At Sabre Limited, we get asked quite often about scheduling and production planning. The trouble is that customers use the term “scheduling” to refer to any of planning, scheduling or sequencing. We need to dig in a little to find out which of these three they really mean.
It's sometimes difficult to understand the difference between these three terms. In this blog post, we will explore the differences between them and how they are used in manufacturing operations.
Planning can be thought of as the high-level process of figuring out what needs to be done and when. It includes what resources are needed and how best to use them. Scheduling is more granular. For example, you may schedule a truck to arrive at a certain dock during a time frame (such as a 2-hour window).
Then, sequencing is the process of creating a very specific order tasks that must be completed in. It is much more specific than either planning or scheduling. This might be that all white painted parts must be done first, followed by yellow then orange etc.
Now let’s look at each of these terms in more detail.
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Production Planning contains Scheduling, Scheduling contains Sequencing
Planning is not scheduling work on the shop floor. It’s the process of making sure materials and capacity are lined up. Making sure you have enough materials and enough capacity to get jobs done at the right time and meet the deadlines you gave the customers.
Planning is a big thing. It is looking at time in buckets of weeks or even months and making decisions about the future.
Once you have a plan, you need to create a schedule for each bucket of time. Then, when you have the schedule, you may look at the order you want things done in and ask yourself, “what's order do these have to happen in?” That’s sequencing.
Sequencing is not just saying you want a truck to arrive at a certain dock in the morning, but saying you want truck number one to arrive at 5 a.m. and truck number two at 5:45 a.m.
Sequencing is not just saying you want a truck to arrive at a certain dock in the morning, but saying you want truck number one to arrive at 5 a.m. and truck number two next. A schedule is saying “Truck one and truck two need to arrive between 5am and 6am.” Saying “Truck one must arrive before truck two” is a sequence.
The above example is for logistics, but it would be the same thing on a piece of production equipment. You arrange for certain jobs to go before certain other jobs in a very specific sequence.
Planning, scheduling and sequencing are a bit like nesting dolls that way: planning contains the schedule, and the schedule contains the sequencing.
More about Buckets
Buckets are an important part of scheduling and planning. The planning or scheduling bucket has to do with the precision of the schedule. Often things are measured to the nearest standard unit of measurement. For example, the nearest foot or yard.
In planning, your bucket size is the standard unit of measurement.
You are measuring to the nearest hour, day, week, or month. If you have a six-week sales lead time, you are taking orders today and delivering the product in the next six weeks. That's your delivery promise that you've given your customer.
It also means that your bucket size is likely a week for each bucket. You are planning your production orders, your material requirements, and your capacity all at a week-by-week level of precision.
Let’s say you have a six-week lead time. You are not necessarily getting into the hour you're going to do the work, or even the day you're going to do the work, because you have six weeks to get it done. The goal would simply be to get it done a week before it must be shipped.
The shipping department will have a schedule that dictates the day you must ship things on. Perhaps even which hour, but the production should have been done well in advance of that date. The buffer between production and shipping protects you from running into any missed deadlines or production delays.
On the other hand, if your sales lead time was twelve weeks, then your bucket might be two weeks. You have even more time to do it. Generally, the larger the planning bucket, the easier it is to run planning.
Your scheduling bucket in either of the above cases might be one to three days. You may be creating a schedule and sending it out to the shop floor workers. You tell them, for example which jobs they need to do over the next three days. But you wouldn’t micromanage the work being done over those three days.
You do not necessarily have to get in there and tell the operators that it needs to be done at 3 o'clock on a Tuesday. It just needs to be done by the end of day on Tuesday. Within that bucket, the specific date-time isn't all that important to you because you're giving yourself some extra slack.
The Planning is the Most Important Part
Most manufacturers who come to us at Sabre are getting their first real ERP system. They are on the first rung of the ERP system ladder. They need planning to get them started.
Remember our nested dolls analogy from earlier? Planning comes first, then scheduling and sequencing. If a manufacturing company doesn’t have the planning yet, it's going to be hard to do any scheduling.
So, when a manufacturing business gets its first ERP system, usually the first thing they use it for is planning.
The planning is the most important part. It's going to coordinate your materials and capacities within those buckets. You're going to be able to look at a week and see you have 200 hours of work scheduled in your factory that week. That’s called your capacity plan.
If you only have 160 hours of available capacity, then ERP software will allow you to take a step back and see, for example, the week before has lots more extra capacity. Obviously, you can just re-plan things to level them out.
Material planning is getting the parts in on time. Capacity planning is making sure you have enough staff and resources available to do whatever it is you're trying to do.
For most manufacturers a “close enough” approach works great. The planning process is just precise enough and with just enough slack, that they're not going to miss any delivery dates. They're not going to have a problem with capacity or materials, presuming that they have some flexibility, and their shop floor supervisors know what they're doing.
I would guess that only about 15% of companies that do planning need to do detailed scheduling in the ERP. Often the plan is close enough that the shop floor can “self-schedule.”
Scheduling gets a bit more granular. Tightening up times and deciding what you are going to run on each day are big factors when it comes to scheduling.
The goal is to get the lead hands on the floor to do some of that production scheduling. You want to have some flexibility within the bucket.
Your lead hands and supervisors will know that Joe is good at doing a certain type of part on the lathe. Joe is going home at 2 o'clock, so they are going to put these parts on Joe's lathe for him to work on. They will make these adjustments and try to increase efficiency.
It can be a hinderance to over schedule your lead hands and supervisors. They know how those efficiencies work and can rearrange the schedule on the fly.
For example, they knew that they already have the tooling for job #1 on the CNC machine, while job #2 still needs some additional tooling. Job #3 has the same tooling job #1, so they will rearrange the order to make it the most efficient. Job #1 and #3 are put together, and job #2 is last. This is what scheduling is designed for.
This is also sometimes called the dispatch list for the machine. The goal is to get it done by the end of the day. It's not important what order you do it in. It's better to do it in the most efficient order or sequence as possible.
It’s important to note that less than 10% of companies that do scheduling need to do sequencing.
Sequencing is starting to really get into the weeds. More detail about the order in which things should happen, compared to scheduling where things just need to get done by the end of the day.
There are typically two reasons why a manufacturing company wants to do sequencing.
The first one is for set-up reduction opportunities if you do your sequence correctly. For example, in a paint shop there is an order (lighter to darker) you can do your jobs that will be more efficient than if you did them randomly.
The second reason is if there is a constraint that requires you to sequence the work in a specific order so that you can do the production. This might be tooling related, or even related to the electricity draw needed to start and run machines.
An example of the first would be if you have a thickness of material that's going through a machine, and you must do adjustments and setups each time you change the thickness. In this case, you want to do all the material that is same thickness at the same time. This reduces your setup time.
An example of the second that is when a plant only has a certain amount of electrical amperage that they can push through at any given time. This means that workers have to start the machines in a specific order and start the jobs running in that sequence.
The most important thing that sets sequencing apart from the planning and scheduling is you get down to a very minute level with sequencing.
To summarize, planning aligns your capacity and your material requirements, so you have the things you need when you need them. Planning is a broad overview of what needs to be done.
Scheduling is more specific and detailed, and sequencing is the most specific and details oriented. All three of these concepts are important in running a successful business operation.
For many companies planning is a huge step forward, and fulfils the goals they were thinking of when they said “scheduling.”
Scheduling, planning and sequencing are all important parts of running a successful business. Without a schedule, it would be difficult to keep track of production goals and meet customer orders. Planning ensures that the right resources are being used in order to meet those goals. And sequencing puts the plan into action so that tasks are completed in a timely manner.
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