Injection Molded Bead Curtain

Most plastic parts we use every day are injection molded, but we usually never see how they actually come to life.

For this project, I wanted to go through the entire process myself, from designing a single plastic bead to building a mold and producing all the parts to assemble a full bead curtain.

Instead of buying ready-made beads, I designed and manufactured my own. The CNC machining for the mold was sponsored by JLC, which made the tooling stage possible.

The idea was simple: take one product and build it the same way it would be made in real manufacturing, just on a small scale.

I didn’t start with the bead. I started with the curtain.

Before anything else, I figured out the size of the doorway, how dense I wanted the curtain to be, and roughly how many beads I would need.

This step matters because it sets the scale for everything else. Once you lock this in, you’re no longer designing a single object, you’re designing a system.

Only after that did I move to the bead itself.

This is where things shift from “designing a shape” to “designing something that can actually be manufactured.”

Injection molding comes with rules:

draft angles, wall thickness, clean part release, and how the part behaves inside a mold.

I used polypropylene because it is easy to process, works well with small injection machines, and is one of the most common plastics in everyday products.

A lot of the material I used actually came from scrap and leftover plastic, which could be remelted and reused.

So even though it is plastic, it is not necessarily single-use in a setup like this.

Before committing to a mold, I 3D printed a few versions of the bead.

This helped me check how it would look when strung together and how the proportions would feel visually.

One thing I was careful about was avoiding flat faces along the string direction. When hundreds of beads line up, those details start becoming very obvious.

After testing, I finalized a few key decisions:

The bead has a 4 mm hole with about 5 degrees of draft so it can release cleanly from the mold.

I also avoided using a separate pin for the hole. Keeping it as part of the mold makes the process simpler and stronger for this scale.

At this point, the bead design was locked.

Now comes the real manufacturing shift.

Instead of designing the product, I had to design the tool that produces the product.

The mold is a simple two-part aluminum mold with two cavities.

I created it using a straightforward Boolean workflow in CAD, basically subtracting the bead shape from a block to form the cavity, then splitting it into two halves.

This works because the part is simple. If it were more complex, the mold design would need proper engineering features beyond just subtraction.

I didn’t compensate for shrinkage because this isn’t a precision mechanical part. It is a decorative bead, so small variation is acceptable.

The mold was CNC machined by JLC from aluminum.

One important thing to understand is this: CNC does not “decide” anything. It only produces what you design.

So if the mold works or fails, that responsibility is completely in the CAD.

I chose aluminum because it is fast to machine, affordable, and more than enough for a low-pressure hand injection setup.

This is not production tooling. It is a functional prototype mold.

Once the mold was ready, I started production using a small hand injection molding machine.

Each shot produces about 15 grams of polypropylene.

I used a REX-C100 controller to keep the temperature stable so the plastic flows consistently.

Then it became repetitive work: melt, inject, eject, repeat.

Slowly, a full batch of beads started building up.

With all the beads ready, I moved to assembly.

Each strand was made by stringing beads one by one, keeping spacing consistent so the pattern stays visually clean.

The doorway I used is arched, so I also had to design a curved top support to match it.

Once everything came together, the curtain started behaving like a single system instead of individual parts.

What started as a single CAD model turned into a full physical product made through a complete manufacturing pipeline.

Design, tooling, production, and assembly were all done in a small-scale setup that mimics how real plastic products are made in industry.

We usually think manufacturing happens in factories at massive scale.

But the core process is actually simple. You design a part, you design a tool, and then you produce it.

Once you understand that chain, even a small setup like this becomes enough to make real products.