| Lowering manufacturing cycle times is a continuous | | | | reduces the time that it needs to pause. If the robot |
| challenge. Reducing machine cycle time helps to | | | | position is not critical for the timing of an output, turn |
| increase production throughput and profits. Cycle time | | | | on the output after a continuous move. The output |
| depends on many factors including conveyors, | | | | will turn on during the cornering to get to the next |
| process times, vision, clamps, tooling, operators, and | | | | point. If the output is turned on after a fine move, |
| robots. This paper presents techniques to reduce | | | | the robot will stop and then turn on the output. |
| robot cycle time. | | | | 7. Material handling applications have several different |
| 1. Cells with multiple robots must be sequenced | | | | timers used to control clamps opening and closing, |
| properly to optimize cycle time. Restructuring | | | | and part present checking. Equipment delay timers |
| interference zones reduce the amount of time the | | | | can be reduced or eliminated if clamp opened and |
| robots need to wait for each other. Robot A | | | | clamp closed switches are used to verify clamp |
| startsthe cycle inside the interference zone while | | | | operation. For special applications, custom subroutines |
| Robot B starts outside the interference zone. Then | | | | can be created to improve the speed of material |
| Robot A moves clear of the zone and Robot B | | | | handling operations. |
| finishes inside the zone. When sequenced correctly | | | | 8. Different Spot Welding timers can be adjusted to |
| both robots minimize interference zone wait times. | | | | improve cycle time. Increase gun close anticipation |
| Multiple overlapping zones can also be used to reduce | | | | time to close the gun before the robot reaches the |
| robot wait times even more. | | | | weld point instead of letting the robot stop at the |
| 2. Rounding corners during the robot's movement will | | | | point and then closing the gun. Reduce the gun open |
| lower cycle time. Rounding corners means that while | | | | delay to enable the robot to begin the next move |
| moving the robot does not reach the exact | | | | before the gun is fully open. By adjusting these |
| programmed point, but starts to move to the next | | | | timers, the gun can be opening or closing while the |
| point a certain distance before the programmed | | | | robot is in motion. When using a KUKA KRC, the |
| point. This method reduces the robot deceleration | | | | settling times for fine points can be changed using |
| between points and creates a rounded path. By | | | | system variables. With lower settling times, the robot |
| reducing the deceleration times, the robot's overall | | | | will move faster between fine points. |
| path will be faster and cycle time lower. Use higher | | | | 9. Several techniques can improve servo gun |
| cornering values when the robot is moving between | | | | operation. While moving between points, keep the |
| fixtures and use lower values when the robot is | | | | gun opening to a minimum to clear the part being |
| moving within the fixture. With ABB and Nachi robots, | | | | welded. Keeping the servo gun opening almost closed |
| the amount of rounding, in millimeters, can be | | | | will reduce the amount of time used to close the gun |
| adjusted for each accuracy level. | | | | at each weld spot. Use continuous moves for weld |
| 3. Use the correct speed for the distance between | | | | spots to reduce motion pauses during the weld |
| points. Every time the robot moves from point to | | | | motions. If the weld spots are fine points, the robot |
| point, the robot accelerates to the programmed | | | | will hesitate at the approach and departure points. |
| speed and then decelerates when the robot | | | | Remove squeeze times from the weld controller. For |
| approaches the end point. If the programmed speed | | | | a pneumatic gun, squeeze time is added to ensure |
| is too high, the robot will accelerate, but not reach | | | | the weld pressure is met. The servo gun does not |
| the programmed speed, and will then rapidly | | | | need the squeeze time delay and will close until |
| decelerate. The robot path is more efficient if the | | | | correct pressure is achieved. 10. Set the robot |
| robot can accelerate, move along the path at the | | | | payload properly to improve overall robot movement |
| programmed speed, and then decelerate smoothly. A | | | | and efficiency. Ensure the payload settings are |
| Motoman robot's acceleration and deceleration for | | | | correct including mass, center of gravity, moments of |
| each move can be adjusted in the detail edit screen. | | | | inertia, and proper armload. The proper payload will |
| By adjusted acceleration and deceleration values, | | | | allow the robot to accelerate and decelerate more |
| individual moves can be made more efficient. | | | | precisely, improving cycle time and accuracy. Cycle |
| 4. On most robot controllers, Joint motions work | | | | time will always be a concern for system builders and |
| something like this:a. The robot's motion planning | | | | production support. The items listed here will help |
| software examines the joint angles at the start and | | | | improve cycle time and overall system efficiency. By |
| end of the move, and then determines the angle | | | | using these various techniques, cycle time can be |
| each motor will need to rotate.b. The motion planner | | | | reduced and production totals increased. |
| software uses each motor's acceleration and | | | | Founded in 1989, Applied Manufacturing Technologies, |
| maximum speed to determine which motor will take | | | | Inc. (AMT) is a leading supplier of complete consulting |
| the longest time to perform its move.c. The motion | | | | and engineering services, offering single-source |
| planner software scales back the speed of all other | | | | engineering solutions to the automation and |
| motors so all axes finish the move simultaneously. | | | | manufacturing industries. The company's service |
| Based on this, spreading large joint angle changes | | | | offerings range from design and simulation to |
| over multiple moves increases path speed | | | | programming, installation and support of industrial |
| byimproving the efficiency of the other axes. For | | | | automation solutions. |
| example, spreading a large wrist movement | | | | Applied Manufacturing Technologieswebsite: phone: |
| overseveral moves is more efficient than if the | | | | 248-409-2100 |
| whole wrist movement was completed in one move. | | | | Report this article |
| 5. Use the signals âopen clamps early' and | | | | This article is free for republishing |
| ârequest tool reposition' correctly to reduce | | | | Source: |
| the process time. Requesting a clamp reposition while | | | | Republish this article |
| the robot is moving and before it is required allows | | | | Ask a Question About this Article |
| the clamp to open/close before the robot reaches it. | | | | >> Facebook fan pages |
| This reduces the time the robot needs to stop and | | | | >> Did Jesus use the word "sin" only three |
| wait for the clamp reposition. âOpen clamps | | | | times? |
| early' signal allows the tooling clamps to open as soon | | | | >> If stress causes weight gain, can relaxation |
| as the robot is clear of the opening clamps. This will | | | | cause weight loss? |
| allow the clamps to open while the robot is moving | | | | >> How do you create a fan page on |
| instead of waiting until the robot reaches home. | | | | Facebook? Do I ... |
| 6. Turning on outputs while the robot is moving | | | | |