FabricAr3v: Metal 3D printing

Open-source printing method for low-cost 3D metal printing comparable to conventional ones

Specifications

3D Printer BaseE3D tool changer printer (ToolChanger & Motion System Bundle)
Head Tool-changer head; T-shaped latch
Extruder Mahor XYZ extruder
Extrusion screwV3 Pellet Extruder
ComputerDuet 2 WIFI control board
Power: 24 V PWM
SoftwareReprap firmware
3D Printing FilamentSpoolWorks Edge Filament
WasherDiameter: 12 mm & 9mm
Fans24 V fan
Printing Parameters (Cura: PolyMIM 316L)
Printing Temperature210C – 220C
Build plate Temperature90C
Printing Speed20 mm/s
Retraction Distance7 mm
Retraction speed30 mm/s
Nozzle size0.8 mm
Layer Height0.3 mm
Flow85%
Output
Maximum angle60-degrees
Small Parts with maximum finenessDiameter: 0.25mm
Working partThickness: 2.2 mm
Final density93-96% (of 316L stainless steel)
Tensile strength 167 MPa, 252 MPa, 430 MPa, 290 MPa.

Overview

This tech spec was submitted by Vincent Martin as part of the University Technology Exposure Program.


Problem / Solution

Many industries nowadays benefit from the development of additive manufacturing of metallic materials. However, the existing equipment for shaping metal through additive manufacturing remains too complex and costly to operate. Other tools are restricted to the manufacturing brand, so users have little room for modification. As a result, manufacturers find it challenging to sell metal 3D printers.

FabricAr3v is an affordable open-source 3D metal printer that offers the same quality and comparable performance as commercially available machines. The product, FabricAr3v, makes printing of metal parts to small structures more affordable by using a mixture of thermoplastic polymer and metal powder. Users can print various materials such as stainless steel, titanium, copper, or ceramic. The product performs similarly to the available printers in the market but is fifteen times less expensive. FabricAr3v also offers the freedom to use metal 3D printing and machining through hybridization.

Design

Creation cycle of a part

 The first step in printing involves transforming the granulates into a mixture of the target material (metal or ceramic) in powder form encased in a polymer matrix. Chemical debinding removes the polymer binder from the initial mixture through increased porosities that convert the polymer into gas. The remaining polymers are destroyed by gradually increasing the temperature. The last stage of thermal treatment uses higher temperatures or sintering to join the powder grains together, making a denser part. The final output is a part composed of the target material free from polymers.

 

The E3D tool changer printer

The Tool Changer printer, by default, has four Fused Filament Fabrication (FFF) extrusion heads that allows users to print using multiple materials. These printheads can also be replaced by different tools so that granular printing, 3D printing, and CNC Machining can be done for the same part. It features a glass heating plate capable of reaching 200°C  that moves along the vertical axis. A "core XY" driveline allows to reduce the inertia of the moving parts and relocate the motors outside the frame.

 

The tool-changer head

The tool-changer head is the central moving part where various tools are attached. Each tool has a fixing plate made to fit and lock into the Tool Changer carrier. More specifically, the tool is positioned by completing three mechanical connections. It is held in place by a rotating T-shaped latch controlled by a stepper motor and six cylinders. These cylinders form three sphere-cylinder mechanical links once in contact with the spheres of the fixing plate. This system then moves horizontally in the XY plane. The size and weight of the tool must be considered to ensure the stability of the assembly.

 

The Mahor XYZ extruder

The Mahor XYZ extruder prints the material from a feedstock in pellet form. The extruder head can fit into the fixing plate using fabricated parts. It is composed of an extrusion screw, a stepper motor, and a hot end. The system's temperature is maintained by a heating cartridge that melts the feedstock and a fan that controls the temperature along the extrusion screw where the molten pellets are transported. The polymer from the pellets is slowly melted by heat conduction as the material is conveyed and compressed as the small extrusion screw rotates. 

 

Extrusion screw

The shape of the extrusion screw and its enclosure are designed for improved conveying and control of the material that flows out of the Mahor V3. It has three sections: the feeding zone, the transition, and the metering zone. At the entry of the screw casing, helicoidal stripes increase the friction factor and move the pellets. In the transition section of the screw's profile, volume is reduced, thereby increasing the pressure to crush the pellets and extrude air bubbles. This yields a homogeneous material string released at the extrusion head.

 

3D Duet board

The E3D Tool Changer printer has a control board equipped with a "Duet 2 WIFI". This open hardware, open-sourced board was designed to give more control to the user using a fully configurable G-code language that allows machine parameters to be quickly modified. The control board also offers numerous connections for components essential to the development of the pellet printing system of FabricAr3v.

 

Performance

The FabricAr3v printer could construct complex shapes and build inclines up to 60° from the vertical without using support structures. Its finer nozzle size, 0.25 mm in diameter, also allows printing smaller parts, while a diameter of 2.2 mm for the working parts. The final density of the parts produced is 93-96% of the density of 316L stainless steel and is comparable to other works that used a thermal sintering step. The measured tensile strength values of 167 MPa, 252 MPa, 430 MPa, and 290 MPa for H2 and RH5 sintering are also in the range of other fabrication techniques.

References

A research paper describing the challenge, design, and outcome of the research.

Vincent Martin, Jean-François Witz, Frédéric Gillon, Denis Najjar, Philippe Quaegebeur, Abdelkader Benabou, Michel Hecquet, Emmanuel Berté, François Lesaffre, Matthieu Meersdam, Delphine Auzene

Wevolver 2023