As a dedicated arc welding model, the QRH390 requires a fundamentally different maintenance approach from general-purpose handling robots. Wear in handling robots is primarily caused by repeated positioning and loads on the mounting flange, while welding robots are exposed to radiant heat from the arc, metal spatter, fume deposits, and frequent twisting as the welding torch changes orientation. The same component can age at entirely different rates and fail in entirely different ways under these two operating conditions. Applying the maintenance intervals and inspection items used for handling equipment often means spending too much time on less critical areas while giving insufficient attention to the areas that actually affect weld quality. A CLOOS robot maintenance plan needs to be reorganized around the actual load characteristics of the arc welding station, concentrating maintenance time on the components most affected by the welding environment.
Seals and cooling passages near the welding area are among the first places to develop problems. During continuous welding with the QRH390, fine welding slag particles and metal dust carried by workshop airflow settle on joint housings, motor end covers, and cover seams. Over time, these deposits form a hard crust that blocks cooling gaps. Prolonged motor operation at high temperatures accelerates insulation aging and slows drive response. Maintenance of a CLOOS welding robot must go beyond wiping exterior surfaces. Accumulated slag at joint interfaces needs to be removed layer by layer, covers opened to check for debris inside, and sealing strips and dust guards inspected for notches burned into them by spatter. Once seals harden and crack, dust can enter the gearbox through gaps in the joints and mix with the lubricant to form an abrasive paste. This damage is not visible from the outside, and by the time abnormal transmission noise appears, wear has already been progressing for some time.
The robot's dress pack is subjected to much greater demands at a welding station than in handling applications. During welding, the QRH390's torch must continually swing, rotate, extend, and retract to follow the angle of the weld seam. The power cables, encoder cables, shielding gas hoses, and wire-feed conduits inside the dress pack repeatedly bend with the joints. Welding wire also generates metal particles as it travels through the wire-feed conduit. These particles collect at bends in the dress pack and, over time, both abrade cable jackets and disrupt smooth wire feeding. During maintenance, open the dress pack section by section to check the outer coverings for tiny holes burned by welding slag and inspect gas hose connections for oily marks that may indicate slight gas leakage. Also readjust the slack in the cables and hoses throughout the joints' range of motion. If the routing is too tight, the cables experience the greatest stress when the robot reaches its extreme poses, increasing the likelihood of fatigue cracking in the insulation. Excessive slack can cause the dress pack to rub against workpieces and fixtures and also needs to be corrected.
Gearbox lubricant deteriorates faster under welding heat loads than at stations operating at ambient temperature. Heat generated by the welding current travels through the robot arm to the joint housings. Combined with the torch's sustained proximity to the heat source, this keeps the grease inside the gearboxes at elevated temperatures for extended periods, reducing its viscosity, accelerating oxidation, and thinning the lubricating film. During maintenance, open the lubricant fill port and take a sample to inspect its color and condition. If the grease has turned black and thickened, or if shiny metal particles are visible, the internal gears or bearings have already begun to wear. The old lubricant must be drained completely before fresh lubricant is added. The refill quantity must strictly follow the requirements for the model. Overfilling increases pressure inside the housing and can cause leakage through the oil seals; underfilling leaves the meshing surfaces inadequately lubricated and can increase operating temperatures further. After replacing the lubricant, run each robot axis back and forth several times at low speed without load to distribute the fresh lubricant evenly, then check for leaks.
The braking system serves a somewhat different role on a welding robot than on a handling robot. During welding, the QRH390 often needs to remain stationary in a particular pose while the torch stays aligned with the seam and continues welding. The brake friction surfaces remain pressed against the same area for extended periods, causing uneven local wear. During CLOOS welding robot maintenance, move the robot into several typical welding poses, cut the power, and check whether any joints drift slowly while holding position. Also listen for crisp engagement and release of the brakes. Once the brake friction surfaces have worn sufficiently, slight movement that is difficult to see may occur while the robot holds position, causing the weld location to shift. What appears to be a weld displaced by just a few millimeters may have its root cause in brake clearance. The torch mounting flange and collision sensor should also be inspected. Loose bolts can cause slight torch vibration during welding, directly affecting arc stability.
The welding torch itself should be maintained more frequently than the robot body. Spatter adhering to the inside of the nozzle changes the gas flow pattern and causes uneven shielding gas distribution, making localized oxidation discoloration more likely on the weld surface. As the contact tip wears, its bore enlarges, reducing wire guidance accuracy and destabilizing the arc. If metal particles are not thoroughly removed from the wire-feed conduit, wire-feed resistance fluctuates, causing the welding current to fluctuate as well. These components directly affect arc quality. Unless their maintenance is managed separately from the robot body's maintenance schedule, the weld defect rate will gradually increase. During maintenance, remove the nozzle and contact tip for cleaning or replacement, blow through the wire-feed conduit from both ends in opposite directions, and then feed welding wire through it to check that it runs smoothly.
Dust accumulates in control cabinets faster in welding shops than in ordinary workshops. Metal particles in welding fumes settle on circuit boards and heat sinks, impairing heat dissipation and posing an electrical conduction risk. During CLOOS welding robot maintenance, remove and clean the filters, use low-pressure air to clean the cooling ducts and drive surfaces, and retighten the wiring terminals one by one. Electromagnetic interference at welding stations is more complex than at handling stations. If the shielding on an encoder cable is damaged, interference picked up by the cable can cause robot positioning drift. This type of fault does not trigger an alarm and only becomes apparent gradually through reduced weld positioning accuracy, making it time-consuming to diagnose. During maintenance, inspect the cable routing for exposed braided shielding and check whether any sealing rings have come loose at the connectors.
Once all maintenance tasks are complete, the robot should not be handed back after only a no-load test run. The QRH390 needs to run a complete weld seam with the torch using the actual production program. Check whether the arc starts cleanly, whether the weld profile is uniform, and whether any axes produce abnormal noise or hesitate during movement. Then verify the coordinates of several critical weld points. The effectiveness of maintenance must ultimately be confirmed under actual arc welding conditions; normal no-load operation does not guarantee normal welding performance. Record the wear points found and the actions taken during each CLOOS robot maintenance session. After several maintenance cycles, the equipment's wear trends will become apparent, allowing wear parts to be prepared ahead of the next service and reducing delays caused by unavailable parts.