Barrel Finishing Plastic Optical Frames
When barrel finishing plastic optical frames, the normal workload for one compartment of a 30″ x 36″ dry tumbling barrel is 200 heavyweight fronts or 250 lightweight fronts. Twice this amount can be added at one time when tumbling temples. The ratio (by volume) of hardwood media to frames should be at least three to one. This applies to all steps listed below. If nose panels are very rough, they should be ashed on a buff before tumbling.
This step will remove tool marks, round off edges and leave a satin finish. The load height should be approximately three inches below center. Start with 5 lb of coarse Dry Abrasive Cream (10 lb if using new pegs). After 16-24 hours, add 5 lb of fine Dry Abrasive Cream (10 lb if using new pegs). Before unloading, run the barrel with screen doors for approximately one hour to remove old compound and extra plastic.
This step will produce a smooth surface and keep parts clean. The load height should be approximately at the center. Use 5 lb of Shynolyte Pre-Polishing Cream (10 lb if using new pegs). Run the barrel for 24 hours. Before unloading, run the barrel with screen doors for approximately one hour. Hinges can be installed after this process.
This step is used to run the parts with hinges installed. This step will remove scratches created when slotting and installing hinges. The load height should be approximately at the center. Use one tablespoon of Shynolyte Pre-Polishing Cream for each run. Run the barrel for about 24 hours. (To break in new pegs, use one pint of Shynolyte Pre-Polishing Cream and run the pegs for a few hours without parts.)
This step will produce a high luster. The load height should be approximately at the center. Use one tablespoon of Microlyte Polishing Cream for each run. Run the barrel for about 24 hours. (To break in new pegs, use one pint of Microlyte Polishing Cream and run the pegs for a few hours without parts.)
For a very high luster and/or to remove film, use Hi-Glos Final Cream. Use one teaspoon of Hi-Glos Final Cream for each run. Run for one to six hours. (To break in new pegs, use one pint of Hi-Glos Final Cream and run the pegs for a few hours without parts. Use one teaspoon of Hi-Glos Final Cream for each run thereafter.) If the pegs get too wet, skip the recharge and run with a screen door until dry.
Note: For injection-molded frames, use fine Dry Cutting Cream, Shynolyte Pre-Polishing Cream and Microlyte Polishing Cream (Hi-Glos Final Cream for super luster), keeping the load level on center to protect the parts.
Tumbling tips for barrel finishing optical frames:
- If your work is getting scratched, the load level may be too low, there may be foreign metal matter in the barrel, the hinges may need to be deburred if being tumbled with them on the fronts or temples of the frames, there may be too many parts in the barrel or the barrel lining may need to be replaced (it can bend and scratch parts).
- Careful and proper matching of your parts will save barrel time. Dull cutting tools create burn marks and untrue tools create chatter marks that lengthen the tumbling operation.
- When you have some heavy cutting to do, use a combination of felt,wood pegs and Dry Cutting Cream.
- Barrel load (parts and media) heights should not be less than 45% of capacity or more than 60%. Load heights of 50-60% reduce the amount of action, but produce a good finish. Load heights of 40-50% produce more action, but a poorer finish. The best load height is 50%.
- Barrel speed is important. The best results are achieved at 28-30 RPM. Kramer machines are set at 28 RPM. Faster speeds will damage the plastic frames, while slower speeds will result in unnecessarily longer runs.
- Keep a close eye on polishing barrels. Dirty pegs will not polish and may scratch temples or fronts.
- Injection molded frames need more careful handling. The plastic is softer and scratches more easily, necessitating a higher rate of pegs to parts. Finer cutting compounds are also required.
- When nose pads are carefully sanded, cutting time will be shortened.
- Slotting and hinging can be done after Shynolyte Pre-Polishing Cream.
- Dirty pegs from cream barrels can be used in the Dry Cutting Cream and Shynolyte Pre-Polishing Cream barrels. Therefore, it is advisable to use the same size peg in all operations.
Procedure for deburring and burnishing hinges for optical frames:
- Two parts media 3/32” burnishing balls) to one part hinges by volume.
- Load height: 50-60% of barrel capacity.
- Water level: 2/3 of load height.
- Three ounces of Kramco 920 burnishing compound to one gallon of water.
- Cycle or running time: 12 hours or overnight.
- 40 to 44 RPM for a 13″-diameter barrel or 135 to 150 surface feet per minute.