Before the widespread use of computers the location of warehouses, stores, franchises were often settled by using a ‘string map’. Pins were stuck in the map at customer’s locations, and string, usually thread or fishing line, looped over them, the weight on the end of each line being proportional to that customer’s deliveries. The ends of the string were knotted together. Where the knot settled was the center of pull (not gravity).
Here’s another example for “sizing the wheel” for a mixed model
fixed repeating schedule.
Given:
- Changeover Time = 100 minutes
- Available Production Time = 2 shifts * 7 hrs/shift * 60 min/hr = 840 min/day
and
| Product |
Daily Demand (pcs) |
Cycle Time (min.) |
Load (min.) |
| A |
80 |
5 |
400 |
| B |
40 |
4 |
160 |
| C |
20 |
4 |
80 |
| D |
10 |
6 |
60 |
|
|
|
700 |
Now some math:
- Total Load = 700 min.
- Time Available for Changeovers = 840 min/day – 700 min/day = 140 min/day
- Changeover Time for group = 100 min * 4 products = 400 min/family
- Changeovers per day = 140 min/day / 400 min/family = 0.35 group/day or a Replenishment Time of 2.85 days/family
So the fixed repeating wheel will turn once in 2.86 days. Production run sizes as follows:
| Product |
Daily Demand * Replen Time |
Cycle Time (min) |
Load (min) |
| A |
229 |
5 |
1145 |
| B |
114 |
4 |
456 |
| C |
57 |
4 |
228 |
| D |
29 |
6 |
174 |
|
|
|
2003 |
Plus 4 changeovers of 100 min each = 2403 min = 2.86 days.
When it comes time to run product A, run 2.86 days worth. Got it?
Would be nice if we could run just one piece. But until we can make the 100 minute changeover go away we’re stuck running a batch of some size.
Table top simulations are always a great training aid, and a debugging tool too. Despite careful instruction and process design reviews misconceptions can be hard to uncover until during implementation. So I always make it a habit to run a role playing simulation with the team. Here take a look.
Many business leaders fail to see the opportunities that an economic downturn provides. To take advantage of opportunities you first need to make a rapid assessment of your vulnerabilities and then move quickly to minimize them. Advantage can be gained by using process improvement tools to increase profitability and competitiveness:
- Drive out waste through Lean Sigma operations
Tools: value stream mapping, line balancing, kaizen to reduce direct and overhead labor
- Customer Collaboration
Tools: customer segmentation, goal alignment, cycle time reduction, product line rationalization
- Supplier Optimization
Tools: supplier & material consolidation, lead time reduction, product design-to-cost
- Accelerate cash flow and aggressively manage working capital
Tools: inventory reduction, excess/slow moving/obsolete inventory analysis, safety stock tuning, cycle time reduction to reduce WIP, receivables and payables management
- Increase Capacity
Tools: overall equipment effectiveness, theory of constraints, quick changeover, product family turnover analysis
- Product Redesign
Tools: component substitution, design for six sigma, design for manufacturability, value engineering
Cut the package size, customers may want less right now.
