Veneer machine: Plastic plain bearings master extreme loads and high temperatures

• What was needed: Slide bearings in the veneer machines, more precisely on the pressure beam bearing for turning and swivelling movements
• Requirements: Resistance to high temperatures, dirt, dust and pressure
• Sector: Wood industry
• Success for the customer: iglidur® plain bearings are less expensive to purchase than conventional bearings, meet the technical requirements of the customer and minimise the service effort, thus guaranteeing a long service life.

Heavy dirt and dust loads in combination with high temperatures make the conditions for bushings in this application more difficult. Heinrich Kuper GmbH also wanted a maintenance- and lubrication-free solution for the bearing points of the veneering machine that would enable long downtimes.

Plastic plain bearings made of iglidur® G offer a lubrication-free solution that is very insensitive to dust and dirt. The occurring loads are absorbed by the pressure-resistant material iglidur® G. Furthermore, the coefficient of friction remains low even under the difficult conditions of the veneer machine and enables a very good solution for continuous use.

Heinrich Kuper GmbH in Rietberg is one of the market leaders in this highly specialised area of mechanical engineering. With the "ACR-Superquick" veneer cross-cutting machine, the company has had a globally successful series in its programme for years - the requirements and expectations were correspondingly high when Kuper began developing the successor series "ACR-Speedstar".
 
The centrepiece of a veneering machine is the gluing beam. It joins the veneer strips together with the help of gluing elements. Pressing forces of up to 20,000 N and temperatures of up to 220 oC are achieved in the joining area. As the veneer strips can be very long, the pressure beam is not exactly small either: it reaches a length of around 3500 mm and weighs around 500 kg.

The fact that the designers and, subsequently, the users of the machine place very high demands on the bearing of the beam is due to the ambient conditions. After all, in addition to its own weight, the beam must also be able to withstand the high pressing forces of up to 20,000 N. One of the reasons why this requirement is not easy to fulfil is that the pressure causes the beam to deflect. One of the tasks of the bearing points is to compensate for these deflections.

To ensure this accessibility, Kuper designed the new machine with a rotating movement: The pressure beam can move 90o towards the operator. And a new approach was also chosen for the bearing of the pressure beam: plastic plain bearings are used here, more precisely iglidur® G-bearing of type GFM 90-95-100, which were split and shortened to a length of 60 mm.
 
This solution has proven itself in practice: The rotary movement swivels the adhesive elements directly towards the operator and is easily accessible for cleaning and maintenance purposes. Due to the pitch of the bearing, the assembly and disassembly of the pressure beam is very simple, and the bearing clearance of the iglidur® bearings very effectively compensates for thermal expansion and deflection of the pressure beam. The bearing and the bearing material do not even reach their load limit: The use of the iglidur®-bearing still leaves room for manoeuvre upwards, so that larger working widths of up to 4000 mm and 25,000 N load are also possible.

The usual ambient conditions in woodworking also speak in favour of the use of plastic plain bearings. Michael von Mutius: "The use of the iglidur® G bearing is also the first choice for us in this case because of its corrosion resistance and insensitivity to the abundant wood dust."
 
This is why Kuper is by no means the only manufacturer of woodworking machines that relies on iglidur® materials for innovative bearing solutions. The fact that iglidur® G is used very frequently is due to the fact that this material is considered the "all-rounder" in the extensive iglidur® programme. iglidur® G is very well suited for swivel and rotary movements at low to medium speeds, even at extremely high loads (temperature, dirt, pressure...) and under adverse environmental conditions - precisely for the application profile for which the Kuper engineers were looking for a solution. And since igus® keeps the iglidur® G bearing in stock in a variety of dimensions from stock, Kuper was able to choose an "off-the-shelf" solution that is always available.