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Old project - Vacuum veneering setup

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Old project - Vacuum veneering setup

Postby Robert » 15 Apr 2015, 14:35

So way back when i bought a vacuum pump from a private seller on ebay.

I'd spent some time looking at pumps on ebay and they seemed to come in 2 types - dry vane and ones that involved oil somewhere. Dry vane seemed like less to worry about so I bid and won one of those.

I'd never vacuum veneered before but I had done some using clamping panels and cauls etc. it wasn't very successful as there were places that had little pressure.

Mt very first vacuum bag - an ordinary poly bag sealed with clear silicone
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And an early version of the pump setup. Think i may have tested it using just the pump but soon decided it needed a vacuum reservoir to allow the pump to rest. Non return mole wrench valve :)
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That first test out of the bag
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It wasn't stuck that well. I'd used cascamite glue which was the same stuff I'd used for hand clamping so in my mind it was not the right stuff for this. I can remember cascamite from school woodwork days and it was really strong but this stuff isn't
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On to building a better pump setup. I used a relay to switch the pump so i could trigger it with microswitches.
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Microswitches. I saw something on youtube once where a syringe was used as a pneumatic cylinder. i connected the vacuum pipe to the place where the needle fits and a spring to the extended plunger. The vacuum in the syringe pulls the plunger in against the spring until the microswitch is triggered to turn the pump off. As pressure falls (air leaks in) the spring wins and the other switch turns the pump back on.
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The clamp is on the pipe to the workpiece just for testing.
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One thing that took some solving was a simple non return valve near the pump as the pump itself does not have one. The pump is a major leak if you turn it off. The thing in the air line above the spring was a non return + flow regulator device. It worked but was a huge resistance in the line as not made for vacuum pressures.
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Top view in its first built version
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Here is a recent version. The calor cylinder is sealed with araldite and a 6mm connector drilled into it. the pump now has a small plastic non return valve near it which is happy to work at vacuum pressures. i've also added a small vacuum gauge so i can see what the pressures are.
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I did do another test using PVA
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No problems this time.
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Re: Old project - Vacuum veneering setup

Postby Andyp » 16 Apr 2015, 07:11

Ingenious and very clever.
I do not think therefore I do not am.

cheers
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Re: Old project - Vacuum veneering setup

Postby TrimTheKing » 16 Apr 2015, 10:28

Very cool! I've often thought about trying vac pressing so when I come to it I will be asking a LOT of questions! ;)

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Re: Old project - Vacuum veneering setup

Postby DaveL » 16 Apr 2015, 10:35

Great post, very useful details, something I would like to try. Thanks for putting it back up again.:cool:
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Re: Old project - Vacuum veneering setup

Postby RogerS » 16 Apr 2015, 11:28

Thanks Robert for posting. I remember reading your original and thinking how elegant it was. Time has not diminished that view.
If opportunity doesn't knock, build a door.
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Re: Old project - Vacuum veneering setup

Postby RogerM » 16 Apr 2015, 12:56

Really pleased to see this thread back for a second view. Thanks for re-posting.
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Re: Old project - Vacuum veneering setup

Postby stephen.wood125 » 16 Apr 2015, 17:53

Wow, what a fantastic design.

The staged refinements are also incredibly helpful to understanding the limitations and solutions along the way.

Bravo and thanks!!
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Re: Old project - Vacuum veneering setup

Postby oddsocks » 19 Nov 2017, 02:00

Hi Robert, I realise this is an old thread but i missed it at the time.

Do you have a supplier / description for the one way vacuum valve that you fitted?

Thanks

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Re: Old project - Vacuum veneering setup

Postby Coley » 19 Nov 2017, 08:18

oddsocks wrote:Hi Robert, I realise this is an old thread but i missed it at the time.

Do you have a supplier / description for the one way vacuum valve that you fitted?

Thanks

Dave
I was thinking the same. The whole setup blows my mind, but I did think if I could start finding a few parts it might all magically become clear. The two contenders I found are ebay numbers 253005988896 and 253005988896. I don't know if 6mm would be the right size or if either of them are the same as Robert used. Superb setup regardless

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Re: Old project - Vacuum veneering setup

Postby Robert » 19 Nov 2017, 11:06

I think the valve would have come from ebay and probably just one for aquarium air lines. I'll have a look through my history. It is difficult to find ones that work with vacuum. I had tried 6mm push fit non return valves but that just blocked the vacuum pressure.

edit. just checked ebay history doesn't go back far enough :(
Last edited by Robert on 19 Nov 2017, 11:10, edited 1 time in total.
Reason: added note
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Re: Old project - Vacuum veneering setup

Postby oddsocks » 19 Nov 2017, 11:16

Thanks Coley and Robert. Coley- you linked to the same number twice, but looking at that link and selecting "non return valve PNRV' the description does say its for air/water/vacuum so a possible contender.

