Batch Processing vs. Continuous Process: Make the Move in 3 Easy Steps
Just about all new products and new processes start out using batch process in the lab. When you’re developing a new product, typically you are testing the heating process in batches, trying out small samples in a bench top oven to figure out the combination of temperature and heating time that produces the best quality product.
Likewise, if you’re starting up a new business you’ll probably begin by producing your product in batches. When you’re just starting out, you may have limited space and capital, and you’re still producing on a small scale.
But when it’s time to think about manufacturing on a larger scale, batch processing becomes less desirable.
How batch processing may be holding you back
- Batch process heating is labor intensive and requires a lot of material handling.
- The start-and-stop nature of the process limits your production capacity. The small capacity of batch ovens and the time required for each batch determines the maximum amount of product you can make.
- Due to the inefficiencies of the process, the production cost is high. This may affect your ability to price your product competitively and impacts your profits and your bottom line.
To grow your capacity and your business, you may be able to speed things up by moving to a continuous heating process.
That being said, there are certain kinds of products and processes that require heating for a very long period of time. If that’s the case, you may be forced to continue with batch heating. An example is the airline industry, where airplane wings made with carbon composites and epoxy need to be heated and cured for a period of hours rather than minutes. In a case like this, batch processing may be the only way.
What you stand to gain with continuous process ovens
The increases in production efficiency and economies of scale that you can gain with continuous processing are enormous.
Let’s assume you currently use batch heating for a product with a relatively short heating time, under one minute. In addition to that heating time, you have to load each batch into the oven and unload when it’s done. That loading and unloading time means it may take several minutes or longer to complete one batch. And the small size of the batch oven limits your capacity still further. Plus every time you open the door, you lose heat from the oven and the temperature drops. You have to add time for the oven to come back to the set point.
Testing may determine that your heating time can be reduced to 5 seconds. With a continuous process oven moving product at one foot per second, a 5 foot long oven can dry 60 feet of product in one minute.
The resulting increase in production capacity and decrease in cost can help you to reduce the price of your product. This is one reason that the price of solar panels has come down dramatically over the past few years. Instead of processing individual panels one at a time, manufacturers are now processing solar cells using rolls of material in a continuous process, applying silicone coatings to polyester film. A 5000 foot roll of material can now be completed in about 1.5 hours without stopping.
To use continuous heating, your process must work with higher rates of heat transfer and shorter heating times. To determine if this is possible, start by performing testing under a range of conditions to see if you can shorten your heating time without negatively impacting product quality.
Choosing the right continuous process ovens
The goal in continuous processing is to reduce the heating time as much as possible. If testing shows that you can reduce the heating time by using a higher temperature or a different type of heating, then moving to a continuous process can greatly increase your efficiencies of scale and decrease your production costs.
So how do you translate your batch heating process to a continuous process that will allow you to produce more product more efficiently? The challenge is determining the right type of heating and the right dryer design to achieve what you need.
Batch ovens use hot air convection, often with doors for manually loading and unloading batches of product in and out. When you move to a continuous process, there are many more options for heating technology and automatic material handling.
In the web processing industry, the material is typically on a roll. It moves through the coater and dryer and is then rewound onto rolls. The length of the dryer depends on the type of coating, thickness of coating and line speed. If your testing confirms that the product can accept high heat, you may be able to use a hybrid dryer that combines infrared (IR) with hot air to reduce both your drying time and the size of the dryer. For the right application, adding an IR pre-dryer in front of a hot air convection dryer can reduce the drying time to seconds, which will significantly reduce the size of the dryer.
The bottom line is that moving to continuous processing ovens requires testing and the expertise to determine the heating technology and oven design that will produce the best results. Your best bet is to find a vendor with a well-equipped lab line so that you can test different options with real product samples. A vendor who offers this service will also have the experience to help you determine the design that’s right for you.
Moving to continuous processing may also mean moving to a new vendor to get the expertise you need for developing the right dryer technology and design. You may be concerned about making a mistake with an unfamiliar vendor that may not do what they promise