If you’ve ever worked with industrial robots—whether on a packaging line, a metal fabrication shop, or a small-part assembly station—you might have heard the term “position resolution” thrown around, and if you’re a 4-axis robot user or decision-maker, it’s a detail that can make or break your application. As a supplier of 4-axis robots, I get questions about this all the time: “Why does resolution matter more for my small assembly tasks than my heavy material handling?” or “Is a higher resolution always better?” Today, I’m breaking down what 4-axis robot position resolution actually is, how it’s measured, and what to look for when choosing the right robot for your work. 4 Axis Robot
First, let’s 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—more 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’s end effector (the tool at the end of the arm, like a gripper or vacuum cup) exactly where you need it is non-negotiable—and that’s where position resolution comes in.
Position resolution, in basic terms, is the smallest increment of movement a robot’s joint can detect and execute. It’s not the same as accuracy, which is how close the robot’s 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.
Now, let’s 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—it 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.
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’s do the math: 360 degrees divided by 10,000 CPR equals 0.036 degrees per count. That’s the angular resolution of the joint. For the linear axis (the fourth axis, which moves up and down), linear encoders measure resolution in micrometers (µm)—for most of our 4-axis robots, that’s between 1 µm and 5 µm.
But here’s the thing: overall end effector resolution isn’t just the sum of each joint’s resolution. It’s the combination of the arm’s 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’re placing a 2mm electronic component onto a circuit board, that difference is huge. If your sensor can’t detect that 0.01-degree movement, you’ll miss the mark.
Now, why does this matter for 4-axis robot applications specifically? Let’s split into two common use cases: high-speed pick-and-place and precision component assembly. For pick-and-place tasks—say, moving a 50g bottle from a conveyor to a packaging line—you 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’t deliver that, you risk misalignment, jammed parts, or defective products.
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 5µm—more 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 1µm. That’s not just marketing fluff; we test each robot’s end effector resolution in our production facility, using laser interferometers to measure actual movement at the tool tip. We’ve had customers come to us after trying lower-resolution robots for their medical assembly line, only to reject 12% of parts due to misalignment—switched to our precision model, and that defect rate dropped to less than 1%.
A common misconception we hear is that a higher resolution sensor is always better. That’s not true. For one, higher resolution sensors add cost. If you’re using a 4-axis robot for palletizing, where parts are large (think 10kg boxes) and tolerance is measured in millimeters, paying for a 1µm linear sensor is unnecessary waste. Second, extremely high resolution can lead to over-compensation by the robot’s 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’t affect their task. The lesson here is: match resolution to your application’s tolerance requirements, not to the highest number available.
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’s 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’t 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’s lifespan.
What about collaborative 4-axis robots, a category that’s 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’ve 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.
Let’s get technical for a minute, for those who want deeper context on sensor specs. When a robot manufacturer states “resolution,” it’s important to check if that’s encoder resolution, joint resolution, or end effector resolution. A lot of low-cost robot suppliers will list encoder CPR as “resolution” on their spec sheet, which is misleading because it doesn’t account for the arm’s geometry or joint play. We always list end effector resolution as well, because that’s what our customers care about when they’re planning their line. For example, our model X150 4-axis pick-and-place robot has an end effector resolution of ±0.1mm in the X and Y axes, ±0.05mm in the Z axis, which is perfect for high-speed handling. Our model P500 precision assembly robot has an end effector resolution of ±0.02mm in X/Y, ±0.01mm in Z, tailored for small components.
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’s a big difference from some entry-level robots, where high vibration can cause the sensor to skip pulses and lose position accuracy.
Now, I know a lot of you are reading this because you’re shopping for a 4-axis robot, and you’re weighing specs against your budget. If your application is:
- Heavy part palletizing: Look for end effector resolution of at least 0.5mm, no need for ultra-high precision.
- Pick-and-place of small parts (1-10mm): Aim for 0.1mm end effector resolution.
- Precision assembly (medical devices, electronics): Need 0.05mm or less end effector resolution.
As a supplier, we don’t push the highest-resolution robot for every job. We take the time to ask customers about their part sizes, cycle times, tolerance requirements, and production environment, then recommend the robot that gives them the right resolution without overspending. That’s why so many of our customers come back when they expand their lines—they know we’ll give them an honest recommendation, not just upsell a higher spec.
I should also note that resolution isn’t a static number. Over time, as the robot’s gears wear, the encoder may need calibration to maintain its resolution. We include annual calibration as part of our service plans, and we have field technicians who can adjust the sensors on-site to keep the robot’s position accuracy and resolution consistent. Unlike some lower-cost suppliers who only offer remote support, our technicians work on your production floor, so downtime for calibration is minimal.
If you’re still unsure about what resolution you need for your application, or if you’ve had issues with misalignment or low throughput from a robot with the wrong sensor resolution, I encourage you to reach out to our team. We’ll walk you through your use case, share data from our in-house testing, and even connect you with current customers in your industry who are using our 4-axis robots for similar tasks. We don’t just sell robots—we partner with you to make sure your automation works for your needs.
4 Axis Servo Manipulator References
- Craig, J. J. (2005). Introduction to Robotics: Mechanics and Control. Pearson Education.
- Robotic Industries Association (RIA). (2022). Industrial Robot Terminology & Performance Guidelines. RIA Publications.
- Sinha, S. K. (2017). Industrial Sensors and Control Systems. CRC Press.
Borunte Robot Co., Ltd.
Borunte Robot Co., Ltd. is one of the leading 4 axis robot manufacturers and suppliers in China. We warmly welcome you to wholesale or buy discount 4 axis robot for sale here from our factory. All customized products used in different applications are with high quality and low price.
Address: NO.93, Shafu Road, Shabu Village, Dalang Town, Dongguan City, Guangdong Province, China
E-mail: borunterobotcoltd@gmail.com
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