{"id":619,"date":"2026-10-21T13:48:45","date_gmt":"2026-10-21T05:48:45","guid":{"rendered":"http:\/\/www.amanecerhealth.com\/blog\/?p=619"},"modified":"2026-10-21T13:48:45","modified_gmt":"2026-10-21T05:48:45","slug":"what-is-the-resolution-of-a-4-axis-robot-s-position-sensors-44af-d24ab4","status":"publish","type":"post","link":"http:\/\/www.amanecerhealth.com\/blog\/2026\/10\/21\/what-is-the-resolution-of-a-4-axis-robot-s-position-sensors-44af-d24ab4\/","title":{"rendered":"What is the resolution of a 4 Axis Robot’s position sensors?"},"content":{"rendered":"

If you\u2019ve ever worked with industrial robots\u2014whether on a packaging line, a metal fabrication shop, or a small-part assembly station\u2014you might have heard the term \u201cposition resolution\u201d thrown around, and if you\u2019re a 4-axis robot user or decision-maker, it\u2019s a detail that can make or break your application. As a supplier of 4-axis robots, I get questions about this all the time: \u201cWhy does resolution matter more for my small assembly tasks than my heavy material handling?\u201d or \u201cIs a higher resolution always better?\u201d Today, I\u2019m breaking down what 4-axis robot position resolution actually is, how it\u2019s measured, and what to look for when choosing the right robot for your work. 4 Axis Robot<\/a><\/p>\n

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First, let\u2019s ground this in what a 4-axis robot is. Unlike a 6-axis collaborative robot that can reach around obstacles with wrist flexibility, a 4-axis robot (sometimes called a selective compliance assembly robot arm, or SCARA, though not all 4-axis robots are SCARA\u2014more on that in a sec) has four main axes of motion: two rotary joints at the base (shoulder and elbow), a rotary joint at the wrist, and a linear joint that extends the arm up or down. That simplified design makes 4-axis robots ideal for repetitive, high-speed tasks like pick-and-place, inserting small components, or moving parts between workstations. For these tasks, the ability to place the robot\u2019s end effector (the tool at the end of the arm, like a gripper or vacuum cup) exactly where you need it is non-negotiable\u2014and that\u2019s where position resolution comes in.<\/p>\n

Position resolution, in basic terms, is the smallest increment of movement a robot\u2019s joint can detect and execute. It\u2019s not the same as accuracy, which is how close the robot\u2019s actual position is to its intended target. Resolution is about the precision of the sensor itself, regardless of external factors like wear, load, or calibration. For a 4-axis robot, every one of its four joints has its own position sensor, and each contributes to the overall position resolution of the end effector.<\/p>\n

Now, let\u2019s get specific about the sensors in a typical 4-axis robot. Most of our models use two types of position sensors: incremental rotary encoders and absolute encoders, sometimes paired with linear encoders for the vertical axis. Incremental encoders count pulses as the joint rotates, so every pulse equals a unit of movement. But if power is lost, the robot loses track of its position\u2014it has to homing cycle to reset. Absolute encoders, on the other hand, send a unique position signal every time the joint moves, even with no power, so you never have to reset. For our 4-axis robots, we use high-resolution absolute encoders because they reduce downtime for users, especially in 24\/7 production environments.<\/p>\n

How do we measure resolution for these sensors? For rotary joints, resolution is usually stated in counts per revolution (CPR) or micro-steps, converted to angular movement. For example, a rotary encoder with 10,000 CPR will give you 10,000 unique position points around a 360-degree rotation. To translate that into something practical, let\u2019s do the math: 360 degrees divided by 10,000 CPR equals 0.036 degrees per count. That\u2019s the angular resolution of the joint. For the linear axis (the fourth axis, which moves up and down), linear encoders measure resolution in micrometers (\u00b5m)\u2014for most of our 4-axis robots, that\u2019s between 1 \u00b5m and 5 \u00b5m.<\/p>\n

But here\u2019s the thing: overall end effector resolution isn\u2019t just the sum of each joint\u2019s resolution. It\u2019s the combination of the arm\u2019s length, the angle of each joint, and how small a movement each sensor can make. For example, a 0.01-degree change in the shoulder joint of a robot with a 1-meter arm moves the end effector by only about 0.17 millimeters at the end of the arm. That sounds small, but if you\u2019re placing a 2mm electronic component onto a circuit board, that difference is huge. If your sensor can\u2019t detect that 0.01-degree movement, you\u2019ll miss the mark.<\/p>\n

