This article takes an in-depth look at curing ovens and their uses.
You will learn more about topics such as:
This chapter delves into the intricacies of curing ovens and the essential techniques involved in heat treatment procedures within these ovens.
A curing oven is specialized thermal processing equipment employed by professionals to enhance the strength and longevity of varied materials. These industrial ovens play a pivotal role in manufacturing processes, including baking, drying, heating, cooking, and curing, all designed to achieve desired effects. Through controlled heating, curing ovens initiate specific chemical reactions. The following image provides an illustration of a curing oven.
Curing ovens fall under the category of heat treating ovens. The process involves raising a material's temperature to within or slightly above a particular threshold. This enhances the material’s physical-chemical bonds, thereby improving mechanical properties. Experts often use catalyzing agents in the curing procedure to fortify and develop more resilient products.
The mantra that "time is money" underscores the importance of maximizing efficiency for financial gain. In curing ovens, catalysts significantly expedite chemical reactions, thereby cutting down processing time. Different catalysts are used depending on the reactants and are effective at specific temperature ranges. Notably, Isocyanate groups are a common catalytic agent used in these processes.
The operation of a curing oven hinges on two core principles:
Heat is crucial to curing ovens' functionality, with primary sources including electricity, steam, direct gas, indirect gas, ultraviolet light, oil, and hot water. These sources also define the classifications of curing ovens.
Electric heat ovens rely on electricity to energize elements that produce the required heat for chemical reactions. They are highly favored in various applications due to the accessibility of electricity, rapid heating, affordable costs, precise temperature management, longevity, and simplicity of operation. Electric ovens are particularly suitable for combustible materials, such as aluminum.
Direct gas ovens apply flames directly to the material, offering effective heating but risking damage to delicate goods. These ovens feature complex systems with high-precision dosing pumps and advanced nozzle designs for heating elements. While maintenance is easier compared to electric ovens, direct gas ovens can be more expensive to purchase.
Indirect gas ovens differ in that the gas flame does not directly affect the material. Heat generated is channeled via a stainless steel heat exchanger. Essential controls often rely on electricity. A fan circulates the heat within the chamber, allowing indirect heat exposure and minimizing potential damage. Though delivering superior results, these ovens are more complex and demand greater maintenance than electric and direct gas ovens.
Steam is praised for its eco-friendliness, cleanliness, cost-efficiency, and ability to reach high temperatures. However, they may have extended heat-up times and are unsuitable with materials prone to rust and corrosion, like iron.
These ovens employ radiator coils for heat transfer using circulating hot water, ideal for clean and eco-friendly heating but not suitable for high-temperature applications, as they generally don't exceed 70°C.
Rarely used in industrial settings, oil-fired ovens serve mostly as backups. They are often less advantageous due to high costs, complexity, and limited user-friendliness.
Airflow patterns are integral to efficient heat distribution in curing ovens, preventing material distortion and safety hazards. Selecting the best airflow pattern is crucial for your process, with options such as horizontal/vertical, vertical, and full horizontal flow. The diagram below demonstrates these airflow configurations.
In this setup, air enters through sidewalls and exits via the ceiling, effective for large parts processing.
This pattern, ideal for suspended materials or small parts on shelves, directs air horizontally from wall to wall, circulating above and below shelves.
With vertical airflow, parts are placed on shelves allowing air to flow from the bottom to the top wall, best for processing small, hung components.
Industrial curing ovens consist of five primary components, listed below.
The enclosure is the part of the oven that creates the environment necessary for the curing process. It is the internal space within the mechanical structure, designed to be sealed to regulate heat flow according to the specific needs of the parts or materials being processed. Key factors to consider when designing an oven include:
The image above displays an oven enclosure, with numbered labels identifying the various components of the design.
Effective heat generation is essential for the curing process, making proper design of this unit crucial. Key components to consider include supply fans, burners, filters, and insulation materials. Accurate calculation of the heat load and heat losses is necessary to properly size and control the burner equipment. Typically, fan motors are sized for cold starts to avoid overloading.
The recirculation system helps conserve air and heat by reintroducing them into the system, ensuring sufficient air for the burner. Ineffective design of the air recirculation system can lead to subpar product quality.
The exhaust air system maintains a clean environment within the oven by removing unwanted gases and fumes.
Industrial curing ovens are primarily categorized into two types:
Batch process ovens function by loading parts into the oven for a set period. These ovens come in various designs, with some featuring rotating mechanisms for even heat distribution, while others keep the parts stationary. Parts are typically loaded and unloaded using transportation carts, and the oven doors are closed afterward. One drawback of batch process ovens compared to continuous ovens is the increased material handling and the need for more workers to set up the process. Additionally, batch ovens may experience uneven heat distribution within the system.
