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Vibrations – Friend or Foe?

22 July 2015
Figure 1

Vibrations can either be a help or a hindrance in high precision manufacturing, but whether they are your friend or enemy, they must be controlled. This is where smart actuators from CEDRAT Technologies (distributed by ORLIN Technologies Ltd in the UK) come in. Their highly-dynamic response allows them to react to changing conditions and their compact size allow for easy integration.

Benefits include:

  • Improvement in product quality
  • Increased manufacturing throughput
  • Savings in energy and lubricant consumption
  • Pollution reduction
  • Ability to manufacture complex parts
 
Vibration & ultrasonic assistance
Figure 2

Many tooling processes can be improved with the careful application of controlled vibrations. Vibrations typically ranging from tens of Hertz up to ultrasonic frequencies, with strokes from tens of microns up to millimetres are utilised. CEDRAT Technologies’ (CTEC) piezoelectric, magnetostrictive and magnetic actuators, in combination with high power drivers, are particularly useful in these applications, with lifetime of several tens of billions of cycles.

  • Vibration assisted machining: The application of sonic forced vibrations in machining processes allows drilling of better quality holes, faster and with no lubricant. This method is much less sensitive to load and external parameters than ultrasonically assisted machining. Gains are also seen in Electro Discharging Machining (EDM) applications involving high amplitude forced vibrations. Frequencies up to 1kHz have been proven to be most efficient and are now possible in an industrial environment with CTEC’s piezo Parallel Prestressed Actuators (PPA) and SA75X high power piezo drivers. Fig 1 shows a drill tool holder with integrated vibration assistance for a major aerospace customer.
    Even higher frequencies of several kHz are used in glass cutting tools, widely used in the manufacture of plasma displays.
  • Friction reduction: High frequency vibrations can act as a kind of lubricant to reduce friction in many material shaping processes such as deep-drawing, extrusion and moulding.
    The same principle is also used for metal or elastomeric extrusion as well as for micro plastic parts injection. Through friction reduction, ultrasound increases the extrusion speed, reduces wear and saves energy while simultaneously improving the quality of manufactured parts.
 

Figure 3

Vibration control

As a complementary technology to vibration generation, a common application of CTEC products is the active control of vibration. Many industrial processes suffer from uncontrolled or undesired vibrations – for example “chatter” in turning operations. The active control of vibration offers large productivity and quality gains, allowing our customers a clear differentiation against their competitors. Two approaches are possible to implement active vibration control: 

  • Direct control: In this mode, the actuator is placed directly between the tool that we want to control and a mechanical reference. Simple in its principle, this architecture requires an actuator capable of withstanding the large stress transmitted by the tool. High stiffness, robustness and dynamic capability make the PPA (Fig 2) particularly suitable for this application. Fig 3 shows an example of a PPA applied in a turning application.
  • Proof mass architecture: The principle behind this architecture is to create a reaction force to damp vibration by dynamically controlling the displacement of a counter mass. In order to ease the mechanical integration, the actuator has to be compact, powerful and controllable. MICA™ actuators (Fig 4) were designed to meet these specifications.  
 
Position control
Figure 4

Highly dynamic capabilities as well as high precision are the main qualities desired for positioning in a production domain. Our products are used in many different kinds of machines, such as micro electronic manufacturing, large machine tools (turning and milling), factory automation and robots. CTEC offers a complete range of complementary piezoelectric and magnetic actuators, motors, mechanisms & drives, covering stroke from 10µm to 10 mm with the same level of reliability in a compact size. Static positioning stability of better than 1 nanometre can be achieved, which allows for ultra-precision manufacturing applications. Dynamic position precision can be better than 1µm at 1kHz over billions of cycles.

 

Some of the applications addressed by our products:

  • Oval piston & optics machining; Fast Servo Tool; Saw actuation 
  • Position control for EDM, Laser machining …
  • Active clamp, Handling, Pick & place, Grippers, End-Effectors
  • Proportional valve actuation, fluid dispensers…

 



 
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