Metal Polishing with Technocon's Steel Media
Applications: Aluminum, Cutlery, Coin Blanks, Hinges, Bearing Cages, Jewelry

Components: Aluminium components burnished with steel media vary from diecastings, extrusions to sheet metal parts. Domestic appliance components of mixer grinder, coffee maker; handicraft items and electrical connectors, brackets, housings are the most popular components which are widely processed in vibratory finishing machines with stainless steel media for cleaning, polishing, burnishing and mirror finishing applications.
Zinc components polished with steel media include zip sliders, buckles, buttons, badges, carburetor body and other housings.

Process: Generally after ultrasonic degreasing the aluminum or zinc components are fed into the vibratory finishing machine and processed with stainless steel, inox media and burnishing chemicals. For batch processes the process time is about 45 minutes whereas for flow-through processes it is around 20 minutes. In flow-through processes, at times the degreasing and cleaning (for light soils) is achieved in the vibratory machine itself and the pre-degreasing in an ultrasonic machine is skipped. If a coating stage does not follow immediately or if the components are to be packed after vibratory polishing, drying of the aluminum components is essential to avoid white oxidation later. This is usually undertaken in a vibratory drier with heated granulated corncob (maizeorb).

Steel Media: For most zinc and aluminum polishing applications a media mix of stainless steel (inox) spheres (round balls) and ballcones is used. The ratio of the steel media usually is 40% 2 mm balls, 40% 3 mm balls and 20% 3 mm ballcones or satellites. If the component has threads and no blind holes or crevices then 1 mm pins are also mixed. The size and shape of media will also vary depending upon the actual configuration of the component.
In many cast aluminium and zinc diecast components which have holes and grooves only ballcones (satellites) are also used as the steel media to prevent clogging or lodging problems.

Process: For the general market, after ultrasonic degreasing the components are fed into the vibratory finishing machine and processed with stainless steel, inox media and a combination of burnishing chemicals. For batch processes the process time is about 90 minutes whereas for flow-through processes it is around 45 minutes. After the vibratory process the cutlery is neutralised in a mildly alkaline solution. This helps in removing the acidic chemical completely from the component and retaining the lustre on the surface. For the medium end market the steel burnishing process is preceded by deburring and smoothening in ceramic media. For the high end market, vibratory finishing may be followed by a buffing stage.

Steel Media: A mix of stainless steel (inox) spheres (round balls) and ballcones is used. The ratio of the steel media usually is 40% 4 mm balls, 40% 3 mm balls and 20% 3 mm ballcones or satellites. The ballcones help in cleaning the engravings.

Both centrifugal hexagonal barrels and round vibrators are used for jewellery burnishing.
The stainless steel (inox) media mix generally comprises of the following:

400 kg - is usually made up of
200 kgs of 3 mm ball or eclipse,
100 kgs of 3 mm ballcone / satellite,
50 kgs of 2 mm dia x 6 mm length diagonal / cylinder and
50 kgs of 1 mm dia x 10 mm length pin.

After heat treatment and annealing, burnishing is employed to make the surface of the coin blanks brighter, remove any surface scaling or discoloration and in some cases apply a minute amount of lubricant to assist in coining. This process is carried out in a Vibratory or Centrifugal Finishing Machine that tumbles the coin blanks with a mixture of stainless steel balls (inox) and special chemicals, which etch and polish and brighten the surface of the coins.
The burnishing operation is also employed after stamping of the coins.
Detailed information on coin blanks polishing application and the steel media used is available on our webpage at:
http://www.steelmedia.com/steel-burnishing-media.htm
 

Components: Steel cages for ball bearings are used to hold the spherical balls in the bearing races. The bearing cage is a pressed component and is made of bearing steel or chrome alloy steel En31 / AISI 52100.
For minimum friction between the ball and the cage, high surface finish and polish is required on the cages. This is achieved by ball burnishing in a Vibratory Finishing Machine.

Process:
After the forming operation in the Press, the cages are loaded in the vibratory finishing machine for degreasing and mild deburring with suitable compounds and low abrasive ceramic media. Process time is about 45 to 60 minutes. After this, proper water rinsing is done so that there is no carryover of soils to the next operation.

The degreasing and deburring is followed by the steel media polishing operation.
Prior to the feeding of the bearing cages, polishing compound and water are added in the vibratory polishing machine. Sufficient foam is generated by running the machine without the components. Foam provides cushioning to the steel cages and prevents them from buckling. After foaming has been achieved, the steel bearing cages are fed in the vibratory machine and processed for 45 minutes.
Continuous flow of chemical solution is preferable for a bright finish.
At the end of the polishing operation, proper rinsing is done with water, followed by a dip in water-displacing rust preventive oil.

Steel Media: A mix of 3 mm diameter round balls and 3x5 mm ballcones are recommended in a 1:1 ratio; i.e. 50% of each media. The ballcones are necessary for polishing the corners of the flat profile where the spherical balls can not access. The spherical balls contribute to the enhanced shine.
Component (bearing cages) to media (steel balls and ballcones) ratio is maintained at 1:5 by volume.

Components: Mild steel hinges for doors, windows and other applications.
Process: After belt grinding and assembly the steel hinges are fed in the vibratory finishing machine for degreasing and surface smoothening. The hinges are processed with ceramic media and suitable compound for 45 to 60mins. After proper rinsing with water they are fed in ball burnishing machine having steel media with suitable polishing compound. Process time is 45 minutes. Proper water-rinsing is done before separation of steel media and the hinges.

Components: Stainless steel hinges for doors, windows and other applications. 
Process: When very bright finish is not required on the hinges, ball burnishing is done instead of buffing. Process time may vary from 1 to 2 hours depending on the brightness required.

Steel Media: A mix of 3 mm diameter balls and 3x5 mm size ball-cones in 1:1 ratio; i.e. 50% of each media is recommended.