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25th February 2018, 11:12 AM #1
Auto-cycling vacuum pump for vaccum bagging veneers and vacuum clamping.
I've finally finished construction of my new auto-cycling vacuum system, so I thought I'd share the journey.
The original goal - to build a vacuum system to be used for vacuum pressing veneers, vacuum clamping stuff to the bench for sanding and routing, and also to connect to a vacuum clamp setup on the lathe.
When I starting researching how to go about it, these were the options I found I had:
- just buy a cheap refrigeration vacuum pump, to connect directly to a vacuum bag (bought or made), that would have to run continuously whilst clamping, till the glue dried (usually overnight).
- Buy a more expensive vacuum pump, that didn't disperse oil to the atmosphere (the problem with the refrigeration pump option). Use this pump, as above, to run continuously till the glue dried.
- Buy a ready made solution (vacupress)
- Build my own from parts sourced wherever.
When considering what path to take, each has pluses and minuses:
- Refrigeration pump
- PLUS - cheap
- PLUS - one purchase, and you're up and running
- MINUS - the pump atomises oil into the atmosphere, which means you either use it outside to protect your lungs, or you risk health issues if using indoors
- MINUS - the atomised oil will settle on everything in your shed, which is bad for many reasons.
- Oilless rocking piston pump (standalone)
- PLUS - no atomised oil
- PLUS - continuous rated - you can leave it running without it breaking, or voiding any warranty.
- MINUS - cost - a good one (continuous rated, with flow rate of ~5CFM) will cost you in the range of $800 - $1000
- MINUS - if used standalone it will run continuously, and whilst not excessively noisy, I don't really want any machinery noise all night that could upset neighbours
- MINUS - difficult to control vacuum pressure, and keep within a specified range.
- MINUS - if it doesn't auto-cycle on/off, you are limiting the life of the pump. The more it runs, the quicker it wears out.
- ready made solution
- PLUS - one purchase, and you're up and running
- MINUS - limited choice. There really is only 1 suitable solution out there that I could find - vacupress.
- MINUS - cost. I got a quote for a 5CFM model, and including postage was approximately $1500 AUD.
- MINUS - all internals are NPT thread as it is made in USA, so when sourcing spares, parts etc, you need to factor in that this is not a standard thread gauge readily available in Australia
- self-built solution
- PLUS - I could make it suit my requirements, without compromise
- MINUS - sourcing parts would take time, and total cost might creep up as I went along, depending on how elaborate I decided to be.
- MINUS - I didn't know much about vacuum pumps, regulators, relays, thread variations, brass fittings, filter options, etc etc etc.
- PLUS - There is good information available on joewoodworker.com about similar setups.
I quickly ruled out option 1 (refrigeration pump standalone). I value my health too much, and given what I ultimately hope to use my setup for, this just wouldn't cut it.
I ruled out option 2 (oilless rocking pump standalone). I can't risk upsetting my neighbours having machinery run all night whilst glue dries, and I just don't like the idea of it running all the time, wearing out quicker, even if it is continuously rated. Sooner or later it'll wear out. Also, not being able to easily keep vaccum pressure in a specified range, whilst not a massive issue when vacuum bagging veneers (as the more pressure the better), but would be a big issue when vacuum clamping on the lathe. This needs carefully controlled vaccum so you don't collapse the walls of thin pieces.
I ruled out option 3 (vacupress) for 2 reasons. Firstly, cost. I nearly died when I got the quote. Secondly, the issue of everything being NPT thread didn't appeal to me. I'd begun investigating a self-build solution, and was having lots of difficulty finding suppliers of brass fittings in BSP thread (which is the Australian standard), let alone trying to find NPT, which is standard in US, but not AUS.
I settled on option 4 - and set about researching everything I'd need to know to build my own solution. At that time I had no idea just how big an undertaking this would turn out to be. It's taken me 2 months to source everything I ended up needing, and many, many nights struggling to get my head around everything I didn't know. Silly little things like 'can I use a 40micron filter designed for air compressors and rated for 150PSI positive pressue, in a vaccum setup?'. The questions were many, and varied, and it's taken me 2 months to answer every question, and source every part. I'm not going to call myself an expert on vacuum pump setups now (that would be egotistical) but I will say I know so much more than I ever thought I'd need to when I started down this path. To quote a famous TV personality - "How hard can it be?" The answer - a hell of a lot harder than you think.
Am I sorry I chose this option - No. It's been a good learning experience (and you're never to old to learn something new, right?). But I do wish there were more options available here in Aus, because a self-build isn't for everyone, but the scope of what I'll be able to use this for I'm only just beginning to understand.
