Roboze PRO 3D printing solutions for paper pulp mold

What is paper pulp?

Molded pulp products are mainly used for packaging and food carrying products such as containers. In the past, paper pulp products were limited to eggs cartons, but in recent years the type of products manufactured has expanded greatly, also thanks to 3D printing. This is because of social, economic, and in particular environmental concerns; in the last decade a strong emphasis has been placed on reducing the use of plastic packaging and shifting to sustainable solutions.

How do you manufacture paper pulp?

Being composed of simply water and wood fibre, paper pulp is a renewable material and a biodegradable solution, making it a perfect substitute for traditional materials such as foam. The typical forming process involves two basic steps: first, a mold is submerged in the pulp-water slurry where the fibres stick to the outside of the dies thanks to a vacuum process; second, the product is removed from the mold and dried in an oven. The paper-water slurry is composed of blended paper products and can include also recycled paper pulp containers, thus closing the manufacturing loop.

Main types of molded pulp products available

There are four basic types of molded pulp products:

• Thick wall (5 – 10 mm): made using an open mold and then dried in an over, they have a rough side and a smooth side;
• Transfer molded (3 – 5 mm): here the product is transferred between two molds, resulting in both sides being smooth;
• Thermoformed (thin wall): like transfer molded packaging, here one of the two molds is heated so there is no need for oven curing;
• Processed: these are types of packaging that require further treatments such as painting or additives.

Thick and transfer molded products are the simplest to make and most common. They include objects such as egg containers, endcaps, and drink holders. Thermoformed products are more recent and have a smoother surface finish, they include cutlery, plates, and cups. Processed paper pulp products simply include an extra step where they are painted or an additive is mixed with the paper-water slurry.

The limits and costs of the production of paper pulp molds

The environmental advantages of paper pulp products are very clear, so more and more companies are turning to this technology for their needs. Unfortunately, like with many other types of products, such as injection molding, the manufacturing of the molds themselves can be a bottleneck since they are expensive and time-consuming to make.

Molds are typically made from aluminium or steel, which are expensive and heavy materials; traditional manufacturing techniques such as CNC machining necessitate that material is removed from stock until the final shape is achieved, resulting in a lot of wasted metal. Being heavy, they are also cumbersome to handle and represent a hazard. In the end, metal molds can range in cost anywhere from 10,000 to 30,000 dollars each and can take weeks if not months to manufacture, greatly slowing down the start of production.

This is even more so when both the main and transfer molds are required, which doubles the cost and time. The shape of paper pulp products can vary from very simple, such as edge protectors, to very complex, such as end caps for laptops and televisions. This complexity is further increased when channels must be included in the mold to allow the suction of the paper-water slurry, adding to the cost.

The solution: Roboze Plus PRO and ToolingX CF composite material

Roboze's experience in the additive manufacturing sector dedicated to optimizing metal replacement parts has led to smarter and more cost-effective solutions to meet the need of improving workflow and workforce capabilities, achieving cost and time savings thanks to faster development and production cycles.

This is the case of the new PRO series, 3D printing systems aimed at supporting production with industrial quality levels with high-performance polymers and composites.

Production of strong and low-cost paper pulp mold with 3D printing

The case of paper pulp molds production is a great way to explain how the process, and the associated investment, changes and evolves. The process involves two phases:

1. selecting an appropriate material for the application;
2. Roboze PRO printer that can take full advantage of it.

The result is fast production of strong, dimensionally accurate, low-cost molds such as the one shown below.

The Roboze material of choice for paper pulp molds is ToolingX CF (Polyphenylene Sulfide loaded with short carbon fibres). ToolingX CF is stronger and more thermally resistant than virgin PPS, able to resist loads of 82 MPa with a tensile modulus of 9.1 GPa and with a very high continuous use temperature of 220°C.

These characteristics make ToolingX CF material able to withstand the mechanical loads of paper pulp manufacturing and can be considered even for thermoforming processes. On top of this, being a plastic, it weighs much less than any metal, resulting in lighter molds that are easier to handle, while reducing risks for operators.

Printing ToolingX CF is easy and fast thanks to the Roboze Plus PRO printer, developed to easily fit in small workshops and manufacturing facilities. Thanks to the layered nature of 3D printing, material waste when manufacturing molds is minimised, reducing their cost. With an appropriate deposition strategy, the mold itself can be made porous enough to allow air to pass while maintaining mechanical strength, eliminating the need for suction holes and simplifying the geometry, thus shortening the printing time.

If you want to get the extraordinary advantages offered by the PRO series systems for the 3D production of molds, contact us! Our experts will be glad to understand your needs and suggest the most suitable solution for you. Increase your competitiveness, we are waiting for you!