3D printing
A free 3D-printed hand
Discover how Atomic Lab turns a thread of plastic into a hand prosthesis provided free of charge. Follow the journey from a digital model to a moving mechanism.
Video in preparation. You can explore all the content on this page right now.
Does a printer know it is making a hand?
No. It follows instructions for position, speed and extrusion. The shape emerges as paths build up, layer upon layer.
01 / First, a file
The 3D model describes the geometry. A slicer divides it into layers and calculates nozzle paths, walls, infill and supports. G-code turns that plan into machine instructions. Changing the model and changing print settings are two different decisions.
02 / One line on another
In the script’s example, a 0.4 mm nozzle deposits 0.2 mm layers. Reaching a height of 20 mm takes 100 layers of that thickness. Line width and layer height are different measurements. Layer bonding, orientation and material all affect strength.
03 / From parts to a mechanism
Printing is only part of the job: supports still need removing, surfaces checking, and parts assembling and adjusting. In the episode’s wrist-driven design, body movement tensions cords and closes the fingers without motors. Atomic Lab provides these prostheses free of charge to the people who need them.
04 / Heat changes the rules
Plastic contracts as it cools: if adhesion is insufficient, corners can lift (warping). Later, a PLA part can also lose stiffness around 60 °C, depending on its formulation and the load. Softening is different from melting for extrusion. The hot-water demonstration uses a disposable sample, never a prosthesis someone is using.
Build a part, layer by layer
Move the control to reveal the layers. Their thickness is exaggerated so you can see them: this is not a real-time printing simulation.
Teaching model · Not results from filming.
A paper slicer
Materials: scrap paper, a pencil and round-tip scissors.
- Draw five outlines of the same object, each slightly different. Cut them out and stack them in order.
- Look at them from the side. What happens to the steps if you double the layer count and use thinner paper?
- Write down your prediction, what you observed and what you would change. Ask an adult for help when using scissors.
Questions to keep you thinking.
Do thinner layers always make a better part?
They improve vertical resolution but add paths and printing time. Strength and finish also depend on orientation, temperature, material and geometry.
How could a mechanical hand hold an egg?
The mechanism transmits force, but grip depends on shape, friction and cord tension. The video will test a cup, a ball and an egg; results will be added after editing.
Can I repeat the hot-water experiment?
The paper model is enough for this activity. The video’s heat test requires an adult, protective equipment, tongs and a disposable sample. Do not heat or modify a prosthesis someone uses.
What did you take away?
Three questions, no grades and no rush. Every answer comes with an explanation.
Answers explained
What turns a model into printing paths?
The slicer. The slicer calculates layers and paths and exports them as G-code.
How many 0.2 mm layers make 20 mm?
100. 20 ÷ 0.2 = 100 layers in this constant-thickness example.
Does softening around 60 °C mean PLA is ready for extrusion?
No, these are different conditions. A part can deform well before it reaches the temperature used to extrude filament.
Keep exploring
Content based on the Hands On Science script. Additional technical references: