This art.: POLCA yes, or POLCA no? (1)
Source: Business-improvement.eu
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QRM: Cellular organization |
![]() POLCA yes, or POLCA no? (1/2) By Dr Jaap van Ede, editor-in-chief, 25-04-2018 [ part 1 ] [ part 2 ] POLCA is a card-based production control system for high mix/low volume, and customer-specific manufacturing. It helps to decrease the throughput time on a shop floor with production cells, and products that have to follow their own route during their assembly or manufacturing. 20 years after he invented POLCA, Rajan Suri published a book which reviews the possibilities and experiences: The Practitioner’s Guide to POLCA. This book helps you to decide: POLCA yes, or POLCA no? It is also a guide to implement it. A very comprehensive and well-written book, be it with a little bias towards the advantages of POLCA. This article is available in Dutch on www.procesverbeteren.nl
Rajan Suri, emeritus professor of industrial engineering at the university of Wisconsin-Madison, introduced a new process improvement method called Quick Response Manufacturing (QRM) in 1998. He described this method in his magnum opus Quick Response Manufacturing: A Company-wide Approach to Reducing Lead Times. Like Lean manufacturing, QRM aims to improve the flow, or throughput. The most important difference is that QRM was developed specifically for high-mix, low-volume and/or customer-specific production.
Quick Response Cells ![]() POLCA-cards regulate the sequence of the jobs in the Quick Response Cells
Before this book is discussed, it is recalled why POLCA was developed, and how that system works (A similar and far more comprehensive description can be found in the book). Kanban However, only a limited number of product variants are allowed, because for Kanban it is necessary to keep intermediate stock for all product types. In a job shop environment, with customer-specific products and varying production routes, Kanban does not work. In that case the amount of intermediate stock controlled with Kanban cards becomes infinite. ![]()
POLCA-cards send the following message to QRC’s upstream: “I just finished one of the jobs you sent me, so you are allowed to send me a new one, since I now have free capacity available to process it”. This way, POLCA regulates that the people in the QRC’s work only on jobs than can continue to flow, because there is free capacity available downstream, instead of piling up and causing traffic jams. Other jobs can better wait a while! POLCA also limits the amount of work-in-progress on the factory floor as a whole. In addition, it instructs the QRC’s to work only on jobs for which all materials are available, and which have the highest delivery-priority. I will come back to those aspects later. Pairs ![]() The POLCA-system. The arrows show the route that is travelled by an intermediary product, along Quick Response Cells A, B and C. First, an A/B-card travels with the product, next a B/C-card. Within cell B, both cards travel with the product. (source: Rajan Suri, adapted for this publication).
Now assume that the next destination for this semi-finished product is C. Then cell B needs a B/C (permission B to C) card to work on it. So, two POLCA-cards travel inside cell B with this particular semi-finished product, a card from the cell it came from (A/B) and a card for the next station to send it to (B/C). This explains the word ‘Overlapping’ in POLCA, Paired-cell Overlapping Loops of Cards with Authorization. When the work is finished at B, the A/B card is returned to cell A. This is the signal for this cell that free capacity has become available at B, so it’s again permitted to execute jobs that need processing at that cell later (then, a new POLCA-cycle starts). This workload control system is comparable to traffic lights, which give traffic access to quiet motorways, but block the entrance to heavily used roads (a metaphor for QRC’s that at a particular moment do not have the capacity to process jobs). Authorization The result is a list of authorization dates for all orders. On those dates, after checking that all materials to process them are available, those orders are released. However, the planning cell does more. The people in it also calculate secondary authorization lists for each QRC, which are refreshed for example once a day. Those lists specify the dates at which specific orders should be received and processed further at specific QRC’s, to be ready in time.
Authors: Rajan Suri is the main author. However, several chapters with case studies were written by guest authors and consultants, that were or are active in companies that implemented POLCA. Besides this, some appendices were written by scientists. Pro’s and con’s: + The book contains six cases with many lessons learned. In most cases these chapters were written by people from within the companies involved, which increases the credibility. Those companies are: Alexandria Industries (USA, aluminum extrusion, using POLCA since 2004), Patheon (Canada, pharmaceuticals, using POLCA since 2011), BOSCH Hinges (Netherlands, metalworking, using POLCA since 2007), Provan (Belgium, metalworking, using POLCA since 2014), Szklo (Poland, glass industry, using POLCA since 2011) and Preter CNC Dreh- und frästechnik (Germany, metalworking, using POLCA since 2014). + It is not necessary to read all the chapters. Halfway through the book (or much earlier) you will have enough information to judge if POLCA is potentially a good solution for your company. + POLCA can easily be tried out, with small investments. To this end the book describes how a pilot (or partial implementation) can be done on a part of the factory floor. - A little bias towards the advantages of POLCA above other solutions. Order?The book can for example be ordered at Amazon.co.uk
So, the in-depth description of ‘standard POLCA’ as Suri now calls it, might already justify the publication of his new book. Standard POLCA and Suri’ s book will be discussed now. Next, some conclusions are drawn regarding the applicabilty of POLCA. Do you need help with the implementation of QRM and/or POLCA?Referral to this article on internet? Use this link: https://www.business-improvement.eu/qrm/Rajan_Suri_QRM_Practitioners_Guide_to_POLCA.php |
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