Lightweight Panel Production Gets Real

“This is probably one of the greatest opportunities for companies producing furniture for retail consumption, where shipping weight and costs are a concern. It’s also an advantage for producers of office furniture and store fixtures when they consider how much labor they may be able to save producing furniture that’s easier to handle and install for one person.”

Stiles Machinery’s Gary Wernlund is talking about lightweight panels, produced with the same basic technology as that used to create hollow-core interior doors. Lightweight panels offer a thick-panel look at a fraction of the heft of standard panels, high rigidity and flexible surfacing options. They are constructed with a stile-and-rail frame, made usually from a composite panel material. The frame is laid on the bottom surface or “skin,” a paper honeycomb material is stretched to all four corners and edges of the core and glued to the bottom skin, and the top skin is glued to the sandwich.

“We’re seeing growing acceptance of this technology in Europe,” says Wernlund. There are a number of factors that drove its development in Europe. From an ergonomic standpoint, consumers like furniture that’s lighter and easier to transport and handle. Consumers are also responding to a current design trend toward thicker panels in their furniture.”

Hollow-core doors have been on the market for years, so why is it only now that lightweight panels are becoming a viable alternative for furniture?

The primary factor that held back production and use in the past was the amount of labor required for panel production.
Gary Wernlund, Stiles Machinery 

The material costs – the framework, the honeycomb and the surface skins – have been relatively low, but because they have been largely assembled manually by up to eight people, the labor costs were very high.

“The design community had been asking for thicker panels over the past few of years but they’re not willing to pay a cost increase; actually, they’re asking for cost reductions. IKEA was the first retailer that had volumes high enough to drive manufacturers to pool their technical resources to come to a good solution.” [See “IKEA’s Big Idea” in the Spring 2004 issue of S&P.]

Wernlund says the prospect of meeting a growing demand for these panels has driven leading European machinery manufacturers to address the cost barrier by creating highly automated manufacturing solutions.

“When the Homag Group developed this process, they did it as a real joining of technology with glue manufacturers, honeycomb manufacturers, hardware suppliers, as well as suppliers from outside of the furniture industry.”

The two basic lightweight panel production systems and have many similarities: throughfeed production, automated handling of the honeycomb material, automatic assembly of the framework, the use of polyurethane reactive (PUR) hotmelt adhesives, and pinch-roller pressing stages. They differ in how the PUR adhesive is applied. One system uses a slot nozzle system; the other uses glue spreader technology.

“The choice for customers really comes down to what they’re most comfortable working with,” says Wernlund. “Some are very adept at working with glue spreaders, and others understand the benefits of slot nozzles. But building up of the frame is a little different as well. I would describe the glue-roller system as a ‘stop- and-go’ process, and the slot nozzle line as more of a continuous throughfeed process.

“Although very similar, the slot nozzle process is a little easier to describe,” says Wernlund. “The bottom sheet is loaded automatically with a vacuum feeder, and the PUR glue is applied to specific areas with slot nozzles to the bottom sheet. The stiles and rails are positioned automatically onto the sheet from hoppers, not unlike how automatic edgebanders handle solid wood edgebanding. The honeycomb is then fed forward and cut to size before being dropped automatically into the framework, and glue is applied to the assembly before the feeding of the top sheet. That completes the sandwich, which is then fed through a roller pressing operation. The panel is then complete.”

It’s a straightforward process, but Wernlund says it requires a fairly complex piece of machinery because it replaces seven or eight pairs of hands doing the feeding and assembly.

“When the manufacturers did a comparison of amount of labor to the amount of output of the throughfeed versus the manual production method, they found that these systems can produce up to three times the panels with only two or three people.”

Not only does this technology make lightweight panels more economical to produce, says Wernlund; the quality of the panel has been improved as well.

“In the past, honeycomb panels have not been very flat or as strong as they need to be. The use of PUR adhesive was a huge leap forward in getting a flat panel that had good strength, and good heat and moisture resistance as well. The traditional method for gluing this type of panel together has been with a water-based adhesive. When water gets trapped in a panel like this it is likely to warp during the hot pressing process. There’s no water in the PUR hotmelt material, thus the panel is flat.”

Solutions for creating non-rectangular lightweight panels are being explored, but Wernlund says to his knowledge none are in production as of yet.

“To make an oval tabletop you would have to answer the question, ‘Can the product perform without a solid framework around the entire perimeter?’ Homag has done some testing to see if they could edgeband a honeycomb without a rail, without a solid edge. Since the thickness of the edgebanding you apply has a lot to do with the performance characteristics of the edge, you couldn’t put a thin edgeband over a honeycomb core and get good bonding or performance characteristics, impact resistance, and maybe not even a good visual because of telegraphing. With a thicker piece of edgebanding, all of these things improve.

“Another thing they have tested is using a liquid foam material to fill in the voids on the edges, and then applying a thin edgeband. Another possibility is to sandwich two layers of honeycomb together and utilize the skin in between as another layer of support for an edge.”

These panels have all the properties necessary to create great, economical and stylish furniture. They’re very sturdy.
Gary Wernlund

Surfacing options are a snap, says Wernlund. The most efficient way to create lightweight panels is to use skins that have already been surfaced with melamine or vinyl. The panels are also sturdy enough to accept most other types of surfaces after construction.

A patented technology called “Woodwelding” (www.woodwelding.com) is utilized to attach fittings to lightweight panels.

Gary Wernlund“Woodwelding uses ultrasonic energy to liquefy the outer surface of a thermoplastic dowel, allowing the plastic to penetrate and solidify within the porous honeycomb material,” says Wernlund. This lets manufacturers attach fittings to lightweight panels, even if they fall in an area where it’s only supported by honeycomb instead of a solid composite panel rail. This process is typically done on the boring machine or a machining center where the hardware insertions are taking place.

“This technology is critical if fittings are required to attach panels together in a casegoods product; it really makes the use of lightweight panels in many types of furniture possible.”

Wernlund says the Nor th American furniture market’s acceptance of lightweight panels hinges on educating consumers and designers.

“These panels have all the properties necessary to create great, economical and stylish furniture. They’re very sturdy. I was surprised the first time I picked one up. I thought because of its light weight I would be able to ‘flex’ the panel, but found that it was as rigid as a traditional furniture panel.”

Kenn Bush | surface&panel | SUMMER | 2004 |