PG Series: Planetary Grinding Machines for Diamond
First a word about diamond Single Crystal Diamond (SCD), be it either a natural or a synthetic crystal, has both ‘hard’ and ‘soft’ crystallographic directions. The direction of grinding must be aligned with a ‘soft’ crystal direction so that progress is made.

The PG3 and PG3B grinding machines have a wheel spindle which can be moved in a planetary motion relative to the tool. Thus the grinding wheel position can altered and a ‘soft’ grinding direction found no matter what orientation the crystal is presented.

The PG3 is a precision machine for producing radii and facetted SCD tools. It uses high conventional performance wheel and pivot bearings. Controlled waviness tools of less than 600 nanometres should be possible, assuming a good wheel surface and after top lapping on a scaife.

The PG3B is an ultra-precision machine which uses air-bearings for both wheel and pivot. This machine allows a suitably skilled worker to produce the most perfect controlled waviness tools of less than 150 nanometres. Again, much also depends on the quality of the wheel and its preparation.

 
 
 
 
THE STRENGTHS - PG3
  • Conical and cylindrical clearance possible.

  • Manual pivot operation against vernier stops.

  • Pivot angle read via ADI (optional extra)

  • In-feed to adjustable stop via dead weight system; this limits grinding load so protecting wheel.

  • Coning fixture available to make rotary tools or for indexing.

  • Tool radii up to 75mm.

  • Wheel can be moved with constant planetary motion or ‘jogged’ to find ‘soft’ grind directions.

  • Wheel can be oscillated – left/right with variable amplitude up to 28mm and variable speed stroke.

  • Microscope projector or VS5-G vision system to inspect tools.

  • Wheel speed range from 0-12,000 rpm.

  • Grinding is done dry.

  • Coning / indexing spindle (CF13) available with max capacity of 12mm to produce cones and facetted tools.
 
THE ADDITIONAL PG3B
     STRENGTHS
  • Synthetic granite base.

  • Controls located off machine to reduce transmitted vibrations.

  • Highly accurate, air-bearing pivot.

  • Air- bearing, water cooled wheel spindle : 0-12,000 rpm.

  • Automatic pivot motion ensures no hand vibrations transmitted to tool.

  • Pivot motion controlled via touch-screen.

  • Left & right pivot stops programmed on touch screen.

  • Left / right “sub-stop” positions can be selected during grinding to address hard spots found in some natural stones.

  • Pivot rotation speed adjustable as is dwell time at end of arc.