. My first attempts were close enough, but probably not the "best" way.

The possibilities for DIY casting are very interesting, but I need to find the right type of materials.. I am also thinking about a possible video housing using a sort of honeycomb or triangular cell structure using this method, but want to get these dive computers up and running first. One is an Oceanic Prodigy, similar to the Data 100s.. The other is a DataMax or something like that (rectangle shaped air integrated computer from the 90s..) Replaced the batteries though, and it still works fine. Just need a stupid rubber button and a plastic nut that threads into the back of the housing..

I hate how a few dollars worth of plastic breaking down makes these things unusable!

Anyway, more info from me soon - I'll try to check out the acrylic adhesive and some other ideas.

 

[Couv]

Greymatterfan, I'm looking forward to your updates.

c

 

[M_Bipartitus]

If you thought the epoxy worked well aside from the heat issue, you may consider using marine epoxy such as

Epoxy by the Leading Epoxy Manufacture | WEST SYSTEM Epoxy

I think they have a version that is intended to be extra clear. As it's intended for boats it is perfectly suited to use in water and outdoors. These are rated up to ~120F, but I suspect any higher than that just about any household resin or plastic would weaken.

 

[mksmith713]

I know the perfect material.
Go to Walmart.....to the crafts section.....to the fake flowers.
There you will find glass vases and other misc items to put in the bottom of said vases.
Look for the Acryllic that you use to make it look like water in the bottom of a vase.
It's part "A" part "B"...... dries clear and hard.
Way back when........I used this stuff to plug holes in bowling balls...then re-drilled them.
It stood up to the force of bowling.

 

[greymatterfan]

Ahhh - Marine Epoxy! That might be the ticket. Hoping it's not too hard to find and not too $$$

I just poured the first half of a new mold using the techniques described on Alumilite's site - you can check it out here:

How to mold auto car parts - tail light

The taillight example translates perfectly for this application because the hockey puck computer housing is very similar - just a clear plastic cylinder really - I won't even need to add any coloring.. We'll see how this round of mold-making goes.

MKSmith - I wonder if you're talking about the standard Castin' Craft type polyester resin? I've worked a little bit with that but haven't tried for this application yet.. If it's not polyester resin, I'll have to look for this 'fake water' stuff - didn't see it at the craft store but might have overlooked.

Going to spec out this marine epoxy next and see what happens.. Will update as progress is made.

 

[stano]

Smooth on has an optical grade castable called crystal clear. If you go to their site and search for "crystal clear" it comes up. For some reason on their site it isn't obvious to find. I have not used it but it looks like what you are after.

Stano

 

[greymatterfan]

Hey Stano - thanks for the info.. Smooth-On is definitely next on my list.. Problem is, seems tricky to find it in smaller quantities - I checked out the crystal clear and it's sold by the gallon for $168... did find a place online to get a pint or qt though, so probably worth a shot if I can get it.

I also looked at Alumilite Crystal Clear, which I might try as well. Both products recommend pressure pot or vacuum degassing to eliminate bubbles, so I might need to rig up a DIY vacuum chamber to do this correctly...

If anyone is still wondering, here's what I've tried so far:

For the mold making: Smooth On - OOMoo 30, and Mann Ease Release 200 have been great. Been re-using the original mold I made for 6-7 castings and it's still holding up well. Tried the brush on liquid latex type mold ('mold builder') prior to that, don't recommend that at all.

For pouring and casting:

Castin' Craft - polyester resin.. clarity ok to poor, detail reproduction ok, but bends when warm even after curing.. raw material dries up pretty fast, had to throw it out after a few months. Smells awful to boot.

Castin' Craft Easy Cast - 2 part epoxy, same problems - flexibility of sidewalls mostly

Ice Resin - 2 part epoxy, listed as 'jewelers grade' - good clarity, good detail reproduction, again, gets bendy when temps get too warm (90-100 deg?).. Some small bubbles, but not enough to impair functionality I think. Poured some smaller parts with this and it seems good for that task, but probably not for this 3D cylinder stuff. Better than castin' craft, but still not good enough IMO.

Took some pics as well...

Original housing & computer:

Details of the crack type:

Similar housing from another oceanic hockey-puck:

And it had similar cracking probs:

What the mold looks like after it cures:

Closer view of thread reproduction:

Copy on left, original on right.. slight color difference, but optically pretty clear:

Detail on the area where the button & o-ring setup lives.. really tough to get this part to come out correctly, lots of little details and places for air bubbles to get trapped:

Will continue to add to this thread once I get the Smooth On product and have some time to try it!