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Heating a vacuum press for veneering

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tcqc

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Hi,

I'm new to woodworking this year so still learning a lot as I go.

I bought a vacuum press for veneering - a vacuum pump and vinyl bag rather than a bench press - The Professional AirPress Vacuum Press System

I'd like to build a proper workshop in a year or two but for now I'm doing everything in an uninsulated garage.

I've been using Urea Formaldehyde glue which I know is temperature sensitive. It's been fine over the summer but if it gets below 10 degrees C in the winter, I'm worried it won't cure even if I use the fastest acting hardener. Also, it would be nice to warm it up just so I can mix one batch of glue and use it for both sides of a panel (I'm just doing one side at a time, with breather mesh on top) rather than having to mix up a batch for each side.

I've been thinking about how to heat it. I looked at heater mats but the only ready to go product I could find is on the Airpress website: AirPress

They're expensive and also need a single phase socket. I don't know what amps but I've just got standard 13A sockets and don't really want to get a 16A socket or whatever since it seems like a waste if I do get a proper space in a few years.

I haven't been able to find much info about making DIY heater mats. If it's possible, it's something I could probably do with some practice. I've got very basic electronics knowledge from doing a few Raspberry Pi projects.

I've thought about building a mini kiln, basically just a box using Kingspan/Celotex insulation, and putting the vacuum bag etc inside. My vacuum bag is 2.6 x 1.35m so I guess a bit bigger than that in size, then whatever height.

My question though is if I do that, does anyone know the best way to actually heat it?

I don't need to go too crazy but it would be good to be able to heat it to about 40-50 degrees C. I don't need any hotter because I wouldn't be using it that often.

I've looked at tubular heaters but I'm not sure since they usually seem to be just for preventing freezing and I don't know if I could get them to heat it up to 40-50 degrees.

I've thought about heat lamps and convection heaters but I'm pretty lost because all the info seems to be for heating greenhouses/sheds etc.

Has anyone done anything similar or has any advice?

Thanks!

Tom
 

guineafowl21

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I've been thinking about how to heat it. I looked at heater mats but the only ready to go product I could find is on the Airpress website: AirPress

They're expensive and also need a single phase socket. I don't know what amps but I've just got standard 13A sockets and don't really want to get a 16A socket or whatever since it seems like a waste if I do get a proper space in a few years.
Those heater mats will plug into your normal sockets. “Single phase” just means a normal household supply.
 

bjm

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Why heat to 40-50 deg if you are happy with the result at ambient (~20+deg) and how long is each press cycle? One simple solution might be to wrap it in an electric blanket for the duration of the pressing but would probably need some experimentation??
 

tcqc

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Those heater mats will plug into your normal sockets. “Single phase” just means a normal household supply.
Thanks, I thought it meant the blue caravan style connectors! I'll look into the heater mats more then.
 

tcqc

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Why heat to 40-50 deg if you are happy with the result at ambient (~20+deg) and how long is each press cycle? One simple solution might be to wrap it in an electric blanket for the duration of the pressing but would probably need some experimentation??
I don't *need* to heat that much but it would be nice to be able to mix up one batch of glue and do multiple sides/panels. It's just a bit annoying pressing at ambient temp and then having to mix a second batch to do the backer side.
 

TheTiddles

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A domestic electric blanket will do what you want, or bring it inside and save the faff?
Aidan
 

bjm

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If you like tinkering then, why not have a look at the heating rolls they use under floor tiles? Not sure if they will reach the temperatures you want but it should be possible to make some sort of 'containment' to suit your needs?

Also, why not use something like titebond? I have veneered doors (7 foot) with it in a veneer press. Takes some planning but quite do-able.
 

tcqc

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Thanks - I had thought about underfloor heating mats, the problem is it's hard to find info on how hot the mats themselves get. Maybe electric blankets are the best option, I wasn't sure if using two (one on top, one beneath) would set off any overheating protection but I guess I should just try and worst case scenario, use one.

I could use titebond, I just haven't got the hang of getting big panels in the bag quickly and also I've had really good results with the UF glue. Using extender I've had no issues with bleed through on oak veneer so I like using it.
 

bjm

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Just had a look at underfloor mats on Toolstation website (won't put up link as it will expire at some point!) It says max floor temp: 40 deg C. There are also contact details for advice from the manufacturer on the site also (under Technical Details). The bigger issue will be the insulation; whatever you use most of it will be heating the air around it so you will need to reduce those losses. Personally, I'd start with one electric blanket and work it out from there.

I've not tried UF glue in the press as I've been happy with TB but if you're happy with it keep using it.
 

Oddbod70

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The airpress is good, but I dont use mine much for large panels because veneered ply or MDF is a lot less hassle. For smaller bookmatched stuff its great. I must admit I use titebond. I’ve never needed the airpress glue.
 

flanajb

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I use an electric blanket and then throw an old sleeping bag over the top. Works a treat even on night's when it's below zero.

Top tip is to turn the blanket on and wrap it in the bag ahead of time so that it's already warm for when you need it.
 

Cabinetman

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As you are only doing a bit here and a bit there, why not just sneak it into the kitchen of an evening, and/or at the very least keep the parts you want to bond in the house to acquire an ambient temperature and then take them outside to glue, The latent? heat in the timber should stop any low temperature problems occurring. Ian
 

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I had a thought. Make a table top with a lip around the perimeter. Drop a sheet of drywall it. Put down the inflow electric heating pad and then pour plaster of Paris to cover the pads. Then you can level the plaster and do you pressing on top of it. Covering the bag with a blanket or two. The thermal mass will help with moderation the temperature. When you are ready to move into the new shop you can break up the plaster to get the pad out.

Pete
 

Droogs

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How about just using steam like in the old days.

Make a table the size you need and insulate with celotex etc and then run pvc pipe in a single run like underfloor heating and line the box in 3mm ply. Have the ends connect up to a 1 or 2 walpaper striper steam boxes and let it run and just make sure you top it/them up. As long as the bag fits in and you have access for the vacumm pipe to get to the pump, you can put an insulated lid on as well. You will easily get up to 70DegC for fast curing your glue
 
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