By Chris Caldwell
Promises of zero maintenance for extended periods from some robot manufacturers may sound good, but are these claims accurate? The answer is, NO! Robot and cobot owners should expect to perform encoder battery replacement and regularly inspect robots as prescribed. So, buyer beware! With this in mind, there are key maintenance concepts robot buyers should consider for maximum return on investment before making a robot purchase:
All Robots Have a Maintenance Schedule
A robot’s maintenance schedule should be a consideration for buyers before making a purchase. Let’s face it, an extended period with absolutely zero maintenance at face value is analogous to saying the robot warranty is now void, and buyers in this situation should be prepared to pay for spare parts and labor when an issue occurs. You should also make sure that you compare various warranty period claims on an equal footing. For reference, here are some comparative robot maintenance schedule stats:
Company A
30,720 hours (2-shifts @ 7.5hrs [15/day], 256 working days per year = 8 years, or 5.1 years in Yaskawa’s terms).
Company B
Components are non-serviceable, and you can’t replace only worn parts. The owner or operator is recommended to perform a biannual inspection and replace any damaged axis units in their entirety. In essence, if an axis has any level of damage, the entire axis of the robot arm must be changed – a very expensive maintenance option.
Yaskawa
36,000 hours (3-shifts @ 8hrs [24/day], 250 working days per year = 6 years, or 9.3 years by Company A’s terms). Yaskawa suggests proper maintenance and offers options to replace worn parts. In addition, the company also recommends maintenance by usage hours or condition. Using Company A’s logic, Yaskawa can facilitate 8 to 9.3 working years (16% longer).
What Do Maintenance Schedule Measuring Differences Mean?
Before making a robot purchase, maintenance schedules should be reviewed and considered, and the real-world implications should be weighed. Yaskawa robot schedules, for example, assume 24-hour operation of each manipulator and include all activities to maximize operation uptime. Other robot companies assume less usage per day. Not understanding this simple difference may give some robot buyers a false sense of security for a period of time. Therefore, before making a robot purchase, decision makers should fully understand the “B.I.G” details that may be glossed over when claims for an extended zero maintenance warranty are made.
B.I.G. Details Overlooked in Extended Period Zero Maintenance Warranty Claims
Once robot integration takes place, there are several maintenance steps robot users will become familiar with – as these things are integral to optimal robot performance and life cycle management:
Batteries
To maximize uptime, encoder batteries need to be changed before end of life. There are two approaches to this reality: 1) schedule maintenance and ensure zero unplanned downtime, or 2) wait for the batteries to die, thereby taking a robot offline in an unplanned manner and replacing the battery.
Note: Company A does not count changing batteries as maintenance. That said, option #1 – where maintenance is scheduled based on condition or at regular intervals – is ideal, and it is the method Yaskawa suggests. Extended period zero maintenance warranties (and the like) fall in line with a hands-off approach, throwing best practices to the wind and introducing unplanned downtime that has potential for negative financial ramifications.
Inspections
Inspections are recommended as a regular maintenance practice. While some of these checks are minimally invasive (i.e., checking for damage or peeling paint, or looking for dirt and debris in the working area), most require some amount of stoppage or power-off downtime. From tightening mounting bolts, cover bolts, end-of-arm tooling bolts, to repairing cables, connectors or ventilation components, there are common checks every robot, regardless of brand, should regularly have. Moreover, if these inspections are not completed, the warranty may be voided in many cases. To reiterate, a zero maintenance guarantee is inviting a hands-off approach to robot maintenance, and it is a recipe for the robot warranty to be voided, with the likely potential to cause pricey unplanned downtime.
Grease
The type of grease, along with routine grease analysis, is vital to top robot performance. Regular grease changes and checks should be performed based on robot usage. Yaskawa recommends that standard grease be tested, evaluated and replaced every 12,000 servo hours, with adjustments to timing of future replacement depending on grease analysis. For example, Yaskawa HC-series (human-collaborative robots) use Food Grade Grease (FGG) as a standard. Due to the differences in the lubricant, as well as the food safety precautions, it is recommended FGG be inspected every 6,000 servo hours, helping to maintain and extend the life of the robot.
To put it in perspective, adhering to zero maintenance would be similar to ignoring the oil in a car and the driver being hopeful the car will run for years. Running gears create friction, and viscous grease is important to the robot performance, helping to avoid repairs and unplanned downtime.
Most Company A collaborative robot models ship with standard grease. For this robot series, specifically, the manufacturer does not advise to perform any type of grease/oil analysis when equipped with standard grease. This seems suspect, as Company A typically suggests robots with standard grease be inspected every 11,000 servo hours or every three years. That said, it is unclear how or why Company A’s collaborative robots with standard grease can perform without inspections and grease changes while they recommend grease changes on their traditional robots with the same grease. Again, robot buyers should be aware of the potential long-term ramifications of not performing regular robot maintenance.
Maintenance Costs vs. Downtime Costs
Robot users should understand how costly downtime is to manufacturing processes. By implementing maintenance checks at regular intervals, robot performance and operational productivity can be maximized. Frequently, unexpected downtime (like what may be required for ordering a new battery to replace a defunct one) is more costly than having a replacement part on hand and changing the battery during a scheduled maintenance check. Since many robots either support other capital equipment or are integrated into larger systems, unplanned downtime can result in potential lost revenues from thousands to hundreds of thousands of dollars per hour.
Planning for zero robot maintenance over an extended period of time, such as 5 to 8 years, is unrealistic. However, this is what some people understand an extended zero maintenance warranty to mean. Robot buyers should be aware that every robot will require some level of downtime (planned or unplanned). Robot suppliers that tout long-term “maintenance free” periods may be planning to cover the cost of items or perform maintenance tasks, such as grease replacement or battery exchange as the need arises. They may also not worry about the potential issues since the physical warranty expires in 1 to 2 years. While the maintenance free concept may seem appealing to buyers, the time spent along with the revenue lost between the back-and-forth conversations and actions required to address issues in a pinch can be more devastating than sticking to a timely maintenance schedule that encourages robot users to keep specific spare parts on hand for reduced downtime.
Chris Caldwell is a Product Manager with Yaskawa.
