We currently use Titebond II or III to glue up our stile and rail parts (stave core with edge bands and skins) for our exterior doors.

In the past we glued up parts at the end of the shift and let them sit overnight. We are getting to the point where we need the glue to dry faster so we can start machining the doors and assembling the same day due to demand and the need to shorten our lead time.

Can anyone advise me as to other glues to use to speed up process? I believe I am looking for a glue that dries quicker but can stand up to the exterior conditions (Type 1 - Exterior Grade - Water Proof or Water Resistant)

Type II and perhaps III will work with a RF glue curer.

http://www.workriteinc.com/products.html

We also use these blankets to cure bent lamination. They get hot and penetrate.
You could use 2, one top and bottom and be cured in 30 minutes.

http://powerblanket.com/

If you go this route, call them they do custom blankets to size and temperature and the customization fee is not significant.

I believe TB II will work with RF drying but you will need to let it cool before unclamping. TB3 may be the same.

Workrite recommends regular TB and that is what we use. We do not use the Workrite with TB II.

You may consider epoxy with a fast hardener if you have a constant temperature where the assembly and cure is occurring. This will speed things up, but will increase glue costs, alter process, and may have an effect on the final product.

I have to wonder why the overnight is not fast enough, since you are not working it on a 2nd or 3rd shift? Are you the first in the industry to put in a drive thru window?

A little planning will go a long way. In fact, I would think you could have stave cores made ahead of time, ready to be pulled from a buffer storage.

Thanks for the feedback - We are not saving much time by keeping inventory of stave core. We still have to glue the edgebands on after we find out what specie the customer wants the door. We also have to deal with thickness even though most of our doors are made 2-1/4". Stile width also makes an impact on keeping inventory. I guess I can keep our species to 1 - 2 choices and our stile widths to a standard - but that is getting away from our core business.

We are also trying a new scheduling system and the gluing process is somewhat of a bottleneck. If I can get the door parts to the CNC faster I can get more flow. For example if we start gluing parts in the morning - we usually can't start machining parts toward the end of the shift or typically the next day. If I could start machining parts sooner I can have much more throughput.

And yes - we can make other parts while the glue is drying and have done that. The concept of the scheduling system is to get something done rather than start another project.

I really don't want to introduce epoxy with a fast hardener.

Dave - have you ever used Radio Frequency to dry glue?

I have done experiments with RF heating and found the joint was not as strong as normal curing. When I built doors I heated my dowels in the microwave, I was able to get the door out of the press in 15 min. Bob

Hi Bob - I am not as worried about the dowels as much as all the parts that make up the door stiles and rails.

Thanks for the info on the RF heating.

Chad - What you are describing are the trade-offs you are encountering for the changes you want to make. More throughput and custom cores may be mutually exclusive. This is why Big Door Co. has all those details specified for their convenience, not for customization. They not only won't change their process, they can't.

I certainly understand maximizing the flow of each individual project, and progressing thru the production process smoothly with no long stops, but the nature of your product simply may not allow that. You might want to explore that as being a landmark and accepting it. Let the marketing people use it to help set yourself above your competitors. Lemons = lemonade, as long as you add some sugar.

While smoothing the process and clearing bottlenecks is certainly a worthy endeavor, you have to realize there are two events that will logically occur eventually: You will fundamentally change the way you make a door, and you will do so several times in the process. Secondly, the desire - commitment - to remove every bottleneck will never end, even well beyond the point of diminishing returns.

This is how we - as an industry - have gone from localized small shop fabrication of stile and rail doors to centralized production of MDF and hardboard doors.

No, I have never used RF to cure glue. I have been in several larger shops that do so, and I believe from the little I have seen that it is a consistent species, size and mass that benefits from it. It is possible to char the wood, or under cure. I figure I have enough variables to wrestle with my conventional methods of gluing that I do not need to introduce more.

I also confess to being somewhat of a Luddite with something like RF that I cannot see. How can you know that it is glued properly unless you destroy it? What if it falls apart in 2 days or 2 months?

