IMAL presents its latest technology for MDF production


The Hi-Jet system designed by IMAL is a fibre resination system which injects resin into the blow line at 100 bar and over, and which has been in operation worldwide for several years now.

This new technology has also been referred to as “nanotechnology” as the concept is principally based on the micronisation of glue lumps and crystals to reduce the size from an average 100 microns to approximately 5 microns. This process takes place in a special refiner equipped with disks that rotate at over 3000 rpm, designed and constructed by IMAL. This device also blends the chemical components in line perfectly.

The process then continues with a dynamic filter, a special high pressure piston pump and a set of self-cleaning, self-adjusting sprayer nozzles mounted directly on the blow line to complete the Hi-Jet system. As a result, glue is distributed accurately over the fibre, which means the press line can run faster; blistered boards are eliminated on the MDF line.

The system also injects steam into the blow line through separate sprayer nozzles that are located opposite the glue nozzles with an application concept different from other systems on the market. IMAL’s system applies less steam as the glue/fibre flow rates rise. No steam is applied when fibre flow rates are low, which is rare.

Such a system has been installed in over 100 MDF facilities and approximately 50 systems have been installed in PB and OSB mills as well.


The quantity of resin in the blow line follows the amount of fibre and in almost all facilities today, the fibre flow rate reference is taken from the rpm of the refiner feeding screw, the accuracy of which is not all that reliable.

The main reason is the frequency with which wood density changes. Adjusting resin flow in relation to refiner revs can lead to serious mistakes when density changes. IMAL has solved this by designing a new system which is mounted at the dryer outfeed, consisting of a bin scale which directly feeds a new sifter.

The particular feature of this system is that the bin scale is as wide as the sifter infeed. We have recently manufactured a bin scale which is 3500mm wide and hence as wide as the entrance to the fibre sifter. It can process 35 tonnes/h of fibre but it may be designed to handle any flow rate. A large weighing scale means a large volume of fibre travelling at low speed and hence, exceptional accuracy. An accurate flow rate readout and fibre density is obtained on line from this weighing scale.

The end part of the scale has been designed in a similar manner to a forming station, from which a completely open shower of fibre feeds the fibre sifter over the whole infeed area and hence over the whole of its width.

The Dynasteam

The Dynasteam Press

In most MDF plants, the fibre sifter is fed by a rotary valve which is narrower than the entrance to the sifter and which feeds it intermittently. IMAL’s solution feeds the sifter with a shower of fibre opened by doffing rolls over the whole of its width. The rotary valve at the dryer outfeed feeds a distributor screw conveyor which in turn feeds the whole width of our bin scale.

Two of the IMAL control systems have been added to complete the system: an infra-red moisture metre mounted on the scale and an online FiberCam for a constant monitoring of the 3D measurements of the fibres. The IMAL FiberCam is equipped with a digital camera that is able to take approximately one million images a minute.

A PC with its own dedicated software continually checks the size of the fibres coming from the dryer. The operator will then be able to utlise this information to adjust disk distance or change the refiner disk segments. The new fibre sifter is fully automatic and controlled by PLC. It will adjust to maintain maximum efficiency in relation to fibre flow rate, air flow rate and air pressure.


The Dynasteam injects steam into the mat before it goes into the press and is mounted at press infeed, above the infeed table.

With the installation of the Dynasteam it is possible to increase line speed by over 10 per cent, even peaking 15 per cent in some cases. The only costs related to this increase in production are those of wood, resin and a little extra power; the other costs have already been paid for by the existing production. It will take a couple of months on average to see returns on investment.

Furthermore, the mat is softer when it enters the press with the Dynasteam and as a result, it is easier and quicker to press at infeed, hence consenting a notable improvement in the density profile.

Furthermore, a drop in the Kw requirements for the steel belt will be noted, leading to less wear and all in all, less strain on the press. Unique on the market too, is the Full Blister Detector which is able to identify blistered areas on the board. The IMAL Full Blister Detector monitors 100 per cent of the surface of the board and is installed on the same beam as the thickness gauge, which, thanks to its level of reliability, comes with a three-year warranty.

Another important tool for accurate monitoring of MDF production is the CDP 700 which, installed after the press and before the diagonal saw, measures the density profile on line. The sensors are not mounted on top where the reading of the top sensor is difficult or where the sensor could be damaged by fumes which the board releases as it exits from the press. Both sensors on the IMAL unit are mounted below the board.

The IMAL PAL GLOBUS group sales will, for the first time, in 2018 exceed EUR200 million.