Discrete vs. Process Manufacturing

Can you take apart a car? – Discrete Manufacturing

If you have a car, can you run the assembly line in reverse? You can. You can take off the tires, remove the windows, remove the engine, remove the transmission, remove the seats, and so on.

It may be time-consuming … and you may need different processes and equipment to help with the disassembly … but it can be done. And in the end, you will have most of the materials and subassemblies that you started with.

That’s because automotive manufacturing is primarily a discrete process. It is primarily physical in nature, and the component parts are not chemically altered, just assembled.

Discrete manufacturing produces distinct items like cars, phones, and furniture. The focus of this process is on tracking the physical components parts, as defined by the Bill of Materials (BOM), as they move through a defined sequence of steps utilizing a Manufacturing Execution System (MES).

Can you take apart a cake? – Process Manufacturing

What about a cake that is manufactured as part of the food and beverage manufacturing process? Can you take the cake apart once it has been baked with sugar, salt, yeast, flour, milk, and water? No, that is not possible.

That’s because food and beverage manufacturing is a type of process manufacturing. In process manufacturing, there is a strong element of chemistry, where the very molecular nature of the raw materials is changed into something of a completely different atomic makeup. No process in the world can turn that cake back into its initial constituent parts.

Process manufacturing produces goods that are measured by volume or weight, like pharmaceuticals, chemicals, food, and beverages. The focus of this process is on tracking recipes, formulas, and the flow of materials through chemical or biological reactions.

Discrete vs. Process Manufacturing Comparison Table – Full Summary

	Discrete Manufacturing	Process Manufacturing
Can You Take It Apart?	Yes	No
Manufacturing Process	Physical Assembly	Chemical Reaction
Industry	• Automotive • Aerospace & Defense • Semiconductor • Industrial Equipment • Medical Devices • Furniture & Home Goods	• Food & Beverage • Chemicals • Pharmaceuticals / Biotechnology • Materials & Metals • Energy & Refining
MES Functionality	• Work Instructions • Component genealogy • Labor tracking	• Batch/lot tracking • Formula & recipe management • Process parameter monitoring & control • Electronic Batch Record (EBR)
APS Functionality	•Reducing changeovers •Bill of Materials explosion •Materials feeding •Constraint-based sequencing/scheduling	•Reducing changeovers •Share resource utilization & capacity planning •Recipe-based scheduling •Shelf-life management

Discrete vs. Process Industries

Discrete Manufacturing Industries

Make to order and make to stock industries that utilize primarily discrete manufacturing include:

• Automotive: Production and assembly of cars, trucks, motorcycles, and buses.
• Aerospace & Defense: Production and assembly of airplanes, helicopters, satellites, spacecraft, and missiles.
• Semiconductor: Assembly and packaging of chips onto PCBs.
• Industrial Equipment: Manufacture and assembly of construction equipment, agricultural equipment, robots, and other equipment needed to run factories.
• Medical Devices: A heavily regulated industry that manufactures MRI machines, X-rays, blood analyzers, pacemakers, and a variety of surgical equipment.
• Furniture & Home Goods: Assembly of tables, chairs, sofas, cabinets, and lighting fixtures.

Process Manufacturing Industries

The industries that utilize process manufacturing primarily include:

• Food & Beverage: Transform raw agricultural products into chemically unique consumable products.
• Chemicals: Transform raw materials into new substances.
• Pharmaceuticals / Biotechnology: Synthesize new health-focused chemical compounds.
• Materials & Metals: Transform raw ores into new standardized and uniform materials.
• Energy & Refining: Extract & transform natural resources into fuels.

Both discrete and process manufacturing utilize manufacturing software, especially manufacturing execution systems (MES) and advanced planning and scheduling systems (APS) to manage operations. But they use MES and APS in critically different ways.

MES in Discrete Manufacturing

1. Work instructions: The MES system contains work instructions, a set of step-by-step, visual instructions for the operator, showing how all of these materials will come together. Of course, each operator is building just a piece of the final assembly, so the MES system screen at their work station will show them just the instructions they need to complete their task.
2. Component genealogy: The MES system will also help track exactly what components went into what products. For example, a finished car will be assigned a vehicle identification number (VIN), and a mobile phone will be assigned a serial number. But the MES will also track the component genealogy, or what specific parts went into that specific car or phone.For example, engine #142 went into the car with VIN AKE8171. Or microprocessor chip Snapdragon 400 #12291 went into the phone with serial number 1182AJIA81.This is important from a traceability standpoint. If there is a problem with a set of products that came off the line, and it is determined that the fault is with a specific subassembly. The MES traceability record will allow the manufacturer to identify all the products with that faulty subassembly and recall or service them if necessary.
3. Labor tracking – The MES system in a discrete manufacturing environment is also important for monitoring the performance of manufacturing equipment and staff. It can detect anomalies in machine performance. It can also track the amount of time that operators take to complete specific tasks, tied to specific operations. This data can be used to optimize the operations.Machines can be flagged for maintenance or tuning to keep them calibrated, running at full capacity, and increase their life span. The performance of machine operators can be improved by optimizing their workflow.

MES in Process Manufacturing

In process manufacturing, there aren’t so many discrete physical units as there are batches of material. In fact, whatever physical raw materials are being used, they will be transformed into a completely different substance. Therefore, tracking the original ingredients through to the end, like in discrete manufacturing, is impossible. The MES system in process manufacturing is used instead to control and record the process of this transformation.

