A brief guide to the design, manufacture and commissioning of assembly lines
Design assembly lines by first defining product BOM, process KCs and required takt. Simulate line balance and ergonomics to ≥87 % efficiency, then create a clash-free 3D layout with digital twin. Manufacture modules under FAT criteria: Cpk ≥1.33, ≤1 stop/8 h. Commission in five steps—hardware, no-load, load, line no-load, line load—until OEE ≥85 %. Use virtual PLC to pre-verify logic and shorten on-site work. Hand over full documentation, spare-parts list and training videos; support 30-day ramp-up to 90 % output and <0.3 % scrap. Continuously collect RFID takt data, rebalance quarterly and update a fault library to keep OEE high and meet IATF/ISO audits.
Detailed Instructions and Guidelines for the Design, Manufacturing and Commissioning of Assembly Lines
I. Design Phase – Do the Right Thing First, Then Do It Fast
- Three-Dimensional Input: Product-Process-Volume
1.1 Explode the product BOM down to the “Minimum Assembly Unit” (MAU) and specify for every MAU: dimensions, mass, fit tolerance, ESD/cleanliness requirements.
1.2 Process routing card: use a three-level tree “operation-step-station”. For every step give:
– Takt time (s), assembly datum, Key Characteristics (KCs), failure modes (PFMEA).
1.3 Volume model: with 90 % equipment availability and 85 % first-pass yield, calculate the Required Takt = available time / demand quantity. - Line Strategy Selection
2.1 Volume ≥ 200 k pcs/month, variants ≤ 3: high-speed in-line (cam index + servo dial).
2.2 Volume 20 k–200 k, variants 3–20: flexible segmented line (dual-speed chain + AGV + interchangeable jig).
2.3 Volume ≤ 20 k, variants > 20: island cells + collaborative robots (mobile cobot). - Line Balancing & Simulation
3.1 Use Value Stream Mapping (VSM); target balance rate ≥ 87 %.
3.2 Build a discrete-event model in Tecnomatix Plant Simulation:
– Input real failure rates (MTBF/MTTR), change-over time (SMED), run 30 virtual days;
– Output: bottleneck stations, buffer length, AGV quantity.
3.3 Ergonomic simulation (Delmia): working height 700–1100 mm, max push force 15 N, 15° viewing angle without obstruction. - 3D Layout & Digital Twin
4.1 NX Line Designer for 3D factory layout; reuse Teamcenter standard parts library to cut modelling time by 30 %.
4.2 Scan existing building with NavVis VLX; compare point cloud to model, deviation ≤ 5 mm, detect clashes early.
4.3 Generate PLC I/O list, pneumatic diagram, power load table (kW·m²) for downstream procurement and tender.
II. Manufacturing Phase – Turn Drawings into Equipment
- Manufacturing Split & Quality Control
1.1 Special-purpose machines: machine critical dimensions (locating pins, clamping surfaces) in one setup, GD&T ≤ 0.02 mm.
1.2 Steel frames: Q235B square tubes, stress-relief after welding, blast to Sa2.5, epoxy-zinc primer 80 µm.
1.3 Purchased parts policy: servo motors, gearboxes, linear guides must show factory report within 6 months; key sensors (Keyence, Sick) need original COO to avoid counterfeits. - Pre-Assembly & FAT (Factory Acceptance Test)
2.1 Build a “mini line” (≥ 3 consecutive stations) in supplier’s workshop with aluminium profiles, run 8 h continuous production.
2.2 FAT pass criteria:
– ≤ 1 unplanned stop / 8 h;
– Assembly accuracy Cpk ≥ 1.33;
– Change-over ≤ 10 min (one operator).
2.3 Take high-resolution photos (≥ 20 MP) of full view and details before shipment to create a birth certificate for future maintenance. - Packing & Transport
3.1 Precision parts (robots, vision) wrapped with VCI film + anti-shock pallet, 50 mm EPE cushion.
3.2 Control cabinet vacuum-bagged separately with desiccant; humidity indicator ≤ 30 %RH on arrival.
III. Commissioning Phase – From Single Machine to Full Line
- Five-Step Commissioning Flow
① Hardware check → ② No-load single → ③ Load single → ④ No-load line → ⑤ Load line + OEE acceptance. 1.1 Hardware Check
– Level: 0.02 mm/m spirit level, record every 2 m on long conveyor;
– Earthing: TN-S system, PE ≤ 4 Ω, individual machine ≤ 10 Ω;
– Insulation: 500 V DC, ≥ 10 MΩ. 1.2 No-load Single
– Servo: speed-loop bandwidth ≥ 400 Hz, position following error ≤ 1 pulse;
– Sensors: repeatability ≤ ±0.1 mm, response ≤ 2 ms. 1.3 Load Single
– Run 2 h with 1.2 × max inertia, motor temperature rise ≤ 70 K;
– Torque tool: dynamic calibration using SK sensor at 10 kHz, Cmk ≥ 1.67. 1.4 No-load Line
– Trigger “virtual parts” flow from PLC, verify all release conditions, stopper cylinders, RFID read/write;
– Line takt deviation ≤ ±3 %, buffers must not run “empty” or “full” > 5 s. 1.5 Load Line + OEE Acceptance
– Run 3 shifts (≥ 22 h) continuously; target: availability ≥ 90 %, performance ≥ 95 %, quality ≥ 99 %, overall OEE ≥ 85 %.
– Collect 50 assembly data for SPC, critical Cpk ≥ 1.33. - Virtual Commissioning (SiL + MiL)
2.1 Use PLCSIM Advanced in Siemens TIA Portal + MATLAB/Simulink mechanics model to verify 80 % of logic offline, cutting on-site time by 30 %.
2.2 Real-time OPC UA keeps digital twin synchronised with real line, allowing “offline program change, online switch in seconds”. - Fault Diagnosis & Optimisation
3.1 Build “fault tree + countermeasure library”:
– Any stop > 2 min must be entered in CMMS with VDMA 66413 code;
– Monthly Pareto of TOP10 faults, define recurrence prevention.
3.2 Parameter self-learning:
– For vision positioning, force-controlled assembly, etc., run few-shot transfer learning with Python + TensorFlow, cut tuning time from 2 h to 15 min.
IV. Hand-over & Continuous Improvement
- Documentation Package (site sign-off required)
– As-built 3D models (STEP + JT);
– Electrical schematics, pneumatic diagram, BOM with order numbers;
– Source code + backup (Git version tagged);
– Spare-parts list (with recommended stock levels);
– Training videos (MP4, ≤ 10 min/module, bilingual subtitles). - Ramp-up Support
Engineer on-site for 30 days after hand-over, target:
– Daily output from 70 % to 90 %;
– Scrap rate < 0.3 %;
– Operators able to perform change-over independently. - Continuous Improvement
Quarterly line-balance re-optimisation:
– RFID collects real takt, auto-update VSM;
– If any station utilisation < 75 %, split or merge operations to keep balance rate ≥ 90 %.
Quick Checklist (print and post on site)
□ Design input: BOM, KC list, Takt time
□ Simulation: VSM, Plant Simulation, Delmia ergonomics
□ Layout: 3D point-cloud vs model, I/O table, power load
□ Manufacturing: FAT passed, Cpk ≥ 1.33
□ Commissioning: 5-step flow, virtual commissioning, OEE ≥ 85 %
□ Hand-over: 3D model + source code + training videos
□ Improvement: RFID takt, quarterly line balance, fault library
Following the above steps reduces project risk by 40 %, cuts ramp-up time by 25 %, and satisfies IATF 16949 / ISO 9001 audits. Wish your project a smooth launch!