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{{Short description|Machine for refining fibres}}
{{distinguish|Defibrillation|Automated external defibrillator}}
{{More citations needed|date=September 2018}}

The '''defibrator''' is a machine used as part of the manufacturing process for [[medium-density fibreboard|MDF]] man-made wooden board. It produces fine wooden fibres, finer than the cut chips used to make [[particle board|chipboard]]. Although small, these fibres retain good structural integrity.

The machine itself is a [[thermo mechanical pulp]]ing refiner in which the pulp material, such as [[wood chips]], is ground in an environment of [[steam]] between a rotating grinding disc (rotor) and a stationary disc (stator) each with radial grooves that provides the grinding surface. Wood chips are fed into the centre and are broken down as the centrifugal force pushes them towards the circumference of the discs where the grooves are finer to produce [[wood fibre]]. The size of the [[refine]]d fibres can to some extent be controlled by altering the distance between the discs where a closer distance produces finer fibres but also requires higher grinding force. The capacity per machine is largely determined by the size of the machine, as well as the motor speed, which can be 1,500 or 1,800{{nbs}}[[rpm]].{{efn-lr|The precise machine speed is unimportant and these are merely the typical motor speeds for [[induction motor|electric motor]]s running on either [[utility frequency|50 Hz or 60 Hz]] [[mains electricity]].}}

==History==
In 1931 the [[Sweden|Swedish]] engineer [[Arne Asplund]] filed a patent on a method to defibrate wood chips.<ref>{{cite patent |country=US |number=2008892 |title=Method of manufacture of pulp| inventor=Arne Johan Arthur Asplund | gdate=1935-07-23 |status=patent}}</ref> As opposed to the [[Masonite]]-method, the defibrator-method (also known as the Asplund-method) uses pressurised steam to soften the wood chips, then grinding discs to pull the wood fibres apart. This grinding unit is what Asplund called the defibrator. It became the key product of his company, [[AB Defibrator]]. The Defibrator trademark is now held by [[Valmet]], the successor of AB Defibrator, for its line of refiners for the panelboard industry.<ref>{{cite web |url=http://www.valmet.com/products/pulping-and-fiber/fiberboard/defibrator-system/ |title=Defibrator system |website=Valmet |access-date=6 April 2016}}</ref>

==References==
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[[Category:Papermaking]]
[[Category:Pulp and paper industry]]


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