The adage “Always use the right tool for the job” is very true when it comes to picking a robot for automated manufacturing. There are many suppliers, makes, models, and price points. So how do you know if you have selected the right one? Here are nine criteria to consider.
Robots come in a wide range of sizes, from the smallest SCARAs moving 1g parts to huge 6-axis bots manipulating the entire body of an SUV. However, heavy lifting isn’t always about how big your object is. Larger robots are also able to move many of the same part at the same time, potentially opening the door to increased efficiency by replacing many small robots with a larger one. Tread carefully as you may find that an overly large robot won’t maneuver well in your workspace!
If you can’t get to the part, you can’t pick it up. The reverse is equally true – if you can’t reach the destination, you can’t place the part. Reach is a key aspect of any robot cell design. But in addition to the direct travel distance, there must be sufficient clearance when the robot is approaching or retreating from the part, and for avoiding obstructions. The robot will not know there is an obstacle in its path. We need to plan for these obstacles and ensure the robot always has a clear path set out. Another important thing to remember is that a robot’s performance changes when at the edge of its reach, especially in comparison to when it is functioning well within its operational window.
Robot speed is paramount as automation is pushing the limits of the mechanical package of many robot systems available today. Understanding the kinematics of the various robot systems (SCARA, Delta, 6-Axis, Collaborative Robots & Flex pickers) is critical to determine which robot is right for you. A 6-Axis robot moving multiple joints at once in opposing directions to maintain product orientation will have a difficult time keeping up with a SCARA robot moving 2 joints in unison.
Picking and placing products is almost always the prime directive of any robot application, and each application requires a varying amount of precision. Being careful not to mix accuracy and precision will greatly ease the challenge of designing a robot cell. Repeatability is the spec that robot vendors will publish, but it does not refer to commanding a robot to move 100mm and seeing the robot move an accurate 100mm. Rather repeatability refers to a robot’s ability to always go to a position once it has been taught. Consider whether your needs require one or both capabilities and select your robot accordingly.
Imagine designing a robot cell with a simple pick and place motion. What path is the best to go from A to B? Luckily most robot vendors do this complicated math for us and will provide an optimized path. However, what happens when you drop a massive obstacle in the middle of the route? What if the robot is in a confined space? We may need to add an intermediate point to detour the obstacle, but where does the intermediate point go? Unfortunately, what side of the obstacle, how far away, or what configuration the robot is in will all have a major impact on cycle time so intermediate points need to be considered carefully.
Robot vendor catalogues are becoming quite extensive including differing mounting options like on tables, ceilings, walls, or even external axes. Choose a robot for your application that considers safe access, interference, available space, suitable surfaces for attaching, etc.
Nearly all robot vendors now include a safety software suite with robot purchases. This software allows the user to implement things like No-Go Zones, Speed Limits, Work Areas, I/O interaction, and even crash detection. For any project, these software tools, in combination with hardware solutions like hard stops or reinforced guarding must be assessed to ensure the robot has no way to reach an operator within or outside the guarding. Not only do we need to consider a robot in motion, but also a robot coming to a stop as this will often drive where no-go zones begin within a cell.
Advances in smart technology in recent years have given rise to collaborative robots, which can safely work in the same space as people and at the same time. If you have an application that requires both manual and automated manipulations within the same footprint, co-bots may be the best solution for you. Collaborative robots use a variety of sensors and area scanners to ensure people stay safe while moving into, through and out of the robot’s working envelope.
Environment: I did the suggested maintenance, but it’s not working
Certain applications may have environmental conditions that impair robot performance, shorten robot life, or limit the suitability of a particular robot. These could include high humidity, oxygen-free, extreme temperatures, excessively dusty, or highly controlled clean environments. As a result, it’s important to ensure the selected robot is rated for the environment. For example, sealed grippers and joints, washdown exteriors, and spindle bellows are all features robot manufacturers offer to ensure compliance with cleanroom requirements.
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