Pulp Molding From Batchsize 1

***This Instruction was made as part of an Project at Folkwang Universität der Künste, in the Design Future masters programm.***

Pulp Molding From Batchsize 1 - Project introduction

Pulp molding, the process used to make products such as egg cartons, is a three-dimensional papermaking technique. In this process, paper is dissolved in water and shaped using a fine mesh. Water is drawn through the mesh, leaving the paper fibers behind to form a solid layer.

The outcome of this course is a tool that can be easily reproduced and applied with simple means. It has the potential to be used in schools, universities, or makerspaces. With this tool, the principle of a material cycle can be experienced in practice: the quality of the molded fiber objects depends directly on the quality of the recycled paper used. Surface explorations created with this tool also serve as a kind of sample catalog, demonstrating how pulp molding can become appealing for designers.

This tool not only allows the production of small series but could also serve as a platform for low-threshold experiments in research. A concrete field of application is material research with additional bio-based fibers. These could be easily formed into defined shapes to test their suitability. Another promising approach lies in the combination of fiber materials with bio-based coatings (e.g., Notpla). In this way, new application areas could be explored without significantly compromising recyclability.

How does Pulp molding work

The industrial pulp molding process begins with the preparation of the raw material. Waste paper or cellulose pulp is shredded and fiberized in water. Unwanted components such as printing inks or foil residues are removed, producing a homogeneous pulp that forms the basis of the entire process.

The forming step takes place using mesh molds. These tools consist of fine metal sieves that are immersed in the pulp. By applying negative pressure, the water is drawn through the sieve—similar to the function of a filter. The fibers remain on the outside of the sieve and build up into a thin, even layer that clings to the tool like a second skin. The longer the sieve remains in the pulp, the thicker this fiber layer becomes. In this way, the geometry of the sieve determines the final shape: from simple cavities, such as those used in egg cartons, to more complex packaging parts.

To ensure stability, a counter mold is used. It closes over the mesh mold, presses out excess water, and compacts the fiber layer. At the same time, it imprints fine details such as ribs, logos, or surface structures that are essential for the functionality and quality of the products.

The next step is drying. In large industrial facilities, the wet molded part is dried with hot air until almost all residual moisture is removed. At this stage, the soft fiber mass is transformed into a lightweight and stable component.

Finally, depending on the intended use, additional processing steps may be carried out, such as punching, trimming, or applying coatings. This way, an apparently worthless raw material—waste paper—is turned into a wide variety of products, ranging from packaging and trays to technical molded parts.

Supplies

1. A Eurobox (15 × 20 cm)
2. A Shopvac ( Wet cleaning capable)
3. Acces to a 3D-Printer
4. M3 Screws and M3 heatset-inserts
5. A blender
6. Some paper scraps

Step 1: Assembly and Setup

1. The Eurobox is modified with a side drilling to connect the vacuum cleaner hose.
2. The workshop vacuum is set to wet vacuum mode.
3. The tool frame is 3D-printed (ideally from PETG with robust print settings) and assembled from two halves.
4. The funnel component is also 3D-printed, ideally from PETG.
5. The mold set is designed in CAD to achieve the desired shape. It is then 3D-printed in PETG with specially adjusted print settings to create the required surface quality. Both halves of the mold are mounted in their respective tool frames.

Step 2: Operation

1. Paper pulp is prepared at a ratio of 1 L of water to 10 g of paper. The paper is torn by hand into small strips, soaked in water, and then blended with a hand blender until smooth.
2. The vacuum cleaner is connected to the Eurobox. The mold (mounted in its frame) is placed on top of the box, and the funnel is set on top of the frame.
3. With the vacuum switched on, a measured amount of pulp is poured into the funnel. The water is drawn through the mold surface, and the fibers remain behind.
4. Once the pulp has been deposited, the funnel is removed. Then press the other tooling side onto the pulp, to squeeze the water out.
5. The molded part can be carefully taken out after some initial drying and left to dry either in the sun or in an oven at the lowest setting.

Step 3: Slicer Settings for the Tooling

Here you can see the effect of the chosen infill pattern on the molded surface. If the pattern becomes too fine, the part tends to stick, if the pattern is large, you get a fuzzy surface, make it even larger and you get holes in your part.

You can also use an offset version of the part as a modifier in your slicer. this allows you to have a very large and open surface pattern, but a finer pattern below this this layer, preventing holes that would otherwise form. this technique was used with the archimedes curve, to give it a supporting mesh beneath. (have a look at the provided 3mf. file for clarification)