Applying Lean to Factory Homebuilding

1. Applying Lean to Factory Homebuilding Dr. Mike Mullens, PE

2. Big Product with Many Large Components

3. Few Small, Fixed Workstations

4. Few Large, Fixed Workstations

5. Many Large, Moving Workstations • Labor and materials flow to product while product flows continuously on line • Little inventory because there is no space • Line used to set pace and facilitate delivery of large components

6. Activity Location Flexibility • Most operations after roof set can and do take place anywhere on line – as long as precedence's are met

7. Some Activities Can Stop the Line

8. Value Added Continuously: Often in Parallel Activities

9. Massive Work Content • Multi-operator teams perform trade-focused activities

10. Massive Work Content • Extended cycle times • Very difficult to measure work content and cycle time for any unit

11. Product Built-to-Order: Varied Product Mix with Customization

12. Product Built-to-Order: Varied Product Mix with Customization

13. Product Built-to-Order: Varied Product Mix with Customization

14. Product Built-to-Order: Varied Product Mix with Customization

15. Product Built-to-Order: Varied Product Mix with Customization

16. Product Built-to-Order: Varied Product Mix with Customization

17. Product Built-to-Order: Varied Product Mix with Customization

18. Product Built-to-Order: Varied Product Mix with Customization • High process variability

19. Product Built-to-Order: Varied Product Mix with Customization • High cycle time variability • Very difficult to predict work content and cycle time for each activity • Not easy to control line balance

20. Cycle vs. TAKT Time • Average cycle time for each activity must be less than TAKT time • Activity with largest average cycle time is bottleneck activity • If bottleneck activity is delayed, line capacity is lost – can happen even if average cycle less than TAKT time

21. Seeing the Waste (and the Opportunity) • Constant imbalance in labor & work content • Production mistakes • Design oversights • Material shortages

22. Floating Bottlenecks: Imbalance in Labor and Work Content • Upstream Queue - Floors

23. Floating Bottlenecks: Imbalance in Labor and Work Content • Downstream line starvation – drywall finishing and interior finishing

24. Floating Bottlenecks: Imbalance in Labor and Work Content • Other Impacts: • Hurry  exhaustion, frustration, rework • Overtime  higher costs, turnover • Unfinished work in yard • Lost production capacity

25. Value-Added vs. Non-Value Added Time

26. Operations Process Chart with Work Measurement

27. Non-Value Added Activities

28. Production Schedule

29. Production Cycle Times Avg. 8 weeks

30. Rework Avg. = 7% 44%

31. Rework • Labor waste • Service problems • Line variability

32. Rework

33. Lean Construction Principles • Keep activities flowing, particularly along critical path and bottleneck activities • Remove uncertainty and variability, especially along critical path and bottleneck activities

34. Lean Construction Approach • Improve quality of task assignments • Be sure preceding activities are complete, task well documented, and materials and tools are available

35. Lean Construction Problem Mitigation • Plan buffers – backlog of activities for crews (queues of work ready to be done – adding to length of critical path and thus to production line) • Surge piles – raw and WIP materials • Flexible capacity – intentionally underutilized crews or flexible use of cross-trained workers