Core Value of This Guide
The ABB IRB 6700 is a powerhouse industrial robot, designed for demanding applications. Central to its performance and longevity is the balancing device – a sophisticated spring-based mechanism that counteracts the weight of the robot's upper arm. This guide helps you understand how to inspect, lubricate, and safely approach repairs or replacements related to the IRB 6700 balancing device, going beyond basic manual steps to grasp the why and how for critical procedures.
Target Audience
- Maintenance Technicians
- Repair Personnel
- Robot Service Engineers
Safety Critical
The balancing device contains high-tension springs storing considerable potential energy. Mishandling during maintenance or failure during operation can be extremely hazardous.
Why the Balancing Device Matters
Reduces Motor Load
It counteracts gravity's effect on the upper arm (primarily axis 2 and 3 movements), significantly lessening the load and torque required from the axis motors.
Improves Performance
By reducing motor strain, it allows for faster acceleration, smoother movements, and potentially higher payload handling within the robot's specifications.
Enhances Energy Efficiency
Less motor effort translates to lower energy consumption, making the robot more efficient during operation.
Increases Component Lifespan
Reduced stress on motors and gearboxes contributes to their longevity, reducing maintenance frequency and extending the service life of the robot.
Routine Inspection: Your First Line of Defense
Regular inspection is key to identifying potential issues before they escalate. Follow the maintenance schedule (Section 3.2.2 in the manual), but also perform checks if any unusual behavior is observed.
Manual Reference
These inspection procedures are detailed in Section 3.3.7 of the product manual (Document ID: 3HAC044266-001).
Listen for Dissonance (Noise)
- Tapping/Banging: Could indicate issues with the internal springs. Requires further investigation, potentially leading to device replacement (Section 4.6.2).
- Squeaking: May suggest worn internal plain bearings, contamination, or insufficient lubrication within the piston rod assembly. Requires deeper maintenance.
- Bearing Noise (Link Ear & Rear Attachments): Listen for grinding or roughness at the front link ear (B) and rear bearing attachments (C). This points towards bearing wear, requiring replacement using specific maintenance kits (Sections 4.6.1, 4.6.3).
Visual Damage Check
- Piston Rod (A): Inspect the visible portion for scratches, scoring, or unevenness. Damage here can compromise seals and internal function.
- General Structure: Look for cracks, deformation, or excessive wear on the housing, link ear, and mounting points.
Check for Grease Leakage (Link Ear)
- The front spherical roller bearing is grease-lubricated. Clean the area around the front shaft seals.
- Run the robot briefly to move the balancing device.
- DANGER: Ensure robot power is OFF and locked out before re-entering.
- Inspect the O-rings (C) and sealing rings (B) for any signs of grease leakage. Leaks must be addressed immediately to prevent bearing failure.
- Replacement O-rings/seals are typically part of the maintenance kit (Section 4.6.1).
Check for Contamination / Lack of Free Space
- Ensure the area around the balancing device inside the robot frame is clean and free from obstructions (tools, debris, fallen parts).
-
The device needs unrestricted movement throughout its operational range (Section 3.3.7, Figure
xx1300000423).
Common Maintenance & Repair Procedures
1. Lubricating the Spherical Roller Bearing (Link Ear)
This bearing handles significant load and requires regular lubrication as per the schedule.
Purpose:
Replenishes grease, prevents wear, ensures smooth articulation.
Procedure
- Safety: Power off and lockout the robot.
- Locate the two M6 screws on the link ear end cover (A in figure
xx1300000773). - Remove both screws.
- Inject the specified grease (Optimol PD0, 3HAC042534-001) into the upper hole until fresh grease emerges from the lower hole. This ensures the bearing is filled.
- Refit the screws and wipe away excess grease.
Key Grease:
Optimol PD0 (ABB Art. No. 3HAC042534-001)
2. Replacing Bearings (Spherical Roller or Rear Bearings)
If inspection reveals bearing noise or damage, replacement is necessary using the appropriate maintenance kit.
Critical Prerequisite
The balancing device must be safely unloaded before attempting any bearing replacement procedure involving shaft removal.
Procedure Highlights:
- Safely unload the balancing device (see dedicated section below).
- Remove the front shaft (for spherical roller bearing) or rear shafts (for rear bearings) using the Dismantle and Mounting Tool (3HAC028920-001).
- Use the same tool kit to press out the old bearing(s) and press in the new ones from the maintenance kit.
- Thoroughly clean all surfaces.
- Properly lubricate new bearings and seals upon assembly as per ABB standards (Section 4.2.2, 4.2.3).
- Reassemble shafts, ensuring correct torque values.
- Restore balancing device tension after reassembly.
Key Tool:
Dismantle and Mounting Tool (3HAC028920-001) and associated hydraulic pump.
Key Parts:
Maintenance Kit Link Ear (3HAC045815-001) or Maintenance Kit Rear Attachment (3HAC045822-001).
3. Replacing the Entire Balancing Device
Required for severe internal damage (e.g., spring failure) or if specified during major overhauls.
Procedure Highlights:
- Safely unload the existing balancing device using the appropriate method (Distance Tool if possible, otherwise Press Tool).
- Disconnect the front and rear shafts.
- Carefully lift and remove the old unit (Weight approx. depending on model, but significant).
- CRITICAL: A new spare balancing device comes fully tensioned. It must be unloaded using the Hydraulic Press Tool (3HAC020902-001) before installation (See Section 4.6.5).
