How (and Why) to Vacuum Degas RTV Silicone Rubber and Casting Resins in a Degassing Chamber
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- Опубликовано: 8 сен 2024
- Buy Online from www.easycompos...
Video tutorial demonstrating the benefits of degassing materials like RTV silicone rubber and casting resins (like Fast Cast polyurethane or water-clears) to improve your moulds and castings. We use our Complete Vacuum Degassing System and demonstrate how simple the process is and why we do it at various stages such as during silicone mould making, before pouring casting resins and also in-mould degassing. For full information see: www.easycompos...
If teachers at public schools were half as good at conveying a message as you guys we'd have our education problems in the past!
Great job!
Thanks for explaining why it's important to turn the vacuum pump valve off first before re-introducing air. You have saved me a lot of time, materials, trouble and my equipment.
Glad it helped
I recently purchased one of these and I can highly recommend it, really does improve the quality of moulding and casting and is extremely well made.
Sooooo satisfying. I do this at work and watching it collapse never gets old.
Always provides lots of satisfaction!
Woot for booobles and ruuuuubar! Joking aside, a really excellent overview of vacuum de-gassing, and reviewing how it applies to pot life! I've learned a great deal watching your videos!
Very good explanation. Very simple & easy to understand.
Excellent. Thank you. I particularly appreciated the fact that you gave so much useful information without plugging your product too much. Makes me much more interested and likely to buy.
Perfect explanation, will consider purchasing from you. Thanks for this.
That's right, no hose clamps because the valves close the hoses off fully so there's no need. Regarding epoxies, it's a preference thing, personally I don't tend to do it and we still get perfect looking results but many of our customers swear by it and so certainly there are benefits for some people. I think temperature makes a difference, at lower temps resins are thicker and so forced degassing might be beneficial.
HI. i'm planing on buying one for a clear polyester resin. but the object will be to big to put back in the pot for a second time. so i'm hoping this will not matter or should i put the resin in its container for a second time before i pore. using the smaller pump to start with.
is the smaller pump ok for small amounts of resin poring.
It's always something we're thinking about!
Excellent System! We make injection molding systems. We have gotten some degasing questions and you seem like a good answer.
Thanks! Lots more coming soon; pre-preg carbon fibre, how to trim and finish carbon fibre parts, how to make split moulds, pattern making... !
Thank u very much ur great idea
very helpful thanks
We can ship a degassing chamber to Canada, no problem. We use FedEx and the service is very fast and reasonably priced. In fact we're sending degassing chambers and complete degassing systems to the USA, Canada and all over the world regularly. You can order on our website and it will be with you in 1-2 days.
outstanding information again guys! 03:25 nice cactus must Matt lol
Thank You for the great explanation of the degassing process.
Is there a benefit to pressurizing the mold between degassing cycles?
Also temperature must have an effect with the high viscosity silicone . . any tips?
Thanks Again
There is no need to pressurise the mould between cycles. Increasing temperature will slightly reduce the viscosity, however it will shorten your pot life.
h7r
wonderful video. thank you
It might be something we will find time to look into in the future along with other forms of mould intensifying for complex moulds.
Thank you
You're welcome
very good video! thank you!
Great video. You dont use any hose clamps on the hoses? Do you recommend degassing for epoxy resins?
Please please please open a US dealership!
Good video, thank you. Is it safe to say that the best combination for this process is to use a low viscosity resin with a long pot life ? Do you have any recommendations?
Thanks for this video. :-) what i would love to see is an instruction video for using bladders. I want to make a copy of my intake plenum in carbon fiber for my car but cant figure out how? Cheers!
Need Help.
My Dual Stage Robinair 8CFM Vacuum pump goes upto -30inch of HG.
It is a DIY Setup.
Used Shinetsu Mould silicone to Degas.( very Viscous)
The bubbles expands but donot self collapse. Tried to Degas 2-3 times but all efforts wasted!
Looks like vacuum degassing created more bubbles than before.
What's the problem I can't understand!
Check for leaks, if it is not full vacuum, it will unlikely collapse. Also check with the product manufacturer.
