| 摘要 |
A control system and method for an apparatus to glow discharge treat (such as ion nitride) a workpiece. The apparatus includes a housing to receive a workpiece and a low pressure atmosphere of ionizable gas (nitrogen and hydrogen for nitriding), and connectors for establishing a glow discharge in the gas with the workpiece connected as the cathode. The control system and method automatically control the apparatus throughout the process, utilizing operator selected parameters (such as warm-up time, processing time, workpiece operating temperature and chamber pressure). The control system divides the selected operating temperature by the selected warm-up time to provide a straight line increase per unit time of the workpiece temperature. Initially the control system accumulates the increases at a rate higher than the straight line increase and then, as the workpiece approaches the selected operating temperature, the control system accumulates the increases at a rate less than the straight line increase. This provides a profile of the desired workpiece temperature. The control system compares the accumulated increases with the measured workpiece temperature and compares the rate of change of the accumulated increases with the rate of change of the measured workpiece temperature. It adjusts the level of electrical energy being supplied to the glow discharge in accordance with the comparison results. When the operator selected operating temperature is reached the control system terminates the profile and operates to maintain that temperature. The control system divides the selected operating pressure by the selected warm-up time to provide a profile of increasing pressure per unit time during warm-up and operates to provide the desired pressure at any time.
|
