Comparative Analysis: Wet Molding Vs. Dry Forming (Dry Molding)
In the ever-evolving landscape of manufacturing technologies for packaging production, the choice between wet molding and dry forming (also known as dry molding) stands as a pivotal decision, with far-reaching implications across industries. As manufacturing processes continue to advance, understanding the nuances between wet and dry molding becomes increasingly crucial for informed decision-making.
This article delves into a comparative analysis of wet molding versus dry forming, dissecting their disparities in manufacturing processes, material compositions, environmental footprints, applications and technology cycle times and costs. By unravelling these key factors, we aim to provide a comprehensive framework for evaluating the optimal approach tailored to specific industry needs and sustainability goals.
Manufacturing Process
Wet Molding Process - There are 3 main types of manufacturing processes for wet molded packaging: one-cast, transfer molding and thermoforming, the latest producing packaging that more closely resembles Yangi’s dry formed packaging.
The wet molded process starts by either collecting and sorting recycled cardboard paper or utilizing virgin wood pulp fibers depending on the final application (respectively lower or higher-grade applications).
The fibers are then dissolved in a pulper to form a slurry. For optimal formation and even distribution, the fiber concentration should be kept low. In many cases, they are gradually diluted through various steps until the fiber content is less than 1%. At times, the fibers also undergo refining to open up their surface and enhance bonding before reaching the final concentration through dilution. At this stage, functional chemistry, such as AKD is also added to the slurry for hydrophobicity.
Once the slurry is ready, the molds are then dipped into the slurry and then subjected to vacuum suction, which accelerates the dewatering process. As a result, the fibers adhere to the mold while excess water is simultaneously drained off.
Following dewatering, the fiber mixture undergoes pressing to further consolidate the fibers and remove additional moisture.
Once adequately compacted, the molded products are transferred to one or several drying steps. The drying can be done in an oven (low-grade applications such as egg cartons), in one or several thermoforming steps or a combination of those, where they are exposed to heat to evaporate the remaining moisture. This drying stage is crucial for ensuring the structural integrity of the final product.
Once molded and dried, in certain cases, one additional surface finishing process is done before trimming, cutting, or surface treatment is applied to achieve the desired appearance and functionality.
Thermoforming “Thin-Wall” Wet Molded Process
Yangi’s Dry Forming Process (also known as dry molding)
The dry forming process starts by selecting optimal cellulose material that has been proven to deliver the highest quality dry formed products. The raw material is fed into a mill that separates the fibers, getting it ready for the airlaid formation technology. Through a specialized air system engineered for optimal fiber formation, the separated fibers are then transported to the airlaid forming station.
The airlaid forming of cellulose fibers technology enables the creation of high-quality and consistent cellulose-based packaging materials by ensuring even distribution and interlocking of fibers. Yangi's Cellera dry forming technology is based on a robust dual drum forming process that produces discrete pad formations designed to generate minimal waste and deliver low variation in grammage weight. The pad geometry and grammage can be tailored to suit specific product requirements. Additionally, the tooling can be easily modified, enabling quick adjustments to grammage as needed.
Once formed, the pads are then transferred to be 3D formed by a unique technology that ensures accurate pad placement in the 3D forming press for consistent results.
The 3D pressing technology complements the airlaid forming process by applying pressure and heat to the cellulose fibers, transforming them into a durable and versatile packaging structure. Heat and pressure are applied to bind the fibers together and form the desired shape without the need to add any process water.
Once formed, finishing processes such as trimming, cutting, or surface treatments may be applied to achieve the desired appearance and functionality.
Depending on product requirements chemical additives can be added in the process to achieve improved product functionality such as water and oil resistance, as well as improved strength.
Yangi Cellera - Dry Forming Process
Material Composition
Wet molded packaging – Depending on the manufacturing method and the intended use of the product, different materials can be employed to create wet molded packaging. Recycled paper grades like corrugated board and newsprint are typically used for type 1 packaging, which is considered low-grade and offers lower performance. For higher-quality packaging, type ¾, virgin fibers such as wood pulp or bagasse are preferred. When packaging comes into direct contact with food, it's essential to use virgin fibers to ensure compliance.