1. Batch/lot tracking: The MES is tasked with tracking the entire batch of material as it moves through the process. Let’s say you are making a pharmaceutical drug. You know that you start with 5000 liters each of Substance A, Substance B, and Substance C. You will maintain a record of those batches. After you mix them together, you produce 15,000 liters of a new batch of material, Substance X, and you assign it a new batch number.
2. Formula & recipe management: The MES will contain the master formula, or recipe, including the ingredients, amounts, and transformation parameters. This is similar to the bill of materials and work instructions for discrete manufacturing, but of course, instead of tracking how specific parts will be assembled, the focus is more on providing instructions on how to mix substances and control the environment to produce the desired chemical reaction.To build on the example above, the recipe management function of the MES may call for 100 liters of Substance A, B, and C to be combined in a special mixer, heated to 25 degrees Celsius, and mixed at a particular speed for 50 minutes.
3. Process parameter monitoring & control: The MES system continuously monitors and records critical process parameters (CPPs) like temperature, pressure, pH, and flow rate. It ensures the process stays within its validated recipe limits.As we are producing substance X, sensors in the equipment can communicate the temperature of the mix as it is heated, sending a reading every second to the MES system. A different set of sensors may measure the flow rate of the substance as it flows out of the mixer when the mixing operation is completed.From the flow rate, we calculate the viscosity of the intermediate substance to make sure that it stays within certain boundaries. If the viscosity is outside of the recipe limits, then we know that there was a problem with the mixing operation, and the MES system can send a warning to the operators. We can correct this problem quickly at this stage of production.
4. Electronic Batch Record (EBR): Each action, material addition, and parameter reading is recorded to create a compliant batch record for regulators, like the FDA. The batch tracking information and execution data are stored for each lot of material. It shows that every action was carried out as specified and every parameter reading was within compliant bounds.This gives us the confidence that we have created a safe, quality product. If there is a problem with the product in the future, then the EBR can be evaluated to help understand where there could have been a problem in the manufacturing process.

APS in Discrete Manufacturing

In discrete manufacturing, the products are usually quite complex, consisting of thousands, if not millions, of parts. The big challenge is figuring out how to coordinate the assembly of those parts … to make sure that they come together correctly … and to do so in a way that is as efficient and cost-effective as possible. Therefore, the role of the advanced planning and scheduling system in discrete manufacturing is primarily one of sequencing and material synchronization.

1. Bill of Materials explosion: All of the components that need to come together in a final product are recorded in the bill of materials (BOM). But to understand what materials are needed at what stage in the production schedule, the assembly process must be run in reverse. The BOM must be decomposed into all the different sub-level assemblies needed per stage.
2. Material feeding: The discrete manufacturing MES will give the operator work instructions on how to assemble those sub-level assemblies, but to make sure that all of those materials get to that operator’s station at the correct time … that is the role of the APS system.This is a complex process because in the modern discrete manufacturing plant, there is rarely just a simple, linear assembly line with all the work stations back to back. In the past, you had just that. In the case of car manufacturing, a big piece of sheet metal would be stamped into a car frame. Then it would be painted. Then the engine and transmission would be added … then the windshield … then the seats … then the wheels and so forth. The subassembly would travel down the assembly line, and pieces would be added to it until it was a finished vehicle … and it would literally then roll off the line.But today, most discrete manufacturing operations are asynchronous. You have a massive number of workstations creating different sub-level assemblies that may not even go into the same product. These subassemblies are moved between workstations in non-linear paths through the factory. Some may be shipped to other factories. Some may be held in Work-In-Process (WIP) buffers.The APS system ensures that the materials, including subassemblies, needed at each station are delivered on time, and ideally just in time.
3. Constraint-based sequencing/scheduling: The asynchronous nature of the discrete manufacturing process may seem unnecessarily complex, but it’s all about optimization. It’s not enough to just put the final product together. To stay competitive a discrete manufacturer must maximize machine and labor utilization, reduce bottlenecks, and balance the workload … because this reduces costs and improves product quality.Discrete manufacturers use advanced sequencing and scheduling algorithms built into APS software to look at;
   1. the billions of possible ways that the factory assets, machines, and operators can be used to build the orders based on the BOM;
   2. the raw materials and sub-assemblies available on hand;
   3. order priority

… and to select the most efficient production sequence or schedule. This schedule is then fed to the MES software for execution, and the factory floor comes to life.

APS in Process Manufacturing

The complexity in process manufacturing space comes not from a large number of parts, because they are usually a limited set of ingredients, but instead from the orchestration of a set of highly sensitive chemical reactions.

1. Reducing changeovers: Whenever you run chemical reactions, you produce residues in the reaction vessels/equipment. Cleaning those vessels is a time-consuming and often expensive process. APS software in the process industries is tasked with figuring out how to reduce such changeovers. If there are some types of reactions that can be run back-to-back in the same vessel without needing a changeover, the APS system will prioritize that sequence.Changeover management in discrete manufacturing is important, too. For example, some equipment must be set up or calibrated differently if changing between product types, and for that reason, discrete manufacturers also try to group similar products together. Fortunately, recalibrating a machine is often less costly, both in terms of time, materials, and waste management than cleaning out large reaction vessels.
2. Share resource utilization & capacity planning: The availability of key process resources like fermentation tanks, reactors, and storage silos is often a key bottleneck. The APS system is used to figure out capacity by looking at the vessel size and cycle time of the chemical reactions. It then calculates the best way to use these shared resources.There is a lot of overlap here with discrete manufacturing, because the discrete process also often includes the use of important shared resources that can be utilized simultaneously to build different subassemblies, at different stages of the production process.
3. Recipe-based scheduling: The process schedule often has a fixed time requirement for each step in the recipe. For example, the mixing time, reaction time, and curing time are finite. The APS system will take this information, as well as the resource availability from the step above, into account when creating a schedule.
4. Shelf-life management: Because we are often dealing with chemically reactive substances in process manufacturing, the shelf life of raw materials and intermediates is a key concern. The APS system must prioritize using materials before they expire.