Lean manufacturing tool series -12 (Theory of constraints)

Theory of Constraints

The Theory of Constraints is a tool that came about in 1984 from the Israeli physicist and business management author Eliyahu M. Goldratt. The theory and philosophy was born from the appropriately named Goldratt book, The Goal, which proclaimed that all systems and processes are driven by a goal or a few goals which are limited in their capacity only by one or a very slight few constraints. It goes on to claim that the only way to fully achieve this goal or goals is to identify the most limiting constraint and either reduce it so it is no longer the limiting  constraint or eliminate it altogether.
While the focus of the theory and the ensuing improvement is the constraint, there are important assumptions that are considered vital to the success, or to some the downfall, of the theory. Goldratt asserts that all organizations and processes can be measured by three characteristics:Throughput, Operating Expense, and Inventory. Of course, by measuring these three characteristics, we can then track and therefore control them. The variations that are inherent in these is what leads to the constraint.
A good example is to look at an organization and its three characteristics.Throughput can be
viewed as sales, or even the revenue generated through these sales, Operating Expense is exactly that, and Inventory is reflected in the investment in goods or services that the organization participates in to sell their own goods and services.
By measuring all of these characteristics, and tracking and controlling them, we can identify the constraints upon which this theory is built. These constraints are the heart of the theory, and state that there is always at least one, and at most very few, constraints that are holding the organization back from either fulfilling the goal or limiting the rate at which the goal is achieved.These constraints may be internal or external. Some examples of internal constraints are
equipment, people, and policy.
The key to success, Goldratt claims, is to follow “five focusing steps”, which assist in identifying the constraint and destroying it such that we are no longer constrained by that specific constraint and instead another constraint takes its place. It is imperative to understand that a
constraint always exists, but the limiting constraint may change as they are identified and improved or cleared.
If you assume that the goal is clearly articulated, then the five focusing steps are:
1. Identifying the constraint. This is the resource or policy that is preventing the organization from achieving the specified goal. This is found by monitoring the three characteristics as  defined previously.
2. Exploiting the constraint. Ensuring the constraint‟s full resources, attention, and intention are  dedicated toward the goal. Then, identifying ways in which more resources, attention, and intention can be focused solely on the limiting constraint.
3. Subordinating all other resources and processes. This entails taking full inventory of the processes and resources available to the organization and dedicating them toward supporting the exploitation determined in step 2. This usually includes aligning the entire organization
around the decision behind step 2.
4. Elevate the constraint, if necessary. If necessary, dedicate more resources or processes toward eliminating the constraint outlined, or perhaps place more resources on the constraint so the constraint‟s capacity is increased.
5. Re-evaluate the constraint, and repeat with step 1. Over the course of accomplishing steps 1-4, the constraint may have shifted or changed. Re-evaluate the constraint and start again from step 1. One very important characteristic to note is the propensity to continue with step 4 indefinitely, not recognizing that there is a new constraint.
If managed correctly, this is a constant cycle which is repeated indefinitely, and is identified by Goldratt as the Process of Ongoing Improvement (POOGI).
Like anything else, there is always variation when we measure our three characteristics. Because of this, Goldratt preaches the use of buffers, particularly during the exploiting and subordinating stages, to eliminate or reduce the variation effect on the constraint. According to the TOC model, the organization should always be able to output up to the capabilities of the constraint. With the buffers, that constraint is constantly the constraint, ensuring no other piece of the organization becomes the constraint.
The Theory of Constraints can be used by any complex system or organization in which the desired outcome is a goal that is either achieved faster or more cost effectively. By systematically reducing the constraints that keep us from attaining this goal, we dedicate more
resources toward the constraint and less toward other operations that are not constraining the process. You should use this tool over others when your organization cannot define what the
single most constraining process is that is affecting your organization‟s process capability.
A good example is one of a widget manufacturing line that has been manufacturing widgets for the last 20 years. The company has used lean and six sigma for the last 10 years to bring its costs down significantly, and is now the leading manufacturer of widgets across the country.
A manager has been brought in to analyze the process used to manufacture the widgets and recommend areas for additional improvement. The manager, has decided to use TOC as a tool.
He then took about 16 weeks to measure the throughput of every workstation and has found that a single workstation is the constraining factor. They are constantly working on a backlog, and while lean processes have cut their production time by half, they are still the weakest link
in the chain.Management decided to put a second workstation dedicated to that constraining factor,therefore doubling the capacity of the constraint, and thus increasing the capacity of the line.
While the cost was increased twofold, so was the production output, allowing the organization to increase their sales offerings and double their revenue.
The Theory of Constraints is a process for ongoing, continuous improvement of a process or organization. By taking this tool onboard and implementing it, you will find the most
constraining factor that is holding back your company from its best performance.