Continuous process ovens use powered transport methods, such as conveyors, to move parts or materials through the oven at a controlled rate. This process typically requires only one operator to oversee and manage the system. Precise calculations determine the exposure time of the materials to heat inside the oven. Parts are continuously moved in and out of the oven via the conveyor system.
Parts of most continuous process ovens include pumps, insulated panels, nozzles, chains, pipe fittings, pressure switches, fans, blowers, burners, flame rods, drives, transmissions, air kits, tooling, regulators, fixtures, controllers, conveyors, fuses, etc.
Ovens can be classified based on various factors such as size, functionality, type of fuel or heat source, and manufacturer specifications. For simplicity and foundational understanding, however, we will categorize them into the two primary types.
| Batch Process Ovens | Continuous Process Ovens | |
|---|---|---|
| Size (Space Occupied) | Relatively big | Relatively small and portable |
| Workers Involved | More than one worker | Usually, one operator |
| Expense | Relatively cheaper | Expensive |
| Material Handling | More material handling involved | Less material handling involved |
| Transportation and Loading | Wheeled carts | Powered conveyor |
| Flexibility | Can take unusually shapes and sizes | Have specific shapes and sizes |
Curing ovens serve a variety of purposes, including but not limited to:
Adhesives are commonly used in industries such as electronics, aerospace, electrical, automotive, transport, clean energy, etc. Depending on the bond strength, adhesives are cured at room temperature, while some require heat (curing oven). Examples of adhesives are white glue, yellow wood glue, super glue, hot glue, spray adhesives, fabric adhesives, epoxy, etc. The figure below shows adhesives that were made using curing ovens.
After painting, curing is used to heat the painted surface, causing the water in the paint to evaporate. This process also strengthens the bonds between paint molecules, enhancing the durability of the surface.
Techniques such as convection and infrared are employed to improve paint curing. Convection curing involves circulating a heated fluid, such as air, oil, or water, around the material, or simply placing the material in heated air. Infrared curing, on the other hand, uses infrared panels within the oven to directly apply energy to the material.
The techniques used in these curing processes include:
This method, also known as radiation curing, involves transferring heat energy through a heated fluid such as air, oil, or water. Most curing ovens utilize air for this purpose. To ensure effective convection, a fan is used to circulate the hot air, along with an exhaust system to maintain proper airflow.
Infrared radiation refers to waves from the electromagnetic spectrum which have longer wavelengths than visible light. In this technique, infrared rays are used for the curing of materials. Infrared ovens are faster than convection ovens. This technique is more efficient than convection because it targets heat points, unlike convection, where heat is distributed everywhere.
The UV curing technique uses ultraviolet light to trigger a photochemical reaction that creates a network of polymers. This method is employed in various applications, including printing, coating, stereolithography, and material assembly. Known for its low-temperature and high-speed process, UV curing is widely utilized in the automation industry.
Polymerization is the process in which small molecules, called monomers, join together to form long molecular chains known as polymers. Curing polymers involves transforming liquid, low-weight polymers into solid, infusible three-dimensional structures. This process typically requires heat (from ovens), high-energy radiation, and catalyzing agents. Common chemical processes for curing include polyester resins and phenol-formaldehyde resins.
Curing ovens are designed to operate within specific temperature ranges. Exposure to these temperatures causes the water or moisture within the material to evaporate, resulting in a strong and hardened product. Drying is crucial for many products because retained moisture can lead to undesired reactions. For instance, in paints, excessive moisture can distort or disrupt chemical bonds, compromising the quality of the finish.
Curing ovens can also be used to preheat materials before coating. In this context, the ovens help remove any excess moisture that could interfere with the coating process.
Finishing refers to the process where curing ovens are used to protect materials and parts from corrosion and rust. By strengthening and hardening the materials, curing ovens enhance their resistance to corrosion and extend their durability. In addition to finishing, curing ovens are also employed for other tasks such as drying, dehydrating, and baking. These processes are crucial for enhancing the appearance and color of materials, achieved through applying heat at various temperatures and using different curing techniques.
The benefits of using curing ovens include:
Unlike traditional ovens, curing ovens are compact and portable, making them easy to transport with small trucks. Technological advancements have led to more efficient and space-saving designs. In the past, ovens were large and costly to transport, maintain, and handle, but modern versions are more accessible and affordable.
Contemporary curing ovens offer versatility, capable of handling a range of applications including drying, baking, and dehydration. Advances in control technology allow these ovens to adapt to various products, temperature settings, and part sizes. Customizations such as adjusting shelf numbers and insulation materials can be made based on processing needs.
