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Denford Conversion to USM

Denford Conversion to CNC Ultrasonic Impact Machining

A Denford 3-axis CNC milling machine with toolchanger was used as a donor 3 axis platform for a full conversion to a CNC controlled Ultrasonic Impact Machining (USM) System. The old Denford controller and software was not suitable for the machine system conversion and was removed. The motors and existing hardware were kept. A gearbox reduction was fitted to the Z axis drive to give extra resolution and control which is critical during USM machining. A new 3 axis controller was installed and configured to the Denford hardware and the system now runs on Mach3. The Ultrasonic impact machining head was integrated into the spindle mounting mechanism and the USM power supply providing the Ultrasonic excitation signal was located next to the machine. Phase one of the system test has been successful. A machining parameter set where stable machining of glass, ceramic and silica has been established. A Kistler load cell has also been integrated into the work piece clamping fixture and has allowed process forces to be extracted from the USM system during machining.

The next phase of work is to mount all the USM and supporting systems into the same control cabinet as the CNC controller. We hope to integrate the control function of the USM system into Mach3 also. We converted the CNC system with a new controller. We installed the Kistler load cell measurement system and provided analysis and support for the testing carried out.

Integration of Kistler Loadcell

A Kistler Load cell was integrated into the work-piece fixture of the machine in order to capture the main force flux during the machining process. Care had to be taken as the USM head has a machining frequency of 40kHz and therefore there were some resonant considerations to account for due to excitation of the load cell it its natural frequency.

Data output

Shown below is a sample result from the Kistler signal in both RAW states as measured from the analogue input DAQ sampling the sensor, and also as decomposed states in the frequency domain.

USM wear tests

A pecking system was setup to carry out characterised amounts of machining in order to assess the wear on the tool using different tool and work-piece materials.