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Use FDM Tools for Paper Pulp Molding

Molded fiber, also known as paper pulp is a common packaging material used in many consumer applications, such as egg cartons, beverage carriers and protective product packaging. Because molded fiber is produced from recycled paper or fiber, it is 100 percent recyclable and biodegradable, making it an environmentally friendly alternative to plastic packaging.

The production of paper pulp packaging is an automated, quick and low-cost manufacturing process. A mixture is made from ground recycled paper or fiber dissolved in water. Then a mold is dipped into the slurry and a vacuum on the backside pulls the slurry onto the mold to form the shape of the package. Type two molded pulp manufacturing involves another step, transferring the piece to a second mold on the opposite side, which is suctioned by an additional vacuum. Then the piece is ejected from the mold and placed in a drying oven.



Where the production is a simple, fast process, the tool making process is typically tedious and labor intensive. A block of aluminum is machined into the shape of the finished package and holes are drilled throughout the entire tool. Then, to prevent clogging in the tool holes, a fine wire screen is sintered, shaped and welded to the tool by hand. Not only is it a tedious process, usually taking at least two weeks to make a large metal tool, one tool costs about $30,000.

Although the investment in a tough aluminum tool makes sense if you’ve validated the tool design and you have production quantities over 10,000, it can be expensive and time consuming during the prototyping phase and not a practical investment for lower volumes.

Manufacturers have discovered Fused Deposition Modeling (FDM) as an alternative. Additive manufacturing tools using FDM can be produced for a fraction of the time and cost of conventional tooling. Also, porosity and rigid contours can be built in one piece with no alteration to the slurry formula or vacuum pressure. Here are four reasons to give FDM paper pulp tools a try:

1. Designing in holes and porosity

FDM’s soluble support materials allow you to produce complex geometries and produce multiple CAD segments with varying fills, all in one build—saving time and money on three separate processes. The outer boundary of the tool can be designed with a solid structure (red segment in image to the right), the screen with porosity between layers (blue segment), and the back of the tool in a rigid mesh structure to accommodate the vacuum draw. This eliminates the need for machining the contour, drilling holes for vacuum pull and attaching the screen to the mold. Also, entire FDM tools are naturally porous, which spreads the vacuum suction and produces a cleaner package with a better surface finish.

2. Design validation

Functional prototyping reveals how your tool will perform and allows you to make design adjustments before investing in metal tooling with a long service life. FDM prototypes are built in production-grade thermoplastics tough enough to withstand the mechanical stress of the fiber molding process for up to 10,000 cycles—plenty of time to test form, fit and function.

3. Bridge to hard tooling

Why wait for your hard tool when you can start making money with an additive manufactured tool? FDM tooling usually takes half of the time to produce than traditional aluminum tools. Start selling and shipping up to 10,000 packages to customers while you wait for a metal tool.

4. Low volumes

FDM tooling is a cost effective alternative when your production quantities and geometries are right. For example, SML Group, a leading supplier various types of packaging, used FDM tooling from Stratasys Direct Manufacturing to produce low quantities of molded pulp packages for an electronics OEM and a retailer, saving $29,400 (98 percent over conventional tooling) and a week in time (50 percent over conventional tooling).

FDM Tooling is easily integrated into any molded fiber operation. Contact one of our manufacturing tooling experts to learn how.

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