Due to their reduced size, curing ovens are less expensive to manufacture than larger counterparts. They are also simpler to clean, maintain, operate, store, and accommodate. Their cost-effectiveness and ease of use have contributed to their growing popularity across different industries.
Curing ovens are readily available and increasingly popular, with many manufacturers offering them at affordable prices. Their widespread availability makes them a convenient choice for various applications.
This chapter will cover the key considerations for selecting curing ovens and the importance of maintaining them.
When choosing a curing oven, several factors should be taken into account:
Before purchasing a curing oven, it’s important to clearly understand its intended use. This involves consulting with a specialist who has thoroughly researched and evaluated whether alternative, more cost-effective methods could replace the oven. It is advisable to invest in these machines only when they represent the most suitable method for processing the product.
Price is a crucial consideration when selecting a curing oven. Prioritize the quality of the product over the cost. It is better to invest in a high-quality machine at a higher price than to settle for a lower-quality oven at a lower cost. However, the ideal situation is to find a competitively priced oven that offers high quality.
Ensure that the oven supplier meets the necessary certification standards for electrical and electronic devices. Verify if the supplier can handle design and maintenance in-house, which is beneficial for addressing any faults or troubleshooting needs.
What types of control systems are in the oven?
How effective is the airflow pattern of the system?
What heating methods are used, and what is their power consumption?
What is the curing rate of the machine?
How effective are the gas or electric heat sources?
Factory acceptance testing involves asking the supplier if they can test or operate the product before shipping it to you. This step helps ensure that the product is free from faults and functions properly before it arrives.
The best maintenance is typically provided by the manufacturer of the product. Inquire whether the company offers after-sale services such as maintenance or installation. This helps in planning for future needs and avoiding unexpected expenses. Consider the durability and expected lifespan of the curing oven: will it last long enough?
Maintaining curing ovens is crucial because malfunctioning parts can lead to undesirable results. Maintenance routines should be performed regularly, with weekly checks recommended for many industrial ovens. Below are some parts that should be regularly inspected if they are part of the oven:
A flame detector is crucial for detecting fuel leaks inside the oven. For highly flammable fuels like gas or diesel, regular checks of the sensor/detector are essential to prevent potential explosions. The detector should be replaced at scheduled intervals rather than waiting for it to fail.
Regular inspection of the burner is important because it generates the spark needed to ignite the fuel. A weak spark may result in incomplete combustion or operational faults.
The air filter should be examined and cleaned if contamination is present. The burner needs clean air to ensure complete combustion.
Regular maintenance of the motor and blower impellers is essential to prevent dirt buildup between the impeller fins and the motor housing. Accumulated dirt can lead to overheating due to poor air circulation. Ultimately, this can affect the efficiency of the system and the quality of the processed material.
The fan distributes air throughout the oven. If the fan isn't functioning properly, some areas of the oven may not receive adequate heat. This can result in uneven material processing, with some parts being too hard or too weak, potentially leading to cracks or burns. The fan should be properly lubricated to ensure it operates at the correct speed for effective processing.
Occasionally, parts may fall or become trapped inside the oven. Maintenance should include retrieving these parts and reinstalling them in their proper positions.
A curing oven can be used by thermal specialists to improve or enhance the strength and durability of materials. Many factory processes such as baking, drying, heating, cooking, and curing require industrial ovens to make a specific product. To achieve this, the material is heated to accelerate a desirable chemical reaction. It is critical to consider various aspects discussed in this article before deciding on the appropriate curing oven for a specific use.
A conveyor oven is a continuous flow oven; it‘s an oven that is open on opposing sides and has a conveying system running from one end of the oven to the other. Designed like a batch oven, conveyor ovens have the additional benefit of keeping products moving while providing continuous and uniform heat...
An industrial oven is a device used to create extremely high temperatures to heat treat parts, condition metals, and cure metal coatings. Common functions for industrial ovens include drying, curing, testing, and coating of parts and products...
An infrared oven is an oven that heats objects or cooks food using infrared radiation instead of conventional conduction or convection heating. People can use infrared ovens in commercial kitchens, homes, or...
Industrial ovens are thermal processing machines used as heating chambers for drying, curing, and baking of foods, parts, and components. The main industries that use industrial ovens are chemical and food processing and electronics manufacturing...
A furnace is a direct fired device used to provide heat for industrial processes that require heat in excess of 400° C (752° F). Any industrial application that relies on heat to create a reaction or heat materials for production uses an industrial furnace...
A normal function of an industrial furnace is to heat treat metals for annealing, tempering, or carburizing and pre-treat materials for forging. Though metal is a common material to be treated using an industrial furnace, other materials are also...