English 
Español 
Français 
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) require precision for shape control call for the removal of flashes.
Therefore, we need a second operation to remove the flashes and burr.
This article shows an example of deflashing rubber parting line with the 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
Rubber parts are notoriously difficult to run in a tumbling process. Before tumbling, you can see the parting line at the 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.
We chose a fast cutting, large-size ceramic media ball to rub the rubber effectively. The tumbling process has removed the raised parting line quite effectively in a short time.
5. Other Considerations:
When it comes to deburring rubber O-rings, the choice of machinery plays a crucial role in the efficiency of the process. For O-rings with a size smaller than 40mm, the recommended equipment is a centrifugal disc machine. This type of machine is ideal for smaller components due to its precise and high-speed deburring capabilities.
On the other hand, for larger O-rings surpassing the 40mm mark, employing a vibratory finishing machine is the way to go. However, it’s important to note that using a vibratory finishing machine comes with a trade-off, as it generally takes approximately 3-4 times longer to complete the deburring process compared to a centrifugal disc machine.
Therefore, when choosing the appropriate deburring method for rubber O-rings, considering the size of the components is paramount to achieving optimal results efficiently
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 a centrifugal disc finishing machine with a heavy cutting ceramic media. This is a short process with low labor involvement.