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25th February 2018 11:12 AM # ADSGoogle Adsense Advertisement
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25th February 2018, 12:55 PM #2.
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Given the flow rates are low, for those still interested in option one, it's very easy to filter most of the oil out of air using a crankcase oil vapour filter.
These can be purchased for about $20 on eBay.
If you wanted to be extra careful just vent the air exiting the filter outside the shed or even locate the whole pump outside the shed.
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25th February 2018, 03:13 PM #3Woodworking mechanic
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Even with option 4) you must have purchased a vacuum source. You ruled out oiless rocking pump standalone and you ruled out a refrigeration standalone pump, so what did you purchase for your vacuum source?
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25th February 2018, 03:18 PM #4
Hey guys, yes, I ruled out using the oilless rocking piston pump standalone (ie 'just turn it on and leave it on'). I ended up buying an oilless rocking piston pump, then integrating that into an auto-cycling solution. (more details and pics to come, on that one).
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25th February 2018, 11:27 PM #5GOLD MEMBER
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Hi TimberNut,
Thanks for sharing this with us. It’s very helpful for people like me who are just at the start of this jourmey.
I’ve looked at pumps from Yareus (Vacupress) - these seem very expensive in Australia. I’ve also looked at pumps from Airpress and Bagpress in the UK. All three seem to use the same type and make of pump, the Becker VT series (VT 4 Series - Becker Pumps - mdi) which are rotary vane pumps rated for continuous use against a vacuum and if I remember correctly Becker give a 4 year warranty. Noise level for the rotary vane pumps (8 m3) is 58db, about the same as a quiet conversation.
At Airpress in the UK their standard 4m3/hr pump is GBP480 plus postage (the pump is around 7kg)
Oil-less rotary vane Becker vacuum pump 4.4 AirPress
At Bagpress in the UK their website shows only a price for a kit including bag, hose, foot switch etc. it is GBP599 4m3 per hour Vacuum Press Kit - Professional Electric Presses - Bagpress
In Victoria, Rob at Bettervac (Carbon Vane Becker Side Channel Blowers DVP Vacuum Pumps Australia) supplies all sorts of vacuum pumps (including Becker) but I haven’t asked for a quote yet.
Like you I’d prefer something that did not run all night so I’m looking forward to hearing more!
Thanks again,
Brian
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25th February 2018, 11:51 PM #6GOLD MEMBER
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When I used to do a lot of vacuum laminating the glue tends to grab very quickly.
I think because the water in the glue evaporates in a vacuum environment the pump can be switched off after a few minutes.
The time is much shorter than the glue's open time and I had a timer on it that would switch the pump off, if I remember correctly, after about 15 mins.
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26th February 2018, 10:53 AM #7Novice
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A rotary vane pump is designed to run continuously. The problem you will encounter with those, is, once you have reached a maximum vacuum, there is very little gas flow. Consequently, oil vapors will migrate out of the inlet, and onto whatever you are pumping on. This will not be wet, but you will be able to smell it on the wood. This is known in vacuum as backstreaming.
I would suspect that the ideal pump you need is a diaphragm pump. Typically they are cheaper ($150 USD). They are dry (no oil). They do not pull as much vacuum, but that is not important for what you are doing.
A good $2000 rotary vane will run for 10 Year’s continuously, and pull to 1 mTorr (1 millionth of atmosphere). A $200 diaphragm will pull to a thousandth of atmosphere. For veneering, either one would work. The diaphragm pumps also run continuously. At least, I have never seen any vacuum pump of any type that wasn’t.
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26th February 2018, 11:15 AM #8GOLD MEMBER
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Would an Air Conditioning vacuum pump used to evacuate systems be used? There are heaps of old Automotive AC units laying around not used as the industry changes to more modern stuff.
CHRIS
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26th February 2018, 11:32 AM #9
I'm using an AirCon vacuum pump and its a ripper: https://hvacdirect.com.au/70-l-pm-2-...m-vacuum-pump/ (recommended by another forumite, but I cannot readily recall whom) .... (edit day after: I just had an email exchange from HVACdirect, Mike, "For your application you would need a single stage pump rather than a double. We do have single stage Value pumps which are pretty much made for that application.")
I've added a one-way valve to stop the fog getting in as well: Off The Edge Sailplanes :: Vacuum Bagging
The idea of BobL to use a cylinder head oil filter on the outlet is excellent. When doing the initial air extraction it releases a light fog. This stops once the vacuum is beginning to form. The pump is quiet and not at all annoying when running.
edit: I bought this pump as its main purpose in life is to evacuate AC systems to a good hard vacuum for a long period of time to eliminate moisture in the systems. I felt this was an excellent predicator for doing stabilising of knife scales and pen blanks with cactus juice.
