Pull- don’t Push

6455 reads

Pull system brings a host of benefits including reduced inventory, which lead to reduced lead time to manufacture. In a pull system parts move one piece at a time or few pieces at a time and this prevents scrap in case of any quality issues. The parts are produced at a rate which customer demands and this rate is called the Takt time.

In the traditional manufacturing system goods are built and passed on to the subsequent system which is known as Push production system. In a Pull production goods are built only when requested by a down stream process.

In Push system demand is anticipated and parts produced based on the anticipated demand, typically what happens in mass production environment where huge inventory is built up; whereas in a Pull system the parts are produced based on customer demand, which ensures low levels of inventory. Pull system reduces the schedule sheets, meetings to discuss shortages, expeditions and premium freight paid to ship materials; the material pull is created using Kanbans or sign boards. If we take an example of lap top manufacturing, if a customer places an order for a lap top, this would trigger off a series of ordering and manufacturing activities for producing parts and procuring raw materials just in time (JIT) and that's the reason companies like Dell are able to maintain very high inventory turns. In the simplest terms no one from upstream will produce goods or provide service until the down stream customer asks for it.

 

The concept is simple and understandable but what is difficult is to bring the change in a place where people are already working in a Push environment. It seems difficult to visualize a more efficient production using the Pull system and typically a shop supervisor believes that the machines and operator should work uninterrupted no matter if the downstream process needs goods or services. If operator speed is very high in China plants I think slowing it down is also very challenging. In one of the projects I was working in one of our Chinese plants wherein we wanted to reduce inventory and improve productivity, the biggest challenge was to ask operators to go slow and work on a Pull system, this was a conveyor driven line and operators were busy pulling parts off the conveyor, working on them and pushing it back on the conveyor. Finally we removed the conveyors and had asked operators to physically pick up parts from the upstream process; which brought in a rhythm and prevented push and build up of inventory. I think that was the turning point in that shop and subsequently in all lines the conveyor was pulled off and a pull system implemented.

 

Pull system brings a host of benefits including reduced inventory, which lead to reduced lead time to manufacture. In a pull system parts move one piece at a time or few pieces at a time and this prevents scrap in case of any quality issues. In case of mass production where in there is huge batch sizes and parts pushed to the subsequent process steps, any quality issues noticed downstream will lead to the whole batch being affected and causing higher percentage of defectives and scarp. The time for a part to move from upstream to downstream is higher in push system as the WIP (work in process) at each stage slows down the travel and hence increased lead time. Increased lead time directly affects flexibility of production planning. When WIP is low, lead times are low and the speed at which part numbers or models can be changed in a production line is faster. The rhythm created by the pull system also creates a very positive and motivating environment in the shop floor.

 

However to have a pull system in place it is essential that the equipments are capable and reliable, the operators multi-skilled (wherever needed), the quality high and no defectives in incoming parts . The line has to be balanced and in pull system parts are produced at a rate which customer demands and this rate is called the Takt time.

 

Let's look at some common examples of pull and push system in our day to day life to understand this concept better. A soda vending machine is a pull system because you get soda only when you drop the coins. The supermarkets typically work on a pull system, because when we pick up soaps or other consumable from the shelf, the gap in the shelf triggers supply of fresh material, which in turn triggers production of the material. Most of the doctors offices are push system, because we got to visit the doctor and wait for our turn, by introducing consultations based on appointment it makes things better for patients though that is not a pure pull system. The flight landing or take off must ensure that they will follow a pull system to prevent accident. In factory canteens when we serve rice on a buffet system it is pull, but when items are served by the caterer it is typically push. If we notice all that is pushed on to the plate would be get wasted, because the person serving is not aware of the consumers taste and also the consumer doesn't feel guilty of wasting food, because it was forced on to him or her. Though the purpose of push system followed by the caterer is to restrict consumption of high cost item, typically more of such food would get wasted. 

 

A good pull system I noticed in a Sushi bar in Shanghai, wherein customers don't have to place an order but just pull-off plates of several standard items from the conveyor; a pull by the conveyor triggers manual introduction of more such plates on to the conveyor. The conveyor has a limited space and this system is called a CONWIP system or constant WIP system, wherein the work in process in the system is defined and fixed by the conveyor capacity. In CONWIP system the part numbers (or types) can he different and in the Sushi bar example too, each plate may have a different items but the cost per plate is standardized.

 

I am sure that you could see many such areas where in Pull system is used or pull system can be implemented to improve efficiency and make life better for all involved.

 

pradeep-kumar-e.tPradeep Kumar E.T. A Master Black Belt in Six Sigma , is the Country Manager- Operational Excellence with Tyco Electronics Corporation India Pvt Ltd. Feedback can be
e- mailed to pradeep@ businessgyan.com

 

Issue BG87 Jun 08

Trending

824
Harvey Mackay's picture

Develop high performance habits

Are you performing up to your potential?  Are you afraid to jump to the next level?  Are your habits pushing you forward or holding you back?The most important book on self-motivation and achieving more than you imagined hit the bookstores
791
Harvey Mackay's picture

Your business depends on your personal touch

Mamie Adams always enjoyed going to a branch post office in her town because the postal employees there were friendly.  She went there to buy stamps just before the holidays one year and the lines were particularly long.  Someone pointed
710
vnbhattacharya's picture

What will you do in this difficult situation?

Instead of writing about my views on business strategy as I do every month, I would like to present an exciting and tricky problem today.It is an issue of decision making similar to what many senior and top managers have to deal with from time to
698
johnsullivan's picture

The New New Thing: Blockchains and Recruiting

If reading about AI is making you feel like Alice in Wonderland, then take heart, there’s something new on the horizon — Blockchains. The technology has been around since 2008 but is now getting more mainstream in business applications, though...
696
hindustantimes's picture

Year of Culture: India’s diversity rocks London audience

 Sufi music, opera singing and Indian folk dances merged seamlessly with British hip-hop and tap dance as more 150 artistes put on a vibrant performance at one of the last events of the UK-India Year of Culture 2017.Billed as the Independence
650
davecrenshaw's picture

How To Get Work Done Without Stretching Yourself Thin – Pick Dave’s Brain

Could you pass the insanity test? This week’s question comes from David in Salem, West Virginia. He asks: I’m following your time management training program, yet often I find I’m putting appointments on my calendar and then not completing them—
636
jackcanfield's picture

5 Leadership Traits of Great Leaders

Whether you’re climbing the corporate ladder, building a network marketing downline, working for social change, or even coaching a Little League team or organizing a civic event, knowing leadership traits of effective leaders will make you more
636
anandmahindra's picture

youtube.com/watch?v=7SNwhZ…

From: twitter.com Via: twitter.com This could constitute a serious threat to Mahindra Odyssea, our boat building company. https://t.co/AwzTQVLp1lYou
626
johnsullivan's picture

AI or IA? Intelligence Augmentation for Recruiting

IBM’s Watson is synonymous with AI. Perhaps IBM should have named it Sherlock. Anyone familiar with the Sherlock Holmes stories knows that Watson wasn’t very bright. But he did have his uses. He was good at collecting and summarizing information,...

Pages