Now, why does this matter for 4-axis robot applications specifically? Let\u2019s split into two common use cases: high-speed pick-and-place and precision component assembly. For pick-and-place tasks\u2014say, moving a 50g bottle from a conveyor to a packaging line\u2014you might not need ultra-high resolution. A resolution of 0.1mm at the end effector is more than enough, and it lets the robot move faster, which is key for throughput. But for assembly tasks, like inserting a 1mm pin into a hole in a medical device, you need resolution of less than 0.05mm. If your sensor can\u2019t deliver that, you risk misalignment, jammed parts, or defective products.<\/p>\n

As a supplier, we design our 4-axis robots to match their resolution to their intended use. Our entry-level 4-axis models, built for general material handling, have a joint resolution of 0.005 degrees and linear resolution of 5\u00b5m\u2014more than enough for fast, heavy tasks. Our precision line, for electronics assembly or small-part insertion, has joint resolution down to 0.0005 degrees and linear resolution of 1\u00b5m. That\u2019s not just marketing fluff; we test each robot\u2019s end effector resolution in our production facility, using laser interferometers to measure actual movement at the tool tip. We\u2019ve had customers come to us after trying lower-resolution robots for their medical assembly line, only to reject 12% of parts due to misalignment\u2014switched to our precision model, and that defect rate dropped to less than 1%.<\/p>\n

A common misconception we hear is that a higher resolution sensor is always better. That\u2019s not true. For one, higher resolution sensors add cost. If you\u2019re using a 4-axis robot for palletizing, where parts are large (think 10kg boxes) and tolerance is measured in millimeters, paying for a 1\u00b5m linear sensor is unnecessary waste. Second, extremely high resolution can lead to over-compensation by the robot\u2019s controller, which can cause jerky movement or slower cycle times. We once had a customer who upgraded a general-purpose robot to a high-resolution model for pick-and-place, only to see their cycle time drop by 20% because the controller was adjusting for tiny movements that didn\u2019t affect their task. The lesson here is: match resolution to your application\u2019s tolerance requirements, not to the highest number available.<\/p>\n

Another factor that affects real-world resolution, not just the spec sheet, is backlash. Backlash is the small amount of play between gears in a joint, which means even if your sensor detects a tiny movement, the gear might not move exactly that far. That\u2019s why we use precision planetary gears in all our 4-axis robots, with backlash measured at less than 0.01 degrees. If backlash is too high, even a 0.001-degree sensor resolution won\u2019t help you get the precision you need. We also regularly service robots to adjust backlash as gears wear, which keeps the resolution consistent over the robot\u2019s lifespan.<\/p>\n

What about collaborative 4-axis robots, a category that\u2019s grown a lot in the last few years? Collaborative robots (cobots) are designed to work alongside human workers, so their sensors often include force torque sensors as well as position encoders. For our 4-axis cobots, the position resolution is still key, but the force sensor adds another layer: if the robot encounters resistance while moving, it adjusts its position without having to overshoot. That makes them safer and more precise for tasks like human-robot co-worked assembly, where two people might be placing a component and the robot is guiding the third part into place. We\u2019ve found that the position resolution of our 4-axis cobots, combined with their force sensors, lets them handle tasks that were once only possible with 6-axis robots, at a lower cost.<\/p>\n

Let\u2019s get technical for a minute, for those who want deeper context on sensor specs. When a robot manufacturer states \u201cresolution,\u201d it\u2019s important to check if that\u2019s encoder resolution, joint resolution, or end effector resolution. A lot of low-cost robot suppliers will list encoder CPR as \u201cresolution\u201d on their spec sheet, which is misleading because it doesn\u2019t account for the arm\u2019s geometry or joint play. We always list end effector resolution as well, because that\u2019s what our customers care about when they\u2019re planning their line. For example, our model X150 4-axis pick-and-place robot has an end effector resolution of \u00b10.1mm in the X and Y axes, \u00b10.05mm in the Z axis, which is perfect for high-speed handling. Our model P500 precision assembly robot has an end effector resolution of \u00b10.02mm in X\/Y, \u00b10.01mm in Z, tailored for small components.<\/p>\n

We also test resolution in real-world conditions, not just in a lab. A customer in the automotive industry used our 4-axis robots to install small fasteners onto car door panels. The robot works in a space with some vibration from nearby stamping machines, and at first they thought vibration would throw off the sensor resolution. But our encoders are sealed and have anti-vibration calibration, so the end effector resolution stayed consistent even on the production floor. That\u2019s a big difference from some entry-level robots, where high vibration can cause the sensor to skip pulses and lose position accuracy.<\/p>\n

Now, I know a lot of you are reading this because you\u2019re shopping for a 4-axis robot, and you\u2019re weighing specs against your budget. If your application is:<\/p>\n