Surface Finishing Stainless Steel

Scope of Work: To mirror polish stainless steel hardness test block

Stage 1 (Lap) Equipment used:

Stage 2 (CMP)

  • Kemet 15” lapping/polishing machine
  • Chem H polishing cloth
  • Plastic faced control ring
  • Dycem faced hand weight
  • Col-K Special

Process breakdown for mirror polishing stainless steel hardness test block

Stage 1 - 1 off test block was placed in the centre of a 15” control ring on a flat Kemet Copper SP2 lapping plate, and a dycem faced hand weight was placed on top which also acts as a fixture. The machine was then cycled for 15 minutes with Kemet liquid diamond 6 micron type K std being dispensed at a ratio of 2 seconds of diamond spray every 40 seconds. The test block was removed and cleaned with CO-42.

Stage 2 - The cleaned up test block was then placed into a plastic faced control ring onto a Chem H polishing pad a dycem faced hand weight was placed on top. The machine was then cycled for 20 minutes with Col-k special being applied buy an aKu-Disp The blank was immediately sprayed with deionized water after process and air lined off.

Ra achieved: 0.0079 µm, Flatness achieved: Better than 1 light band (0.3 µm)

Before Surface Finishing Stainless Steel Hardness Test Block

before Surface Finishing stainless steel hardness test block

After Surface Finishing Stainless Steel Hardness Test Block

after Surface Finishing stainless steel hardness test block

Scope of Work: To develop a process to polish a stainless steel spherical cap to better than Ra 0.4 µm

Polishing process - Equipment used:

  • Kemet SpheriMatch machine
  • NLH cloth
  • Kemet Liquid diamond 3 micron type K slurry
  • Customised lap
  • 15” pressure weight
  • CO-42 cleaning fluid

Process breakdown for Stainless Steel Spherical Cap

The spherical cap was fixed on to a 15” pressure weight using foam tape, then the pressure weight was placed into the jaws of the SpheriMatch chuck and tightened using the key. The customised lap was placed on the sweep arm and positioned so was covering half the area of the cap and the sweep length was then adjusted to give a slight sweep of about 10mm. The machine was then run for 10 minute cycles while applying Kemet Liquid diamond 3 micron type K from a trigger spray every 2 minutes. It was run for a total of around 6 cycles to achieve the finish, but would be quicker with a purpose made lap using the same radius as the cap. Part was then cleaned off with CO-42 cleaning fluid.

Ra required: 0.4 µm, Ra achieved: 0.0122 µm

Scope of Work: To find best process to lap and mirror polish 3 x 100mm diameter stainless steel rotor parts

Stage 1 (Lap) Equipment used:

Stage 2 (Polish)

  • Kemet 24” lapping/polishing machine
  • ASFL polishing cloth, 24” diameter
  • Plastic faced control ring
  • Kemet Liquid diamond 3 micron type K std
  • Dycem backed pressure weight

Process breakdown for stainless steel rotor parts

Stage 1 (Lap) - 3 off parts were spaced evenly inside a 24” control ring sitting on a flat Kemet Iron lapping plate. A Dycem faced pressure weight was then placed on top to hold the parts in place. The machine was then cycled for 10 minutes with Kemet liquid diamond 10 micron type K std being dispensed at a ratio of 2 seconds of spray every 40 seconds. The parts were taken off, then cleaned with CO-42 cleaning fluid to check whether the face had cleaned up, then flipped over and the process was repeated on the other face.

Stage 2 (Polish) - 3 off parts were spaced evenly inside a 24” plastic faced control ring sitting on an ASFL polishing cloth. A Dycem faced pressure weight was then placed on top to holds the parts in place. The machine was then cycled for 10 minutes with Kemet liquid diamond 3 micron type K std being dispensed at a ratio of 2 seconds of spray every 45 seconds. The parts were taken off, then cleaned with CO-42 cleaning fluid to check whether the face had cleaned up then flipped over and process was repeated on the other face.

Ra required: 0.8 µm, Ra achieved: 0.0064 µm

Note: The parts could have also been processed on a Kemet 15 diamond lapping machine which can process parts up to 140mm diameter

Before Processing stainless steel rotor parts

Before Processing stainless steel rotor parts

After stage 1 Processing stainless steel rotor parts

After stage 1 Processing stainless steel rotor parts

After stage 2 Processing stainless steel rotor parts

After stage 2 Processing stainless steel rotor parts

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