How to Reduce APS Implementation Time by Leveraging ERP Routing Data
Mike Liddell, CEO of Lean Scheduling International and Author of “The Little Blue Book on Scheduling”
Implementing an Advanced Planning & Scheduling (APS) system would be easy if you could just import data from your ERP system and use it to create a schedule. But unfortunately, that is rarely the case. The key data that drives APS is the routing data. Routing data in most ERP systems is more often used to support costing needs than production needs. This problem needs to be fully understood and resolved before implementing an APS system.
The obvious answer to this problem is to add a new, stand alone, routing file that provides the level of detail you need. But that approach may not be the best answer for a couple of reasons. First it takes you twice the effort to maintain two sets of data and, over time, the two sets of data could have major discrepancies. Ideally you want to maintain data in one place wherever possible and your costing data should reflect what happens in production.
A better approach is to leverage the ERP data by improving the accuracy of your ERP data while adapting some techniques that can be used to convert the ERP data into meaningful production APS data.
Limitations of ERP Routing Data
Listed below you will find three typical limitations of ERP routing data.
- ERP routings identify the resource required for each step at the Work Center level and the time required for each step. In the world of scheduling we need to assign jobs at the individual machine level because:
- There may be several machines in a work center, but they may not all be able to do the same work.
- Each machine may run at a different speed
- Each machine may take a different time to setup
- The run speed identified in the ERP routing is often an average and meant to cover many time variables. The only guarantee you have is that it is always inaccurate
- ERP routings often use something they call an average setup time when the setup time is usually sequence dependent.
- ERP routings often include something called an Average Queue Time into the time at each operation. This number makes no sense because it is not possible in advance to know the number of jobs waiting at a work center.
- ERP routings seldom include product attributes (such as width and color) that are often used by APS to determine efficient job sequencing. This information is kept and maintained in a separate database such as Access or Excel.
Because ERP systems use infinite capacities, time buckets, and backward scheduling, they have no way of accurately projecting future events, so it covers its tracks by stacking buffers of inventory and time at every opportunity. In fact, this is the only way that your ERP planning system can function at all. The underlying theory is that it is better to overestimate how much time and inventory you need than to underestimate. Of course, the problem with this is that it leads to excess raw materials, WIP and finished goods which is fundamentally why every manufacturer needs a better way of scheduling and that better way is with an APS system.
APS systems have none of the limitations that ERP planning systems. Because they can accurately handle time they can accurately synchronize multiple constraints (such as machines, materials and tooling) while projecting potential cause and effect.
A good APS system should integrate tightly with your ERP system giving you the best of both worlds. Your APS system will give you the speed and agility you need to manage change and your company, a powerful strategic competitive advantage.