Have you tried Google Instant? It’s an eye-opener. You visit the site, start typing and Google immediately spits back results based just on what you typed. Type “the” and I get listings for a thesaurus. Type “The Fab,” and you get results for The Fabulous Fox Theatres in Atlanta, St. Louis, and elsewhere. Type “The Fabri” and I get www.thefabricator.com. Thing is, you may get something different when you type in these same letters. It depends on your location and your search history. The information is based on conditions of not a few minutes or seconds ago--but now.
Google happened to introduce the service while I was on the road last week in Columbus, Ohio, at a job shop conference organized by Shahrukh Irani at The Ohio State University’s Department of Integrated Systems Engineering. The conference’s overarching theme: There is no one “right” way to improve job shop operations. Low-volume, high-mix operations may use elements of lean manufacturing, Six Sigma, theory of constraints, and other strategies to get the most out of their shop floors.
I noticed one common thread throughout, though. Like Google, metal fabricators today focus on the now, the current shop floor conditions and current orders. Some recent conversations I’ve had with shop managers support that statement.
For instance, the October print edition of The FABRICATOR will cover Robinson Laser, a large cutting operation in East Chicago, Ind., with a whopping 40 lasers. The company, which has origins in the steel business, built a custom, online RFQ and part tracking system that focuses everything on current shop floor conditions. Engineers receive immediate quotes and place orders quickly. It examines shop floor conditions at the instant the engineer clicks Order and confirms the due date or proposes a new one if shop conditions have changed between the time of the initial quote and the actual order placement.
While in Columbus last week I stopped by C.O.W. (Central Ohio Welding) Industries, a job shop with an average lead-time of seven days. And that includes taking the order, scheduling it, fabricating it, and shipping it. When it comes to actual manufacturing time, some products take only three days to make it through the shop, from laser cutting or punching to bending, welding, grinding, painting, and assembly.
How does this low-volume, high-mix operation do it? Shop employees focus on the now.
Specifically, the shop uses a drum-buffer-rope application of the theory of constraints. The drumbeat of their operation is the weakest link, or the bottleneck. It beats the cycle time of the entire operation. The buffer is the work-in-process (technically, the time it takes to process the WIP) to protect against unforeseen variability, so that the drum never stops beating. The rope is the work release schedule based on due dates.
For C.O.W., the drum--the principal bottleneck--usually is the welding area, so managers never release jobs until the buffer at the drum reaches a certain level. At that point orders are released through cutting and bending, and then they arrive at the welding cell just in time to maintain that minimal buffer of WIP to ensure that drum never stops beating.
As Gary Foreman, vice president of manufacturing at C.O.W. said, quick lead-times hinge on managing those job releases so that the floor isn’t flooded with WIP, which reduces inventory, frees up cash, and shortens the cash cycle (“cash out” for materials to “cash in” for payment of the job).
And they do it all by focusing on that drumbeat, the now of the shop floor.
About the Author: Tim Heston
Hi Tim,
Good article.
The only watch out is that with "off the shelf" drum buffer rope there is one constraint, one drum beat. But in many highly custom job shops the mix of work can change day to day or week to week. In that case the constraint can move. Velocity Scheduling System was developed for highly complex shops where the constraint may move or be in the market.
Dr Lisa
Theory of Constraints Expert