Note: following the guidelines in this article is considered using the robot outside of its specified operational parameters and is performed at the customer’s own risk.

Here is a recommended best practice for starting up a robot in cold environments:

Universal Robots joints use strain wave gear technology which are sealed, self-contained, and self-lubricated for the life of the product (no need to exchange or add grease). During normal operation, the lubrication gets naturally recirculated and distributed around the gears and bearings to keep the mechanical systems properly lubricated.

Temperature has an impact on the grease viscosity and gears friction values, Universal Robots recommend to power on the robot, and do slow movements until it reaches internal operating temperature before reaching higher speeds. 

Robot cannot operate with high speed if the joints has not reached internal operating temperature, that is > 0°C.

Warm-Up Routines for Cold Environments​

The following program has been developed to gently warm the robot to enable it to move at higher speeds in cold environments. The resulting values are the outcome of internal tests that have been performed in a climate chamber, where robots were cooled to joint temperatures of -15 °C, in -20 °C ambient.

The program has a strict limitation of the size of the movements, which means that it only moves the robot within a very small footprint.

Note: The warm-up program and routine followed is just one example showing the principle. Requires to be adapted to specific use. Also, depending on the work cell, it may be necessary to re-teach the robot's initial position.

Program Description

• A thread monitors the temperature of the elbow joint, as this joint generally seems to be cooler than the others.
• To start the routine, the robot is moved to the starting position at joint speed = 10°/s.
• The program moves the robot between two waypoints.
• Depending on the temperature, one of 4 different speed/acceleration parameters is chosen for this movement.
• If the joint temperature is above 0 °C, the program will remain at idle until the joint temperature drops below 0 °C.

The table below shows the target speed and acceleration depending on the temperature of the elbow.