Just-in-Sequence for Automotive Manufacturing Explained
The demand for customization continues to increase in automotive manufacturing. Those utilizing a just-in-time (JIT) process have found it’s still not enough and continue to look for additional ways to cut costs and reduce errors and scrap on the line. With the JIT model, manufacturers found a way to get their parts delivered to the assembly line “just-in-time” as they were ready to be assembled, but different colors and other vehicle specifications existing on one line have introduced other variables that operators have to take into account. There has to be a way to maintain the efficiency that JIT gives manufacturers while also meeting consumer demands for customization.
Just-in-sequence (JIS) manufacturing is considered an evolution of just-in-time. It delivers the right parts to the right assembly line in the right order. Unlike JIT, just-in-sequence models allow line operators to follow a simple sequence of various parts without having to make decisions about what part gets attached to the main component. Line operators working in a JIT-driven environment have less inventory to pick their parts, which reduces their time spent searching for the right one, but they still have to rely on their own logic to decide which part to choose. When a JIS system is implemented, the sequence is already determined, therefore operators can simply take the next component in the sequence and assemble it.
Just-in-sequence is perfect for automotive manufacturing environments because production tends to be high-variety and low-volume. In theory, any component that has a large number of variants can be a great candidate for this type of sequencing.
Types of Just-in-Sequence Manufacturing
Within the just-in-sequence model, manufacturers can sequence the line at different points in the production process. All About Lean effectively describes the three main types of sequencing: pick to sequence, ship to sequence and build to sequence:
Pick to Sequence
“One option is pick to sequence… You have an inventory, and a worker (or a computer system) picks the required parts from the inventory and creates a sequence.
The worker (or computer) would need to know the sequence of production, and then simply select the matching parts for this sequence in the right order. Often, a small buffer is added between the picking and the actual assembly to reduce waiting times of both the pickers (if the main line is slower) and the main line (if the picker is slower). On the plus side, if you have the parts in the inventory, this approach is most flexible to adjust for short-term changes in the sequence.
Ship to Sequence
It is also possible to have the products shipped in sequence. The supplier loads the part on the trucks in the right sequence and drives the goods to the main line. There, the goods are unloaded and brought directly to the line, maintaining sequence all the way to the line.
Build to Sequence
Finally, there is Build to Sequence, also known as Make to Sequence, Assemble to Sequence, or Produce to Sequence. The preceding production processes produce parts exactly in the right sequence needed for the main line. This is regardless if the preceding process is right next to the line or if it is in another plant a few hours away. If it is on the other side of the earth, the effort may not be worth the benefits. You just have to maintain the sequence between the preceding production process and the use at the main line.”
Benefits of Just-in-Sequence Manufacturing
Like just-in-time systems, one of the benefits of just-in-sequence is that it opens up more free space on the plant floor to allow for safer and more efficient processes. Since the next part in the sequence is delivered to the line as it’s ready for assembly, inventory on the plant floor remains low. This allows automotive manufacturers to cut down on the costs of storing large components, such as bodies of cars, on the plant floor.
The biggest benefit that JIS offers over JIT is the reduction in part handling by line operators. Although just-in-time systems deliver parts to the floor only when they’re ready for assembly, this system still requires operators to leave the assembly line to hunt for the next component in the sequence. This reduction in human handling in turn reduces errors since the decision formerly required by the operator is already made before the part is ready to be assembled.
Because of the fewer errors and faster assembly that comes with just-in sequence, manufacturers can increase their production time and output and even take on new clients to begin growing their company.
Challenges of Just-in-Sequence Manufacturing
Since the entire point of just-in-sequence manufacturing is to reduce handling and human decision-making, if your sequence breaks along the way, your efforts will be wasted. It’s less common that the sequence will be originally designed incorrectly, so if a sequence breaks, it’s probably due to a part missing in the sequence or from a defected part. Chances are, the part won’t be replaced in time for assembly. It can be catastrophic if the break in sequence isn’t realized since every subsequent part will be a mismatch.
Since mistakes will happen, manufacturers just need to make sure the right people are always aware of these breaks in the sequence. If a part needs to be removed for repair or rework, you can substitute that part for a matching one and slip it into the sequence to fill that gap. This way, you maintain the sequence and avoid any downtime associated with the defective part. You can do the same thing if a part is missing in the sequence altogether. Of course, this requires that you do maintain some inventory on site, but as mentioned in the different types of sequencing, chances are you’ll always have some inventory, even if it is low. All About Lean reiterates the difference between JIS and JIT in terms of inventory: “…while Just in Sequence benefits from low inventories, it is not a primary cause of low inventories. Granted, you can reduce inventory a bit more, but this is a side effect of what I see as the main benefit.”
Automotive component suppliers are getting hit from all sides; OEMs want and expect variable high-quality parts… and they want it now. Because of these lofty demands and the increasingly competitive landscape, manufacturers will no longer profit from just producing components in batch. If a supplier wants to remain competitive and be considered for new programs, they need to be able to meet demand while maintaining efficiency and accuracy with just-in-sequence manufacturing models.
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