Anyone cast their own plastic parts?

[dibble]

If you pressurise will any air bubbles that do form be at 70psi and likely to pop at stp?

[PeteS]

If you mix your molding materials and casting materials slowly, air bubbles are not much of a problem. Keep it simple. It looks like you will need to clamp you two pieces of mold together better though. Maybe just use a big C clamp and some disks made to fit your molds.

Pete

[Toystoretom]

Stuart on the RE5 forum (T140V) has made some nice tennis ball lenses and sells them on E Bay. (Tennis ball lenses are for the 1975 RE5 M are the turn signal lenses for the Italian styled space cowboy bike that no one liked back in the day but everyone wants now). NOS or even nice used are unobtainium now....

http://re5rotary.proboards.com/thread/2062/reproduction-indicator-lenses-relist-191662638473

Possibly he could help?

Tom

[rbm]

To do laminating work, vacuum bags are sold that have a "Ziploc" style opening to introduce the object and a vacuum port to extract the air.  The act of drawing the vacuum will draw air bubbles out of the solution as the air is removed from the closed bag.  Furthermore, atmospheric pressure on the mould at full vacuum will provide the pressure needed to close all the gaps in the mould halves (14 PSI at sea level).

An old refrigerator compressor can be repurposed as a vacuum pump.  Many designs available on the Internet.  Search Google for "vacuum bagging"

[canuck750]

The Suzuki lens; look great!

I may look for a used pressure pot, looks to be the best way to go.

[bmc5733946]

 Any vessel that would contain pressure will also contain vacuum.  Vacuum can be made several ways.  Automotive shops use vacuum pumps to evacuate moisture from A/C systems.  I have seen venturi type modules that use only shop air to create vacuum on one side.  Here's an example (http://www.instructables.com/id/Venturi-Vacuum/)   These can also be purchased at auto supply houses.  A/C systems need thirty inches of vacuum to remove moisture from the system but I think you could get by with much less for your use.  Pressure can't remove the air only compress it, that might work.  Vacuum will remove the air from the vessel and therefore from the mold.  Since the whole affair would be under vacuum the air would be removed leaving behind the resin in the mold.  So you would put the mold in your vessel, seal it, pump a vacuum, leave the vacuum pump running on it for the cure time.  Your vessel wouldn't need to be perfectly sealed as the pump (or other vacuum creator) would continue running.  Just spitballing here.

Brian

[PeteS]

The Suzuki lens; look great!

I may look for a used pressure pot, looks to be the best way to go.

Are you seeing air bubbles in your lens? They are not evident in your pictures. The only problem I see is liquid seeping into the mold joint. One of the advantages of using materials designed for mold making vs things like epoxy or silicone glues are any air bubbles will escape quickly as long as you only stir and not shake the mixture. I have tried vacuum pumps and they only complicate the problem. Not had the need to add pressure other than clamp the molds together.

Pete

[lucian]

Maybe the air bubbles would escape sooner if the resin mix could be of a thinner viscosity. I would ask your supplier if the resin can be thinned, also it may only need to be a little warmer to achieve the same goal. I don't know if perhaps vibration may be an option also as in concrete. Just thinking out loud as I follow this. The form leakage should be easily solved and I would only guess that a thinner visc.resin may give better fine detail as well as allowing trapped bubbles the ability to rise out. Best of luck with the next attempt.  dave

[canuck750]

Are you seeing air bubbles in your lens? They are not evident in your pictures. The only problem I see is liquid seeping into the mold joint. One of the advantages of using materials designed for mold making vs things like epoxy or silicone glues are any air bubbles will escape quickly as long as you only stir and not shake the mixture. I have tried vacuum pumps and they only complicate the problem. Not had the need to add pressure other than clamp the molds together.

Pete

On my first attempt there were very tiny bubbles in the casting, hardly noticeable and I could live with them. The resin leaking past the mold joint cam from the resin left in the fill and vent tubes and as the resin cured it continued to draw down the tubes past the cast part and left the 'holes' in the casting as the resin ran out the mold joint. I think If I can get the mold halves to be tightly sealed the results will be better.

