6.6 Control Mechanisms in Operative Management
6.6.4 Decreasing the Material Waste per Activity
Therefore three possible strategies result to minimize the material quantity per activity or per time unit:
I. Reducing the sensitivity to waste amplifiers (minimize β) II. Controlling the values of waste amplifiers (minimize X)
III. Reduce the technology and product variant specific constant (minimize ε) Strategy III is very limited within the constraints of an existing production system without changes to product structure and therefore is not pursued further. The potential for lowering the activity-specific consumption of operating materials is discussed as a delinking strategy in Section 6.6.3.
6.6.4.1 Potential for Desensitizing the System to Waste Amplifiers
Lack of successive product variant commonality: to desensitize the manufacturing process to the lingering effects of the last product variant different measures can be taken based on the type of discommonality between
the product variants. For example if residues left in the machine from the predecessor variant can contaminate the new product, technical measures may be taken to lessen the buildup of residues in a machine, including equipment coatings. Alternatively, some machines may be cleaned without using cleaning materials, though this generally requires large quantities of hot water or manual scrubbing, potentially adding to the setup duration.
For product variants requiring different process settings, e.g. temperature, accelerating the process stabilization rate after a setup generally requires equipment modification (e.g. an additional heat source) and machining reprogramming investments. Therefore, it is considered unfeasible for an operative decision maker.
If the product sequence sensitivity is related to employee confusion, Poka-yoke mechanisms in the workstation can reduce the likelihood of employee mix-ups. Examples include bin covers to reduce the risk of employees grasping incorrect screws. Further poka-yoke measures can be taken in product design to prevent errors in the workflow, though outside the scope of operative decision-making. Employee training and sensitization to the product differences can also decrease incorrect builds.
Unsuitability of machine/product variant combination: based on the relative definition of this waste amplifier, i.e. if unsuitability has no effect, the unsuitability is non-existent. Therefore for unsuitability, only reducing the magnitude of unsuitability, controlling its value, remedies the increased material waste rates.
Advanced equipment age: preventative maintenance and repairs can effectively improve the condition of older equipment, and therefore lessen the system’s sensitivity to the machine’s age, without changing the make year of equipment.
Large lot size/long production runs: technical measures, including process monitoring, can be taken to ensure the consistency of machine parameters over
a production run, making adjustments when needed. Process monitoring could be executed in an automated system or manually, allowing larger lots to be run without increased waste.
Low employee qualification: increased process automation can lessen the sensitivity of the system to less qualified employees. However, process automation requires investment and is not within the authority of an operative decision maker.
Out-of-range ambient conditions: Physically enclosing processes shields the effects of out-of-range ambient conditions. Enclosures, however, require capital investment and therefore exceed the authority of an operative decision maker.
Too long or too short holding times: material properties are subject to change over time. In some cases this is desired, in others less so. If material waste through inventory deterioration is modelled at the point of discovery, the likelihood of its can be modelled as a function of holding time.
Overall desensitization of the factory system to the identified waste amplifiers without capital investment is limited, as shown in Table 19 (see evaluation criteria in Section 6.6). Nevertheless, operative decision makers can utilize organizational instruments.
Table 19: Waste minimization through desensitizing the system to waste amplifiers
Tactics Addressed activity and linked
waste forms
Scope of material savings Feasibility within operative decision- making Desensitizing to lack of successive
product variant commonality:
Residue prevention
- barrier mechanisms (coatings) - manual / material-waste free cleaning
Workpiece or batch processing:
defects
- Startups: startup losses - Cleaning: cleaners
◐ ◔
Desensitizing to lack of successive product variant commonality:
Accelerating process stabilization - technical measures
Workpiece or batch processing:
defects
- Startups: startup losses - Cleaning: cleaners
◐ ◔
Desensitizing to lack of successive product variant commonality:
Preventing employee confusion - poka-yoke mechanisms - training
Workpiece or batch processing:
defects
- Startups: startup losses - Cleaning: cleaners
◐ ◕
Desensitizing to advanced equipment age:
Preventative maintenance activities
Workpiece or batch processing:
defects
- Startups: startup losses - Cleaning: cleaners
◐ ◕
Desensitizing to large lot sizes:
Process monitoring and parameter adjustment
Workpiece or batch processing:
defects
- Startups: startup losses - Cleaning: cleaners
◐ ◐
Desensitizing to low employee qualification:
Increase process automation
Workpiece or batch processing:
defects
- Startups: startup losses - Cleaning: cleaners - Transport: transport loss - Material replenishment: trim loss
◐ ◔
Desensitizing to out-of-range ambient conditions:
Enclose processes
Workpiece or batch processing:
defects
- Startups: startup losses - Cleaning: cleaners - Transport: transport loss
◐ ◔
Total score ◐ ◐
6.6.4.2 Potential for Controlling Waste Amplifiers
Lack of product variant commonality: To increase product variant commonality of any two successive product variants, there are two approaches which can be taken: either make every product variant physically more
similar, in both product design and process specifications or alternatively only run product variants successively that possess a minimum level of commonality.
