Getting a Good Bond with HPL Edgebanding

Good priming and a warm working temperature are important for good adhesion when applying high pressure laminate edgebanding. May 12, 2013

I recently acquired a lightly used Holz Her 1432 HF edgebander and last week did about 200 lf of horizontal grade HPL strip banding. After some tweaking of the various stations I was very happy with the results. Seemed like a great job. Then, after I'd finished, I discovered that if you picked off the end of the strip on a panel, you could rip the whole strip of HPL off pretty easily in one piece. The glue left behind on the edge of the panel (MDF with HPL both sides) is stuck to the panel really well and does not come off without a huge fight, but the bond to the HPL is poor. There is very little glue residue on the back of the HPL strip when pulled off.

So now I'm very worried about a major failure after installation. These are all kitchen cabinet box parts, not doors, so failure after installation would be even more disastrous.

The temperature in the shop and the temperature of the parts being banded was about 50 degrees. The glue is Dorus HKP 25 and the temp on the bander is set to about 205 deg. I assume the cold panel pulled too much heat out of the glue, leaving it too cold by the time the HPL was pressed on, resulting in poor bond.

Reading around on WOODWEB, it seems I also should have primed the HPL and now will likely have to rip all the banding off, prime and redo it all. If I rip off all the banding, do you think I should also take 1/32" off the panel to remove the old glue, or is it fine to leave this on and have it be reactivated by the next pass through the bander?

Should I buy the Dorus primer, or is ordinary aerosol spray adhesive (like the 3M product sold at Home Depot, etc. or some other brand?) just as good or better? How about techniques for priming uniformly and quickly without a mess? Does the primer tend to get all over the feed station before it gets applied? Should I raise my temperature? How much?

Forum Responses
(Cabinetmaking Forum)
From contributor S:
We are in Phoenix and occasionally in winter our shop gets that cold. We've had the same problem and solved it by raising the glue temp to 212. I've heard of priming but we didn't need to once we raised the temp.

From the original questioner:
That's encouraging. Without too much trouble I could rip off the 200 feet of banding that I've done, leaving the glue on the panel edge, and just run it through again. The glue has a really good bond to the panel, so the only downside of running it again (applying a second glue line) is that I'd have an extra thick glue line, right? Any other downside I'm not seeing with that approach?

I would like to avoid having to cut off the glue since it's a lot of double-sided parts and the scoring motor on my saw is currently out of commission.

From contributor S:
Should be okay. Our machinery tech also suggested bringing the laminate strips into a warm office for a while so they wouldn't be so cold. I'd probably do a test piece to see how noticeable the glue line is.

From contributor J:
As you found, you must prime your hpl strips before banding. You can either buy a primer such as Dorus, or just spray the back of the sheet up with contact cement before you strip it. Let it dry for an hour and band away.

From contributor I:
I backspray the laminate sheet with laminate spray adhesive, then cut it into strips.

From the original questioner:
Any particular brand of contact cement? And are we talking about aerosol type or a spray rig? I do very few commercial jobs so I don't have the equipment for spray adhesive for laminate work.

From contributor P:
I had similar problems a few years ago with PVC banding at around 50 degrees. The cold board was sucking so much heat from the glue in the short space between glue application and meeting the banding that there was no adhesion on pre-primed banding. Adding a space heater to get the shop to 65 or better and turning up the gluepot temperature seems to have solved the problem.

From contributor M:
There are primers for exactly this purpose. If you have the cartridge system and you want the ultimate bond, try using poly-glue. It is great for long runs but you must remove the glue and run a cleaner through the system when finished with the run. But this is an easy process that takes 10 or 20 minutes.

Try priming with whatever contact cement you have laying around. Just a thin coat to give the back that wet look. Run a few pieces after it is good and hot and see how that works. If it is not good enough, ask your supplier about a primer. Poly is the last resort, but that stuff is super strong. I've used it on aluminum, plastics, laminates and PVC.

From contributor L:
We always use the Dorus primer on HPL and solid wood. For small jobs just put it on with a foam brush - dries quickly. Bigger jobs we put it in a paint gun and spray the sheets. HPL may have contamination from the release agent used in manufacturing. Not a real good idea to turn the adhesive temp higher than recommended. I bought the option of a hot air blower that keeps the glue line hot between the application roller and the pressure section on my first bander. It came as a kit from the manufacturer (IDM).

For all the potential problems of banding failure, I think I'd turn up the shop heat well ahead of time so everything was warmer.

From contributor M:
Contributor L has a good point (no surprise). I forget that most of you are freezing your butts off right now. I have seen all the following used to keep temps in check.

- Heated infeed fence
- Using heated blankets at night to keep machine and materials warm
- Heat guns
- Disabling the glue pots idle heating function

As said by others, raising the pot temp is a bad solution. Not quite so bad is to raise the nozzle heater (Holz Her) or roller temp.