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My First Vacuum Veneering Project

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My First Vacuum Veneering Project

Postby 9fingers » 12 Nov 2017, 17:01

Firstly let me say that I am indebted to two member Robert and Woodbloke here without whose inspiration and help I possibly would not have undertaken this,
With the help of Rob and his mega throated bandsaw and drum sander he cut some oak into 2.5mm veneers for me.

You may recall this post from Robert viewtopic.php?f=26&t=1022 which I largely copied to make my vacumm pump.

I have also followed his improvised bagging methods which have work far better than I could have imagined so on my second run, I took photos and did this write up. I think Roberts original posts were lost when Woodhaven died.


Firstly I took some fairly heavy gauge polythene sheet cut from industial waste sacks (domestic bin liner are too fragile) enough to cover the workpieces twice with about 100mm to spare all round.
here with the substrate in place
Vacuum bagging 007.jpg
(270.54 KiB)


and with the substrate removed to see the location of the vacuum pipe

Vacuum bagging 009.jpg
(276.01 KiB)

My pipe is 6mm hard nylon and is curved due to it being supplied on a coil so I used masking tape to try and hold it straight.
Vacuum bagging 008.jpg
(196.06 KiB)


I did two pieces with veneer on both sides in one go and cut another piece of polythene as an interveaving sheet to avaoid any risk of gluing the two panels together.

Here is one piece of book matched veneer taped ready for glue in the traditional manner.
Vacuum bagging 006.jpg
(233.41 KiB)


I've not shown the glue application but I applied ordinary pva with a 100mm foam roller to the back of the veneer. I chose to apply to the veneer as my substrate is MDF and I wanted to minmise the risk of it swelling with the wet glue before I was ready to apply the vacuum pressure.

Here is the stack of 4 veneers and two substrates with the interleaving sheet place on the polythene sheet.

Vacuum bagging 005.jpg
(258.29 KiB)


Now for the seal. run a bead of ordinary silicone sealant arounf three sides in a continuous run with an extra blob where the pipe goes in. Not that the smasking tape stops short of the silicone. and the bead extends at both ends a little to make sure there is enough on the fold.

some of the masking tape decided to let go as I took the photo but that was easily reapplied before applying the vacuum.

Vacuum bagging 004.jpg
(190.11 KiB)


Now fold the upper half of the polythene over the top of the stack, gently form round the edges and then lightly press onto the silicone without deforming it much.
Switch on the vacuum and it soon looks like this

Vacuum bagging 003.jpg
(250.18 KiB)

You can hear any slight leaks apply a bit of finger pressure or in extremis an extra squirt of silicone in the offending area.

Soon the vaccuum gauge looked like this and the pump switched off. I've not heard it come back on so no leaks!
Vacuum bagging 012.jpg
(340.49 KiB)


I also lightly clamped the tube as it comes up from under the bench to remove any risk of the polythene being dragged aside

Vacuum bagging 001.jpg
(284.79 KiB)


I recall some of my military colleagues saying "Preparation and planning prevents * poor performance"
Certainly applies here. Do some dry run practice first but it is very straight forward with a bit of preparation.

Thanks for reading

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
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Re: My First Vacuum Veneering Project

Postby Malc2098 » 12 Nov 2017, 17:40

Fascinating, Bob.

Where do you get the vacuum pump from?
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Re: My First Vacuum Veneering Project

Postby 9fingers » 12 Nov 2017, 17:59

Malc2098 wrote:Fascinating, Bob.

Where do you get the vacuum pump from?


Freecycle for nothing more that the cost of the diesel to collect it believe it or not.
I rigged it up much the same way as Roberts with a gas cylinder reservoir, vacuum switch and separate motor with a belt drive.
Just lives under the bench and a 6mm pipe to deliver the suck!

I spent too long thinking about the possible problems with the improvised bagging when there were none.

Bob
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Email:motors@minchin.org.uk
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Re: My First Vacuum Veneering Project

Postby Malc2098 » 12 Nov 2017, 18:42

Nice.
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Re: My First Vacuum Veneering Project

Postby Andyp » 12 Nov 2017, 21:15

Clever, but them I’ve learned to expect nothing less.
I do not think therefore I do not am.

cheers
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Re: My First Vacuum Veneering Project

Postby 9fingers » 12 Nov 2017, 21:20

Andyp wrote:Clever, but them I’ve learned to expect nothing less.



No credit due to me Andy! I simply copied others but wrote it up because I think we lost a lot of the original work put in by Robert.
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Re: My First Vacuum Veneering Project

Postby Robert » 12 Nov 2017, 23:52

Praise indeed :)

Hope the silicone was pretty much dry by the time you opened it up. Dry elastic silicone is easier to deal with than stuff that is still wet.

There's pictures of my pump here viewtopic.php?f=26&t=1022 and my black plastic doing exactly as Bob's red can be seen in this old thread viewtopic.php?f=26&t=657
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Re: My First Vacuum Veneering Project

Postby Rod » 13 Nov 2017, 01:03

That’s a neat idea re the sheeting, I played around with one of those plastic vacuum storage bags without success.

