White Paper: Robots Automation and the “Three-Point Tradeoff”

EpsonJune 4, 2024

A practical look at the role of PRECISION in project requirements

A robotics automation project can have many different requirements, however the three most important are typically speed, precision, and payload. When implementing automation there will always be trade-offs, thus the importance of understanding your specific needs in these three key areas. For example, many customers would love to have a robot moving at the highest speed, achieving the highest level of precision, and carrying the heaviest payload. Unfortunately, this is not physically possible. It’s therefore critical to understand your goals and expectations, because as you define your requirements you will very likely need to make some compromises. And those compromises must be aligned with your business objectives.

Let’s take a closer look at the role precision plays, where you need it and a growing trend that makes precision even more important.

PRECISION requirements are often tied to smaller and smaller components that become unmanageable to assemble or handle by existing systems or manual processes. This is a growing trend across all industries, particularly in electronics.

You know you want precision, but do you know where you want it? Many times, customers have a desire to improve precision, but they haven’t yet defined exactly where in the system they want the precision. Remember, you need to consider your entire system with all its parts working in harmony. You need to know exactly which area you’re looking for improvement and how much improvement you’re looking for.

Your precision needs can vary. For example, do you need it in the end of arm tooling (EOAT)? In the robot arm? Would it make the most impact in a peripheral tool, like a conveyor? Precision improvements in your manufacturing process can make a big impact in improving product quality and throughput, but you need to first make sure that you’re investing in the right place.

Precision is not accuracy

When defining precision, recall that it’s not the same concept as accuracy. A good way to illustrate the difference between precision and accuracy is the common bull’s eye image. If you throw a dart at a bull’s eye and it lands off center, but in the same off-center place time and time again, that’s precision. If the dart is in the dead center, it’s accurate, but if you throw it again and it lands outside, it’s not precise. In robotics, precision is what most engineers are looking for, and they often refer to this concept as repeatability.

Now that you know how to define your precision, take a look at your entire system. Each piece of that system has its own effects on precision and tolerance. Some factors you can consider are:

End of Arm Tool (EOAT)

  • Know the type of EOAT required to work with your parts. Higher precision environments often use custom tools. Use an experienced tools designer to design and build the EOAT appropriately.
  • Are you using mechanical or vacuum grippers? Although the negative pressure from a vacuum can tell you the product has been picked up, it will have less precision than a mechanical gripper. One option is to go with a custom-molded vacuum gripper which offers greater precision, yet at the tradeoff of cost. Peripheral equipment that is brought into the automation work cell

Peripheral equipment that is brought into the automation workcell

  • Peripherals are a key part of the system. Look at the feedback you’re getting from them. This also includes things such as manufactured parts, conveyors and pallets.
  • Do you need a vision system or a smart sensor? Equipment like this can produce incremental precision gains.
  • A manufacturer will often use parts from two or more different manufacturers for redundancy and back-up. Because these parts come from different manufacturers, make sure to evaluate each of these parts as their precision and tolerances might be different.
  • Also consider any pull or rigidity that power, air or communications cables may place on your robot arm

Determining the level of precision

Now that you’ve considered every part of your system, you can determine the level of precision that’s required to move and place all these parts and which robot to go with.

If you’re unsure of your precision requirements, you may ultimately choose the wrong robot or end up with one that is insufficient (or even maybe in excess) of your needs. For example, if you don’t require complex movements of parts such as roll and pitch, you might not need a 6-axis robot. Don’t be hesitant to rely on qualified robot vendors or system integrators because they can help define tolerances and precision tolerances for your application. And remember, precision will have trade-offs with speed and payload!

Ready to learn more about areas to consider when optimizing for precision?

Download the Epson Robots Automation 201 white paper for tips and questions to consider. We take a deep dive into clarifying your requirements for project success with a closer look at all three primary requirements that impact nearly all automation projects: Speed, Precision, and Payload.

To learn more about Epson Robots, visit Epson.com/about-robots