The Operator Who Made Mistakes (No Aids)
We built a manual assembly station (an operator assembles the part by hand). The station was a table (a bench). On the floor, the operator made mistakes (he forgot a screw, he put the part in wrong). The problem: no aids (the operator had to remember the steps). The operator was human (he forgot). We added aids: a picture (the assembly steps, on a board), a parts bin (each part in a labeled bin, article 170), and a poka-yoke (article 200, a sensor that checks the part is right). The mistakes dropped (the operator followed the picture, the bins guided him, the poka-yoke caught the errors). The mistake was not adding aids (the operator was expected to remember).
Manual assembly station aids the operator (reduce errors). This article covers the design.
The Operator’s Aids
A manual station has an operator (human). The human makes errors (forgets, mixes parts). The aids reduce the errors:
- The picture (work instructions): The assembly steps (with photos) on a board. The operator follows the picture (not memory).
- The parts bins: Each part in a labeled bin (article 170). The operator picks from the bin (the right part, labeled).
- The poka-yoke (article 200): A sensor that checks (the part is right, the screw is in).
- The tools: The right tools (a torque screwdriver, article 34). The operator uses the right tool.
Step 1: The Picture (Work Instructions)
The picture (a board, above the station) shows the assembly steps (with photos). Step 1: put the base. Step 2: add the screw. The operator follows the picture. Don’t rely on the operator’s memory (he forgets). The picture is clear (photos, not text).
The manual station rule: Aid the operator (picture, bins, poka-yoke). The operator who made mistakes had no aids (remember the steps). Add a picture (the steps). Label the bins (article 170). Add a poka-yoke (article 200). The mistakes drop.
Step 2: The Parts Bins (Article 170)
Each part is in a labeled bin (article 170). The bin has the part’s name (and a photo). The operator picks the part (from the bin). Don’t pile the parts (mixed, hard to pick). Use separate bins (labeled).
Step 3: The Ergonomics (Article 163)
The station is ergonomic (article 163). The work height (the part is at the operator’s elbow). The tools are within reach. The operator doesn’t bend (or stretch). A fatigue-free station (article 163).
Step 4: The Quality Check (Poka-Yoke, Article 200)
A sensor (a poka-yoke, article 200) checks the assembly (e.g., a sensor that detects the screw is in). If the operator forgot the screw, the sensor catches it (the station won’t release the part). The errors are caught (not shipped).
| Aid | Purpose |
|---|---|
| Picture (steps) | Follow (not memory) |
| Labeled bins | Right part |
| Ergonomic height | No fatigue (article 163) |
| Poka-yoke (sensor) | Check (article 200) |
A Manual Station Checklist
- Is there a picture? (Steps?)
- Are the bins labeled? (Article 170?)
- Is the height ergonomic? (Article 163?)
- Are the tools right? (Torque? Article 34?)
- Is there a poka-yoke? (Article 200?)
- Does it catch the errors? (Test?)
- Is the lighting good? (Article 193?)
- Is the operator trained? (Practice?)
- Is the cycle OK? (Takt? Article 130?)
- Is the quality consistent? (Audit?)
The Bottom Line
Manual assembly station aids the operator. The operator who made mistakes had no aids. Add a picture, labeled bins, ergonomic height, and poka-yoke (article 200). The station that didn’t make mistakes wasn’t the best operator — it had aids.