Aidan (Tiddles) late of this parish, gave me a small pump many moons ago.

Will have to give it another go sometime.

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Re: My First Vacuum Veneering Project

Postby 9fingers » 13 Nov 2017, 12:10

Robert wrote:Praise indeed :)

Hope the silicone was pretty much dry by the time you opened it up. Dry elastic silicone is easier to deal with than stuff that is still wet.

There's pictures of my pump here viewtopic.php?f=26&t=1022 and my black plastic doing exactly as Bob's red can be seen in this old thread viewtopic.php?f=26&t=657



I left everything under vacuum overnight to cure and took it out this morning. The silicone was only partially cured as there would have been nowhere for the acetic acid to evaporate to over most of the seal.
It was a little messy to handle with snots of semi cured silicone covered in uncured silicone just wait to drop on the surface of my precious panels.
Doing this again I would suggest that the fold on the polythene should be on a short edge so it can be folded back out of harms way or preferably another interleaving sheet on the top of the stack.

All in all I'm pleased with the result and the ease of the process. Here is a quick shot of one of the panels after the tapes removed a quick whizz over with the ROS and the grain popped with a little white spirit.

Vacuum bagging.jpg
(338.28 KiB)


These panels will become the tops of coffee tables I've been making - sorry no write up as I did not start out taking pictures but will post some of the results - eventually.

As for vacuum bags, I'm not sure if they are worth it for low volume, amateur use to be honest. Poly sheet is cheap and for modest size jobs can be cut from bags or Screwfix sell 12 sqm packs for a tenner, which I shall be using later today for a much larger panel.

Bob
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Re: My First Vacuum Veneering Project

Postby Mike G » 13 Nov 2017, 12:25

Nice experiment. As I've said, I'm not sure I'm ready for veneers just yet.....

Instead of silicon, couldn't you heat-seal the sheets of plastic? I have heard of people with heat sealing kit at home, but I have no idea of its cost or limitations.
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Re: My First Vacuum Veneering Project

Postby 9fingers » 13 Nov 2017, 12:47

Mike G wrote:Nice experiment. As I've said, I'm not sure I'm ready for veneers just yet.....

Instead of silicon, couldn't you heat-seal the sheets of plastic? I have heard of people with heat sealing kit at home, but I have no idea of its cost or limitations.


The silicone is quick and easy and also does the seal around the tube. You need a method that would seal right first time as especially with bigger jobs the glue can be starting to go off as you bag it and no time to regroup after any failure
I don't know how well the overlap between successive heat seal joints works.

Bob
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Re: My First Vacuum Veneering Project

Postby Robert » 13 Nov 2017, 14:38

I used vacuum storage bags when I started out. They are more trouble than they are worth.

You have to get the work inside a bag not just lay it down and the veneer moves as you fight with it. Also they are not that strong and the pressure on sharp corners can cause leaks meaning you have to tape over the holes to finish the job.
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Re: My First Vacuum Veneering Project

Postby oddsocks » 19 Nov 2017, 01:58

9fingers wrote:
Malc2098 wrote:Fascinating, Bob.

Where do you get the vacuum pump from?


Freecycle for nothing more that the cost of the diesel to collect it believe it or not.

Bob


Thanks for posting this Bob - like you, I managed to get my pump from freecycle (my thread was also lost with the demise of woodhaven). From memory once I got it home and did some research I realised it was worth at least few hundred £; it had come from a large old style commercial printing tool. I also intended to make something similar to Robert's control system but didn't at the time, so whenever I vacuum the pump runs continuously, so thanks (to you and Robert) for posting the info on this forum. I'd missed Roberts detailed solution build thread until now.

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Re: My First Vacuum Veneering Project

Postby RogerM » 21 Nov 2017, 20:36

+ another thanks for posting this Bob. I've only just discovered this thread and I love that bagging idea. I have a circular table 1400mm in diameter to veneer after Xmas and I was wondering how I was going to manoeuvre it into a bag. This seems like the answer! Looks to be simple and effective.

Unless I've missed something, does the silicon peel off the polythene sheet when the pressing is complete, or do you have to cut off the area that has been stuck down?

And having now read the links provided above, thanks to Robert for writing up the bagging technique in his media unit thread. I really cannot understand how I missed that one the first time around!
Last edited by RogerM on 21 Nov 2017, 20:49, edited 1 time in total.
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Re: My First Vacuum Veneering Project

Postby 9fingers » 21 Nov 2017, 20:48

The silicone does not cure fully during a typical session so I've treated the polythene as a consumable.

ALSO I'd advise a further interleaving sheet on the top surface of the stack. This can be waxed paper or any old poly sheet and not necessarily a single piece.

When you release the vacuum, peel the polythene( and its wet silicone) back and the interleaving sheet will protect the surface from getting silicone on it.

good luck

Bob
Information on induction motors here
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