Vacuum veneering

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Graham N

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27 Sep 2022
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Chandler's Ford, Southampton
Just starting on using a vacuum bag for veneering and laminating and would appreciate some advice. I have a large bagpress from Axminster and bought a pump to use with it. I am unsure where to install the bag connector. I have seen two different sets of instructions about where to install the coupling on the bag. One shows the connector installed near the end of the bag, off the veneer, while the other shows it resting on top of the veneer item. I guess that runs the risk of marking the veneer, is that the point? The connector is aluminium as on the attached image
image.png
. Any advice for a newbie very much appreciated. Thank you, Graham
 
On mine I have it towards a corner, where I can get to it, and use a strip of breather material to lay over the pieces from the outlet, but I have also made MDF platen boards with grooves in to assist with the vacuum, picture explains better:

vac bag.jpg
 
On mine I have it towards a corner, where I can get to it, and use a strip of breather material to lay over the pieces from the outlet, but I have also made MDF platen boards with grooves in to assist with the vacuum, picture explains better:

View attachment 182953
Thanks for the quick reply, that is really helpful. What did you use for the breather? I wondered about a grooved platten but read it wasn't necessary with a breather in place.
 
I use both a grooved platten (a piece of MDF with lines 'scored on it with a track saw and then the whole thing waxed so glue doesn't stick to it) and a breather which came with the Bagpress vacuum pump - a piece of scotchbrite would do so that there is some air passage between where the connector is and the platter
 
You can buy plastic sheeting which has grooves moulded into its surface. This is designed for vacuum pressing to give a perfect load distribution, however it is expensive. I found a very cheap alternative - greenhouse shading sheet. It has 2 sets of grooves moulded at right angles to each other just as the 'proper' stuff but on a smaller scale. It's available at decent garden centres.
Brian
 
A little note, from my experience with platen boards, I had a wide one, but was laminating pieces that werent as wide and as a consequence the pressure
in the vacuum pulled up the platen, and basically folded it up and snapped it, so I now make/have a few that are just marginally wider than the pieces I'm gluing.

I found a very cheap alternative - greenhouse shading sheet.
That sounds useful, is it a rigid sheet?
 
I make my own vacuum bags from material from easy composites
I use a woven polyester fabric as a breather strip (it used in green roof construction). This is essential otherwise the bag can semi seal and not evacuate properly .
I dont think it matters where the vacuum extraction point is
 
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