To keep a complex system running at peak performance requires routine
maintenance. Your arc welding robot or cobot
is just such a system.
Following are a few maintenance tips that, when done properly and regularly,
will help you maximize your robot’s uptime, life span, and return on
investment.
Without oversimplifying things, we can begin by separating the major
components of an arc welding system into two categories. The first category
is the robot and controller. The second category is the actual welding
process equipment.
Robot and Controller Maintenance: Daily Reviews
These items could be included on a daily inspection check list for your robot
and controller.
1. Check for liquids and spatter. Look for signs of liquids
on the floor or on the machine. This is an indication that you may have a
loose or broken fitting. It also might indicate damaged hoses or hard
tubing.
Any exposed hoses are going to be subjected to strong ultraviolet (UV) light
from the welding process, which will typically break down the materials in
most flexible hoses over time.
The same holds true for the protective coating of electrical wires. They,
too, will break down and crack with exposure to UV light. They also could be
subjected to high heat and weld spatter. Some inexpensive covers such as
fabric sheaths can be used to extend the life of your flexible hoses without
restricting their movement. These covers should be considered for hoses
routed through and on the robot and also for end-of-arm tooling or
fixed-tooling stations.
The buildup of spatter over time can degrade or destroy your air and
hydraulic clamps. There is also the risk of spatter or slag burning a hole
through the tubing, causing a possible fire hazard. Extra consideration is
needed when the hydraulic tooling is under high pressure. A small pinhole
under pressure can cause a lot of damage to the surrounding area when
ignited. And, yes, I’m speaking from experience.
Along the same lines, there have been great improvements in hydraulic fluid
that is more fire-resistant than standard fluid and should be considered for
such an application.
2. Visually check the robot hardware. As you continue into
the workcell, visually inspect the hardware on the robot and the surrounding
tooling for signs of loose or missing bolts. Visually identify and verify
that any applicable safety covers are in place. If your robot has gearboxes
that use oil instead of grease, they may have a sight glass that can be used
for a quick inspection of fluid level and color. Things to look for are low
fluid level, which indicates a leak, and darker fluid color, which indicates
either high temperatures or contamination.
3. Aurally check for leaks. Next, if possible, listen for
air leaks in the cell. This, too, could be an indicator of an air line with
a burn hole or a fitting that has worked its way loose. And, if possible,
listen to the equipment while running production. Grinding noises or unusual
vibrations may be an indicator of a mechanical problem.
4. Check the master position. The final item I would include
on my daily inspection would be the robot master position and corresponding
User Tool values to validate everything is located properly and accurately
before starting production. There are some tools available that can perform
these functions automatically on a set interval, for example, after every
part.
Robot and Controller Maintenance: Production-based Timed Reviews
The following items should be inspected at some interval dictated by either
the time the machine is running or a period of time established by your
team.
5. Check the grease in the robot and positioner gearboxes.
Again, look at the level and color of the grease; a dark color suggests high
heat or contamination.
6. Check the batteries. If your robot uses batteries to back
up the robot position or programs, you will need to replace them regularly,
usually yearly.
7. Check for cleanliness. While you are inside the robot
control cabinet, be sure all the fans and fan ducts are clean of debris.
Also, verify the inside of the control cabinet is clean. If it is not, you
may be missing some covers on cable entries or a door seal may be damaged.
If your robot is in a fabrication shop where cutting and grinding operations
are nearby, you will especially want to make sure those airborne
contaminants don’t get inside the controller and onto exposed circuit
boards. The dust and oil can lead to a short or, worse, a fire.
8. Back up your software. Make it a habit to back up your
robot software regularly. With the complexity of today’s robot systems
it is easy to get into trouble quickly with a few bad programming techniques
that could potentially shut down production for long periods of time. By
restoring a previous working backup software package, that robot can return
to production much quicker.
Weld Equipment Maintenance
After inspecting the robot and controller, you should next focus your efforts
on your weld equipment. The frequency of these checks will also vary, but
should be on your list nonetheless.
9. Check the welding leads. Be sure to check the cable
condition and pay special attention to the connection points. If the
connection points are loose or the cable strands are showing signs of wear,
this will add resistance to the overall system and not only affect weld
performance, but will also cause the cables to generate more heat. If you
use rotary grounds, verify they are properly lubed with conductive grease.
10. Check for cleanliness. Similar to the robot, if the
factory environment has machining or grinding processes nearby, make sure
the cooling system for the power supply and possibly the welding torch are
clean and able to exchange heat efficiently.
11. Check coolant levels. If you are using a water cooler
for your welding process, verify the fluid levels and clarity of water or
cooling fluid. If not maintained properly, the water or coolant can grow
algae, which will in turn diminish the cooling performance of the system.
This will shorten the life of the components.
12. Check gas connections. In welding applications where a shielding gas
is present, it’s good practice to occasionally check all the gas
connections and fittings for leaks, and validate that pressure and flow are
within your specified limits. Too much gas flow can be just as detrimental
to the weld process as too little.
13. Check your consumables. Consumables to check include
wire guide rolls, wire delivery systems, torch liners, tips, nozzles, and
diffusers. The condition of these items will all vary based on usage, as
will the frequency of when they need to be addressed. General
recommendations for that frequency can be obtained from the welding
equipment supplier.
Predictive Maintenance: The Future
Great strides have been made in getting factory automation to communicate
with PCs and with other factory automation. With the invention of Ethernet
communication, a whole new world of data has been made readily accessible.
Especially now with the internet of things (IoT), more data is being
collected per machine than ever before.
Following are a few maintenance tips that, when done properly
and regularly, will help you maximize your robot’s uptime, life
span, and return on investment.
That abundance of information has made it possible to add more intelligence
to automation and collect data to be used with various algorithms and trend
analyses. This makes it possible to monitor and, in some instances, predict
when a machine needs attention. This technology is helping to reduce robot
downtime caused by unscheduled and unforeseen events.
For instance, it is now possible to tell, based on duty cycle, when a
robot’s grease or oil needs to be replaced. Based on previous
performance data, it is possible to know when a particular machine is not
meeting established requirements. In some cases, this information also can
be pulled from welding power supplies independently or through the robot to
help provide an overall status report on the health of that weld cell.
Adopting a regular routine for inspecting your arc welding robot cell will help ensure
your end product stays at the quality level you expect and will aid you in
getting the longest possible life out of your equipment. New technology is
gradually becoming capable of making this process simpler proactively rather
than reactively.