We should avoid waste to reduce costs and increase long-term performance. In lean manufacturing, waste is anything that adds cost or delays production without adding value. This article will discuss different types of wastes in lean manufacturing and how they can be avoided.
Eight Types of Wastes
Taiichi Ohno, who is considered the father of Toyota Production System (TPS), first identified seven types of waste (or Muda). To remember these seven waste, you might use a mnemonic, TIM WOOD or TIMWOOD. It stands for: Transportation, Inventory, Motion, Waiting, Over Production, Over Processing and Defects.
The eighth item was added later to this list: "Skills." That can be remembered by a mnemonic TIM WOODS or TIMWOODS.
Let's understand each of these wastes.
1. Transportation Waste
Waste of transportation means movement of material from one place to another without any value added work done on it. Transportation wastes money because you move something when you could use it right away.
In the office environment, the transportation waste includes using mail where email could be used.
We need to minimize the number of movements (the movement of paperwork is a type of transport waste).
2. Inventory Waste
Inventory waste occurs when we have too many items on hand. There are three categories of inventory: raw material, work-in-progress and finished products inventory.
Excess inventory could occur because of over-purchasing the raw material, keeping too much inventory between processes, or keeping too many finished products.
Many Japanese companies are using the "Just-in-time" approach. It helps them to manage their inventories better. That way, they receive material from their suppliers just when they need it. Also, each process produces based on the demand from the next operation. Also, complete manufacturing is driven by customer demand.
Inventory is considered the worst form of waste, leading to much bigger problems.
3. Motion Waste
Motion waste is the unnecessary movement within a process. The unnecessary movement between different processes is the Transportation waste that we have already discussed above.
For working on an activity, if the operator has to stretch or reach out to pick an item, it is a motion waste. The operator should have easy and unrestricted access to the material or tools needed to perform a process.
4. Waiting Waste
Waiting waste occurs when people wait for other people to finish their jobs before starting theirs. If you are waiting for someone to complete their tasks, you are probably wasting time. This can be caused by the machine in the previous step, people or the information. This may lead to idle equipment waiting for inputs.
This could result from poor planning, coordination between people or processes.
5. Overproduction Waste
Overproduction waste happens when we produce more materials than required for the next production stage. Overproduction waste occurs when there is excess capacity in a process.
Overproduction leads to excessive inventory between processes (work-in-progress inventory) or excessive finished product inventory. As we have discussed earlier in the inventory waste, both of these are bad.
6. Overprocessing Waste
Overprocessing waste is caused when operators spend too much time performing a task that the customer does not require. In simple terms, you might call it "gold-plating."
For example, high quality painting the areas that are not visible, producing with tighter tolerances than required by the product etc.
7. Defects waste
A defect is an error in product design, manufacture, assembly, testing or inspection. Defects waste results in wastage of resources like raw material, manpower and time. The defects waste may include the following: cosmetic flaws such as paint blemishes, scratches, dents, nicks, scrapes, cracks, splits, holes, warpage, delamination, surface roughness, waviness, porosity, edge chipping, metal loss, defective product and dimensional changes etc.
A defect identified in time requires rework and needs to be retested. A defect that is not identified in time can cause a problem during the product's life cycle.
8. Skill Waste (Under-utilization of human talent)
Under utilization of skill was the eighth waste added to the list later. Many studies have shown that most of the employees are underutilized. So if you want to improve productivity, you must increase the utilization of employees' skills. This waste happens specifically in organizations, that have a very clear role distinction between managers and employees. These companies work on the principle that managers are responsible for planning and directing, and employees should just follow the instructions given to them by their managers.
This way, they fail to utilize the potential of workers to improve processes.
Examples of 7 Types of Wastes in an office environment
1. Transportation Waste - Document movement between offices
2. Inventory Waste - Deliverable documents produced well ahead of the planned date
3. Motion Waste - Employee's need to move around the office to do their job, e.g. Printer away from the desk
4. Waiting Waste - Employees sitting idle while others complete the previous step
5. Overproduction Waste - Making extra copies of documents
6. Overprocessing Waste - Redoing tasks unnecessarily
7. Defects Waste - Incorrect data analysis, spelling mistakes
Examples of 7 Types of Wastes in a hospital
1. Transportation Waste – Moving a patient from one department to another (e.g. for X-ray)
2. Inventory Waste – Excessive stock of supplies (some getting expired)
3. Motion Waste – Poorly organized work spaces leading to excessive motion (e.g. for registration clerk)
4. Waiting Waste - Patient waiting for lab results, waiting for registration
5. Overproduction Waste – Making extra food for patients.
6. Overprocessing Waste – Unnecessary diagnostic tests
7. Defects Waste – Misdiagnosis, incorrect labeling
In lean manufacturing, waste is defined as anything that adds costs or delays production without adding value for the customer. It is important to identify these wastes so that corrective actions can be taken.
Muri: it means processes or operations are strained or overburdened
Mura: it means there is imbalance/ unevenness, i.e., processes, operations, machines or manpower are sometimes overburdened and sometimes underutilized,
Muda: it means waste, i.e. not optimally utilizing resources.