Intro

There are three main tools you can use to plan with SyteLine:

• MRP
• APS, finite
• APS, infinite (APSI)

These key factors will help you decide which planning tool best fits your needs:

1. Constraint behavior
2. Accurate times
3. Motivation

There are also a few secondary factors that may affect your choice. We’ll explain each below

Constraint behavior

Do you want constraints to push out plans or do you want a fixed target?

Here are the constraints that may move plans out:

• Material availability
• Capacity
• Time on-shift
• Today

APS backwards plans. If any of the first three constraints is not available between today and the due date, and it lies on the critical path, the system will push the plans out and backwards plan from the new date. If the plan is moved out, then ALL plans for that order are moved out.

For example, a user receives a customer order. If the user constrains on a material and its lead time is such that it affects the critical path, then APS will move all plans (all purchase orders, manufacturing orders for subassemblies, etc.) for the meeting the customer order out. You can turn off this constraint at the item level, but if a constraining material is not available and on the critical path, APS will move ALL plans for the end order out.

Another example. If you do not have capacity, APS will search for earlier time when you do. If you have none, it will push out the plan to find available capacity. And because the plan for manufacturing is pushed out, so are all the need dates for purchased materials. (Time on-shift works like capacity in that APS applies your times to a working calendar, if you choose, instead of a 24×7 calendar.)

The whole concept of pushing out plans is tied to the just-in-time philosophy. So if you have capacity constraints, the APS approach will minimize the inventory by synchronizing its arrival with its use. APS provides tools to see plans that are late. You can then work to resolve those issues and meet your due date. If you want any of these constraints to move your plan dates, you’re probably a candidate for APS or APSI.

However, some users do not want constraints to move out target dates. They want a fixed target for a plan. They want to see what they need to do to ship at a certain date. They want to clearly see when something is supposed to happen and will expedite and increase capacity to make it happen. These users do NOT want to see moving release dates and non-critical item pushing out the critical path; they simply want to freeze the plan until they’ve exhausted all expedite and capacity solutions.

If you want a fixed target, you are a candidate for APSI or MRP. Generally, such users have the following characteristics

To-order environment with revenue targets and cyclical order bookings

Most of their products are engineer-to-order, assemble-to-order, or make-to-order. They often sell configured products so they can’t make them ahead of time and level their production. The best they can do is plan for common sub-assemblies and purchased parts using planning BOMs and forecasts or dummy MPS lines with a kit of these common items.

These users have quarterly revenue targets and most of the order bookings come later in the quarter. There’s a rush to sell and ship product to meet the revenue targets at the end of the quarter, then a slow period at the beginning of the next quarter.

These users don’t want their plans to move. They want a fixed target and will do whatever it takes to get it out the door.

Material, not capacity, is the critical constraint

Backlogged orders or late shipments are most often caused by material shortages. Such users would rather get material in, even if months early, than experience a shortage. Variability in lead time only adds to this issue. A lean, JIT environment poses too much risk of material shortages for these users.

Capacity is not an issue for these users. They only need to know WHEN they need the capacity and HOW MUCH. Then they’ll make sure it happens.

No negotiation power with customers

Users who have little negotiation power with their customers usually have the following characteristics:

• Often a majority of their business comes from a handful of customers.
• The customers require them to feed their production schedule, and if they’re late they’re heavily fined.
• It’s cheaper to expedite than miss the customer deadlines.
• A highly competitive environment and meeting due dates is critical.

In these situations, the user wants a fixed target for production. They want to know when they need materials in and when they need to increase capacity. They will do whatever it takes to make the date.

Accurate times

Do you have accurate operation times for mfg items and lead times for purchased parts? If not, are you willing to spend time to update them?

APS will push plans forward using mfg times and lead times. If users can identify the critical materials and operations and have accurate times for these, they will find APS results reasonable. In complex manufacturing or assembly environments, balancing/synchronizing material and capacity is more important, and APS can help if a user has accurate data.

Note: in such situations a user does NOT need accurate data on all operations and materials–they only need it for the critical materials and the bottleneck resources.

If a user does not have accurate time information for the critical resources and materials and does not want to do what is required to update those times, then that user is a good candidate for MRP or APSI. In these situations, the user is comfortable with MRP or APSI backwards planning without constraint and working with a rough idea of how much expediting is needed for a given item.

Motivation

Are you actively looking for a solution to improve your planning or are you satisfied with MRP?

APS approaches planning different from MRP. Here are some of the key differences:

• Constraints pushing out plans
• Using projected late instead of past due to flag problems
• Consolidation
• Load (APS provides)
• BOM data needed (can run MRP on lead times, good routing times not  required), good lead times defined
• New parameters

Moving from MRP to APS or APSI requires a significant change. It requires commitment and energy to revise appropriate business processes, obtain accurate date for critical resources and materials, and train the users. Many APS and APSI users have realized significant benefits in reduced lead times, reduced inventory, and increased on-time deliveries. However, if a user is simply trying to move from SL6 to SL7 to take advantage of the Microsoft platform or is happy with the results of MRP, then they are not a candidate for APS or APSI.

Secondary factors

There are a few other factors that differ between MRP and APS. Consider these when making a decision.

Load views

APS and APSI will show you capacity. MRP will not. If you want a view of the load, even if you want an MRP-like plan, and are not using scheduler, then you’ll want to use APS or APSI.

What-if analysis

Only APS and APSI provide what-if analysis with the Analyzer.

Consolidation

Will the difference in consolidation hurt your process? Can you set consolidation times to be equal at all levels of a BOM or use order mins and multiples to manage inventory?

Decision Table

The 3 key questions you need to answer:

Notice that in many instances a user can run APSI like MRP, yet take advantage of some of the tools in APS. To do this you need to make some specific settings.

How to set up APSI to run like MRP

If you want the load data, Analyzer what-if capability, and order visibility provided by APSI, but want it to run like MRP, you’ll need to set a few fields. The table below describes what you should do.