Batch Process Flashcards
What is a batch process?
A batch process is a type of production in which units are produced in batches instead of one by one (individually).
Batch processes and setup go hand in hand.
What is setup (time)?
Setup time is by PER BATCH basis.
In this module, setup time is fixed. It is a constant value in this module.
Setup time and batch size interacts in such a way as to reduce the process capacity.
Also known as change over time or switch over time.
Setup time is required to change production from one type of product to another.
During this change, the time used to complete this activity does not depend directly on the number of units produce.
For example: Making clothes. We need to change the dye to obtain clothes of different colors. This time used to change the dye is the setup time.
Batch processes and setup go hand in hand.
What is a batch size?
This refers to the number of flow units on each tray going into the oven.
What is a production cycle?
A repeating sequence of produced units that can include set up time, production time and idle time.
It is the total sum of when the process starts and when the whole process ends, includes the fixed cost time (setup time).
Production time is how much time the flow unit is being worked on. Different from production cycle.
What is capacity?
Capacity = (# of units processed) / (total time taken)
= b / time for a production cycle
, where b = batch size.
Time for a production cycle = b x unit processing time + setup time.
- Setup time must add every changes there is in the process.
- Unit processing time needs to include the unit processing time of all the different processes in the batch process. If there are two activities in the production cycle, the total unit processing time will be the sum of the processing time of both the activities.
What is a batch?
The group of flow units(cookies) on a tray that is going into the oven to be cook.
In this module, we are assuming that at any point of time, no flow units will be taken out of that group until the whole batch is processed.
When batch is greater than 1, it makes the flow time of the flow unit longer.
What affects the process capacity?
- Batch size
- Setup time
Setup and set down time. How do we read set down time?
Set down time is considered as part of setup time as it is required before the production can continue.
What is Cml?
The capacity of a resource. This is a rate. If capacity is fixed, the processing time will be fixed at 1/Cml.
How can a process capacity changed when the capacity of resources are fixed?
It is because:
1. Setup time.
2. Batch size.
Capacity with Setup and Batch = Cbs.
We need to assume that the setup is non zero and batch size is greater than 1.
Batch size of one is basically the flow unit itself.
Cbs
= Total units processed / Total time taken
= B / (S + pB)
1 cycle = S + pB
If setup is 0, what happens?
When there is no setup time, and using the formula of B / (S + pB), we can recover Cml = B / pB. -> B = batch size
With the presence of setup time, it will affect the process.
Setup time is always a bad thing as it always reduces the capacity, Cbs.
When setup is 0, we achieve the ideal situation.
Reducing setup time is always the right option to help improve Cbs.
In the presence of set up time, is large batch size better or small batch size better?
When there is setup time, we will prefer the batch size to be larger by theory.
When there is very large batching, what can happen?
When batch size goes infinite, Cbs = 1 / p = Cml.
We can recover the original machine-label capacity.
Large batch size is a good thing. (It will be generally better than reducing the setup time)
How can one increase process capacity?
Increase the batch size. Reducing setup time can be more difficult to achieve than increase the batch size. Hence, choose increasing the batch size is better than reducing the setup time.
Increasing the batch size is the first option. If that is not possible, then we choose reduce the setup time.
