M7120 plane grinding machine is widely used in plane grinder electromagnetic sucker is a, M7120 type planar grinder magnetic worktable, with various types of magnetic adsorption workpiece, realizes the positioning of the workpiece and grinding. In order to ensure the safe production, only when the electromagnetic chuck to work, just allow grinding machine and the hydraulic pump to work, so the electromagnetic sucker control circuit is safe and reliable, is the M7120 grinder working premise and necessary condition.
The original control circuit
M7120 electric control schematic diagram of electromagnetic sucker control circuit as shown in figure 1.
Figure VC for the whole Takimoto device; KM5, KM6 two contactors and the main contact for discharge circuit; RC; YH for electromagnetic sucker lines without; X2 connector; KA under voltage relay.
The design philosophy is: to the under voltage relay KA both ends voltage, as electromagnetic sucker foot not the normal work of the signal voltage relay. A normally open contact of the series in several other motors public control loop circuit. When the supply voltage is 380 V normal access grinder, line without fault, under voltage relay action, the normally open contact of KA closed. Grinder can be put to work; if the voltage is not normal, not operating under voltage relay. Other infants motors can work.
Existing problems
From the diagram we can analysis, as long as the rectifier circuit working under normal circumstances, was enough to attract the power and voltage relay. Public loop is switched on. Several drive motor can work normally. But this time, if the main contact of the contactor, connectors, wire jump or ask connection line. Have poor contact or disconnection, electromagnetic sucker YH may be the current inadequate or no current, thus causing electromagnetic sucker suction inadequate or no suction, grinding wheel machine will continue to work, the workpiece will be inertial throw. Very dangerous, that is to say under voltage relay can not fully play a safety interlock function.
The improved control circuit
In the way of electromagnetic sucker, remove less electricity and relay, access under current relay KA, and adjust the action current value, as shown in Figure 2 below.
Under current relay line and with electromagnetic sucker loop current size of input signal. In the work process, no matter what the fault reason, as long as the current is reduced to the contingent value following, namely the line friends is sufficient to generate the processing time required magnetic field strength. Under current relay is released, KA normally open contact reset disconnect. Grinding machine drives the electric motor to automatically stop the work, ensure safety in production.
The improved circuit, overcomes the shortcomings of the original design, electromagnetic sucker lines in any cause of coil current inadequate or no current, can protect the interlocking function. This improvement does not increase line cost and can achieve the purpose of safety.
