Robot 3D Printing Trajectory Correction for Backlash and Injection Forces
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Solution Overview
Problem
3D printers using industrial robots face issues with accuracy deterioration due to backlash in the speed reduction mechanism and reaction forces during resin injection, leading to insufficient strength and rigidity in modeled objects.
Innovation Solution
A robot controller is implemented with input-side and output-side encoders to detect angle information, a deviation estimation unit to calculate actual motion trajectories, and a control command correction unit to adjust the print path, ensuring high precision by accounting for backlash and reaction forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a robot is used for 3D printing to enable arbitrary lamination direction changes, then the strength and rigidity of the modeled object can be improved, but the accuracy of the movement trajectory deteriorates due to backlash in the speed reduction mechanism and reaction forces during resin injection
Solution Approach 1:
The system employs feedback control by continuously monitoring the actual movement trajectory of the robot and comparing it with the intended trajectory. The deviation detection unit identifies discrepancies caused by backlash and reaction forces, and the trajectory correction unit adjusts subsequent movement commands to compensate for these deviations, thereby maintaining high positioning accuracy despite the use of a robot with speed reduction mechanisms
Solution Approach 2:
The system dynamically changes control parameters by adjusting the movement trajectory based on detected deviations. The trajectory correction unit modifies movement speed, position, and timing parameters in real-time to compensate for backlash effects and reaction forces, enabling the robot to maintain precise positioning accuracy while performing 3D printing operations
2Device complexity
If only an input-side encoder is provided to the motor for driving each axis of the robot, then the device complexity is reduced, but it becomes difficult to accurately measure or estimate the influence of the backlash of the speed reducer and correct the movement trajectory
Solution Approach 1:
The system introduces an intermediary calculation process that uses the output-side encoder as a mediator to indirectly measure backlash effects. By comparing the relationship between input shaft rotation (from input-side encoder) and output shaft rotation (from output-side encoder), the system can estimate backlash influence without requiring complex direct measurement devices on the output side
Solution Approach 2:
The system replaces direct mechanical measurement of backlash with an electronic/software-based calculation approach. Instead of using complex mechanical measurement devices to directly quantify backlash, the system substitutes this with computational methods that calculate backlash effects based on encoder data from both input and output sides, thereby simplifying the physical measurement system while maintaining measurement precision
Data Source
AI summary
Provided are: a 3D printer using a robot and enabling molding of an article with high strength and high accuracy; and a control apparatus for said robot. A robot used as this 3D printer has: an input-side encoder that acquires information regarding the angle of an input axis of a joint of the robot operated on the basis of a control command; and an output-side encoder that acquires information regarding the angle of an output axis. A calculation unit of this control apparatus has: a control command storage unit having stored therein a control command for motors of respective axes of the robot; a deviation estimation unit that receives results of detection by both of the input-side encoder and the output-side encoder and estimates the deviation of an actual trajectory of the robot from the control command; and a control command correction unit that corrects the control command by using the estimation result by the deviation estimation unit.