It seems I should also run an inline filter to stop accidental ingestion of goop (this has been discussed on another thread).
Any suggestions on hosing would be appreciated.
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26th February 2018, 11:44 AM #10Senior Member
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Yeah the Vacupress aren't cheap, still can't get the head around the pricing here vs the states.
Did you consider, just getting a Festool VAC SYS Vac pump.
only does 2.2 cfm, but that should be plenty, if you aren't doing huge sheets.
From what i understand it cycles and is $999, plus the hose connection, and also a pre filter
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26th February 2018, 12:32 PM #11
Build info: Part 2:
Following on from my first post.
I'd decided on Option 4, and spoke to Rob @ Bettervac. I purchased the 140RVD. It's continuous rated, ~5CFM flow rate, and quiet. With no oil atomisation to worry about.
20180117_195040.jpg
So now I had the pump, it was time to figure the rest out.
A call to Rob confirmed the fitting on the pump was 1/4 BSP. This meant nothing much to me, so after a lot of investigation I concluded that BSP thread is standard in Aus, and if I'd bought a similar pump from the US,it would have come threaded with 1/4NPT instead. Given that BSP is our standard I decided I didn't want to mess around with adaptors and different thread gauges etc, so everything I had to find would need to be 1/4BSP. I figured, it's the Aus standard, so fittings should be easy to find, right? Well, maybe if you know the right suppliers to ask, yeah, but I didn't, and this decision would cost me 2 solid weeks of searching. I could have ordered them from ebay and waited a month for them to arrive, but as this was a bespoke solution I didn't really know what fittings I'd need, and would have to get them in several steps as things took shape, so I needed a local supplier I could run to, to get the odd fitting or 2. I decided to shelve that problem for now, and sort other stuff first.
For the pressure vessel, I'd read that you need to be using 'Class 12 Water Pressure Pipe', and the plans on joewoodworker.com call for 2x lengths of 4" pipe @ 15in long (x2 tanks). According to my calculations, each tank is ~3L volume. I scoured the net trying to locate suppliers of 100mm Class 12 pressure pipe, and they are only readily available at irrigation suppliers. That wasn't an option for me, so I decided that 50mm would do, as I could pick it up at Bunnings.
So, having decided on 50mm pipe, I needed to cram as much as I could into a toolbox to house everything. So at my local Bunnings, it was back and forth between the plumbing section to get PVC elbows, and T joints, and the tools section where all the toolboxes were, to try to figure out what I could realistically get into a toolbox, along with the pump, plus all the brass fittings to make the manifolds I'd need. The staff couldn't work out why I was pulling out every toolbox, and inserting PVC elbows and T's into them, this way and that, with a confused look on my face.
In the end I settled on this toolbox.
20180225_095910.jpg
Then I set about trying to come up with an arrangement of pipework that would give me the largest volume possible, leaving just enough room for other stuff to be purchased later. I was aiming for 6L capacity.
This is where I got to. It works out to be ~5.25L or thereabouts. It was the maximum I could cram in, so it would have to do. As it turns out, the is ample volume. It doesn't take too long to evacuate, but gives a good initial supply when connecting to a bag to be evacuated for initial pull down.
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26th February 2018, 12:47 PM #12GOLD MEMBER
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26th February 2018, 02:25 PM #13.
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I know you wanted to have yours all self contained.
Otherwise what about using a 4kg LPG cylinder as a reservoir?
There's plenty of the available for free.
I know it takes a long time to get rid of the mercaptan smell out of them but new ones only cost $30 and that includes a tap so it will hold any vacuum that it has already attained.
Just thinking it would be safer than plastic?
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26th February 2018, 03:22 PM #14
Hi Bob, yes, I actually considered a 4kg LPG cylinder. I looked at the price of one new from SupaCheap Autos, and was surprised that it wasn't that expensive. I decided against it because of the size, and the weight. I was testing mine over the weekend, and took it down to 25in/hg and it will retain the vacuum in excess of 21in/hg for over 12 hours, without any issue. So I'm confident that there's no danger of it collapsing. The Class 12 PVC Pressure Pipe is a must though. I don't think I'd be so lucky if using regular thin walled PVC.
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27th February 2018, 12:41 PM #15GOLD MEMBER
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I use a discarded copper fire extinguisher. The correct model even has a standard pipe thread on top.
It is also used as a pressure vessel when I am on the end of a long air hose with a nail gun.
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