My local silicone supplier is closed for two weeks so this project gets sidelined for a bit. I need to rebuild the female half of the silicone mold. I also have read up on other clear casting materials and found a two part epoxy that is tintable and is supposed to cure quicker and be much more rigid. The first part I made is still flexible after three days. The resin I used achieves full strength in 7 days.

I enjoy figuring out how to make things as part of my Motorcycling pastime so this is just another skill worth learning that I can see will come in handy to make all sorts of small things.

Its back to wheel building on my 750S project, no shortage of projects to keep busy

[canuguzzi]

I need some help with this vacuum idea, how do I make one, what do I need?

Trying to figure out how a vacuum will draw the resin into the mold and not suck the resin out of the mold??

Any direction would be appreciated.

Thanks

Jim

Big model of the seal a meal. Vacuum draws out air.

[PeteS]

The problem with using a vacuum is tiny air bubbles become large air bubbles. If your casting begins to harden before those bubbles are able to escape they will be more obvious than they would be if you hadn't applied a vacuum. You can observe the effect of a vacuum by putting the hose of a vacuum cleaner on a cup of water. Its essential that you have no air leaks over the cup.
Experiment with a small sample of resin before committing a vacuum to your mold.

Pete

[Larry Wiechman]

 
 It is essential to use vacuum to degas the resin. I put the cup of resin in a pressure pot and apply vacuum. I use a paper cone for a sprue. This allows for a surplus of resin to apply a constant fill pressure. Plastic soda straws make fine vents; just make sure they're taller than the sprue. 

[canuguzzi]

You could bypass all the vacuum , pressure, and other stuff and try UV activated casting resin.

That way you can let the air bubble escape if there are any and not encounter a time sensitive setup.

The resin doesn't set until you hit it with UV light.  Just use clear silicon for the moulds.

[tiger_one]

Would a small DIY centrifuge work while curing?

[canuck750]

After a couple more failed attempts I think I have had some reasonable results.

I tried a different silicone casting material, a more elastic type of product from the same manufacturer Smooth-On.

For the CEV fuse box cover I made another mold with the new product







And I made a clamping jig for the signal light lens, very little pressure needed, I used to much at pressure and 'closed' the mold sections and had half a signal light formed





For the lid I just used elastic bands and some strips of plexiglass to distribute the pressure



The results are decent but not perfect, small air bubbles are evident but for the fuse box lid I don;t think it will matter or be noticeable, the signal lens is acceptable



I just need to trim off the fill tube residue, they are part of the CEV lid where the decal is affixed by snap clips and on the signal they are where the mounting screws pass through.



Now to start the one off assembly line

[SED]

Great photo essay and recommendations.  You are a true craftsman. 
Thanks!
Shawn

[jbell]

Great end result, Jim.

[canuck750]

I am still having difficulty to get all the air out and the resin to completely fill the forms, hit and miss, about 50% success rate. I have been experimenting with injecting the mold very slowly with resin, plugging the fill and bent holes and spinning the mold etc...   The resin always fills and pours out the vent holes but sometimes air gets trapped at the top of the mold and the casting is missing a bit on the edges, enough to make the part useless.

Definitely a trial and error exercise.  At least I got two successful fuse box lids which was the original need to go down this road.

[rboe]

Have you tried holding a finish sander against the mold to vibrate it and shake the bubbles out?

[Matt Story]

Those parts look great! 

We did a bit of low production resin casting at a place I used to work.  To avoid bubbles we would mix the resin, then place it in a vacuum chamber for 10-15 minutes before pouring/injection.  Also helps to be careful with the method used to mix so as not to introduce any air.

[earemike]

Fantastic 

[canuck750]

Have you tried holding a finish sander against the mold to vibrate it and shake the bubbles out?

I like that idea, will give it a try

Thanks

Jim