Prepared by:Md. Tarikul Islam Jony
Mail:jonytex073@gmail.com
+8801912885383

Lean manufacturing tool series part - 11

Takt Time - the Rhythm of lean manufacturing
Do you know how long it will take you to read this article? If you glanced at your watch before
you opened this article, look at it again when you are done. Then, read ten more articles and
take the average reading time. Is that fast? Or is it slow? Should you be reading faster in order
to meet your reading goals? Or should you slow down to maximize comprehension and quality
of the reading? Takt time can answer this question.

Takt time is derived from the German work, Taktzeit, and can be literally translated to mean
“cycle time”. Using the previous example, if your boss came to you and told you to read an
article next week, you would know exactly how much time you would have to block out of your
day to read articles. If you weren‟t feeling well, or thought you were particularly distracted, you
could compare your time to the time you just derived.

Traditionally, Takt time is the maximum time per unit that a production line is allowed to
produce a quality product in order to meet demand. After it is benchmarked, it sets the pace
and the standard for further production from the same line or workstation. It can show
managers and quality teams where to focus their attention and resources in attempting to
improve the overall process. It can also alert managers to bottlenecks and choke points that
need attention to process resources.

The Takt time is computed by dividing the time demand (units required per day) by the net
time available to work (minutes of work per day). This will give you a unit of minutes of work
per unit required, and provides for a good description of what Takt Time really is.

The end goal of determining the Takt time is to produce products at a pace that mirrors what
the customer‟s demand is. By meeting the demand from the customer, the inventory is kept to
a minimum and thus costs are also minimized. Of course, no machine or person is perfect, and
there are inefficiencies in every process, so a good manager and quality specialist will take
these variations into account when determining the required rate to run the line at. Sometimes
it simply takes trial and error to find the ideal rate to run the line at. Additionally, most
companies will have the ability to adjust the required time by adjusting daily working time,
increasing workers, and other things that will indirectly affect the line time.

It is very important to realize the difference between cycle time and Takt time. Takt time is only
determined by the demand and the amount of time available to work. It actually is not affected
by the actual performance of the line or workstation whatsoever. Cycle time, however, is the
amount of time it actually takes to complete the production of the unit. They are separate, and
most people, particularly those who are relatively unfamiliar to lean processes. While they are
not the same thing, Takt time and Cycle time should always be compared to each other for a
relative gage of your process‟s ability to meet the necessary demand.

When a car company comes out with a new model car, they perform market analysis, surveys,
and forecasts that decide what the demand for the new model will most likely be. This, along
with the supply chain management team, can determine what the production goals will be for a
certain factory, and consequently, the line. For example, let‟s say that they will need 30 new
models per day.

In order to get the production team off the ground, produce quality products, and provide
training to the team, management has decided to limit amount of production time available to
the line to 5 hours per day. Therefore, the Takt time is 30 units per day / 5 hours per day, or 6
units per hour required to produce to meet customer demand, and can be further broken down to 1 unit every 10 minutes. This will lead to every car that comes off the line being shipped and no inventory being held at the factory… the ideal way to run the business.
This can be further broken down to workstations. For example, the door installation workstation
for the new, 4-door model car would also need to put out one car per ten minutes. However,
since there are 4 doors, the workstation will have to install one door every 2.5 minutes. While this may seem obvious, what may not seem obvious is that this is beyond the capacity of a single workstation, and will lead to a bottleneck , and subsequently a focused lean project which will bring the cycle time to the Takt time, leading to an efficient process.