I am sure there are others that are more expert on RF curing than me but there seems to be some miss conceptions. Here is my understanding of RF curing. We use it sparingly in our shop for processes that make sense.

1.) In my experience RF curing takes you from zero to one hour of curing time. Not from Zero to fully cured. You also need to let the joint cool a bit before you take the clamps off.

If done correctly with the correct glue the joint should be as strong as conventional curing.

If you want to experiment you can get a workrite wood welder at auction for around $400. If you are in Southeast MI you are welcome to come try ours.

The large easel/clamp machines are quite expensive and take up a lot of space. You would have to have volume to justify that.

The blanket I described in the beginning could fully cure your joint in an hour or so (I am guessing here). We do not use material as thick as you describe and heating that thickness of wood up could cause problems.

We do veneer curing under IR lights and once we get it to 120F for 20 minutes it is fully cured.

No matter your cure method if you machine it too early before the moisture is gone you will get depressions at the glue line when the wood does fully dry out.

Hopefully Gene W will hoop in here and add or correct what I have said.

We always allow a day at least after gluing staves with the edges before we machine and apply the face veneers. And we do use an RF with a catalyzed PVA. When gluing with water based glues you are introducing moisture and the components take on that moisture and will shrink back after a certain amount of time but at different rates. If you machine the parts to quickly before the opportunity to dry completely you can have failures at the edges or strange telegraphing. Kind of like sanding a panel right after you glue then the joint shrinks. My advice is let it dry and schedule jobs accordingly.

I agree with JT. You need to spend time scheduling other operations to keep the CNC busy.

Rushing a door thru in 1 day is asking for trouble down the line.

If you are hell bent on speeding things up you need to get away from evaporative adhesives.

There are newer fast cure epoxy adhesives that come in special caulking guns. They have different dry times. Conventional epoxy resins(ie West System) will not cure in less than a day regardless if you use the fast hardener.

You can get adhesive formulations that cure faster. This is possibly the best solution.

Heat also helps fast curing, but heating slowly also means that there is a risk of drying the wood, causing shrinkage and therefore stress on the joint before the joint is fully cured, leading to failures.

RF is an easy way to apply heat and cure a joint quickly, but it is only partially cured...full strength does take 24 hours or so. A properly made RF joint will be as strong as a conventional joint, as both will have a joint stronger than the wood itself, IF PROPERLY MADE.

One main reason for waiting after applying the adhesive is that the water in the adhesive causes some local swelling of the wood. If the wood is processed before the water disperses and the swelling goes down, then the swelling will go down after processing, possibly creating a defect.

Another reason for waiting is that the strength of the freshly glued joint increases with time.

If you are waiting overnight, do you keep the heat on in the building? You should, as cool means slower curing.

Do you use a clamp carrier? If so, perhaps you have room to add some additional sections to this machine so that you can increase production but maintain the same curing time.

I appreciate the feedback from everyone. I have brought back all this information to my team and it is agreed not to mess with the gluing process and to schedule the time where parts are glued up toward the end of the shift or we have other processes to perform while the parts are drying.

I came from a large window manufacturing company where they employeed engineers to take seconds out of a process. I considered waiting on glue to dry as low hanging fruit to improve a process.

We have a wood rite (wood welder) best tool i have in my shop. Yes if you overheat the glue it has less strength and some glues need cool down. We use weldwood plastic resin for the most for my doors and windows. If we need a long set up time we will uses Titebond II slow set with it but you need to give it longer clamp time and time before you work the item. We do not use the woodrite with a vacuum bag press. We put more than one hole in it.
One thing you have to remember is NO metal around the joint you are welding. Keep your hand away from it, we require good rubber glues when using it.
We do not use it on any manufacture wood products (PB Plywood mdf LVL) any metal will cause the machine to arc. If done right maybe 2 mins after you have done the last joint you can unclamp the piece. We give it another hour before we start sanding and working the piece.