Recommendations for CNC tending applications

Tending CNC machine tools is one of the most common applications for UR cobots thanks to their flexibility, small footprint, and ease-of-use. In most cases, the robot will work non-stop for years at peak performance. However, in some of these applications, the combination of the cutting fluid used in the machining process and a high and continuous exposure of the robot to such fluid, can reduce the robot’s performance in the long term.

Therefore, to ensure optimal performance in CNC applications where the robot is continuously exposed to this kind of fluids, it is recommended to consider the following preventive maintenance tips:

Tip 1: Wipe the robot down daily

Continuous exposure to cutting fluid can cause it to build up on the robot and increases the likelihood of degrading the sealing components.

Due to that, it is important to remove any excess of fluid from the robot regularly (every day or every shift) as a standard maintenance procedure.

This procedure limits to wiping the robot down with a dry high-absorption cloth or workshop paper towels, trying to clean off as much fluid as possible.

Tip 2: Visually check the robot’s sealing rings

It is important to ensure the sealing rings of the robot are in good condition and properly seated to ensure maximum effectiveness.

Sealing capabilities of these rings can be affected in the long term by mechanical wear-and-tear (e.g. if a cable/hose is constantly impacting/rubbing against them while the robot moves) or by chemical erosion if the cutting fluid contains highly aggressive agents in its composition.

For this reason, it is recommended to do a quick visual check regularly (ideally, daily after wiping the robot down as recommended in the previous tip).

If any damage is appreciated in any of the rings or if they tend to pop out of their nominal position frequently, it is highly recommended to contact your robot service provider as soon as possible to have them replaced.

Find more information here: https://www.universal-robots.com/articles/ur/robot-care-maintenance/inspection-and-maintenance-plan/

Tip 3: Install lids with increased chemical resistance for eSeries/CB3 (spare part)

Specially formulated, chemical resistant joint lids have been introduced in 2024 (see below for part numbers). These lids are intended to combat deterioration from coolants and cleaning solutions that have proven detrimental to the standard joint lids. These lids are available as a spare part lid set for any eSeries and CB3 robot models. Find more information here: https://www.universal-robots.com/articles/ur/robot-care-maintenance/product-change-notification-new-lids-kits-for-e-series/

Tip 4: Design paths to reduce exposure to cutting fluid

Even though cutting fluid is not directly projected on the robot (as the CNC door is closed during the machining operation, keeping the robot outside), there can be still situations where the robot is highly exposed to such fluids. Specially, when moving under parts of the machine where fluid drips more intensely (like the turret, cutting tools or fluid nozzles). Also, it is common for the robot to encounter splash or incidental contact during cleaning operations of the part, workholding or cutting tools.

For that reason, it is recommended to optimize the robot paths so that exposure to cutting fluid is reduced, as graphically described in the diagrams below.

Tip 5: avoid letting the M8 tool connector exposed

The tool flange is the part of the robot that gets exposed to cutting fluid the most. If the connector in the tool flange is not in use (no tool cable is connected to it), it is important to use the connector’s cap to avoid direct exposure of the electrical pins.

The M8 male connector (for CB3 robots and eSeries robots previous to September 1, 2024) uses an aluminum cap made of aluminum and screwed around the connector. The M8 female connector (for UR20, UR30, and eSeries robots after September 1, 2024) uses a rubber cap that is inserted around the connector. Connector caps can be acquired as spare parts in case they get misplaced.

Find more information on the tool connector in this article: https://www.universal-robots.com/products/ur-developer-suite/hardware-and-motion/electrical-interfaces-tool-connector/

Relevant part numbers