Additive manufacturing of metals
Bovisa Campus, Building B16
via La Masa, 34 20156 Milano - Italy

Description

The research carried out within this lab spans across different fundamental and applied disciplines, both using experimental and computational methods. The activities mainly focus on design for additive manufacturing, development of technological solutions, and structural/functional design and testing of materials and components.

References

BLM group, Fonderia Maspero, Marposs, Sapio, Titalia, Ansaldo Group, Agusta Westland, Aidro, European Space Agency.

Instrumentation & Facilities

Renishaw AM250

Renishaw AM250 is a selective laser melting (SLM) machine that operates with a build area of 250 mm x 250 mm and height of 300 mm. The system implemented a 200 W active fiber laser (R4 from SPI, Southampton, UK). The estimated beam diameter is 75 µm on the focal plane. During the preparation phase, the system applies vacuum the processing chamber down to -950 mbar pressure and then it is flooded with Ar reaching 15 mbar overpressure. Throughout the process the oxygen content of chamber is maintained below 1000 ppm. The system employs pulsed wave (PW) emission. Build plate can be preheated up to 170°C by employing a soaking cycle applied prior to the process. The system requires extensive cleaning and change of parts for a material change. On the other hand, the Reduced Build Volume (RBV) platform can be employed with the system, which limits the build chamber to 78x78x50 mm3 while employing limited quantity of powder for processing new materials (<3 kg).

  • Build volume 250 mm x 250 mm x 300 mm
  • 200 W Yb:glass active fiber laser with 70 µm minimum spot size operating in PW
  • External powder sieve, possibility to refill during the build, 40 l silo
  • Operates with Ar at O2<1000 ppm, low gas consumption thanks to vacuum prior to purging
  • Materialise Magics, post processor, supports and structures modules for build preparation
  • Glove compartment to clean the build chamber
  • Baseplate preheating up to 170°C
  • Reduced build volum (RBV) for processing small quantities of powder. Build volume 78x78x50 mm3
3DNT

Industrial grade open Selective Laser Melting machine. The system is designated to testing new processing, monitoring, and material development. The machine is configured to high precision processing being equipped with beam shaping capability, focal point regulation, and a high precision build platform axis. The machine is equipped with a novel powder bed preheating system based on UV lamps. Both the hardware and the software are open to the user. The hardware can be manipulated to integrate different laser types, scanner heads, monitoring sensors, and control systems. The laser can be run in both pulsed and continuous emission modes. The optical arrangement is designed to allow the insertion of cameras and sensors off-axis and coaxially. The machine operates with a dedicated CAM software and post processor from DMC.

  • Build volume ø150 mm x 150 mm
  • 1000 W Yb:Glass nLIGHT fiber laser
  • Raylase scanner with 254 mm focal lens
  • Focus shifter with +/-1.5mm travel
  • Z-axis resolution 0.25 µm
  • Process atmosphere control with oxygen, temperature, and humidity sensor and gas speed regulation
  • Dedicated CAM software from DMC
  • UV lamp for powder bed heating
BLM Additube

Robotic cell for Laser Metal Deposition, laser cladding, and laser repairing. The cladding head is mounted on the end-effector of the 6-axis anthropomorphic robot, while the workpiece is fixed on the 2 axis rotating and tilting table. Robot and table movements combined together results in a fully integrated 8-axis robitised LMD cell . The cladding head provides the focused laser beam, the powder jet as well as the shielding gas. To do this the cladding head is equipped with two interchangeable nozzles: a coaxial nozzle for thin deposits and a 3-jet nozzle for massive deposits. The cladding head is also equipped with monitoring and sensing hardware, including a NIR camera, a two-lambda pyrometer, and a heigh sensor. A two-cylinder powder feeder feeds the head with powder, enabling single material or multimaterial deposition. Additube works within a close workpiece volume for what concerns laser emission (class 1) and powder dispersion (thanks to the suction system for non reactive and reactive powder).