Products can be made more similar by changing the color, material, shape, and required manufacturing processes. Modularity enables increased commonality in upstream fabrication processes, by using the same base modules, though downstream final assembly may lead to an increased risk of mix-ups, if all unique product characteristics are encapsulated. However, making any design changes is outside the limits of operative decision-making, and therefore will not be further considered.
Campaign-building bundles product variants with commonality together to larger batches or “campaigns”. The shift to another campaign and the corresponding instance of low commonality occurs less frequently.
Another approach to limit the instances of low commonality in a machine park with multiple, interchangeable machines is to assign parts with low commonality to different machines, thereby segmenting the production.
Unsuitability of machine/product variant combination: Assuming two mutually exclusive groups of suitability, product segmentation can be carried out, so that only suitable products are assigned to each machine type. These are also called “dedicated” machines. If one group of product variants is suitable for production on all machines, but other product variants are only suitable for one machine type, prioritization of the less-universally suitable product variant orders can reduce the likelihood of an unsuitable product variant – machine pairing.
Alternatively, technical measures can be taken to make all machines universally suitable and therefore interchangeable, or product design measures can make all products suitable for production on any machines. Both approaches are, however, outside of the scope of this work.
Advanced equipment age: Avoiding advanced equipment age on the utilized machines can be avoided through two mechanisms. One is to eliminate all machines above a certain age limit, and therefore requires an immediate capital investment for most firms, as well as increased machining costs due to shorter depreciation periods. The second mechanism is to prioritize the use of newer machines and use only the old machines under exceptional conditions (i.e. high season). This is only effective when factories have a surplus of machine capacity.
Large lot size/long production runs: Avoiding long production runs or large lot sizes can be realized through changes to the production plan, i.e. making short stops for parameter readjustment or to setup for another product variant.
However, this is only an option for facilities with a machine capacity surplus that can afford to perform more frequent setups.
Low employee qualification: Increasing employee qualification is easily implemented as long as employee retention rates are high in the company, and adequate resources are provided for training.
Out-of-range ambient conditions: Ambient conditions can be regulated by controlling conditions within the production hall. This includes installing and maintaining HVAC systems, dehumidifiers, and condition monitoring systems. Furthermore, advantageous ambient conditions can be maintained by containing local changes in ambient conditions (i.e. cutting fluid mist containment). Both approaches require capital investment.
Manufacturers can also avoid exceeding acceptable ambient condition levels by timing the production of only robust product variants on high temperature, high-humidity days.
Table 20: Waste minimization through controlling waste amplifiers
Tactics Addressed activity and linked
waste forms
Scope of material savings Feasibility within operative decision- making Controlling successive product
variant commonality:
a. Product standardization, modularization
b. Campaigns/ bundling batches with high commonality c. Assigning uncommon product
variants to opposing machines
- Processing defects - Startups losses - Cleaning: cleaners
◐ ○
◐ ◕
◐ ◕
Controlling unsuitability of machine / product variant combination:
a. Assigning product variants only to the most suitable machine b. Product simplification c. Machine universality
- Processing defects - Startups losses - Cleaning: cleaners - Transport: transport loss - Stock unit replenishment: trim loss
◐ ◕
◐ ○
◐ ○
Controlling advanced equipment age:
a. Investment in new machines b. Prioritize utilization of newer
machines
- Processing defects - Startups losses - Cleaning: cleaners - Transport: transport loss - Stock unit replenishment: trim loss
◐ ○
Controlling large lot sizes:
Run small lots
- Processing defects - Startups losses - Cleaning: cleaners - Transport: transport loss - Stock unit replenishment: trim loss
◐ ◐
Controlling low employee qualification:
Train employees
- Processing defects - Startups losses - Cleaning: cleaners - Transport: transport loss - Stock unit replenishment: trim loss
◐ ◕
Controlling ambient conditions:
a. Controlling and containing ambient conditions
b. Producing only robust-product variants in periods of undesirable ambient conditions
- Processing defects - Startups losses - Cleaning: cleaners - Transport: transport loss - Stock unit replenishment: trim loss
◐ ○
◐ ◐
Total score ◐ ◐
Table 20 presents an evaluation of the tactics for controlling the values of the waste amplifiers using the evaluation criteria from Section 6.6. While technical measures present a very effective method to control the values of waste-amplifying factors, machine segmentation, campaign building, order prioritization, and the timing of order processing hold potential to reduce material waste.