The problem of operation and modernization of sawmill equipment at small enterprises
Small enterprises include production with a capacity of up to 25 thousand m3 per year or up to 70 m3 per shift, with a 30-day monthly load and one-shift work.
In small enterprises, various equipment is used for sawing: band saws and circular saws, frame multi-saw machines. By the type of lumber cutting, the machines are divided into multi-saw and single-saw. Most often, multisaw machines are frame and circular saws.
The disadvantage of multi-saw frame machines is significant dynamic loads in the vertical plane, for this reason, the sawing speed is reduced, as well as productivity in general.
Frame and circular saw machines operate according to the breakup and beam-breakup schemes (Pi 1).
Circular saw machines are divided into machines of the first (for sawing round logs) and the second (for sawing timber and carriage) row.
The disadvantages of band saws include the possible undulation of lumber i.e. different thickness of the boards.
The disadvantage of circular sawing machines is the large thickness of the saws and solders, which leads to a decrease in the yield of finished lumber relative to the amount of raw material at the entrance.
The advantages of band saws and circular saws include the absence of vertical loads and, as a result, the lack of the need for a powerful foundation.
When sawing on single-saw machines, as a rule, only log feeding operations are mechanized - or carriage drives, auxiliary ones are performed manually with a lot of time and physical effort.
According to experts, Roundwood production in the Russian Federation will grow 1.6–2 times by 2030 and amount to over 300 million m3, while export growth will not be significant. The growth in sawn timber production is expected to be 2.7 times and will reach about 66.2 million m3.
Along with the growth in the production of Roundwood and lumber, requirements for its quality also increase. Therefore, most manufacturers tend to choose disk machines when choosing new equipment, since when using them, the geometry of the resulting lumber is almost always perfect, these machines are not demanding on the availability of qualified personnel. At the same time, a significant factor in favour of choosing one or another equipment is the percentage of the output of finished lumber.
As calculations show, an increase in the thickness of saws and solders and, as a consequence, the width of cuts, leads to a decrease in the output of lumber (Fig. 2).
Sawing large logs requires the use of thicker saws of larger diameter (which reduces the yield of lumber). An alternative to the use of large saws is the use of machines with a dual arrangement of shafts (twin-shaft). Such machines can reduce the amount of waste (compared with the single-shaft version). For saws with a diameter of 600-700 mm (with single-shaft sawing), the thickness of the brazing is on average 5.1 mm, for saws with a diameter of 350 mm (with two-shaft sawing) the thickness of the braze is 3.8 mm. It turns out that with single-shaft sawing, the thickness of the cut was greater than with double-shaft sawing by about 25%.
In addition to the amount of lumber obtained on various machines, a huge role in productivity is played by combining them in a line (flow).
Elements of mechanization of sawmill equipment include log drives with the single issue directly to the machine or to the drive log, automatic separators of slabs and boards, automatic centring of timber and boards, drive tables and dumpers, sawdust removal systems, etc. The use of near-machine mechanization drastically reduces the number of labour costs and, therefore, the cost of maintenance personnel.
Until recently, only foreign manufacturers offered complex sawing lines, and the majority of domestic ones cared little for mechanization and automation. Recently, in the wake of the increase in the difference in the value of the national currency and other world currencies, the situation began to change. There was a demand for similar foreign equipment, and accordingly, a proposal appeared. Not so long ago, some domestic manufacturers began to offer comprehensive solutions that not only reduce the number of service personnel but also use the equipment for processing secondary raw materials (slabs, etc.) as part of technological lines, which make it possible to increase the yield of finished products, while a significant reduction in waste.
To summarize, we add that the steadily developing small and medium-sized timber processing enterprises often replace their machines with multi-sawn twin-shaft discs. Increasingly, they are introducing mechanization and automation systems, minimizing production costs.
