Some aspects of the LEGO production process are not publicly documented in enough detail to establish precise design rules. Therefore, I made some assumptions based on the general principles of injection molding and pad printing:
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Overmolding and side actions are more expensive than creating two separate molds.
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Pad printing from four different angles on a character is more costly than overmolding.
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Pad printing cannot reach deep undercuts if applied from the same direction as the mold.
Solving the mystery of how this part was made led to the assumptions about pad printing. It has pad printed Horns but overmolded ears.
Wooden Shoes
3D modeling in Rhino
Process: Basic (no side actions)
While applying for the Element Designer position, I realized the benefits of learning Rhino, particularly its superior NURBS functionality compared to what I used in Blender.
To explore this, I chose the perfect object to model: wooden shoes. Their shape follows a precise curvature in 3D space, which would be incredibly difficult to recreate accurately using sculpting, subdivision surface modeling, or parametric tools.
Although I'm still in the process of learning Rhino, I’m pleased that I identified it as the optimal tool for this task. Despite my limited experience, I was able to achieve this result in a short amount of time.
Rayla's hair
Finding a solution for too many colors
Process: Overmolding + basic (no side actions)
Overmolding is necessary for many elements based on characters in media, as they are designed without the constraints of the production process. Rayla's ears are smaller than other LEGO elements and positioned in a way that does not easily allow pad printing, making overmolding essential. However, this is not required for the horns. Rayla's hair allows for some creative freedom without losing recognizability, creating enough space to insert a separate element.
Not only does this reduce production
costs, but it also allows for greater
customization. For example, a fantasy
character could have antlers instead
of horns.
Twig
Matching the LEGO aesthetic
Process: Basic (no side actions)
Most LEGO animals are designed to stay within the width of the bricks that support them, resulting in a more blocky appearance. My goal was to translate a very rounded character into this blocky style.
A significant challenge was finding a pose that eliminated undercuts. To achieve this, I designed the ears to face outward. This still allows a minifigure to stand next to Twig, as he leans forward on the stud he can be placed on, giving the ears just enough room.
Zym's Dragonhead
Dealing with difficult angles
Process: 3x Basic (no side actions)
I initially expected this model to require side actions due to Zym's hair being at complex angles. However, after experimentation, I realized I could achieve all those angles with just one core and cavity.
LEGO designers often design dragon heads to be released from the mold vertically. However, the hair required a horizontal release. I solved this by incorporating existing bricks between separate sections instead of relying on a more complex mold.
The result is a three-piece design that is cost-effective to produce, though the hairpiece has limited functionality in other LEGO sets.
Red Panda Meilin
Adaptability
Process: Basic (no side actions)
I originally planned to create a more organic LEGO piece for this project. However, during the pre-sculpting modeling stage, I found that a flat head was a better fit. The design remains organic apart from the flat head, which just proves the importance of keeping an open mind during the design process.
I initially expected to need a slider to create a connection point at the bottom of the head. However, I realized that for a buildable big fig, a ball joint could be sufficient.
I recommend using prints instead of overmolding, as the ears could be printed white only on the front. This way, all prints can be applied from the same angle.
Can you guess the best parting line? (This is a textbook example!)
Teemo
Odd head for hats
Process: Overmolding + Basic (no side actions)
It seems obvious to create Teemo's head and hat as separate pieces. The parts are large enough, and the width of the hat would limit design flexibility for the face due to undercuts. However, this approach presents a challenge: the hat should be compatible with other LEGO figures, as it is nearly the same size as standard LEGO hats. This also means the top of Teemo's head should be designed to fit with other LEGO headgear.
For production, pad printing would work for the glasses and possibly the ears when applied from the front. However, the headband could only be pad printed from the top, if at all. Overmolding the headband seems like the most viable solution.
I'm also pleased that I managed to recreate the fluffy cheeks without introducing undercuts.
Momo (Avatar)
Organic shapes
Process: Injection molding with one slider
Momo's big ears and rounded shapes did not lend themselves to the blocky aesthetic of LEGO animals. This allowed me to finally create a more organic piece. However, this complex shape could only be achieved using a core-cavity combination from the front and back. At this scale, there are no clever solutions for adding a hole for studs, so a slider is required for this specific task.
The face and ears can easily be pad printed. The tail on the back, however, could be left white—but this would surely upset some of the more passionate fans of the TV show.
This is not the only LEGO Momo at minifigure scale. However, the official version is widely considered—by many, myself included—to be one of LEGO's worst creations.
Coat Hanger
Reduce cycle time
Process: Basic (no side actions)
Students were tasked with redesigning a coat hanger to reduce the cycle time of the injection molding process and to evaluate the outcome using flow simulations. The first adjustment was straightforward: changing the cross-section from a rounded shape to an H-profile. This design provided higher strength with less material and thinner walls, leading to a shorter cooling time.
The second adjustment resulted from a careful examination of the assignment's requirements. The hanger needed to support a specific weight at its outer ends while also withstanding force applied at any point. The latter requirement necessitated a rather large support beam, as it needed to remain durable when force was applied solely to the beam. This increased material usage compared to an alternative design without a beam but with a thicker base. Therefore, counterintuitively, it was better to omit the support beam.
TT Buddy
Prototyped and designed for sale
Process: Basic (no side actions)
Groups of three students were tasked with creating a PID controller for the TT Buddy to launch ping pong balls a specified distance. Since we completed our assignment ahead of schedule, our professor challenged us to further improve the product.
Our prototype included 3D-printed components to house the additional parts we wanted to integrate. We modified the housing element at the bottom of the product to accommodate these new components. This part was injection molded, and we calculated the optimal wall thickness for the new servomotor to minimize production cycle time.
Our professor encouraged us to reach out to the company manufacturing TT Buddies with our improvement suggestions. However, they declined, stating that they had no need to enhance their product at that time.
WakaWaka
Removal of unnecessary adhesive
Process: Basic (no side actions)
Another university assignment involved redesigning the WakaWaka solar power bank. The added features required extra openings in the casing, which were easily incorporated along the seam where the two casing elements meet.
Another issue with the older version was the adhesive on the solar panel becoming loose over time. Since the two casing parts were already screwed together, creating a stable connection, the redesign leveraged this by incorporating an extruding element from the top case to securely press the solar panel against the bottom case.
All of these changes were made to align with the constraints of the injection molding manufacturing process.
Stud Reversal
On my personal wishlist
Process: 2x Basic (no side actions)
Most LEGO builders eventually find themselves wanting to reverse studs, but the current solutions require far too much space!
Reversing studs within a single plate is not possible due to the LEGO logo on the studs. However, this issue can be avoided by making the piece half a stud taller. This adjustment would still fit within the LEGO system, thanks to elements like headlight bricks and brackets.
For a unique brick intended for frequent use, I prefer to keep one rounded edge. This allows builders to decide whether they want the rounded edge facing outward.
(A half-rounded solution would create ugly gaps.)
Pencil case
Creative use of a limiting tool
Process: Blow molding
Blow molding is often used to shape plastics, producing hollow forms with uniform wall thickness when executed properly. Similar design rules apply to this process, as the final product must be easily released from the mold.
Students were required to create something using a production process of their choice—or, in my case, my second choice.
The pencil case consists of two blow-molded parts: one white and one blue. The white outer part is designed to be more rigid, providing protection for its contents. It is cut on three out of four sides, leaving the final side as the weakest point, allowing it to flex for opening and closing. The blue part is made of a more flexible material with thinner walls, enabling some undercuts while still allowing the part to be released from the mold. These flexible undercuts serve to securely hold pencils and other utensils in place.
