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Processes & Skills : Ultrasonic machining

This technology was implemented as part of a transfer of technology from ONERA – National Laboratory for Aerospace Research – who developed it for its own needs. The technology contributed amongst other things to the manufacturing of electrode plates in silica for space accelerometers – GOCE project from ESA.

Principle

The principle is based on an electrical current – at a given frequency that fits within the field of ultrasounds –converted into a mechanical vibration that is transferred to a machining tool. The vibration frequency of the tool corresponds to the frequency of the electrical signal – in this case 20 KHZ.

Our ultrasonic machining process differentiates itself from other processes because machining is carried out without contact between the tool and the part.

Equipment

A resonating block made up of piezoelectric ceramics transfers the vibration to the tool through the sonotrode. The mechanical expansion of the tool – so-called tool elongation – can be adjusted and can vary from 0,005 mm to 0,07 mm. The device is fitted onto a NC machining unit and the tool moves along X,Y,Z axis without rotating.

Machining process

The vibration enables an abrasive fluid to be projected onto the part. This fluid is purposely injected at a very high frequency between the tool and the part to be machined and results in the machining of the material due to the rubbing of the abrasive on the part. The efficiency and quality of the machining then depend upon the following parameters : abrasive quality and content, tool grade, machining speed, vibration range.

Benefits

The benefits of this technology compared with usual machining techniques are :

  • capability to machine such fragile materials as silica since there is no contact between the tool and the part
  • capability to machine such hard materials as boron carbide, silicon carbide, silicon nitride
  • machining of such peculiar shapes as square or hexagonal holes even in very small dimensions - less than 1 mm
  • drilling of long holes - ratio diameter-to-length greater than 10 for small diameters

This machining technique also makes it possible to carry out usual drilling operations of small diameter holes - about 0.4 mm.

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  • produits microcertec
  • produits microcertec