- Lift the new, unloaded device into place.
- Reconnect shafts, ensuring proper alignment and torque.
- Restore tension using the Hydraulic Press Tool (See Section 4.6.6).
- Lubricate bearings as required.
The Critical Step: Safely Unloading & Restoring Tension
DANGER: EXTREME HAZARD
THIS IS THE MOST DANGEROUS PART OF BALANCING DEVICE MAINTENANCE. The stored energy is immense.
Manual Reference: Sections 4.6.5, 4.6.6
Understanding the Tools
Distance Tool
Tool Number: 3HAC030662-001
Function: Locks the balancing device in a compressed state.
Usage: ONLY fitted or removed when the robot's axis 2 is jogged to approx. -20° or +20° (compressing the springs). It does not unload tension itself; it just holds it once compressed by the robot's movement.
Use Case: Used when removing/refitting the same balancing device unit, and the robot is functional enough to jog axis 2 to the required compression position.
Hydraulic Press Tool
Tool Set: 3HAC020902-001 with Hydraulic Cylinder (3HAC11731-1) & Pump (3HAC13086-1)
Function: Used to actively compress (unload) or allow controlled decompression (restore) the internal springs.
Usage: Fitted to the rear of the balancing device. The hydraulic pump applies force to compress the springs. A locking plate secures the tool in the compressed state. Reversing the process restores tension.
Use Case: Essential for installing a new (tensioned) balancing device, or when the robot cannot be jogged to compress the springs sufficiently for the Distance Tool.
Unloading Procedure (Using Press Tool)
Manual Reference: Section 4.6.5
- Safety: Power off, lockout robot. Secure lower arm if necessary.
- Remove the rear cover of the balancing device. DANGER: Do NOT remove any other screws.
- Mount the correct press device onto the Press Tool.
- Mount the Press Tool onto the balancing device rear, torquing bolts correctly (45 Nm).
- Attach the hydraulic cylinder and pump.
- Slowly increase pressure until the moving pin (E) aligns with the press block (A) mark.
- Turn the fix plate (G) to "Closed" to lock the tool.
- Release hydraulic pressure. The device is now unloaded but the tool holds the tension. The cylinder can be removed if needed, but DO NOT REMOVE THE PRESS TOOL ITSELF.
Restoring Procedure (Using Press Tool)
Manual Reference: Section 4.6.6
- Safety: Ensure device is securely reinstalled on the robot, shafts connected.
- Re-attach hydraulic cylinder/pump to the locked Press Tool.
- Apply slight pressure, just enough to allow the fix plate (G) to be turned to "Open".
- SLOWLY AND CAREFULLY release the hydraulic pressure, allowing the internal springs to expand and restore tension to the device. Monitor the moving pin (E).
- Once fully restored (no pressure), remove the hydraulic cylinder.
- Remove the Press Tool bolts.
- Refit the rear cover using locking liquid (e.g., Loctite 577) and sealant (e.g., Sikaflex 521FC). DANGER: This cover is a safety device.
Decision Flowchart: Choosing the Right Unloading Tool
flowchart TD
A[Start Maintenance Task] --> B{Robot Joggable?}
B -->|Yes| C{Same Unit Reinstall?}
B -->|No| D[Use Hydraulic Press Tool]
C -->|Yes| E[Use Distance Tool]
C -->|No| F{New Unit Installation?}
F -->|Yes| G[Use Hydraulic Press Tool]
F -->|No| H[Consult Manual/ABB Support]
classDef decision fill:#f9a825,stroke:#f57f17,color:#000
classDef action fill:#1e88e5,stroke:#0d47a1,color:#fff
classDef danger fill:#d32f2f,stroke:#b71c1c,color:#fff
class B,C,F decision
class E,D,G,H action
Tool Selection Clarification
Understanding when to use which tool is critical for both safety and procedural correctness. Using the Distance Tool when the Press Tool is required (or vice-versa) can lead to dangerous situations or inability to complete the task.
Safety First: Essential Precautions
Stored Energy
NEVER attempt to disassemble the balancing device housing itself. Treat it with extreme caution. Assume it is under tension unless proven otherwise with correct tooling.
Correct Tools
Use ONLY the specified ABB tools (Distance Tool or Press Tool) for unloading/restoring. Improvisation is extremely dangerous.
Lockout/Tagout
Always ensure the robot is completely powered down and locked out before starting work.
Secure Arms
If removing components that affect arm stability (like the balancing device itself or axis motors), securely support the robot arms mechanically before releasing brakes or removing parts. Use lock screws (e.g., M16x120 for axis 2) where specified.
Lifting
Use appropriately rated lifting accessories (shackles, chains, cranes) when removing the balancing device or connected robot arms. Note the specified weights.
Lubricants
Follow safety data sheet recommendations when handling grease. Wear appropriate PPE (gloves, safety glasses).
Conclusion
The IRB 6700's balancing device is a robust but critical component requiring diligent inspection and precise, safety-conscious maintenance. Understanding its function, recognizing warning signs, and rigorously following the correct procedures—especially regarding the safe handling of stored energy using specified ABB tools—are paramount. Never underestimate the potential hazards involved. When in doubt, always consult the official ABB documentation or contact an authorized ABB service representative. Proactive maintenance ensures continued performance and, most importantly, a safe working environment.