Abstract
A saw chain is one of the most important functional parts of a chain saw machine and various studies have been made, however a vital problem remains unsolved. This report deals with the basic part of the studies on the characteristics of wood cutting force of the whole saw chain used in a chain saw machine. To determine the effects of various factors on the cutting process during chain sawing, a special test stand with devices for measuring cutting and feeding forces and cutting energy was designed. The results were as follows:
1) The mechanism for driving the saw chain unit consists of a three phase induction motor (3.7kW, 2900rpm), a variable speed gear (1:4), and dual V-belt drive system as shown in Fig. 1. By this it was confirmed that the sprocket wheel speed for the saw chain drive was able to be controlled in the range from 1, 125 to 8, 500rpm steplessly.
2) The variable feed rate mechanism for timber cutting has drive parts which consist of a ringcone motor (1.5kW, 125-1, 250rpm), variable speed gear (1:4), reduction gear (1:20), chain and sprocket wheel, bevel gear, and rack & pinion to obtain a linear motion as shown in Fig. 2. From this system, the rise and fall of the table mounted on the saw chain unit can be controlled by manual shift; the raising and lowering comes to total of 500mm at the rate from 1.6 to 60mm/s steplessly.
3) The measuring device was designed to measure tangential cutting resistance force and normal cutting resistance force separately at the timber supporting frame. By this system the measured force was independent of frictional resistance between saw chain and bar rail, and the reaction due to discharge saw dust as shown in Figs. 4 and 5.
The obtained bridge output sensitivities of this two-dimensional dynamometer were 9.134×10-6/kg (non-linearity ±10%) for the tangential cutting resistance force and 6.516×10-6/kg (non-linearity ±7%) for the normal cutting resistance force respectively as shown in Fig. 6. Therefore, the sensitivity of the latter was found to be 30% smaller than that of the former unexpectedly.
