Friday, October 27, 2017

Takt-based scheduling? Yes, but just not really…

Takt is a German word. It’s used in the music world. A conductor uses a baton primarily to regulate the tempo of the music. So why would we use takt to schedule production? Well… maybe to regulate the tempo of production? I see managers everywhere, trying to regulate the flow of production lines. And we intuitively know that when things flow we get better results as when things get stuck. And then there is a multitude of literature, white papers and theory that suggests many solutions, all geared towards a noise-less, well moving, uninterrupted production program to fulfill customer demand in the most efficient way. Therefore, we try to get things flowing.

…and we do so when working on the design of the production shop floor and assembly lines. Pull systems (Kanban cards) are used, a takt counter provided, scheduling boards (Heijunka boards) pop up everywhere, sirens go off when there’s a problem (in one plant in Juarez, Mexico they play ‘Für Elise’ by Ludwig van Beethoven instead) and the assembly line is organized in a way to support a balanced workload from station to station.

Do you see yourself in that picture? Yes? So what about your ERP system? Does it allow you to schedule for that setup?
Here are a few answers that I get when asking that question (in no particular order):
- We are a lean shop… we don’t need ERP to schedule production
- No, our ERP cannot support a takt-based schedule
- What do you mean…?
- Yes, we developed a great solution into our SAP system. We have a transaction called Z_SCHEDULE that does a great job reshuffling our production orders
- Yes, we have a very good production scheduler who figured this all out… yes, he works with EXCEL spreadsheets but updates everything into SAP on a regular basis so our cost controllers will get everything they need

As you can see there’s not a lot of system support for a takt-based flow line… at least perceptively. In fact, I personally have seen many, many shop floors (especially assembly lines) that are run by takt, but I have not ever seen any of those setups supported by an ERP system (as I primarily work with customers who run SAP, I’d like to limit this observation to SAP-ERP or APO). There is always a work-around (which never works)… or no support at all… when SAP has the perfect support for that… all with standard transactions! (It would be too much for an article like this to elaborate on how to set up takt-based scheduling in SAP. But I am more than happy to elaborate to specific requests – let me just point out here that SAP ERP provides transactions for line balancing, takt calculations and takt-based sequencing. It does so in its repetitive manufacturing module and from early 2018 on for a discrete setup as well by way of an SAP Add-On Tool)

At this point I just would like to point out the difference between truly scheduling takt and what is done much more often: lead time scheduling. In lead time scheduling, the operations are backward scheduled from the requirements date of the product whereas in takt-based scheduling the operations are distributed – without violations – in the provided takt time

This (takt-based scheduling) has the affect that work is evenly distributed across a production line and therefore allows the product to flow. In lead time scheduling this is not the case because WiP builds up in front of a station that has more work to do (longer operation times) than the station before. 

So don’t use lead time scheduling in an ERP system if you truly try to run by takt time. Your ERP system doesn’t work very well if it supports a different animal than the one you own. A very smart man told me recently “if it quakes like a duck, walks like a duck and looks like a duck… chances are: it’s a (f…) duck!” And then you should treat it like it’s a duck.