o ring surface finishing

Rubber O-Ring Parting Lining Removing

A “parting line”  is the line of separation on the part where the two halves of the mold meet.  Engineering applications (seals, tight running molded parts) that require precision for shape control, call for the removal of flashes.  Therefore, we need the secondary operation to remove the flashes and burr.

This article we show an example of deflashing rubber parting line with mass finishing process which is efficient and cost-effective than hand trimming.


1.   Parts condition before finishing

Material: rubber

Appearance: smooth surface with parting line internal and external circle

Size: various

Shape: o-ring shape

Process before: injection molding

The process after: ultrasonic cleaning


2.   Parts surface requirement

  • Remove the parting line
  • Create a homogeneous surface
  • Impart a matte finish for the secondary process


3.   How we process the parts

Step (1)Grinding (2) Cleaning
Machine The centrifugal disc finishing machine An ultrasonic cleaning machine, remove the abrasive adhesion
Tumbling Speed 50/60HZ (full speed)
Chip Type Ceramic media ball
Media to Parts Ratio 3:1
Compound Type LC-13, PH 8 (mild grinding compound)
Water Level Just cover the mass
Tumble Time 30 minutes 10 minutes
Notes— Can also use the automatic system Can also use the automatic system


4.   Parts condition before and after polishing


plastic o ring before and after finishing
plastic o ring before and after finishing


Rubber parts are notoriously difficult to run in a tumbling process. Before tumbling, you can see the parting line at inner ring and outer ring. For this part, the goal was to remove the mold parting line and impart a matte finish for a second post process.


plastic o ring before and after deflashing_
plastic o ring before and after deflashing


We chose a fast cutting, large size ceramic media ball in order to effectively abrade the rubber. The tumbling process has removed the raised parting line quite effectively in a short period of time.


5. Other Considerations:

Rubber o-ring parting lining removing process also called deflashing process. Besides centrifugal disc finishing machine, we can also use vibratory finishing machine to carry out the job.

Vibratory finishing machines are well suited for bigger size o-ring with big quantity. The mode with separation sieve is proposed to reduce labor cost.


6. Conclusion

In this article, we discuss the rubber o-ring parts before and after finishing. Our goal is to remove the parting line flashes from injection molding. Our method is to use centrifugal disc finishing machine with a heavy cutting ceramic media. This is a short process with low labor involvement.

The same process can also be used for compression molding parts for plastic and rubber.