Modular Ball Socket Joints - TPU Insert

A hybrid PLA + TPU modular ball-socket joint system designed for flexible armatures, posable figures, doll skeletons, puppets, small tripods and adjustable structures. The key feature is the separate TPU socket insert: instead of a PLA ball rubbing directly inside a PLA socket, the ball moves against a flexible TPU 95A inner socket, acting like a cartilage/friction layer. This helps reduce rigid plastic wear and keeps the joint grip more consistent during repeated posing or movement.

The system is scalable, modular and printed without AMS: rigid parts are printed in PLA, while the grip inserts and end feet are printed separately in TPU.

Included parts

PLA rigid parts

• Ball Socket Link – main repeating module, with ball on top and socket below
• Inverted Y Node – for doll legs and split connections
• Cross Shoulder Node – for arms, shoulders or 4-way structures
• Double Cross Connector – for more complex front/back assemblies
• Tripod Node – one ball on top and three sockets below

TPU flexible parts

• TPU Socket Insert – press-fit internal socket that creates the grip layer
• TPU End Foot – flexible end cap for tripod legs or terminal points

3MF plate layout

The uploaded 3MF contains 4 plates:

• PLA Core Links – No Supports
  37 × Ball Socket Links
• PLA Complex Nodes – Supports Required
  4 × complex connector nodes
• TPU End Feet – No Supports
  9 × TPU end feet
• TPU Socket Inserts – No Supports
  37 × TPU socket inserts

PLA and TPU are printed separately, so no AMS is required.

Assembly

1. Print the PLA and TPU parts separately.
2. Press the TPU socket insert firmly into the PLA socket.
3. Push the PLA ball into the TPU-lined socket.
4. Repeat with as many modules as needed.

The fit is intentionally tight so the TPU insert can provide friction and grip.

Printing notes

• PLA recommended for the rigid parts
• Successfully tested with TPU 95A for inserts and end feet
• Core repeating PLA links print without supports
• TPU parts print without supports
• Only the optional complex PLA nodes require supports
• For a tighter joint / higher friction, you can slightly increase TPU flow for the socket inserts
• If the joint becomes too tight, reduce TPU flow or scale/test one insert first
• After scaling the model, test tolerances and grip before printing a full set