I did not know that a vacuum chamber could be used to cast resin parts. Would not the resin overflow. You should make a video to demonstrate this.
As long as the container you are mixing in and the mould have suitable expansion spaces then you won't have any problems with overflow.
Easy Composites Ltd I done some test, and the urethane resin react with the the silicone mould and turn into foam when the vacuum reach -25. While the same exact batch of resin degases normally inside the plastic cup . So witch silicone do you recommend to avoid such a reaction ?
I may also try to bake the mould to remove any moisture that may be trapped inside the silicone.
How would 70wt mineral oil respond in this system? WOuld the air eventually return to it? WHat about distilled water? Would it attack acrylic?
This is a great concept. How far do you draw down the vacuum on the gauge in order to get this silicone degassed?
Pro and cons over positive pressure over degassing?
bery good
OK I'm fine with degassing the silicone mould, but have trouble when degassing the polyurethane resin. If I degas after pouring it into the mould, it tends to produce so many bubbles that they expand out of the sprue holes and I'm left with a half empty mould. I suspect that this is because the pressure is too low and the mixture is in fact boiling, but i'm not sure. All I really want is to get rid of the air in the undercuts, and I don't need to actually suck out the dissolved air. Would this need a less extreme vacuum, and if so can you recommend how low I should go?
how do we know if there is no more air left in the chamber?
does it also vapourises solvents..?
The instruction manual with my pump says that shut off the pump when the needle on the gauge is no longer moving or has reached the max. I am doing that but I find that it has never gotten rid of all the bubbles in the epoxy. It takes about 45 seconds to reach 30 kp, and then I shut down the pump and leave it in the chamber for approx 5 minutes. On a number of occasions I have let air out of the chamber and turn the pump on again and this helps but it takes about 15 minutes to get rid of most of the bubbles, and then I still need to use a torch to get rid of the rest if I am lucky. Any suggestions as to what I am doing wrong would be much appreciated. Thank you for the informative video.
We tend to run the pump throughout any degassing operation. The pumps we offer are perfectly capable of being run throughout the degassing operation. Degassing resin also depends on the viscosity of the material. Some resins degas easier than others. Also be aware some resins have a solvent content which can outgas during very high levels of vacuum.
Thank you very much for taking the time to respond to my question.
What pump do I need to build 17ft fiberglass kayak? I'm just looking for one!
Do you know where you can purchase pourable black RTV silicone for molds? Thanks
We don't supply a black version but we do have a black pigment.
Can you use this after you poured Resin into a mold to have a bubble free cast as well? I heard of people using Pressure pots but can this degas silicone for a bubble free mold and degas resin for a bubble free cast without having to use a Pressure pot? If so for the resin, would you degas it after its been poured into the mold to get a bubble free cast or? Your response is much appreciated! Thanks!
Yes you can. Some people prefer to degas the resin both before pouring and after. The only limit is the practicality of fitting the mould into the chamber if the mould is very large.
So basically we can use vacuum degassing for removing bubble out of silicon rubber and epoxy resin. No more money to spend on pressure pot ? Am I right ?
That is correct. Generally you would use one or the other. A pressure pot shrinks down bubbles to a tiny size. The degassing chamber makes them expand and be expelled from the liquid - any remaining bubbles will shrink as atmospheric pressure is restored.
Where can I buy a degassing chamber? I'm in the Toronto area.
Great video!! I'm looking to purchase a vacuum pump can You tell me the specs of the pump you use in the video? I was told I need a 7 CFM that can pull -28 inches of Mercury to degas my smooth sil 940 platinum silicone rubber.
The current range of pumps we sell are made for us by DVP. For your flow and vacuum requirements you would need the EC.20 pump for which full details can be found at this link: www.easycomposites.co.uk/#!/vacuum-equipment-and-supplies/vacuum-pumps-and-equipment/DVP-EC20-1-Industrial-Vacuum-Pump.html
question: I degass the resin, cast it in the mold e put the mold again in the vacuum chamber.
in this situation am I allowed to have no vent holes in the mold? They are no longer necessary, right?
