Working with Foam - Page 4

GoHybrid · 12-07-2006, 02:04 PM

I got the black bezel installed last night! I think it matches well enough that i can leave well enough alone. Sweet!

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Parksgm, thanks for the props!

DakarM3 · 12-07-2006, 09:46 PM

how much does that foam cost? Did you get full sheet?

GoHybrid · 12-07-2006, 10:27 PM

i think it cost something like $450 for a 4x8x4" board including shipping... but I do alot of prototyping and model making so it was something of an investment.

Freeman sells partial boards in lower thicknesses that you can get into for well under $100 i would think. If you check out the different types of RenShape on their website you can request a quote for a certain quantity.

turbocad6 · 12-07-2006, 11:27 PM

this is a really cool method of fabricating parts from nothing... thanks for showing this... I got a question... when you do that bombs away pour... do you have to pour the whole mould in one shot, or can it be done in several pours?... I guess with something the volume of yours it's easy to just do it one pour, but what about larger parts? if a few mix & pours are done sucessively, would that work?

GoHybrid · 12-08-2006, 12:11 AM

The pot life on this silicone is 1.5-2.5 hours so if you can't fill your mold in that amount of time then there's a better way to create that mold than a simple mass casting. Check out this video on glove molding for a process that might lend itself better to doing large parts.

It only took about 5-10 minutes, if that, to fill my mold which was about 40 cubic inches. If it's the speed of the pouring you're concerned about, it goes quite a bit faster than it looks. The other alternative, vacuum degassing, obviates the need for the bombs away method so you can pour deaired silicone at a much higher rate.

I'm told silicone will stick to itself in the absence of a proper mold release so i suppose if you wanted to modify an existing mold you could pour on top of that... Does that answer your question?

turbocad6 · 12-08-2006, 12:30 PM

yeap, thanks

shotgunefx · 12-08-2006, 05:09 PM

Nice work, alumilite, a name I haven't heard in a decade.

A couple thoughts.

For sources of molding stuff, Burman Industries has a nice selection. Alcone in NY used to, don't know if they do these days. Their website is all about there stage makeup lines. Both are big suppliers to FX houses, movie production.

One way to get rid of bubbles it to attach a motor to the table, the vibration helps vibrate the air bubble up away from the surface. On some molding compounds, this is a no-no (some closed cell foams, etc), but IIRC, it's dandy for silicone.

I used to do a lot of this stuff as a teen (hence shotgun EFX), but it's been well over a decade now.

GoHybrid · 12-08-2006, 05:52 PM

Yep! I used to build makeshift jitterbugs for casting concrete!

Giuliano · 12-08-2006, 09:27 PM

Freeman Supply has some very interesting streaming videos on mold making and casting:

http://www.freemansupply.com/video.htm

Cool stuff.. I'm going to order some RenFoam 440 for carving / machining prototypes..

GoHybrid · 12-09-2006, 12:23 AM

Hey Giuliano, let me know what you think of the 440 and how easy it is to work by hand. I've always found 15-20lb density to be the ideal range for fast manual prototyping, but i've never really had anything else to try either. Keep us posted!

Giuliano · 12-09-2006, 03:28 AM

Freeman Supply is offering me a 2" x 20" x 60" board of 440 for a special price of $167..

It's more expensive than the lighter density stuff, but at least it's not an entire 8' sheet.. I'd have a difficult time getting an 8' sheet in my car.

turbocad6 · 12-09-2006, 06:33 PM

hey giuliano, what's up.. long time no see... hope all's well...

Giuliano · 12-09-2006, 06:55 PM

Doing well.. took a break for the last 6-9 months, then I got a new car - a WRX STi.

This foam brings out some interesting possibilities for prototyping things.

About a year ago I bought a mini milling machine, and now I'm considering retrofitting it to full CNC capacity.

There's a guy out there making a CNC kit with something like a 24" x 8" travel bed made out of epoxied concrete for about $400, and all you add is motors and electronics.

The denser 440 foam is about $35 per 2"x20"x12", which is not so bad.. though I wonder if wax would be cheaper for mold prototyping.

GoHybrid · 12-09-2006, 07:43 PM

I think wax would be good if your intent were to use it in lost wax casting to make a metal part. I don't see any issues with using your mill on it, but i have my doubts about the ease of smoothing the surface. In other words, your mill is going to leave tooling marks over all the surfaces... so how do you get those out? I don't think you can sand wax. Silicone picks up every detail too, so i'd be interested in seeing solutions for using wax in this way.

What are you planning for your subie?

Giuliano · 12-09-2006, 08:33 PM

Not lost wax for metal casting, but rather for silicone molds and polyurethane casting (plastic).

The idea is that I would mill the master out of RenFoam or wax or something, and then cast the final part in plastic.

The idea I had with wax was that if I'm doing a few runs on the mill and mess up, I can melt the wax and re-use what I have left... maybe, maybe not.

As for the STi, I'm planning on putting a 9.0" widescreen LVDS LCD panel in the dash, which will require a custom mounting assembly and bezel.

Reference threads:

9.0" Wide LCD in 2005 Subaru Impreza WRX STi - Fabrication thread about makinga frame / bezel for the LCD panel. Originally going to be bent aluminum, now possibly carved and / or machined out of Renfoam and duplicated in plastic.

9.0" Wide LVDS LCD Panel? - thread in LCD/Display about the panel itself, obtaining it, and so on. Looks like I may be able to get them with Transflective upgrades.

Kontron 986LCD-M/mITX, and 800x480 LVDS. - thread in Hardware about the motherboard I've chosen, and getting 800x480 support on LVDS LCD panels.

Yeah, it's a lot of cross-posting, but it's the only way I can keep my threads sane.. ;-)