Yangi's dry formed cellulose packaging – Our selection of raw materials is rigorously curated to guarantee a robust process and to achieve high, uniform quality, and transparency. At Yangi, we prioritize certified wood pulp fibers sourced from sustainable forestry practices, reflecting our commitment to environmental responsibility and ethical production practices. Depending on the intended application, we carefully choose the most optimal quality in terms of origin, fiber length, and properties. In our pursuit of excellence with dry formed fibers, we understand that the choice of materials is crucial.
Environmental Impact
Wet molded packaging is eco-friendly as it's made from recycled materials and is biodegradable. Though its production may use more water and energy than dry molding, it offers positive environmental impacts. Biodegradable and compostable, it breaks down naturally, minimizing pollution. Overall, wet molded packaging provides an eco-friendly alternative, supporting sustainable resource management and waste reduction.
Yangi's dry formed packaging is a sustainable solution and with cellulose fibers being the only material that currently fits into existing recycling systems globally, of which more than 70% is recycled and where the fibers can be recycled back more than seven times, cellulose fiber offers positive environmental impacts. With a manufacturing process consuming significantly less energy and water than wet molding resulting in lower CO2 emissions, and fibers sourced sustainably, it ensures long-term sustainability, contributing to a circular economy.
Applications
Image Source: pulpmodlingchina.com
Wet molded products – Due to form (geometry) and aesthetic limitations, molded pulp products have historically been restricted to the egg tray market for many years. However, demand is now increasing due to their sustainable qualities which propelled advancements in the wet molding process, with the most recent development being “Thermoformed” (“Thin-wall”) molded pulp products. This process produces high-quality thin-walled items with good dimensional accuracy, and smooth, rigid surfaces. The result resembles the appearance of thermoformed plastic items and delivers products that are comparable to Yangi’s dry formed 3D formed products.
Yangi's dry formed products – Versatile and suitable for a variety of applications across industries, dry formed products are known for their strength, rigidity, and precise shape. Additionally, they offer unique possibilities compared to other cellulose materials in terms of formability, aesthetics, and appearance. When formed, the surface is smooth, and the tactility can range from hard to soft feeling. Patterns inside and outside of the product are possible and create a lot of options for branding.
The most notable difference between wet and dry applications is the height requirement of the product, in other words, deep versus shallow products. Dry molding excels with shallow products, offering unparalleled effectiveness. Conversely, for deeper and more intricate products, like multi-compartment items exceeding 5 cm in depth, wet molding has proven less problematic this far. That being said, at Yangi, we are fully committed to ongoing research and development aimed at expanding the depth of our product offerings to cater to a broader range of applications.
Technology Cost & Cycle Time
Dry forming packaging generally incurs lower costs compared to wet molded packaging due to several factors.
Firstly, dry forming process require less water and energy consumption, resulting in reduced operating costs.
Dry forming features shorter cycle times, approximately 4 seconds depending on grammage and product shape, resulting in heightened production efficiency and reduced labor costs. Conversely, wet molding generally entail longer cycle times, around 30-70 seconds depending on product complexity, due to required drying stages, potentially extending production time and labor costs.
Finally, wet molded packaging may involve higher initial investment costs due to the need for specialized equipment and infrastructure for handling water-based processes.
Overall, while both dry formed and wet molded packaging have their unique advantages and challenges, dry forming generally offers cost savings and shorter cycle times compared to wet molding.
Conclusion
Wet molding stands as a well-established technology, yet its potential for optimal runnability and product functionality remains largely untapped. Challenges lie in water and energy consumption, along with extended cycle times. However, it offers unparalleled flexibility in product depth and designs.
On the other hand, dry forming emerges as a newer technology, albeit with more limited possibilities in terms of depth due to the constrained formation of fibers compared to wet molding. Nonetheless, dry forming boasts advantages such as shorter cycle times, reduced energy and water consumption (no need for water handling systems), a smaller machine footprint, and premium aesthetics with robust technology and processes, as exemplified by Yangi. Additionally, the dry forming technology requires minimal cleaning, offers faster tooling commissioning (less than 2 hours), cheaper tooling costs as well as greater flexibility in adjusting grammage.
Each technology has its own set of advantages and challenges, and there is no universal solution that fits all scenarios. If you're unsure about whether Yangi's dry forming technology is the right fit for your current requirements or if you would like to learn more about the difference between the wet molded and dry forming technologies, feel free to reach out to us.