Dedusting of metal powders for additive manufacturing (3D ... · 3-D Printing Metal powders for 3-D printing (additive manufacturing) are produced from molten, atomized metals. The

Grinding & Dispersing

Dedusting of metal powders for additive manufacturing

InPrint 2017 | 15.11.2017 | Christian Höfels3-D Printing

Agenda

1. Introduction

2. Basics of Classification

3. NETZSCH Classifier

4. Application Examples

Introduction – 3-D Printing

Dedusting of metal powders | Grinding & Dispersing | November 2017 4

Source: https://en.wikipedia.org/wiki/Selective_laser_sintering

Process Group Example Abbreviation Working Principle

Sintering

Selective Laser Sintering SLSLocal melting of

Polymer powders (SLS)OrMetal powders (SLM)

Selective Laser Melting SLM

Laser Metal Deposition LMD

Electron Beam Sintering EBS

Extruding Fused Deposition Modeling FDMExtrusion of fused/molten polymers using a nozzle

UV-Curing

Stereolithography SLA

Local inducedCo-polymerization

Multi-Jet-Modeling MJM

Continuous Liquid Interface Production

CLIP

LCM LCMLocal inducedCo-polymerization+ Sintering process

3-D Printing

Metal powders for 3-D printing (additive manufacturing) are produced from molten, atomized metals. The manufacturing process prohibits the achievement of an exact particle distribution.


Source: https://en.wikipedia.org/wiki/Selective_laser_sintering

3-D Printing

Various and wide PSD is created

Small Particles:

influence the flow ability and dust behavior

Sinter too fast/are melted

Large Particles:

Destroying the surface of the layer

Are not heated/melted enough

Grading and classification is necessary


Source: http://advancedpowders.com/plasma-atomization-technology/our-technology/

3-D Printing


Benefits Limits

• Increased design freedom• Non weldable metals cannot be

processed

• Light weight structures• Material properties: tend to show

anisotropy in construction direction

• New functions such as complex internal channels

• Part size: standard powder bed system are 250 x 250 x 250 mm

• Less raw material consumption• Part design: overhang angles < 45° need

removable supports

• No tools needed

• Complex parts can be produced

• Recommended for small series

Introduction – A real exampleCGS 10 classifier wheel


Material 1.4404

3-D printed

Material 1.4571

Conventional 3 parts soldered

Agenda

1. Introduction




Definition of Classification

An air classifier uses the aerodynamic differences of particles in a two-phase flow (gas and solid substances) in order to separate them according to their rate of descent.

Two different types of force have an effect during air classifying:

Drag force (FW)

Gravity (FG) and centrifugal forces respectively


v

FW

FG

FW

FG

FW

FG

Fine Fraction

Coarse Fraction

Process Fundamentals


Drag force: ∗ ∗ ∗ Gravity force: ∗ ∗

Area of circle: A ∗ Volume of sphere: V ∗

~ ~ ~ ~

Particle Size A-Factor d2 V-Factor d3

0.01 10-4 > 10-6

0.1 10-2 > 10-3

1 1 ~ 1

10 102 < 103

Separation Forces in Centrifugal Classifiers

In a dynamic classifier the particles experience the following two types of force within the flow:

The drag force caused by the radial components of the flow

The centrifugal force caused by the tangential components of the flow


[1] Prof. Dr. Matthias Stieß: Mechanische Verfahrenstechnik-Partikeltechnologie 1, 3. Auflage 2009

[1]

Standard Classifier Wheel vs. CONVOR® Classifier Wheel


HF = constant

vr constant

HF constant

vr = constant

Agenda

1. Introduction


3. NETZSCH Classifiers


NETZSCH Fine Classifier CFS


1 Product inlet2 Air inlet3 Guide vane4 Classifier wheel5 Fines outlet6 Coarse outlet

NETZSCH Fine Classifier CFS – Design


NETZSCH High-efficiency Fine Classifier CFS/HD-S


1 Product inlet2 Air inlet3 Classifier wheel4 Guide vanes5 Separating wall6 Coarse outlet

NETZSCH High-efficiency Fine Classifier CFS/HD-S –Design


NETZSCH High-efficiency Fine Classifier CFS/HD-S –Plant Example

Classifying plant for inert gas operation


Agenda

1. Introduction




Application

Stainless steel (AISI 316L)

Particle size distribution of:

d10 ~ 17 µm

d50 ~ 37 µm

d90 ~ 63 µm

Bulk density = 4520 g/l

The goal is the limitation of the fine fraction to < 5 % < 15 µm in the coarse

actual: d5 ~ 11 µm

The d50 is not indicated, it results after classification


Test Results

A pilot test carried out on a CFS 8 HD-S.

Due to the relatively high density of the stainless steel, the rotational speed of the classifier was low: 2000 rpm (max: 12000 rpm)

The load was kept constant at 0.1 kg/m³

d5 of the coarse material ~ 21.2 µm

Yield: 98.7 % coarse material


Feed PSD

Coarse material PSD

Fine material PSD

SEM Pictures


FEED FINE COARSE

Magnification

500x

1000x

Raw Material

Examples of applied materials:

Stainless steel

Tool-steel

Aluminum and aluminum alloys

Titanium and titanium alloys

Chrome-Cobalt-Molybdenum alloys

Bronze alloys

Nickel-based alloys

Copper alloys

Ceramics

Plastics (Procedure: Laser Sintering)


Source: https://de.wikipedia.org/wiki/Selektives_Laserschmelzen

Summary

3-D Printing is a rising technology with a huge industrial potential

Dynamic air classifiers are used to grade the 3-D printing raw materials

High dispersion classifier dedust sharply CFS HD-S

High efficiency and yield

Standard classifier can operate in the coarser range

Improvement of the productivity

Replacing sieves

CFS Standard

CONVOR®-wheel for finest products and HF-wheel for coarser products


Thank you for your attention!

Christian HöfelsProcess Technology Development

NETZSCH Trockenmahltechnik GmbHTel.: +49 6181 506 277Fax: +49 6181 571 270

[email protected]

Documents

Dedusting of metal powders for additive manufacturing (3D ... · 3-D Printing Metal powders for 3-D printing (additive manufacturing) are produced from molten, atomized metals. The