Takt time can be used in many applications that aren‟t necessarily the traditional line manufacturing application. It can be used in order processing, call center operation, project management tasks, or anything in a business that can be measured by processing time.

A good tool to have in your toolbox, Takt time will give a company an insight into what the capacity of a method or process must be in order to meet the demand a customer places on it.
By doing this, the company can set a benchmark that will guide the company toward the ideal
situation of perfect supply chain management.

Prepared by :
Tarikul Islam jony
+8801912885383
jonytex073@gmail.com

Lean manufacturing tools series -part 10

SMED - Makes Lean Flexible
concept of Single Minute Exchange of Die, or SMED. Quick changeover, as it is called in many
manufacturing. The actions needed to take, while simple, have a long lasting impact on the
business and the quality, speed, and capability of the line to react to demand changes.

To completely understand SMED, you have to understand assembly lines in exacting detail, and
it helps to know what the objectives of lean processes in general are. Primarily, assembly lines
produce a very specific product by utilizing specific work cells or work stations that produce
pieces of that product with a high degree of efficiency, quality, and speed. Unfortunately, while
this may be able to produce the product quickly, one of the major drawbacks is that the line is only able to produce a single class of product.

The general concept behind lean processes is to reduce or eliminate waste and cut costs by
simplification or process changes. Now that you know about the skeletal model of assembly line
manufacturing and lean processing, you should be able to see the value of enabling a single
assembly line to produce many different products or variations of products.

By doing this, the company reduces the amount of space necessary for them to occupy, they
are able to react to demand shifts in product lines, and overhead is severely cut down so many
products become profitable for the company to produce. This is where SMED comes into play.

If a company were following the SMED philosophy exactly, they would be able to produce a
company and manufacturing layout that could change the dies and robotic programming in the
assembly line so that the assembly line can shift from producing one model to another in a very
short amount of time. By doing this, the company will not need as many assembly lines, or as
many branches on a single line, therefore reducing the square footage necessary to
manufacture a wide line of products. They also will not need a completely different set of
employees to keep the assembly line moving, and will not need to upkeep, buy, or power any
additional equipment associated with the second or third line.

Finally, since the company can quickly adjust the line to manufacture which ever product they
would like, they can quickly change the assembly line to manufacture the product that is seeing
a higher demand and cut back on the product that is seeing a lower demand. By achieving this
incredibly agile position, a company can easily manage its inventory and maintain a large amount of liquidity in their company. The first time a company embarks on a quest to enable SMED, they will not be able to change
over the manufacturing lines as quickly as they would like. The end goal is to be able to shift
the assembly line from one product to another in less than 100 minutes, therefore reducing the
amount of downtime associated with the shift. The company will not realize this significant
progress until a few months of lean studies and process evaluation.

While this is something that anybody can suggest, it is a very high level concept that has to be
evaluated not only at the manager level, but at the upper management level as well. The
effects are far reaching, and without careful planning, a company can possibly negatively affect
their output capacity, leaving a shortage of inventory in the supply chain.

SMED is a very effective way of significantly changing the way a company does business. It
should be fully explored, particularly if a company is in the manufacturing business.

Collected by:
Tarikul Islam jony
01912885383
jonytex073@gmail.com

How to eliminate Fabric Shade Variation in Garments

Shade variation in garments is caused mainly due to fabric problem. Fabrics are dyed in dyeing machine that has a certain capacity of dyeing fabrics at a time. So, where fabrics are dyed in multiple lots, there is chance of having shade variation between different fabric lots if dyeing process is not controlled.

Shade variation in fabric may appear as

• Within same fabric roll there may be shade variation like 'center to selvage' and 'salvage to salvage'
• Within same fabric roll length wise shade variation 
• Shade variation in between fabric rolls

Shade variation in garments (between different components of the same garment) can be controlled if a SOP is set and employees follow that SOP to reduce shade variation in garments. From fabric inspection to garment finishing in each step you have to be pro-active and take action to prevent shade variation in finished garments.