  • 6 axis robot ABB IRB 4600-45/2.05 with rotary & tilting table ABB IRBP A-250
  • 6kW Yb:Glass IPG photonics fiber laser with 100, 200, 400 micron passive fiber
  • KUKA Industries MWO-I deposition head
  • COAX-40-F and 3-JET-SO16-S from ILT coaxial nozzle
  • GTV Powder Feeder TWIN PF 2/2-MF
  • Lasermet Laser Castle, Class 1 Passive Enclosure with Sideros suction system
  • ABB RobotStudio for offline programming and Siemens NX Additive for path programming (with ad hoc Team 3D post processor)
  • Coaxial sensing: NIR camera, 2-lambda Mergenthaler pyrometer, coaxial sensor of deposit height 
Arcam A2 (Politecnico di Milano: MAD.Lab - Electron Beam Melting for Metal Additive Manufacturing)

The main specifications of the the Arcam A2 Electron Beam Melting system for additive production of metal parts are the following:

  • Max build volume: 210 mm x 210 mm x 350 mm
  • Electron beam power: 50 – 3500 W
  • Minimum electron beam spot size: 0.2 mm
  • Scan speed: up to 8000 m/s
  • Pre-heating temperature: up to about 1200 °C
  • Build rate: 55/80 cm3/h (Ti6Al4V)
  • N° of spots in multi-spot scanning mode: 1 – 100
  • Chamber pressure (ultra high vacuum): <1 x 10-4 mBar
Trumpf Powerweld µLMWD system

Powerweld is used both as a pulsed welding station and a µLMWD system. The system is composed of a welding station and in-house built wire feeder. The welding station is equipped with a Nd:YAG source, producing µs to ms pulses with at Hz-level pulse repetition rates. Maximum peak power available to the pulses is 5 kW and resultant maximum average power and pulse energy are 120 W and 50 J respectively. The system is equipped with 0.4 mm fiber, 200 mm collimating and 150 mm focal lenses producing a minimum spot diameter of 0.3 mm. The optical chain can be automatically adjusted to vary the spot diameter between 0.3 and 1 mm. The welding station is equipped with 3 linear and 1 rotational axis. The machine can be operated manually and with G-code. For manual welding operation, the machine allows safe use with a binocular to adjust the workpiece position and a dedicated laser closure. Exhaust system extracts process fumes. The wire feeder system is controlled through a Labview interface. The system can also accomodate a dedicated shielding gas box with dedicated oxygen sensor.

  • Build volume ø150 mm x 150 mm   
  • Flash pumped Nd:YAG, Pavg=120 W, Ppeak=5 kW, ton=0.3-20 ms, PRR=1-300 Hz   
  • Optical system with fiber delivery and beam size regulation, minimum beam size of 0.3 mm   
  • Pathprogramming with G-code on machine PLC   
  • Maximum wire feed rate 900 mm/min   
  • Wire diameters 0.3-0.5 mm   
  • Dedicated shielding gas box with oxygen sensor
Desktop Metal Studio System+ (BMD Extrusion AM technology)

Metal feedstock extrusion AM system capable of obtaining fully sintering complex AM parts.
The system is both industrial-ready and office-friendly and is composed by three stations (Printer + Solvent debinding units, Sintering Furnace). The raw material processed in form of bars, is a feedstock composed by atomized build material mixed with thermoplastic binder. The machine is equipped with two extrusion heads (build material and ceramic interface) and forms high quality “Green” parts where supports are attached to the parts with an interlayer of ceramic material that provides tool-free support removal capacities. The green parts are then debinded in the solvent debinding station to remove wax from the binder, creating the “brown” parts that are then further cleaned via thermal treatments in the furnace. Sintering cycle follows in Ar+3%H2 atmosphere, reaching fully dense parts. Available materials 17-4PH, 316L, Copper.

  • Printer: Build Area 30 x 20 x 20 cm (12 x 8 x 8 in); Print Head: 250 um high-resolution nozzle, 400 um standard-resolution nozzle; Max build rate 16 cm3 /hr; Minimum Layer height 50 µm high resolution printhead, 100-220 µm standard resolution printhead
  • Max build weight for all parts in job 6.5 kg (14.3 lbs) in green state
  • Furnace: Retort Size 30 x 20 x 20cm (12 x 8 x 8 in); Peak Temperature 1400°C (2552°F), Environment Argon, Argon + Hydrogen Blend, Inert vacuum sintering
  • Software: Integrated Fabricate® software for automatic setup of operations.
ExOne Innovent+

