This Focused Performance Weblog is a "business management blog" containing links and commentary related primarily to organizational effectiveness with a "Theory of Constraints" perspective. TOC is noted for its applications in Project Management and Multi-Project Management (Critical Chain) and Operations Management (Drum-Buffer-Rope), as well as in Marketing, Strategic Planning and Change Management (TOC Thinking Processes). If you are on an archive page, current postings are found here.
Tuesday, December 17, 2002
• Simplified Drum Buffer Rope (pdf, 216K, requires Adobe Acrobat or Mac OS X) -- A recent discussion on the usually excellent APICS Constraints Management discussion list delved into a "simplified" version of Drum-Buffer-Rope, the TOC solution for the management of manufacturing and production-like operations. Introduced by some friends and competitors of mine in their book, Manufacturing at Warp Speed: Optimizing Supply Chain Financial Performance, this approach is useful when there is no clear constraining internal constraining resource, or for the very common situation of many small shops that find that they have a demand constraint (aka market, marketing, or sales constraint) rather than one in their ability to supply.
This discussion was timely for me personally, as I am currently in the process of aiding the implementation of such a process. Admittedly, in the case of my client, the border between DBR and S-DBR is a bit fuzzy, as they're a job shop that has as the possible critical constraint resource a set of relatively interchangeable machines that also serve as the gating operation for their products. As a result, the material release schedule, pulled by the market demand, is tighlty coupled to what would be the "drum schedule" in a basic DBR set-up.
It's going to work nicely. A simple Excel spreadsheet is being finetuned right now that take desired ship dates, calculates ropes for different categories of parts, provides a material release date, and backs that date off ("bulldozing) them back in time) to avoid possible overload of the gating operations. That last bit makes sure that they don't try to force 10 punds of ... through their 5 pound plant, only to create mountains of inventory.
Once the schedule is set, it boils down to behaviors on the shop-floor. Allowing "road-runner behavior" is what all the scheduling is about. Like the "beep-beep" cartoon character that has only two speeds (stop and full speed), operators are being directed to work in the same manner. When there's work in front of the operation, work it. When there isn't, don't work on unnecessary stuff. As one person on the discussion list put it, the simplicity of tying a "rope" between demand and material release (or between demand and a critical resource schedule), and then letting the natural capabilities of other operation pull the work through the shop unimpeded, is so much simpler than designing a system of kanbans.
If I've always viewed DBR as a simplified approach to Lean Manufacturing, then Simplified DBR has the potential to take the process to another level of "speed to results."
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