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REALLY need help selecting a vacuum setup

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REALLY need help selecting a vacuum setup

Postby Machinepriest » Sun Feb 16, 2014 11:58 pm

Hello there!
I thought I would take the plunge and get started with degassing my silicone and resin in combination with my pressure tank to get rid of those pesky bubbles.

However, It's a bit of a jungle out there when you're a novice without a clue regarding degassing equipment (The math is confusing as well...) :oops:
Finding the right gear in Sweden makes it even harder, so I've been looking for gear in the UK and Germany.

So I was wondering if you could advice me on a set up that doesn't cost a fortune and both my arms.
I've been looking around the forum and also on eBay and came across a few different pumps and kits.

First: viewtopic.php?f=32&t=961
Really liking this set from Pinselknecht.
It includes everything, but for 403€ including shipping to Sweden it's a bit on the expensive side (I think... Maybe you can't get a complete set up for less money)

Second: http://www.ebay.co.uk/itm/Hot-sale-EFRI ... 2585039016
I found a few different 8.0CFM pumps from British sellers on eBay which means I need to get a converter for the plug which isn't a big deal, but finding a degassing pot in the UK seems to be harder.
Do you think this pump would do a good job degassing a 8-10 litre pot ?


Third:
Here's a set this guy on a swedish scale model forum has offered me
The pump is old but apparently in working condition. I'm not sure if it's strong enough though.
Image
Image


Would really appreciate any help I could get.
I've been putting this off for way too long.

Cheers // Andreas
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Re: REALLY need help selecting a vacuum setup

Postby mangozac » Mon Feb 17, 2014 8:58 pm

Hey Andreas, it sounds like you've been doing your homework!

So you already have a pressure pot, correct? If so then I recommend the middle option as it should be the cheapest by far. 8CFM is a good size for evacuating a 10L pot. It's what I use.

If you want to use vacuum + pressure for casting it's actually preferable to use the pressure pot, as it means you can do both operations without changing chambers - this saves a lot of time.

The Pinselknecht system is certainly nice and if you didn't already have the pressure set up I would certainly suggest it's a good option.

How much is the guy on the Swedish forum offering the chamber and pump for? By my calculations the pump is very undersized at just 2.5 CFM.
Oh yeah I can make that....
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Re: REALLY need help selecting a vacuum setup

Postby Fleafa » Tue Feb 18, 2014 1:53 am

First: Good kit. I have the pump he is selling, from wiltec gmbh, and it is great.
Second: Price looks too good to be true. Check it is a two-stage pump, as I would expect a single-stage at that price.
Third: What Zac said.
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Re: REALLY need help selecting a vacuum setup

Postby Machinepriest » Tue Feb 18, 2014 5:51 am

Thanks for the feedback fellas! I really appreciate it :)

I considered using my pressure tank as a vacuum chamber but I'm sceptical for a couple of reasons.
Not being able to see the degassing process is one of them :P I also have it halfway filled with sand in order to pressurize faster which means I probably won't fit the big containers needed for degassing in there. Also, modding the lid for pressurizing and degassing or making a new one from plastic seems like a hassle.


The guy on the forum wants £93 for the setup which feels a bit steep for an ancient pump that's not very strong. Not buying it.


I think I might just go for Pinselknecht's system, a bit pricy but it seems like good equipment.
Wish the pump and the hose came in different colours though :P


I mentioned my current gear.
I'm starting to think my compressor isn't up for the job of pressurizing my 9 litre pot effectively. I guess I could just get silicone and resin with a slower curing time...
Here's my current setup:
Image

The compressor I'm using: http://www.faller.de/App/WebObjects/XSeMIPS.woa/cms/page/pid.14.17.91/agid.1114/atid.2017/lg.en/ecm.at/index.html
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Re: REALLY need help selecting a vacuum setup

Postby mangozac » Tue Feb 18, 2014 8:18 am

The 8CFM pump on ebay is identical to the one I have. You could argue that a more powerful motor might be a bit better, but this pump has been doing me well for a couple of years now. I'm pretty sure it's cheaper than what I paid for mine, but when I do an ebay search locally the same pumps are available for a comparable price to the one you linked to.

No problem with having the sand in there while vacuuming - I do that too! And it's only a couple of times that I've missed the ability to watch the degassing. Most of the time you're just doing things based on time anyway. If you were really worried you could get a perspex lid made up to place on top of the pot.

