Most of these machines (in mobile configuration) both have horizontal feed, and then almost everything is different.
The FlexHammer™ go from underneath upwards, while most fixed hammers go downwards against a rigid anvil. This anvil is exposed to heavy wear from the feed material and it has to be maintained very often.
Fixed Hammer Mill
Material to be processed in the fixed hammer mill goes directly to the bottomgrate. Uncrushable feed materials first of all create a heavy impact to the anvil and then they are heavily pushed against the grate. A grate, which in a way has a release arrangement (in many cases), but on the contrary and because the grate is solid and often very heavy, the release goes slowly. During the time when the break pins brake and the grate has the chance to drop, the uncrushable item will be conveyed to the top part of the machine where there is no escape way and consequently the unlimited compaction forces will destroy the machine’s top shell or bend the rotor shaft which one is the weakest. The principle of rotation direction against a solid and firm anvil also may result in counter forces, which try to lift or crack the rotor bearings´ housings.
The FlexHammer™ Mill
The FlexHammer™ machine has the opposite rotor direction and it works without anvil. Crushing takes place in several moments and under flexible conditions. Uncrushable items are stopped on top of the “knives”, the hammers are bending backwards, hiding between the rotor discs and at the same time lifting the object from the “knives”, against the reject door, which opens and allows the object to drop out. A combination of incidents, which work well in line with the desire to avoid heavy impacts and damages.
The FlexHammer™ ´s “knives” prevent uncrushable objects to enter between rotor and grate while Fixed Hammer machine has no protection against the same.
The real purpose of the machine, to provide an effective and controlled processing must not be forgotten.
The FlexHammer™ machine’s crushing takes place in several steps, at feed entrance, material to material, against roof, against reject door, over and/or between the “knives” and finally through the bottom grate.
The “knives” in particular have great importance to the finished product. They are arranged crosswise to the grate bars and therefore limit production of longer material (oversize). Also elastic materials are effectively processed thanks to the “knives”.
The Fixed Hammer type of machines works directly from entrance to bottom grate which results in a brutal operation, which gives no room for sensitive processing.
On the contrary a FlexHammer™ has a simple design with a lot of flexibility built into it.
It is an easy work to change the grate when there is a need for a different finished product. Contaminations in form of uncrushable objects make no harm to the machine, capacity as well as reliability are very high. Experienced design since 1969.