If I get enough free time in the few months I'll have a go at making a setup so its ready when I actually have a vacuum project.

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Re: Old project - Vacuum veneering setup

Postby Robert » 19 Nov 2017, 12:20

searched my old emails and found it.

https://www.ebay.co.uk/itm/One-Way-Valv ... OC:GB:3160

Still for sale.

I use 6mm nylon pipe so I bought the 4mm size. 2 for £3.95.

I've not used the pump for some time now. AFAIK the valve still works..
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Re: Old project - Vacuum veneering setup

Postby 9fingers » 19 Nov 2017, 17:51

oddsocks wrote:Thanks Coley and Robert. Coley- you linked to the same number twice, but looking at that link and selecting "non return valve PNRV' the description does say its for air/water/vacuum so a possible contender.

If I get enough free time in the few months I'll have a go at making a setup so its ready when I actually have a vacuum project.

Dave



I used that type of NRV and also one of their shut off valves. In the listing 253005988896, the one I used is marked as for use with water but it is working fine for vacuum. Maybe it is specified for water to provide some lubrication but no hint of stickiness in use experienced so far. It is a pain to mount however so the one with screw holes might be more convenient.

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Re: Old project - Vacuum veneering setup

Postby 9fingers » 19 Nov 2017, 17:56

I did not use the syringe type regulator switch as I did not seem to have a suitable spring in my junk box.
Although considerably more expensive I used one of these.

http://cpc.farnell.com/multicomp/psf109 ... dp/SN36440

A short piece of 5mm silicone hose about 25mm long made a good coupler between the switch and the 6mm nylon tubing.

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Re: Old project - Vacuum veneering setup

Postby oddsocks » 20 Nov 2017, 22:55

9fingers wrote:I did not use the syringe type regulator switch as I did not seem to have a suitable spring in my junk box.
Although considerably more expensive I used one of these.

http://cpc.farnell.com/multicomp/psf109 ... dp/SN36440

Bob


Thanks for the link Bob, I see that there a quite a few options on that site for pressure switches, but I'm trying to understand what the operating pressure ranges actually mean...most seem to say they can be adjusted, but that one has the biggest range between max and min operating pressures.....does that imply the hysteresis loop, so when near vacuum is reached it will shut off (is that the 11.9 or 2.9 end of the scale?) and only cut back in once the vacuum drops enough to reach the other threshold.
I suspect I'll be looking for a vacuuming project just to have a 'reason' to build this!

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Re: Old project - Vacuum veneering setup

Postby 9fingers » 20 Nov 2017, 23:26

The data is pretty poor.
In practise the hysteresis is about 2-3 psi.
The adjustment screw is down the sensor input which is a bit weird.
I set it to max which is about 13.5 psi - plenty for the application.

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Re: Old project - Vacuum veneering setup

Postby RogerM » 21 Nov 2017, 21:07

9fingers wrote:The data is pretty poor.
In practise the hysteresis is about 2-3 psi.
The adjustment screw is down the sensor input which is a bit weird.
I set it to max which is about 13.5 psi - plenty for the application.

Bob


Not sure I understand this spec. Given that the valve boasts a VACUUM -2.9 TO -11.9PSI, and assuming a normal atmospheric pressure of 15PSI, does this mean that the percentage vacuum is 11.9/15PSI, or about 80%? My pump advertises an ultimate vacuum of 99.995% so If this is the case, my guess is that Roberts ingenious Heath Robinson piston gismo might actually allow a greater vacuum, and therefore greater pressure?
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Re: Old project - Vacuum veneering setup

Postby 9fingers » 21 Nov 2017, 21:35

It can be confusing and further confused by talking %

Take the case of no vacuum, there is equal pressure inside and outside the bag so no net pressure on the job.

Take all the air out, then all the atmospheric pressure on the outside of the bag has nothing to oppose it so all the pressure is on the job.

Compared to localised pressure applied with clamps and cauls, even a few pounds per square inch is streets ahead of clamps.
Even 11 pounds per square inch will apply plenty of force ( I chose 11lbs carefully) this is the weight of 5 bags of sugar on every single square inch of the job.

Connect up your super dooper pump and you could get down to 15 ish pounds per sq inch. all that does is add another 1.8 bags of sugar.
Not a great deal of difference on a veneering job.


NOW if you are bending laminations around a curved form, then the pressure is working against the spring in the wood and every last PSI (or bag of sugar!) is important and your super pump will be very helpful.

hth
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