I'm sure the PK system will work really well. Yes, you're paying a premium for it but knowing PK I'm sure it will be nothing but high quality (it's German!).

The compressor you're using looks like an airbrush compressor? There's not much wrong with the compressor itself (so long as it can reach the required pressure), it's more the small size tank attached. You want a compressor with at least a 20L tank so that you can transfer the air quickly.
Oh yeah I can make that....
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Re: REALLY need help selecting a vacuum setup

Postby Fleafa » Tue Feb 18, 2014 7:55 pm

mangozac wrote:You want a compressor with at least a 20L tank so that you can transfer the air quickly.

Seconded. A tank twice the capacity of the pressure pot allows for rapid pressurisation.
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Re: REALLY need help selecting a vacuum setup

Postby Machinepriest » Wed Feb 19, 2014 3:03 am

Thanks again guys!

Yeah, the compressor is mainly used for airbrushing.
I've only tried out the tank a couple of times and it does take some time to fill it up, but I'm thinking I've been doing it wrong.
I suppose you let the compressor run till the tank is full, and then you hook it to the pressure chamber to transfer the air (4 litres in my case) quickly, right?
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Re: REALLY need help selecting a vacuum setup

Postby mangozac » Wed Feb 19, 2014 7:53 am

You should have a ball valve in line with the pressure hose when it enters the tank. Before you mix the resin you run the compressor, it fills the tank and then shuts itself off. Mix the resin and place the moulds in the chamber. Clamp the lid down and then open the valve to fill the chamber.

Note that completely opening the valve immediately can cause pretty violent air movement inside the chamber. Many people fit a T-piece on the inside of the lid so that the air is diverted sideways (and not straight into the moulds, where it can blow the resin everywhere).
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Re: REALLY need help selecting a vacuum setup

Postby Fleafa » Thu Feb 20, 2014 11:38 pm

mangozac wrote:Note that completely opening the valve immediately can cause pretty violent air movement inside the chamber. Many people fit a T-piece on the inside of the lid so that the air is diverted sideways (and not straight into the moulds, where it can blow the resin everywhere).


My friend sourced me a nice little air diffuser from Rolls Royce :)
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Re: REALLY need help selecting a vacuum setup

Postby mangozac » Fri Feb 21, 2014 6:30 am

Nice! Does he work for Rolls? Can you show us a pic?
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Re: REALLY need help selecting a vacuum setup

Postby johncast » Sun Feb 23, 2014 7:45 am

All interesting to read and very helpful info, I hadn't thought of filling the pressure pot with sand. I have filled it a bit with some old rubber spin moulds to help flatten of the bottom of the pot. Might dig some sand out of my practice golf bunker LOL.

As for setting up a pressure pot for casting ,After buying a new pump last year for my vacuum system with a 6cfm I would recommend any system have 6cfm or more . My old pump was 3cfm and it is tooooo slow. If you are setting up a chamber a 8cfm or even more is required..
buy the highest capacity pump you can afford.

This brings up another question as far as pumps are concerned . Ebay has many pumps around the 8 to 10 cfm , why is there few , if any pumps over the 10cfm capacity available.
Where are the 15cfm or 18cfm pumps ? or is this a issue of machanics and or price . Once we get to pumps of this capacity is there a big jump in design and mechanics needed for pumps like this. My latest adjustment to my vacuum system may need a pump of this higher capacity and find little in the way of pumps around the 15 cfm or higher at a reasonable price.

Thanks Johncast
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Re: REALLY need help selecting a vacuum setup

Postby mangozac » Sun Feb 23, 2014 8:46 pm

johncast wrote:This brings up another question as far as pumps are concerned . Ebay has many pumps around the 8 to 10 cfm , why is there few , if any pumps over the 10cfm capacity available.
Where are the 15cfm or 18cfm pumps ? or is this a issue of machanics and or price . Once we get to pumps of this capacity is there a big jump in design and mechanics needed for pumps like this.

I don't think jumping up to 15-20CFM requires much difference in the mechanism used - you just would have a larger/more powerful motor, etc. My guess is that it just comes down to demand: the primary application for these pumps is for refrigeration gassing and it's quite possible that anything above 10CFM is seldom required. Not to mention a larger size pump would become heavier and less portable.
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