Tag Archives: Inventory

What Is 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?

How to Deal With Long Delivery Times

Lean has a bunch of advanced but good tools for material delivery, like Just in Time, Just in Sequence, and Ship to Line. Using them is much easier on short distances and with short delivery times. Yet, sometimes you just don’t have the option of short delivery times. This blog post deals with the issues related to long lead times and delivery times. Continue reading How to Deal With Long Delivery Times

What to Do with SMED: Reduce Lot Size or Increase Work Time?

SMED (Single Minute Exchange of Die) is a very useful tool to reduce changeover time. Reducing changeover time will free up time for other uses. Western management often wants to use this time to produce more goods. However, the rule of thumb at Toyota is to use this newly available time to do more changeovers rather than more products. This increase in changeover has the potential to significantly reduce the lot size, which often has much larger benefits than the additional work time. In this blog post I want to look in more detail at this relation between changeover duration, productivity, and lot size. Continue reading What to Do with SMED: Reduce Lot Size or Increase Work Time?

Toyota’s and Denso’s Relentless Quest for Lot Size One

Relay Race Hand Over
Just when you need it …

A famous step toward perfection in a lean production system is a lot size of one. However, few people realize what enormous effort and rigor Toyota applies to achieve this goal. During my visit to a Toyota plant and the APMS conference in Tokyo in 2015, I saw quite a few stunning examples of this quest. Let me show you … Continue reading Toyota’s and Denso’s Relentless Quest for Lot Size One

Can you tell your Bottleneck from your Inventory?

HourglassOn the shop floor it is common wisdom to find the bottleneck based on the inventory. If the buffer is full, the bottleneck is downstream. If the buffer is empty, the bottleneck is upstream. Is this true? My student Carolin Romeser and I spent quite some time verifying this, and found some interesting results. In general it is true, but … the devil is in the details. Continue reading Can you tell your Bottleneck from your Inventory?