Tips to reduce and control shade variation in garments:

1. Fabric inspection: Whether it is in-house dyeing or dyed fabric from outside processors, all fabric rolls need to inspect for shade variation. Categorize fabric rolls based on fabric shades.  If there is a wide range of shade variation and fabric shade is out of the standard one, you can reject that lot and sent back rejected to your fabric processors for re-processing.

2. Preparing Shade band: Develop shade bands and get approval for all shade bands you have in your bulk fabric. Mark shade band no. to each fabric roll / than. Shade bands help in fabric layering and shorting in cutting room.

3. Communicate with clear information: When you have an order with varied shades of fabrics, information must be shared with cutting department as well as production department. While issuing fabric to cutting, intimate cutting department that fabric has different shades and fabric lots should not be get mixed.

4. Fabric layering: As advised in point#2, you have to categorize rolls according to shade band. While spreading fabrics for cutting, spread fabrics of same shade band no. in a lay. Don't mix fabrics roll of different shades. When you need to spread fabric of another shade on the same lay place separator to identify cutting of different rolls easily at the time of shorting and bundling. 

5. Marker placement: In case fabric has shade variation of 'center to selvage' and 'side to side' place garment pattern on the fabric layer in such a way that shade variation would not be prominent (visible) in garment. Like you can set markers as 'one garment one side' and 'side to side' marker

6. Numbering of layers: Use ply numbering system and number all garment components. Like, all components of a garment should have same sequence number. In case you spread fabrics of multiple lots in a same lay (cut) use separator for each rolls/ lots. Then while you make bundles make separate bundles for each lots/rolls 

7. Bundle movement in sewing: After following above steps strictly, one even have shade variation in garment if bundles are not maintained in sewing lines. Sewing operators need to close bundles after completing sewing of a bundle. Ensure that when operators join two component they should check ply number on sticker and sew component with same ply numbers.

8. Replace defective garment part: Check garment component shade variation at the end of line inspection (at the end of sewing process). Garments found with fabric shade variation (varied shade of different components if that is not a design feature) need to be separated from the good garments. Later defective garments (due to shade variation) can be corrected by replacing parts. For the part changing, be careful to cut parts from the matching lots. 

9. Single piece garment bundling: If you can't stop ply mixing in sewing you can introduce single piece bundle system in production. In this system, there is no way to sew garment components form different fabric plies. I am not suggesting you to change your bundling system but just showing you an option for getting rid off shade variation problem in finished garments. 

Above steps are not difficult to implement in garment production. Try it yourself and share with us how you have improved and handled shade variation issue in your factory.

 Collected By: Md. Tarikul Islam

                         01912885383

                         jonytex073@gmail.com

5 most visible reasons that cause the delay in shipment.

Making a plan and execution of the plan is ‘must do’ task to meet the lead time. As a standard procedure factories make plans and do extensive follow up of tasks. Still factories do not meet their target dates for final inspection and fail to ship good on agreed shipment date. In this article I have explained the 5 most visible reasons that cause the delay in shipment.

1. Product development and Sampling: Product development and sampling stage fall under pre-production processes. Other pre-production processes include sample approvals, finalising vendors and cost negotiation with raw material suppliers. Most of the factories do not consider including development stage schedule under plan. It results no control on pre-production processes. It goes long and long. When sample approval gets detailed, consequentially ordering of trims and fabric get delayed. A complete plan is done when you include sampling plan under your planning. Out of total lead time most part is consumed by pre-production functions. As a result planned cut date (PCD) gets postponed. 
2. Delay in sourcing of raw material: Normally factory planner discuss with supplier about their lead time for sourcing goods such as fabric and trims prior to making the final production scheduling. Suppliers fail to send good on time due to too many uncertainties. Sourcing delays also consumed extra time and make it difficult to start in-house processes on time. Few export houses experienced that yet after loading of cutting and stitching, trims such as care label, laces or main label are yet to be sourced. Partly stitched garments start piling up in the line and line supervisor load another style keeping running style aside from the line until they receive trims. How many factories can manage delay in such situation? 
3. Inferior quality in sourced goods: Fabrics, trims and accessories get in-housed at last. Goods are passed through quality checks before using in product or cutting. Unorganised factories mostly source fabric from power loom and face quality related problem. It may be shade variation/matching, wrong GSM quality, low quality print etc. If an inferior quality of raw material found, fabrics are send for re-processing or resourcing. It causes further day in PCD. 
4. Production urgency: Pressure and urgency increases when factory starts production processes (such as cutting, preparatory and sewing), as order has already eaten up bigger part of total time scheduled for the production processes (production to finishing). Not having much time on hand, managers push everything on fast pace. They even push their whole team on quantity production. In this stage they forget to care of quality of the product. Once they start ignoring standard procedures they get stuck on stitching quality or related problem rises. Repair and re-inspection become a main process. These process increases production time. 
5. Delay from Sub-contracting Jobs: For high fashion product, few value added processes such as panel printing, embroidery, bead work or dyeing are needed. For these value added processes factory normally send fabric or half stitch garment to sub-contractors for job-works. Sub-contractors also come with their big commitments on delivery and quality. But when factory receives goods, they had to count some more days on their delays. This happen due to absence of planning at subcontractor factory.
   Prepared By: Md. Tarikul Islam
                           01912885383
                            jonytex073@gmail.com