ExOne Innovent+ is a binder jetting (BJ) machine with a building volume of 160 mm x 65 mm x 65 mm (length x width x height). The system is research-oriented and it features a large number of adjustable parameters (layer thickness, binder saturation, recoat speed, roller speed, roller transverse speed, ultrasonic intensity, bed temperature…) to optimize the process accordingly to specific powders. A wide selection of materials can be printed, from metals (316L and 17-4PH stainless steels, copper alloys, nickel alloys) to ceramics (Al2O3, YSZ, electroceramics) and cemented carbides. Ultrafine powders (D50 ~ 2 µm) can be processed to achieve optimal packing and sintered density.
The system features a hopper equipped with an ultrasonic motor that allows the deposition of the material on the building plate. A counter-rotating roller is employed to spread the powder layer with a thickness varying from 30 µm to 200 µm to achieve a high lateral resolution. A piezoelectric printhead selectively deposits 30 pL droplets of an aqueous- or solvent-based binder to form the provided CAD geometry. The system is also equipped with an IR heating lamp to pre-heat the powder bed. The powder bed is cured in a static air oven to obtain mechanically resistant and geometrically accurate green components, which are sintered according to the powder requirements.

  • Build Volume: 160 mm x 65 mm x 65 mm; Print Head: 30 pL high-resolution nozzle; Max Build Rate: 166 cm3/hr; Min Layer Height: 30 µm
  • Custom-made reduced volume hopper to process small-batch materials, to a minimum of 200-300 g depending on the powder apparent density
High-pressure Cold Spray System Impact Innovations 5/8

Solid state metal deposition powder capable of spraying on metal, glass and polymeric substrates. The system can be used both for additive manufacturing net-shape 3D free standing parts, surface coating deposition, structural repair of damaged parts. The deposition of the powder is obtained by accelerating at supersonic speed the powder to activate the solid-state adhesion by means of pre-heated and pressurized gas. It is possible to spray a mix of different powders for functionalized and multimodal materials. The deposition rate is up to 12 kg/h and there is no need for an environmental chamber with controlled atmosphere. The maximum length of the parts that can be processed is 2m. The maximum pre-heating gas temperature and pressure are 800°C and 50bar.
The main parts of the system are a control unit, a powder feeder, a nozzle chiller and a gun with a water cooled supersonic nozzle. The gun is moved with a robot KUKA.

The materials that can be processed are metal powders (Steel, Al alloys, Ti alloys, Inconel, Cu, HEA,….).

  • Gun: Impact Gun 5/8
  • Powder feeder: Impact Powder Feeder 5/11
  • Nozzle water cooling Impact 5/11
  • Printable volume: 0.4m x 0.4m x 2m
  • Process gas: Nitrogen.
  • Max gas temperature: 800°C
  • Max gas pressure: 50bar
  • Build volume: 40cm x 40cm x 200cm
  • Max deposition rate: 12 kg/h
  • Installed power: 40kw.


A 3D X-Ray CT Scan microtomograph for non-destructive inspection of parts is also available to support the lab activities (Politecnico di Milano: AMALA - Advanced MAnufacturing LAboratory).

Activities

The main research activities of the lab are listed in the following

  • Design for Additive Manufacturing: structural/functional design and optimization of parts and systems
  • Light-Weight Design: system inertia reduction with Topological Optimization and Lattice Structures
  • Process optimization and monitoring
  • Process development and optimization for AM of metals
  • Process modeling and simulations by analytical and numerical methods and experimental validation
  • Inline monitoring strategies based on optical and mechanical methods for defect recognition
  • Statistical process control methods and analytical solutions for data analysis and possible applications of closed-loop process control
  • Development and characterization of alloys for AM
  • Design and testing of new alloys (steels, Al-base, Ti-base)
  • Characterization & testing of SLM processed materials.
  • Optimization of thermal treatments of additive manufactured alloys
  • Optimization of debinding and sintering heat treatments
  • Investigation on surface coating and surface finishing of AM parts
  • Characterization of AM products and evaluation
  • Non-destructive testing of AM parts by X-ray CT-microtomography
  • Material characterization by microstructural and mechanical (static and dynamic) testing
  • Testing of structural performance of parts.

 

Lab Brochure