In key stations such as automotive tire assembly, chassis marriage, and gearbox assembly, multi-spindle synchronous tightening has become a mainstream process. Multiple tightening spindles work in coordination to ensure the synchronicity and uniform force distribution of a group of bolts during assembly. However, in actual production, an abnormality in tightening a single bolt can easily trigger a chain reaction of reworking the entire group and halting the production line. Efficiency losses and quality risks coexist, becoming a major obstacle restricting the improvement of vehicle component assembly capacity.

Danikor's Synchronous Online Rework strategy breaks away from traditional rework approaches by integrating bolt abnormality repair into the normal production process. It completes fault repair without taking the workpiece off the line, without interrupting production line operation, and without disturbing the tightening status of other bolts, providing a reliable quality solution for various multi-spindle synchronous tightening conditions.

I. Real-World Pain Points of Traditional Multi-Spindle Tightening Rework Modes

At multi-spindle synchronous tightening stations, traditional rework methods have obvious shortcomings in terms of efficiency, quality, and cost.

First is the takt time loss caused by production line stoppage. When a single tightening spindle outputs unqualified torque, the traditional approach requires moving the workpiece off the main line into a rework area, putting the entire station into a waiting state. Taking the tire tightening process as an example, among several bolts on a wheel, even if only one bolt has an abnormal tightening result, all bolts must be uniformly loosened and then re-tightened. Rework consumes a large amount of production time, directly causing station downtime, leading to material accumulation in upstream and downstream processes, and significantly affecting overall capacity.

Second is the additional quality risk caused by expanded rework scope. Under the mode of reworking the entire group of bolts, bolts that already meet standards must also undergo the loosening and re-tightening process again. Repeated application of force changes the state of the thread contact surface, making it prone to thread wear and preload deviation. Bolts that were originally qualified may instead develop new assembly defects, making it difficult to maintain assembly consistency of the component bolt group.

Finally is the high investment in rework supporting resources and limited adaptability. Offline rework requires separately configuring fixtures, tightening tools, and operators. Rework processes for different component stations cannot be universally applied. When facing changeover production of various specifications of workpieces such as chassis, gearboxes, and battery packs, traditional rework solutions are difficult to adapt flexibly, which instead limits the flexible production capacity of the line.

II. Synchronous Online Rework Strategy: Completing Abnormality Repair During Production Operation

In response to the various shortcomings of traditional rework modes, Danikor's Synchronous Online Rework strategy establishes three core principles: do not interrupt production line takt time, do not expand the rework scope, and do not interfere with other normal tightening spindles. This makes abnormality handling a component of the production process rather than a cause of production interruption.

This solution relies on a synchronous node coordination mechanism to achieve a logical closed loop. Under traditional modes, once a fault occurs, the production line must be stopped to address the problem. The Synchronous Online Rework strategy, however, performs differentiated scheduling for different tightening spindles. During station operation, the system continuously collects torque data from each spindle. Once a tightening abnormality is identified, it instructs the faulty spindle to execute a reverse-loosening rework action. Other spindles that have completed qualified tightening do not directly jump to the next process but enter a standby waiting state. After the abnormal spindle completes repair and all indicators return to the qualified range, all tightening spindles converge at a preset synchronous node and jointly execute subsequent tightening actions.

Taking the automotive tire tightening condition as an example, if a single tightening spindle has substandard torque, the system immediately starts the rework program for that spindle, while other spindles maintain their current state and wait. After the fault is repaired, all spindles synchronously advance the operation. The workpiece remains at the main line station throughout, without needing disassembly or transfer, and the production rhythm of the line is not interrupted by the abnormal bolt. The entire rework process only targets the problematic bolt. Other bolts that are already qualified do not participate in secondary operations, avoiding hidden risks such as thread damage caused by repeated work. Normal tightening spindles only wait briefly and do not alter the tightening state already formed, so tool wear and workpiece wear are also controlled.

III. Achieving the Transition from Control Synchronization to Quality Synchronization

Synchronous Online Rework not only achieves coordination at the multi-spindle action level but also pursues synchronization and unification of the final assembly quality results. The system records the complete torque change process of each tightening spindle throughout, fully capturing data across the entire cycle of torque rise, peak output, and torque holding, precisely locating the tightening status of each bolt.

The operation curve of normal tightening spindles remains stable and does not undergo additional force changes due to waiting. Rework operations do not affect qualified workpieces. This entire logic incorporates abnormality repair into the tightening quality closed loop. Rework is no longer a post-event remedial measure but a built-in quality assurance step in the assembly process. The assembly data of each bolt can be fully retained for subsequent quality traceability.

IV. Broad Adaptability to Multiple Types of Multi-Spindle Tightening Assembly Scenarios

Danikor's Synchronous Online Rework strategy is not limited to the automotive tire tightening process. It can adapt to numerous multi-bolt synchronous assembly conditions. It can be applied to automotive chassis marriage stations, gearbox assembly, multi-point fastening of new energy battery packs, and various assembly multi-spindle tightening production lines.

This strategy can be used in conjunction with Danikor's TQC series tightening spindles and tightening controllers. The entire capability is integrated into the existing tightening control system, without the need to build additional independent rework stations. When facing mixed-line production of multiple product varieties, it can flexibly complete changeovers following the production line, reducing additional tooling investment, and balancing production efficiency, assembly quality, and production line flexibility.