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Uniform Flow and Mixed-Model Scheduling

35 important questions on Uniform Flow and Mixed-Model Scheduling

What is a characteristic of an efficient production system?

that jobs and materials flow smoothly through the system, most production lead time is value-added processing, and jobs hardly ever have to wait.

Where do variation in scheduled batch size and batch intervals come from?

management's attempts to match production level with demand
&
variability inherent in the production process.

Why do demand levels vary?

- Sales fluctuations
- Promotions
- End-of-month quotas
- and so on

Which factors reduce output expectations?

- material shortages
- worker absenteeism
- Equipment problems

How can upstream stages of production-distribution chain absorb variation in scheduled production for a finished product?

Carry buffer stocks of raw and in-process material

What do buffer stocks provide?

- some degree of certainty
-During periods of slack demand they keep materials flowing and workcenters productive

What are tactics for leveling production?

- in-process buffer stocks and work backlogs are one tactic for leveling production

What are drawbacks of leveling production with buffer stocks?

- Consequences of high inventories
- Vast(=veel) quantity of inventory that accumulates plant-wide when organization relies on buffer stocks to level production

What is level the production schedule?

establish a master production shedule (MPS), where every product is produced on a regular basis and in a fixed-size batch.

Provides same benefits as WIP buffer stocks without the drawbacks

What is an uniform level production schedule?

The same quantity is made each production run for a product, and the production runs occur at regularly scheduled intervals. Batch size, batch intervals for given product are constant

What are benefits of level schedules?

- Supervisors and workers more time to focus on the work on hand
- Fewer distractions from changing workloads, and fewer problems from work expediting and slowdowns
- Workers have more time to identify areas of the process that need improvement and develop solutions and implement them

What are the requirements for leveling production schedules?

- stable production demand
- shorten setup
- match production with demand

When is keeping a buffer stock of finished products practical?

- Only if demand is somewhat continuous
- Not with sporadic demand

How can companies manage demand to minimize variation?

One way to do that is segregate customers into tiers:
- First tier: High volume , common processes (no special setups or operations)
- Second tier: Substantial volume and much process commonality
- Third tier: Low volume, sporadic orders with little process commonality

First 2 are often possible to work with to circumvent abrupt changes in demand

In peak demand periods focus should be on satisfying 1st and 2nd tier customers

Why should setup times be short?

- Lengthy changeovers consume too much of workday and leave relatively less time for actual production
Also they mandate larger batch sizes, which restrict allowable degree of production leveling

What should the frequency and batch size of production runs in leveled production correspond with?

Roughly with the average actual demand for the product.

Why should scheduled production quantity of leveling production be periodically readjusted?

- To match average demand level over specified time period
- Initial stock of inventory must be available
- Demand declines result in large stock of inventory
- Demand forecasts become more unreliable with time

Why is the forecast for aggregate demand more accurate?

- because numbers in aggregate forecast are larger than for individual forecast, and patterns for large numbers are inherently more stable than patterns for small numbers
- More stable = more predictable
- Aggregate cancels out high and low estimates, giving more accuracy

Where should focus be on in organizations that produce a variety of products (in leveling focus)?

on leveling the schedules for the highest-volume products. will substantially reduce workload variation and uncertainty for most workcenters

What are the 3 MPS alternatives of leveling multiple products?

- Producing different products subsequently (feasible when changeover times are long)
- Weekly leveled schedule
- Daily leveled schedule

How did the large Korean electronics manufacturer (Case of Park) implement level scheduling?

in steps:
1. cutting original batches in half
2. Producing to fill up shipping containers
3. by leveling daily production

What is MMP? What is the Japanese term for it?

Mixed-model production.
Japanese: Heijunka

Production of multiple kinds of products on a repetitive basis, in a mixed fashion on a single line/assembly station

Why is in pull production working with small WIP modus operandi?

Given that size of batches at final assembly somewhat dictates size of batches elsewhere in production system, then to keep WIP small everywhere, the batch size at final assembly must also be small

What are the steps to establishing a MMP schedule?

1. determine daily production requirements
2. Determine repeating sequence
- determine largest integer (heel getal) that divides evenly into the daily requirements of all products
- Calculate minimum ratio among the products by dividing daily requirement of each product by the integer divisor
3. Determine product ordering within repeating sequence (keep in mind takt time and changeover times, packaging)

What are the minimal requirements for MMP?

Same as for level production schedules

+

All familiar aspects of lean production:
-flexible workers,
-total quality assurance,
-small-lot deliveries of material

What are the advantages of MMP?

Same as advantages of level production schedules (low variation, low WIP inventory, reduced lead times, ability to meet demand with lower average production capacity)

+

- Elimination of losses due to line changeover
- Process improvement
- Balanced work loads
- Fewer losses from material shortages

What are the 3 most common production philosophies?

- Make to Stock (MTS): produces in anticipation of demand
- Assemble to order (ATO):Produce subassemblies to forecst and combine unique combinations to customer order
- Make to order (MTO): Produce products in response to actual customer orders

What is the difference between scheduling for MPS and scheduling for final assembly?

- immediacy: MPS often portrays anticipated orders or forecast demands. FAS portrays actual orders

How can MTS products be schedules?

using MMP, providing that demand is somewhat continuous

How can ATO be schedules?

It is impossible to anticipate demand and plan production for each of the combination of assmembly parts. BOM (bill of material) is used and demand of modules is estimated instead of for products. Acceptable lead time at final assembly is important criterion for choosing appropriate level of subassembly to call an end item a module

What are planning bills?

Type of modular bill used for production scheduling. Simplify production scheduling.

What is an alternative for planning bills?

Forecast demand for each option directly using time series of historical requirements for each option and taking into account anticipated trends

How can MTO products be scheduled?

Maintain backlog of orders:
marketing enters orders into backlog at receive of order
when order confirmed production starts fitting order in schedule

lead time can be shortened if:
1. marketing send to production only confirmed orders
2. production minimizes time to execute orders

How are scheduling problems minimized?

1. Simplify the BOMs
2. Use group technology and standard parts
3. Make only whats needed
4. produce in lot sizes that are small and easy to count
5. Use simple visual control systems
6. Do not overload the shop or particular operations
7. Use das or hours for planning lead times

What is a hybrid system?

combination ATO and MTO production activities

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The question on the page originate from the summary of the following study material:

Lean Production for Competitive Advantage A Comprehensive Guide to Lean Methodologies and Management Practices | 9781439894163 | John Nicholas

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