Seals are a vital component in robots, particularly in hydraulic and
pneumatic systems. Although seals themselves are relatively inexpensive, their
failure can lead to significant downtime, repair costs, and operational
disruptions. In this article, we will explore the common failures caused by
robot seal issues and how to establish a preventive replacement cycle that
minimizes risk and ensures smooth operations.
Failures Caused by Seal Issues
Inaccurate Movement and Reduced Precision
Seals in hydraulic or pneumatic cylinders are crucial for maintaining pressure. When seals wear out or fail, internal leakage increases, causing pressure drops and inaccurate movements. This leads to issues like misalignment, reduced grip force of robotic arms, and improper assembly. These issues may cause the entire production line to stop for adjustments.
Inability to Maintain Load
Some robot components, such as lifting shafts and balancing cylinders, rely on pressure to maintain position. When the seals fail, leakage occurs, causing the load to slowly drop or shake. This creates safety risks and requires immediate shutdown for inspection and repair.
Oil Leakage and Contamination
Seal failure leads to oil leakage, contaminating components such as guides, cables, and even workpieces. This not only increases cleaning costs but can also result in product contamination and waste, potentially halting production for quality investigations and rework.
System Alarms Triggering Shutdown
Robot systems often rely on PLCs to monitor parameters like pressure and temperature. Seal leakage can trigger alarms when oil pressure drops or temperatures rise, automatically shutting down the robot to prevent further damage.
Long-Term Degradation Leading to Major Repairs
Many seals fail gradually, starting with slight leakage. If not addressed
early, the problem can escalate, causing significant damage to components like
hydraulic cylinders. Full repairs will involve disassembly, oil replacement, and
cleaning, resulting in extended downtime and increased costs.
How to Set a Preventive Replacement Cycle?
Categorize by Operating Conditions
The working conditions of a robot significantly impact the lifespan of its seals. Environments with high temperatures, high pressures, or contamination can accelerate seal wear. By categorizing seals based on their working conditions, you can tailor replacement cycles to prolong the robot's lifespan.
Record and Analyze Actual Failure Data
While theoretical lifespans are helpful, real-world data is essential. By tracking when leakage occurs, total operating hours, pressure, and temperature ranges, you can assess the failure patterns of seals and establish more accurate replacement cycles.
Set the Replacement Before Failure Occurs
Preventive replacement should occur before seals fail completely. For instance, if a seal starts leaking at 3.5 million cycles and typically fails at 4-5 million cycles, set the preventive replacement cycle at 2.5-3 million cycles to avoid entering a high-risk zone.
Differentiating Critical and Non-Critical Components
For critical components like lifting axes or main oil cylinders, set shorter replacement intervals. For less critical parts like auxiliary systems, replacement can be done when minor leakage is detected. Non-critical components like protective cover seals can be replaced based on their condition.
Routine Inspections and Early Detection
Seal failures often show early signs, such as increased oil traces, rising
replenishment frequency, or irregular motion. By regularly inspecting seals and
monitoring these early warning signs, you can address potential issues before
they cause significant downtime.
Establishing a proper preventive replacement cycle for seals ensures that
robots operate smoothly and prevents costly downtime and repairs. By considering
factors like operating conditions, historical data, and regular inspections,
companies can set replacement intervals that are both efficient and effective,
reducing the risks associated with seal failure.