You will still need vent/pour holes to get the resin into the mould and also as a path for any air to escape from the mould during the degassing procedure.
How long do you keep the resin under vacuum? Is it more of a visual decision? (If you said it in the video, I apologize)
For the silicones it was around the 2 minute mark when the foam of bubbles collapsed.
nice channels :D, subscribed :)
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Could the lack of degassing be why my silicone castings come out quite rough to touch? I've been casting silicone onto 3d printed moulds with layer lines that I sand down and coat with primer and gloss but it's never properly smooth after the silicone comes out.
If the mould surface is perfectly smooth then the silicone should be smooth. It could be a lot of air in the silicone causing surface to feel rough due to the open bubbles.
@@easycompositestv thanks for that. It does look very cloudy once I have mixed it despite the part A being clear so I think you are right
How can I order
Through our website: www.easycomposites.co.uk/
If degassing PU resin in the mould does that encourage the resin to flow into all the parts of the mould or is that reliant on viscosity? I want to cast fine parts [ model aircraft]
Yes; if you run a degas and then re-pressurise cycle whilst the resin is still within its pot-life then this will effectively force the resin into all the fine surface detail (including smaller undercuts or difficult areas. If the undercuts are large then you need a slight surplus of resin (almost like a 'header') that can feed resin into the undercuts when your re-pressurise the chamber.
is this work for degassing quick-cured resin like polyurethane? mine is cured in 3 minutes. my idea is pour it to my mold then put it to vacuum camber until resin cured? will it okay?
+afadario Yes but if you have such a quick resin then you might want to reduce the volume of the chamber by loading it with some ballast (like house bricks or something else to take up the space in the chamber); this will mean that the same pump will draw down the chamber to vac pressure more quickly. Don't forget that it's essential you re-pressurise the chamber before the resin cures - simply loading it in a pulling a vac until it cures to definitely wrong and won't give you good results.
is there a difference between a pressure pot and a degassing chamber? If yes, what are they best for?
Yes, they're basically the opposite things to eachother. A degassing chamber is evacualted to remove all the air - materials are degassed because the trapped air inside the liquid expands (in the low pressure) and bubbles out. A pressure pot is pressured with multiple times atmospheric pressure (example 5 bar) which compresses bubbles in a liquid. The advantage to degassing is that the material can be removed from the degassing chamber once degassing has occured and can cure at ambient pressure. With a pressure pot, the trapped air is still inside the liquid and so it must be cured inside the pressure pot under pressure, otherwise as soon as the pressure it let off, the trapped air will expand again. It might help to think that a pressure pot shrinks the air bubbles and then the curing process locks in the trapped air at this reduced volume. A degassing chamber removes the trapped air.
thanks a ton.
Hey do you know how to clean the vacuum pump oil?? I've tried filtering through kitchen towels and freezing and seperating to remove water (what they recommend for freeze drying pumps) but my oil is still cloudy??? Not sure if it's silicone or PU fumes seperating out into the oil or something? Would be great not to go through so much oil..
Thanks!
We would recommend replacing the oil at this stage. You can help reduce contamination, especially by particulate matter by using an inline filter such as our VF1 Vacuum pump inlet filter which you can find here: www.easycomposites.co.uk/#!/vacuum-equipment-and-supplies/vacuum-pumps-and-equipment
When your done degassing the mold the 2nd time, do you leave it inside the chamber to fully cure after releasing the vacuum? I did this with some molds recently for the first time but ran into some issues with bubbles poping up slowly over time
You can do either as it shouldn't make any difference to the cure as long as you are careful removing the mould from the chamber. If you still have some bubbles popping up perhaps give it a degas for a little longer. If it is a mould with undercuts, it might help to slightly prop the edge of the mould at a very slight angle to help any air entrapped under the undercut to flow upwards.
I did notice in the video you gave it a full 5 mins to degass. That is likely my problem then, as I was only giving it 2-3 mins. They are simple open pour molds like the one in your video, no undercuts at all.
