Research On Automatic Control System For Keyhole Plasma Arc Welding Penetration

The plasma arc welding have a high energy density, thick welding thickness that can weld for single time. Accounting on the compressed arc whose stability is affected by many factors, it is difficult to keep the effective canonical parameters. Besides of use stabilize performance plasma arc welding torch and welding equipment system, it's a best way to use closed loop penetration controlment to solve this problem. This paper put forward a way which take the electric pressure of the keyhole which can reflect the state of welding as controlled quantity, and take the current and velocity in welding as performance and also singlechip MSP430F155 as core controller, to effectuate the closed loop automatic control engage of keyhole PAW.This paper analyzed the experimental data from welding flat sheet of 30CrMnSi and 1Cr18Ni9Ti, study the relationship from the welding current, ionized gas flow and welding rate to keyhole voltage which reflect the length of keyhole diameter. Based on just mentioned put forward a basic thought of realizing the automatic control system of keyhole plasma arc welding and designed ensemble control programme.Taking the MSP430F155 which is a high performance singlechip as key device, this paper developed a automatic control system for plasma arc welding with integral function, consist of starting, single parameter control, two-parameter control, keyhole voltage short-circuit processing and arc ending .The law of welding current and welding rate modulation progress is followed with the partition of collected keyhole voltage, which is used to solve the conflict of nonlinear affection and stability of control system.The result of the debugging and testing of the welding current controlling process showed that the control system can finely adjust welding current according to the different partition of keyhole voltage, and regulated value of welding current anastomosed the measured value of welding current very well. The phasic research achievement of this paper have some theretical and use value to realize the automatic control system of keyhole plasma arc welding and enhance the stability of welding quality.