What is the commutation process like in a metalworking tool grinder?

What is the commutation process like in a metalworking tool grinder? A metalworking tool grinder is a commonly used machining tool that places high demands on motion stability, commutation accuracy, and commutation frequency. Currently, surface grinders are trending toward larger sizes and higher speeds.

        Hardware tool grinder What is the commutation process like?

　　A metalworking grinder is a commonly used machine tool. It places high demands on motion stability, reversing accuracy, and reversing frequency. Currently, surface grinders are trending toward larger sizes and higher speeds.

　　The reversing method and reversing control parameters of metalworking tool grinders play a decisive role in the reversing impact. Metalworking tool grinders utilize hydraulic transmission. So, what exactly is the reversing process in a metalworking tool grinder?

　　1. Use a travel-direction valve for directional control.

　　The directional control valve spool in the metalworking tool grinder is connected to a pull rod. The directional control valve spool changes direction by means of a stroke-operated directional valve. A stroke stop on the worktable is used to push the pull rod, thereby achieving automatic directional switching. When the worktable moves slowly, as the directional valve reaches its mid-position, either the left or right chamber of the hydraulic cylinder is filled with pressurized oil, or both chambers are filled with return oil, or both chambers are completely closed. At this point, the worktable comes to a halt without any hydraulic pressure, preventing the directional valve from reaching the other end—thus creating what is known as a “dead center.” Moreover, when the worktable is moving at high speed, the limit switch pushes the pull rod, causing the directional valve to change direction extremely rapidly. As a result, the pressure in one chamber of the hydraulic cylinder suddenly drops from the working pressure p to zero, while the pressure in the other chamber suddenly rises from zero to p, leading to significant shock during directional switching. Currently, this system is widely used in small grinding machines.

　　2. Use an electro-hydraulic directional control valve for direction switching.

　　Then, the control oil actuates the main valve to change direction. Since the pilot valve of the hardware tool grinder does not shift forward, an electro-hydraulic directional control valve is used instead of a solenoid directional control valve, thus creating a new switching method. The electro-hydraulic directional control valve consists of a pilot valve’s solenoid spool valve and a main valve’s hydraulic spool valve. In this system, the oil circuit is controlled by reversing the pilot valve. The flow direction of the control oil remains unchanged, ensuring that the directional control valve always stays in its original position, and the main oil circuit direction remains constant, allowing the worktable to keep moving forward. Once the control oil flow direction is switched, the spool of the main valve moves to the other working position at a preset speed, thereby changing the direction of the main oil circuit and causing the worktable to reverse its movement, effectively preventing improper switching.

　　In this way, the kinetic energy of the metalworking tool grinder can be dissipated as thermal energy through throttling. The size of the oil ports controlled by the main spool of the electro-hydraulic directional control valve can be adjusted, thereby extending the switching time t. This effectively reduces the impact of switching. However, its switching parameters can only be preset in advance and cannot adapt to changes in operating conditions, making it impossible for systems with constantly varying conditions to achieve ideal switching performance. In contrast, the surface grinder employs a hydraulic drive system equipped with an electro-hydraulic proportional valve, featuring an ideal control curve. This system realizes an intelligent control-based switching mechanism: by actively reducing the flow rate, the speed is lowered, ultimately achieving smooth, shock-free switching. Even under changing operating conditions, this system can still deliver ideal switching performance. Such an electro-hydraulic drive switching system enables intelligent control over output displacement or velocity, making the switching process to some extent controllable and thus possessing extremely broad application potential.