Method Study And System Development Of Contacting Tool Collision Prevention For Engraving Machine

Due to the popularity of CNC machine tools, equipment accidents happen a lot during teaching and applying, tool collision is among those that frequently take place. Tool collision refers to the movement of the tool or bench deviate from the correct trajectory, so lead to tool accidentally colliding machine parts or accessories. Once tool collision occurs,consequence ranges from tools abrasion, products damage to equipment accuracy influence,or even threatening safety of the manipulator. Prevention methods of tool collision are important for safety production and practice teaching.Based on the existing engraving machine, combining experimental study and system development, separately simulating the collision between tool and fixture, tool and workpiece to verify the accuracy tools collision signal, The machine emergency measures are taken by electrical and mechanical brake combined, to reduce economic losses and personal injury.The detailed study was as below:(1) Study electrical conductivity cutting of cutting fluid and crumbs liquid mixture,revealing the extent of the interference of the tool cutting fluid and jig tool collision signal,provide the basis for signal detection tool striking fixture;(2) Studied signal of collision between tool and fixture. Analyze the process of the actual processing machine, using the principle of tool and fixture contact with the conductive, put forward tandem potentiometer partial pressure method, depending on the level of branch voltage level determines whether the tool jig strike;(3) Researched motor current signal changes before and after tool strikes jig, Reveals the motor current threshold of tool knocked. Presented the use of current transformer motor current into a voltage signal, after the signal is amplified, the microcontroller detects tool striking piece;(4) Studied electronically braking and mechanical braking on CNC screw, proposed the emergency brake method of the power-lost brake locking screw;(5) Develop prevented collision control System, including detection signal of the collision, the collision warning circuit, the controlled brake circuit, the mechanical brake circuit, and the corresponding software program;(6) Test experiments were done, to verify the performance in collision control system,The results of test experiments showed that: this system can accurately detect thecollision signal in tool collided fixture and tool collided workpiece, after detecting tool collision signal, the screw brake start and the brake effect is obvious, however, the tool will damage if the tool’s speed or table feed speed are too fast.Three innovations are as below:(1) Resolved detection problem in tool colliding fixture under the interference effect of cutting fluid, presented in tandem potentiometer partial pressure method, depending on the level of branch voltage level determines whether the tool jig strike;(2) Proposed the signal detection method of tool colliding workpiece. Tools deform after the tool and workpiece collision, electrical current of the motor increased by the resistance, current transformer current is converted to a voltage signal, after amplification and judgment, MCU pin to detect its level of judgment collision between tool and workpiece;(3) In addition to using electronically braking controlled, mechanical braking method was also used.