In low-volume, high-mix production, manual assembly stations have become the backbone of flexible manufacturing thanks to their core advantages of “fast change-over and high adaptability”. Unlike automated lines, they require no costly retrofits; however, human operators are prone to mistakes—wrong parts, missing screws, reversed sequences—caused by fatigue, inexperience, or lapses in attention, which often push defect rates stubbornly high. An integrated mistake-proofing solution that combines graphic guidance software, smart electric screwdrivers, and positioning torque arms preserves the flexibility of manual stations while imposing strict process control.

Guidance-Based Mistake-Proofing: Dynamic Graphical Instructions Make Every Step “Rule-Based”

• After an operator scans the QR code on the product housing or work order, the system automatically identifies the current product variant and loads its unique assembly flowchart. Unlike traditional paper SOPs, the software interface presents each step dynamically, indicating the screw specification, bit type, and hole location required. Even new employees can follow along without memorizing complex sequences.

• The next proces cannot be entered until the current step is completed and verified. When a screw specification changes, the software pops up a prompt to change the bit, and a lighted socket selector indicates the correct bit location. The green light turns on only when the right bit is removed; the prompt then disappears and the next step is unlocked. Otherwise, the software remains on the prompt screen.

Physical Mistake-Proofing: Positioning Arm + Tool Lockout Eliminate Wrong-Fastening at the Hardware Level

• The positioning arm is the heart of physical mistake-proofing. Encoders preset the coordinates of every screw hole. As the operator moves the smart electric screwdriver fixed to the arm’s end, encoders capture the real-time position and compare it with the target coordinates. If the deviation is within tolerance, the system judges “position correct” and sends an “unlock” signal to the screwdriver; the operator can press the trigger and tighten. If the deviation exceeds tolerance, the system judges “position wrong” and locks the screwdriver.

• For different product variants, there is no need to re-enter product data or re-teach hole coordinates each time. All process flows are pre-stored in the software and linked to product barcodes. At change-over, the operator simply scans the new product barcode; the encoders automatically load the new hole parameters, satisfying frequent variant switches in low-volume production.

Quality-Based Mistake-Proofing: Smart Tightening + Data Storage Make Assembly Quality “Monitorable & Traceable”

• The smart electric screwdriver, the core execution unit, integrates sensing, data transmission, and intelligent control. It monitors tightening parameters in real time; if floating threads, cam-outs, or other anomalies occur, the screwdriver stops immediately, alarms, and displays the exception in the guidance software while logging the fault data for quick troubleshooting.

• Every screw tightening generates a torque-vs-time curve that visually reveals the tightening signature for later analysis. All tightening data are synchronized in real time to the plant’s MES and bound to the product serial number. Afterwards, any product’s complete assembly record (station ID, operator ID, tightening parameters, etc.) can be retrieved instantly via its serial number to pinpoint root causes.