Postforming Methods and Equipment

Postforming Equipment

Most methods of postforming are based on the principle of first gluing the laminate to the flat area of the panel or worktop, which has been previously shaped on its edge to the required profile, and forming and bonding the laminate simultaneously over the rounded edge. Whilst gluing processes differ, there are only two basic methods of postforming the laminate, stationary forming and continuous forming. In the former the workpiece remains static during the forming operation, whilst in the latter it is carried on a moving belt through the heating and forming zones of the machine.

Stationary or Static Forming

In their basic forms, static forming machines are simple bending rigs. Essentially they consist of a flat stout bed to which the panel is pneumatically clamped with the overhanging laminate edge projecting. A retractable radiant heater descends and dwells over the laminate until the required forming temperature is reached, then the heater is retracted and an angled section folds the heated laminate over the edge profile and holds it in position until it is cool. An advantage of these machines is that they can be used for forming down-bends with large drop fronts.
Another process involves the replacement of the infra-red radiant heater by a narrow heated platen, which actually contacts the laminate surface and literally irons it around the prepared profile. Bonding takes place simultaneously with the forming process. Because this process is, in reality, a small mobile press it can use almost any type of adhesive. These machines are fully automatic and once set to a particular profile they will follow it repeatedly at the touch of a button.

Continuous Forming

Continuous forming machines vary considerably in their size and output capacity, but they all operate in a similar manner, in that the panel, which has had the edges curved and the laminate bonded to the flat area, is carried by means of a chain or belt-drive through an infrared heating zone, and past stainless steel bars which turn the now softened laminate over the profiled edge. Shaped rubber or metal rollers then take over and press the formed laminate edge in place until the adhesive is cured. Finally, the surplus laminate is trimmed off.

Continuous machines can be divided into two groups using different adhesive systems, i.e. PVAc and Contact Adhesives.

Continuous Process Using PVAc Adhesives
These machines are favoured in the mass production kitchen furniture industry because of the high degree of automation, and their ability to utilise adhesives which require no special extraction facilities and present no fire hazard. The panels or worktops are first veneered in a flat bonding press, with the laminate overhanging the profiled edges. The postforming machines are self-contained units: forming, gluing and trimming in one pass.

Continuous Process Using Contact Adhesives

These machines are usually double-sided and capable of considerable width adjustment. The panel or worktop is first veneered by spraying both the laminate and core-board (including the profiled edges) with neoprene adhesive, and bonding them under pressure by passing the assembly through rubber covered nip rollers.

During the postforming process the laminate is first heated by passing through an infra-red heating zone to reach forming temperature. The heat reactivates the adhesive so that when the laminate is formed and pressed home by the rollers, it will instantly bond with the adhesive coating on the profiled edges of the core-board.