| abstract |
A hydraulic drill unit for drilling multimaterial, thick layer stock having a conventional hydraulic drill modified to have its feed controlled by a servo valve and its spindle speed controlled by a servo valve. A linear encoder is attached to the drill to provide an indication of drill position. The linear encoded provides 20,000 forward and reverse pulses per inch, depending upon the direction of travel, which are used to determine net feed rate. The net feed rate signal is compared with a command feed rate to control the feed servo valve. A magnetic pickup is used to provide a pulse signal proportional to RPM. This signal is compared with a command speed signal to control the spindle speed servo valve. Differential pressure transducers are used to measure pressure across the hydraulic feed pistion and the hydraulic drill motor to provide signals which can be used as indications of chip packing or a dull drill. Displays are provided to indicate Torque, Thrust, RPM, Inches of travel per revolution and relative displacement of the drill. These displays are used for the manual control of the drill. Torque, Thrust, RPM and absolute displacement information is supplied to a computer for the automatic operation of the hydraulic drill. Since optimized speeds and feeds are generally known for specific drill diameters and materials, this information has been programmed into the computer to provide the command feed and command speed levels for the various materials in a stack to provide the error signals for controlling the feed and speed servo valves. Torque and Thrust buildup are used by the computer for indications of chip packing or dull drill. Four solenoid valves are used to provide rapid advancement and rapid retraction of the drill. |