Job shops are a mess. Period. The increased and uneven levels of inventory cause a host of other problems. In my last post I described how these inventory imbalances are caused by irregular material flow, how subsequent safety buffers increase inventory even more, and how this causes staff to change their workplace irregularly in a job shop. In this post I will continue the long list of ills in a job shop with staff changeover losses, extra searching and organizing, fluctuating lead times, and general un-plannability of job shops. Continue reading Why Are Job Shops Always Such a Chaotic Mess? Part 2
Job shops have a strong tendency toward chaos. Even well managed plants struggle to maintain order in a job shop. This is due to the inherent nature of a job shop, and there are no good solutions to manage job shops. The only good way to improve a job shop is to turn it into a flow shop. I will talk more about such changes later in this short series, but first let me explain why job shops are always a mess. Continue reading Why Are Job Shops Always Such a Chaotic Mess? Part 1
In my previous posts I explained how POLCA works and discussed the pros and cons of POLCA. In this post I will explain how to calculate the number of POLCA cards. While POLCA is overall a feasible method, I do have some critical comments on the method to calculate the number of POLCA cards. Continue reading Calculating the Number of POLCA Cards
In my previous post I described how POLCA (Paired-Cell Overlapping Loops of Cards) is supposed to work. Now let me look at the advantages and disadvantages of the method. Overall POLCA is a valid method of managing job shops. If it is the right one for you depends very much on your production system. Continue reading Advantages and Disadvantages of POLCA
POLCA stands for Paired-Cell Overlapping Loops of Cards with Authorization and was developed by Rajan Suri around 1990. It is sometimes mentioned alongside kanban and CONWIP as a production control system. Let me explain to you how POLCA works. In my next post I look at the pros and cons of POLCA. In my last post of this mini-series, I will show you the calculation for the number of POLCA cards, including some critical comments.
The similar-sounding word Polka is also a Czech dance music and textile pattern, hence the colorful illustration of the polka dots on the left (don’t worry, more technical diagrams will follow below). Continue reading What Is POLCA?