Full vacuum so 30" mercury or 1 bar vacuum.
right now I'm having a mental problem where I would let air into the chamber once it hits 30" - can I just leave the vacuum pump running once the needle taps out at max on the chamber meter?
how many cfm is the larger pump?
Our largest pump is just under 12CFM
do you leave the liquid in the vacuum guage. i have bought one of your vacuum chambers and followed the instructions to the book but my guage does not budge it stay's still i did remove the bung and then put it back on i did not pore the liquid out as i guess your supposed to leave it in. i have the small pump but my vacuum guage does not move.
The liquid is meant to remain inside the gauge. The bung needs to be pierced to allow the gauge to equalise with atmospheric pressure. Assuming there is no leak anywhere and the pump and system is pulling a full vacuum, then It sounds like your gauge has been damaged at some point. If you contact us with your details we will happily send you a replacement gauge. You can contact us on technical@easycomposites.co.uk
@@easycompositestv HI thank you i only took the bung of then put it back on i never pierced it so i will pierce it this time and see if it works and if not i will get in touch with my details. thank you for your help.
I'm on a very tight budget, and I've got some oomoo 30, Smooth-on 305, and one vacuum chamber. I'm trying to cast a 5" action figure with ball joints, hands, intricate facial details, separate moving parts, etc. I know how to make the mold through degassing, but I was wondering if I could get by using ONLY the vacuum chamber for resin casting. The Smooth-on 305 has a pretty long and helpful pot life of 7 minutes, and the molds have sockets that NEED to be filled in if the figure is to work properly when assembled. Is all of this a recipe for success or disaster?
You can certainly place the mould into the chamber and degas that way. Your pot life is reasonable in this case so you should be able to complete a degas cycle with time to spare.
Great! Thank you for your help.
Can you use your chambers with a vacuum injector and a compressed air supply?
You could however the problem with venturi vacuum generators is that they don't tend to achieve particularly high levels of vacuum. It's normally at the very high end of the vacuum scale (28" mercury or 99% vacuum) that the degassing really starts to happen, especially for materials like silicone which can be quite reluctant to self-collapse until the highest vac levels are reached.
Thanks for getting back to me, I guessed as much or there would be plenty of people using a cheap ejector instead of an expensive pump!.
One more question please, can your chambers be used on their sides?. I'm setting up to cast some figurines over a foot tall so the second degassing once the RTV is poured over the master will need to be laid horizontal, then the resin will need degassing with the mould vertical.
You're welcome. Yes, no problem at all using them on their side.
The vacuum guage will tell you.
What level of vacuum do you pull?
As close to absolute vacuum as you can possibly get. There are a lot of different vacuum units but 99.98% vacuum is a common target (virtually -29.92 inches mercury).
So as hard as possible then. Doesn't this make some of the more volitile components evaporate?
Epoxy resin has virtually zero volatile contents in it, so you do not get any issues with being close to a full vacuum.
Most silicones do not contain VOCs (or only negligible VOCs). Other materials such as some resins (especially styrene-based ones such as polyester or vinylester) do have high VOC content and in that situation you may choose to either moderate the vacuum level by hand (opening and closing the valve) or by using a vacuum regulator.
how is possible that you guys charge 94$ shipping for something that will cost 74? can u explain that
+Aldo Allende Oliva : We're in the UK, I'm not sure where you're based but I assume the US. Dangerous good by aeroplane is possible but requires extensive paperwork and carries a surcharge levied by the airline; therefore, it is possible to have shipping charges that exceed the value of the goods. Sometimes it works the other way too, smaller, non-DG items can be very high value and ship to the US for less than £20 ($30). It would be fantastic if we could send large, heavy or dangerous items from the UK to the USA for a very low price but unfortunately air freight is not cheap these days. The service is VERY quick though (around 1-2 days to the USA).
You degraded twice. I've seen write-ups and other tutorials that do degass first, followed by a compression run in a pressure pot. Care to explain the differences?
stupid autocorrection on the phone puts in words! - must??
why am i watching this