Interested in Vacuum pump / bag for veneering flat and curved

[Robert Engel]

I have an vacuum pump for AC use, I've been told it will work, but I've never tried it.

I think its worth looking for used pumps, as they can be quite expensive and hard to justify if you don't use much.

[Jim Morgan]

What is an "mcp cookie sheet?"

[Kevin Jenness]

What is an "mcp cookie sheet?"

A piece of melamine coated particleboard under the layup, atop the grooved base platen.

[Kevin Jenness]

I have an vacuum pump for AC use, I've been told it will work, but I've never tried it.

I think its worth looking for used pumps, as they can be quite expensive and hard to justify if you don't use much.

AC pumps are typically very high vacuum low volume units. For veneer pressing you want a pump that will draw at least 2cfm at >20" hg.

[Dwayne Watt]

The inexpensive, yet very effective route is a hand pump or a venturi pump. I have a venturi setup and can evacuate my roughly 4' x 4' bag in less than 2 minutes using a pancake air compressor. I have used this a total of 6 times in the 10 -12 years that I have owned it. The investment was about perfect in my case. Unless one has plans to veneer pieces on a near daily basis, there is little need to invest in a vacuum pump. Of course, that same or similar pump could potentially be used to power a vacuum chuck if you are a wood turner.

[Jeff Roltgen]

Anyone using a bag system, regardless of vacuum source: have your shop-vac at the ready. Once bag is closed, manually hold vac-hose over nipple on the vacuum bag. (Festool's rubber hose fitting is particularly good at this) It will empty a 4x8' bag in 10-15 seconds, even registering a few inches of pull. Now do a fast swap back to actual vac-pump fitting, and things will be snug in seconds, not minutes.

The faster you can get those veneers snugged down, the higher the likelihood of a very successful bond.

I use a Vacu-press air powered (venturi) style, which is very good in and of itself, but once I discovered this trick, I employ it every time. Especially helpful with the volume of air involved with bent-laminations and other various types of formers.

jeff

[Jim Becker]

That's kewel tip, Jeff!!

[Don Stephan]

A 3/4" bottom platen offers the best chance for a flat pressing to be truly flat. Breather mesh without a 3/4" bottom platen doesn't offer the same likelihood for a flat pressing to be truly flat. To each their own.

[Bruce Wrenn]

AC pumps are typically very high vacuum low volume units. For veneer pressing you want a pump that will draw at least 2cfm at >20" hg.

The ones I have pull about 6 CFM. Main thing is some kind of filter between bag and pump, as it will suck in glue vapors. For Venturi pumps, go to Air-Vac Engineering's web site. Their AVR093H is the basis for many small commercial systems.

[Kevin Jenness]

The ones I have pull about 6 CFM. Main thing is some kind of filter between bag and pump, as it will suck in glue vapors. For Venturi pumps, go to Air-Vac Engineering's web site. Their AVR093H is the basis for many small commercial systems.

My mistake. Thanks for setting me straight.

[Mike Henderson]

The CFM is mainly an issue of how fast you can get the air out of the bag after you turn the vacuum pump on. Once you have vacuum pulled, a very small pump will maintain it.

If you have a low CFM pump, you can use your shop vac to pull the initial air out, and then quickly switch over to your vacuum pump.

The reason you want to pull vacuum fairly quickly is that we often use water based glue and only apply it to the substrate. Once we lay the veneer on the substrate the veneer starts absorbing the water and will expand or otherwise cause problems. So the process is, roll your glue on the substrate, lay the veneer on and put blue tape to keep it in place, put a caul on top and get it into the bag as quick as you can. A helper is good to have to hold the bag open as you slide the work in.

Then close the opening and hook up your vacuum pump. Once the vacuum is pulled, the veneer is not going to cause problems so you want to get the work under vacuum as quickly as possible.

Mike

[Mike King]

The CFM is mainly an issue of how fast you can get the air out of the bag after you turn the vacuum pump on. Once you have vacuum pulled, a very small pump will maintain it.

If you have a low CFM pump, you can use your shop vac to pull the initial air out, and then quickly switch over to your vacuum pump.

The reason you want to pull vacuum fairly quickly is that we often use water based glue and only apply it to the substrate. Once we lay the veneer on the substrate the veneer starts absorbing the water and will expand or otherwise cause problems. So the process is, roll your glue on the substrate, lay the veneer on and put blue tape to keep it in place, put a caul on top and get it into the bag as quick as you can. A helper is good to have to hold the bag open as you slide the work in.

Then close the opening and hook up your vacuum pump. Once the vacuum is pulled, the veneer is not going to cause problems so you want to get the work under vacuum as quickly as possible.

Mike

Note that PVA glues (water based) will not dry in the vacuum bag. They will become more stable, but they will need to dry and set when you remove them from the vacuum and expose them to an atmosphere that allows the water to flash. So, be careful about your adhesive, the time in the bag, and as importantly the time out of the bag to allow them to set before working the resulting piece.