Lean Manufacturing Tools Series-" work cells " (part-9)

Work Cells – A building block of lean manufacturing
                If Lean Manufacturing were a building, then the bricks that lay the foundation of lean manufacturing, particularly with assembly lines, would be work cells. The fruit of the work cell implementation is a more efficient, stronger assembly line with higher quality products, happier employees, and a safer work environment. Work cells belong to a type of manufacturing referred to as cellular manufacturing. The concept behind this type of setup is exactly how it sounds: on a certain floor or line, there exists a string of equipment and workstations that promotes an efficient flow of inventory and materials from raw material to final, assembled product. The important aspect to note about cellular manufacturing is the idea that it minimizes transportation and waiting time, which makes the process ideal for quality leaders to implement. Using the concept of cellular manufacturing as a base, then the work cell is a group of equipment, workstations, and/or personnel that are physically located in a single area and allows for the group of workers and equipment to produce an entire product or group of products completely from start to finish. It can be thought of as a small version of the entire assembly line, complete with its own specific processes, teams, equipment, operating guidelines, and quality standards. The alternative to cellular manufacturing is the “batch and queue” system, in which the product is produced in stages, then allowed to sit for a period of time in a queue while it is waiting to get to the next workstation.If the production line is large enough, this leads to large amounts of inventory waiting in various queues, incurring costs to the company and taking resources away from the production line. Additionally, the line must become much more complex because additional machines and personnel are needed to transport the product between batches. With cellular manufacturing, the work cell absorbs the queue and ensures that inventory is kept to a minimum by constantly producing a quality product inside of the cell.
              The company that should be most interested in using this tool is the one that finds themselves bogged down by excess inventory and slow processes. Another, less obvious telltale sign that cellular manufacturing is necessary is workers that are unhappy with their job, because production is directly proportional to job satisfaction. The company will also find themselves very slow to react to demand changes and cost reduction techniques. The excess inventory directly drives these factors. Not every company is a good candidate for shifting to work cells and cellular manufacturing. Some companies simply do not have a manufacturing process that is long and complicated enough to justify work cells. Other companies produce products that are not able to be split into different assembly steps, leading to a convergent line at the very end of the line, and not allowing any room for work cells. While these are a couple of situations in which work cells will not necessarily be the best choice for a company, a large majority of companies would benefit greatly from the positive impact this model has on their inventory and production costs and times.                           Work cells should be designed at the highest levels. While the workers must be trained in the conduct of business inside of the work cells, the actual system should be designed with a 30,000 foot view. Managers should also be trained to operate their cells efficiently to keep the bottlenecks to a minimum.
            If utilized properly, a work cell system can reduce and possibly eliminate the need for inventory. It will also foster higher quality due to constant improvement and a continuous worker from one end of the cell to the other.

Everyday I will publish one tool's description.So visit my blog for next article where I will discuss about"SMED"

Prepared By: Md. Tarikul Islam

                        01912885383

                         jonytex073@gmail.com