Robotic Sewing of Pre-Stitched Covers Without Surface Scratches
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Solution Overview
Problem
The manual sewing of leather covers onto steering wheels is labor-intensive and time-consuming, necessitating an automated assembly process using industrial robots.
Innovation Solution
A robot system with a robotic arm and controller that performs sewing by causing a needle to go across pre-stitches on a flexible material's surface, avoiding direct penetration and minimizing scratches, using cameras and force sensors for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a needle directly penetrates the body of the object for sewing, then the sewing operation can be completed, but scratches are caused on the flexible outer surface
Solution Approach 1:
Pre-stitches are formed on the outer surface of the flexible material before the actual sewing operation. These pre-stitches create designated pathways that guide the needle, allowing it to pass through the material without randomly scratching the surface. The pre-stitches are prepared in advance to define safe penetration zones.
Solution Approach 2:
The pre-stitches act as an intermediary structure between the needle and the flexible outer surface. Instead of the needle directly interacting with and potentially damaging the outer surface, it passes through the pre-established thread pathways, which mediate the interaction and protect the surface from scratches.
2Manufacturing precision
If manual sewing is performed stitch by stitch, then precise control over the sewing process is achieved, but the process becomes labor intensive and time-consuming
Solution Approach 1:
The manual mechanical sewing process is replaced with an automated robotic system. A robotic arm equipped with a needle holder and controlled by a controller performs the sewing operations automatically. The controller receives image data and automatically determines sewing positions and needle postures, replacing the manual dexterity and precision of human operators with automated vision-guided control.
Solution Approach 2:
An image capturing device (camera) is used to capture images of the object, and the controller processes this visual feedback to automatically determine the positions to be sewn and the tangent angles for needle orientation. This closed-loop feedback system enables the robot to adapt to the actual object geometry and perform precise sewing automatically.
3Productivity
If the needle is moved quickly across the thread section to improve productivity, then sewing speed increases, but the risk of accidental contact and scratches increases
Solution Approach 1:
The pre-stitches are formed in advance to create predetermined safe pathways for needle traversal. These pre-established guides allow the needle to move quickly across the material without risking accidental contact with the outer surface, as the pathways are already defined and constrained by the pre-stitch structure.
Solution Approach 2:
The pre-stitches serve as an intermediary structure that constrains and guides the needle's movement path. This intermediary structure enables high-speed needle traversal by providing a predetermined safe corridor, mediating between the fast-moving needle and the vulnerable outer surface to prevent scratches even at high speeds.
Data Source
AI summary
A robot and a method for sewing an object. The robot includes a robotic arm configured to hold a needle. The needle is tied with a thread. The robot includes a controller configured to move the needle, wherein the object includes a flexible outer surface and pre-stitches formed on the outer surface. Each of the pre-stitches includes a thread section including a top side and an opposite bottom side facing the outer surface. The controller is configured to perform a sewing operation by causing the needle to go across the thread section along a path defined between the bottom side of the thread section and the outer surface of the object.