Main factors affecting the quality of wood chips

Main factors affecting the quality of wood chips

The cutting quality of ring flaker is mainly restricted by two factors, one is the quality of wood itself, the other is the mechanical factor.

(1) Wood chip quality

The quality of wood chips should be as follows: healthy material, smooth cut, uniform size and suitable moisture content. High quality particles can be made from high quality wood chips. Otherwise, the quality of particles will not only be difficult to guarantee, but also the debris will increase substantially.

(2) Several parameters of flaker

The parameters of the planer mainly include the amount of the cutter extension, the size of the gap under the cutter and the radial clearance (Fig. 2-29).

Main technical parameters of ring flaker

Figure 2-29 Main technical parameters of ring flaker

1. Planer 2. Cutter wheel 3. Blade 4. Wood or debris H. Cutter protrusion s. Cutter gap R. Radial clearance UNP. Cutter wheel rotation direction UKP, impeller rotation direction

The radial distance from the cutting edge to the inner edge of the cutter wheel. It is usually controlled at h=0.3-0.6mm. With the increase of H value, the thickness of particles increases. Therefore, the thickness of particles can be controlled by adjusting the extension of the knife. However, due to the elastic deformation of wood in the cutting process, and some large shavings can be mixed into qualified shavings through the gap under the knife. Therefore, the average thickness of particles should be slightly larger than the amount of the knife extension. Of course, the above results are only valid on the premise that the cutting edge is sharp and enough centrifugal force can be generated. In addition, the inconsistency of knife extension will make the thickness of particles uneven.

The size of the gap under the cutter s the gap between the cutting edge and the back pressure plate. The gap under the knife is the discharge channel, the s value is too small, easy to plug; the s value is too large, and easy to leak, so that too large particles are mixed into qualified particles. Usually s = 2-3 mm.

Radial distance between blade vertex of radial clearance R and inner edge of cutter wheel. If r < h, the blade and impeller will be bitten and can not be cut at all. If R is far greater than h, the wood will be subjected to torsional force while withstanding the cutting force, and the cutting conditions will not be good, and the quality of particles will be poor. Ideally, there should be r = h, so that good cutting conditions can be formed. However, due to the existence of various deviations and the influence of the radial jump of the axis, it is necessary to make R > h, generally taking r = 1.5mm.

(3) Wear of planer and blade

When the shaving cutter becomes blunt, the wood chips will be pushed inward, and the shaving thickness can not be effectively controlled. If the thrust is greater than the centrifugal force of wood chips, the cutting conditions will be completely destroyed. When the blades are worn, the wood chips will be subjected to cutting force as well as extrusion force, which will decrease the quality of particles and increase the amount of crushing. At the same time, the wear of the inner edge of the cutter wheel increases with the increase of cutting resistance.

Cutting process of wood chips in ring flaker

Cutting process of wood chips in ring flaker

Figure 2-30 Cutting Process of Wood Chips in Ring Shaver

(a) Normal cutting process (b) Abnormal cutting process

1. Blade baffle 2. Cutter wheel 3. Planer

(4) Feed volume

The feeding quantity of flaker should be balanced, fluctuation should be reduced and load should be moderate. Otherwise, too much feed will not only make the machine run overload, but also make it difficult to guarantee the quality of particles; too little feed will make the load coefficient of the machine tool smaller and waste energy.

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