3D Block Printing: Additive Manufacturing by Assembly

This paper overviews a robotic 3D block printer. It can fabricate 3D forms from their CAD models by assembling toy blocks as digital materials. It can achievemass customization through the combination of mass-produced building blocks and automatic assembly planning for customized shapes. In this paper, wepresent mechanical analysis for assembly planning of toy blocks and ROS-based implementation of the system for high interoperability with various robots.

3D Block Printing [Maeda 2016 IROS] [Sugimoto 2017 CASE]

Mechanical Analysis of Block Assembly

ROS-based Implementation of Block Printer

Yusuke MAEDA, Mikiya KOHAMA and Chiharu SUGIMOTO(Yokohama National University)

Maeda Lab, Dept. of Mech. Eng., Yokohama National University https://www.iir.me.ynu.ac.jp/

Additive manufacturing by assembly of digital materials

• Mass customization using mass-produced building blocks• Multiple colors and materials• High repeatability by using precision digital materials and their

self-alignment• Material reuse through disassembly• Fabrication of shapes with function using functional blocks

(e.g., electric circuits)

Potential Advantages

Block assemblability test is necessary for assembly planning

A new implementation of block printerbased on ROS and MoveIt

Experimental Setup

System Architecture

Interoperability with Various Robots

• For higher interoperability with various robots• Motion planning for collision avoidance

Our 3D Block Printer

• Using nanoblocks (LEGO-like, but smaller)• Layer-by-layer assembly from bottom to top• Automatic assembly planning from a CAD model

Dealing with unprintable shapes

• e.g., overhang

☹ Place A before B

☺ Place B before A

Block modelCAD model Subassemblies with support blocks

Final assembly

manual assembly

Assembly Example

6-axis CartesianSCARA

• Our previous study: empirical assemblability test• Using variously-sized blocks was difficult

Assemblability test for block placement

Capacity [Luo 2015]

• A force margin of inter-block connection• Applicable to evaluation of the physical stability of LEGO-like block sculptures• Only for assembled block sculptures

Must be extended for the physical stability of block sculptures during the placement of each block

Check whether the minimum capacity is positive by solving the following linear programming problem:

Normal Force ℱ

Friction Force ℱ

Normal Force ℱ

𝑥

𝑧

𝑥

𝑦

𝑥

𝑦

𝑥

𝑧

Normal Force ℱ

Friction Force ℱ

Normal Force ℱ

Front view (1x1)Top view (1x1) Front view (2x2)Top view (2x2)

minimum capacity

capacity at the i-th connection

external wrench exerted to thej-th block including insertion force

auto-conversion auto-assembly

using support blocks

decomposing into subassemblies

AB

A B

Manipulator

Assembly Pad

Block Feeder

Gripper

Model Reader

Interface

PickPlanner

PlacePlanner

MotionCommander

Core

Robot Control Package

Block ModelPick

Calibration

PlaceCalibration

MoveIt!Interface

MoveIt!

ObjectSpawner

Robot Model(URDF)

Hardware

RobotController

Robot

ROS Parameter

ROS Node

… Command FlowGripper

GripperController Hardware

GripperCalibration

Block Feeder

Manipulator(VP‐6242‐G)

Gripper(ESG1‐FS‐2840)

Assembly Pad