Packaging Design: Experimenting With Paper Pulp Molding

Packaging design is truly amazing. It’s my absolute favorite design field because of how complex yet fun, pretty, and challenging it can be. Some people might argue that packaging is just a box or container, but in reality, there are numerous factors to consider such as government regulations, shipping requirements, and the safety of your package during transit.

I mostly sell my jewelry internationally. Not that I have anything against selling locally, but the local market is just not looking for what I make. The issue with international sales specifically for me is that, for a reason I don’t understand and no one has been able to explain to me, I can’t ship silver or gold jewelry using any courier… except UPS… and UPS is expensive, and it’s even more expensive with heavier/bigger packages (volumetric weight).

That volumetric weight detail limits what I can use as packaging a lot, as most jewelry packaging is designed to look good, not to be efficient or lightweight. If I used traditional packaging, I would have to use a lot of bubble wrap or other bulky packaging materials, and that would drive the price up a lot.

And there’s another “issue,” many countries, mostly in the EU, are introducing legislation to reduce the amount of waste caused by packaging, even charging sellers fees to cover the recycling or waste they introduce into their countries. IMO that’s some very reasonable legislation, and I wish more countries had laws like that. But it also limits even more what I can ship to those countries.

So far I had been improvising packaging with cardboard and bubble wrap, it wasn’t pretty, but it was economical and allowed me to add a lot of protection to the package. But I can’t keep going like this, so I finally started working on something I had thought of about a year ago.

I’m not sure if I got a random video on YouTube, or maybe I saw it on Reddit, but one day I learned how egg cartons are made, and I really wanted to design packaging using that process “Paper Pulp Molding” (PPM).

PPM is incredibly simple, you just need a mold and a way to suck through it along its surface. When you have your mold ready, submerge it in a tub of paper pulp with a lot of water and suck on it, and that’s pretty much it. You just need to find a way to remove the finished product from the mold to dry it.

Traditionally, the molds are made from milled aluminum with holes for the vacuum to go through. A fine mesh is molded over it to allow the vacuum to suck evenly over the entire surface.

However, after researching, I found that a lot of companies are switching to 3D printed molds, which allows more flexibility in the designs and lowers the cost of the molds. Stratasys has an interesting paper on the process (link here). It’s very proprietary, so it’s almost useless, but it did give me the idea to use only infill instead of a mesh.

3D printed molds are incredibly simple (at least the ones I designed). You just 3D print your design with a high infill percentage (60%~80%) using gyroid and no walls. I’ve been using a 0.4mm nozzle and a 0.3 layer height and it has worked great. And for the vacuum I’ve been using a vacuum cleaner.

Of course, just printing with no walls would be dumb though, you’d be losing vacuum pressure. So you need to remove the walls only on the areas of the mold you need. It’s not technically a hard thing to do, but I’ve been using Cura Slicer and it makes it incredibly annoying.

I’ll make the 3D printing process another post because this one is already going to be very long and Cura forced me to get creative with it so there’s lots to talk about that.

BTW, this is an ongoing project so I don’t have a final design and things will change a lot. This is just a log of the process.

While the molds made with PPM are surprisingly strong, they’re also very weak on big flat surfaces. so I wanted to minimize those, which so far made me reject the idea of a simple cube.

My first idea was to go for an octagonal prism. Sliced as 8 triangles, it would create a lot of surfaces, so it would have a lot of material to make it strong, or so was my train of thought. It also made for a small mold, and because the infill is so dense, I wanted to start small so if the prototype failed, I wouldn’t have wasted 500 grams of plastic.

First mold prototype

The first mold I printed was at 80% infill density. It kind of worked, but for the geometry of my mold, it was too dense. The vacuum wouldn’t reach some parts with enough strength. Also, I messed up, and the geometry was inverted from what it should have been. But so far, it was a success because I got the paper pulp to mold around it!

Second Mold Prototype

So I corrected the geometry and printed it again. this one worked even better, but I was having a really hard time de-molding it. And while the paper parts that where successful where coming out kinda ok, the success rate molding them correctly was low because the paper pulp was so thick it wouldn’t fill all the way in some parts.

After looking at some videos of the process on YouTube I realized my paper pulp was indeed too thick, so I kept adding water until it looked like the videos, it was like 10X the amount I had been using. I haven’t done any real calculation of a paper to water ratio, but from my experiments the more water the better unless you want your molds to be very thick. I think as long as your vacuum can handle it you could have mostly water and it would work.

For de-molding I put the vacuum in reverse to act sort of like a leaf blower and that pushes the mold out. It’s not the best way to do it tho, it’s pretty hard to control, and if the flat walls are not incredibly thick they get blown up like balloons and can even break from that.

This was the first prototype tho, and at this point I knew it was not a design I want to use. So I made about 12 pieces just to test the process and they came out pretty decent. Drying them is a bit of a hassle, they need a support structure when de-molding, and maybe while drying they drying, otherwise they warp. I did not have one so they’re all a bit deformed.

Conclusion

Had it worked as I expected I would have printed a big mold with the 8 pieces together, but it didn’t so I’ll test different designs for the next attempt.

Anyway, this is how it looks with all 8 modules “assembled”.

And this is as far as I’ve gotten. Right after this my 3D printer nozzle clogged and then everything else on the extruder head broke, and as of posting this I’m still waiting for a new extruder to arrive.