Process Control for Additive Manufacturing. Lesson 3 Measurement & Control of Heat Input

Transcription

1 Process Control for Additive Manufacturing Lesson 3 Measurement & Control of Heat Input

2 Why is this important to you? It has been well established in the welding industry that heat input has a direct influence on the mechanical properties of the substrate being welded. In additive manufacturing we are depositing many welds simultaneously to build 3D parts. Current approaches use IR cameras to monitor melt pool (size and temperature), mainly to control geometry and surface finish but have no mention of providing repeatable mechanical properties. AM is a dynamic process and many factors will influence heat input, therefore a way to accurately measure and control this will be critical to its future success. Heat Input Measurement & Control 2

3 Proposed Solution: Mechanical Properties Net Heat Input (P net ), J/mm Amount of energy absorbed into workpiece Measured Energy Density, W/mm 3 Function of beam dimensions, power, hatch, thickness and travel speed Deposition Rate, g/min: Function of travel speed and powder feed rate Heat Input Measurement & Control 3

4 Introduction: Power Definitions Heat Input Measurement & Control 4

5 Schematic Layout P LENS : -Power entered in LENS Control software. P in : -Power measured via thermopile sensor. P net : -Power measured via calorimeter. Heat Input Measurement & Control 5

6 Energy Balance Laser/Powder/Meltpool (first events) Heat Input Measurement & Control 6

7 Energy Balance: First Events + Build/Substrate Heat Input Measurement & Control 7

8 Power Measurement Calorimetric System (PMCS) 1. Calorimeter 2. Pendant 3. Water and electrical control 4. Calibration device 5. Water supply 6. Auxiliary calorimeters Heat Input Measurement & Control 8

9 Calibration Analysis of PMCS Heat Input Measurement & Control 9

10 Calibration Analysis of PMCS Heat Input Measurement & Control 10

11 Calibration Analysis of PMCS Heat Input Measurement & Control 11

12 Calibration Analysis of PMCS Heat Input Measurement & Control 12

13 Calibration Analysis of PMCS Heat Input Measurement & Control 13

14 Calibration Analysis of PMCS Heat Input Measurement & Control 14

15 Calibration Analysis of PMCS Calibration achieved 98-99% measured efficiency Published article in July 2006 issue of Welding Journal Heat Input Measurement & Control 15

16 Calibration Analysis of PMCS Initial studies show that for 1018 steel absorbed energy is maxed at 57% after 3 kw Heat Input Measurement & Control 16

17 Experimental Data Pnet (Energy Absorbed) of 1018 steel using HPDDL % Absorbed Pin (W) Heat Input Measurement & Control 17

18 Physics-Based Additive Mfg. Models For Process Control & Quality Assurance Project Objectives A comprehensive suite of integrated tools for process control and Additive Manufacturing part qualification Devise and test models that enable predictive process adjustments during the layer-by-layer, three-dimensional manufacturing method Guide development of customized engineered materials tailored to the capabilities of specific AM technologies, eliminating much trial-and-error testing Heat Input Measurement & Control 18

19 Physics-Based Additive Mfg. Models For Process Control & Quality Assurance Project Lead: Collaborators: Northern Illinois University, DeKalb, Ill. Northwestern University, Evanston, Ill. Quad City Manufacturing Laboratory, Rock Island, Ill. Illinois Manufacturing Excellence Center, Peoria, Ill. Fabricators & Manufacturers Association, International, Rockford, Ill. NIST Funding: $2.4 million Project Period: October 2013 to September Heat Input Measurement & Control 19

20 Using PMCS for Additive Manufacturing The calorimeter allows us to directly measure: net heat input, H net (J/mm), energy transfer efficiency, k, absorbed net energy, E net, and average net power during processing, P net. As a result of this it is possible to then determine the measured energy density, J/mm 3 of the part built. By then correlating this information to the mechanical properties of the parts built we can develop an understanding of the global energy requirements that will enable high quality repeatable builds. Heat Input Measurement & Control 20

21 Definition of Energy Density It is possible to determine Global Energy Density which is per unit area, and is defined as GED = Laser Power/Travel Speed * beam diameter = J/mm 2 One can also determine Measured Energy Density which is per unit volume, MED = Laser Power/Travel Speed * hatch distance * powder layer thickness=j/mm 3 GED will enable a quick assessment of required metrics for corresponding mechanical properties, the MED will enable user to ensure they are within acceptable range. Heat Input Measurement & Control 21

22 NIU s NEAT Manufacturing Solution Center LENS System OPTOMEC LENS 850-M -Equipped with an IPG YLS-3000 fiber laser (100 um fiber diameter). -Argon shielding -1 kw capability -3-axis positioning (xyz) NEAT MSC s objective is to support local industry using AM in: refurbishment, new product development, R&D in materials Heat Input Measurement & Control 22

23 NIU s NEAT Manufacturing Solution Center LENS System Heat Input Measurement & Control 23

24 Evolution of Calorimeter Data Analysis Measured Net Heat Input, J/mm Measured Net Heat Input: J/mm J/mm J/mm J/mm2 Trend GED, J/mm2 Laser Path Length (Contours + passes) x n n = number of layers MED, J/mm 3 MED: Measured Energy Density, J/mm J/mm J/mm J/mm2 Trend GED, J/mm2 Volumetric Based on build volume, x y z Heat Input Measurement & Control 24

25 TENSILE DATA FACILITY MATERIAL UTS(MPa) Modulus Of Elasticity (GPa) NIST-MSAM 316L Stainless 638 ± ± 44 Ti-6Al-4V 1139 ± ± 14 EOS 316L Stainless 640 ± Ti-6Al-4V 1230 ± ± 10 ASTM 316L Stainless 485 min. 190 Ti-6Al-4V 950 min Heat Input Measurement & Control 25

26 HARDNESS DATA FACILITY MATERIAL HRB NIU 316L Stainless 85 ± 0.4 Ti-6Al-4V N/A EOS 316L Stainless 85 Ti-6Al-4V 107* ASTM 316L Stainless 95 Max Ti-6Al-4V 109* 316L Stainless Steel ASTM Reference F138-13a for wrought material Ti-6Al-4V Titanium ASTM Reference F136 for wrought material *Numbers in red converted from Rockwell C scale to Rockwell B Heat Input Measurement & Control 26

27 Resources Northern Illinois University (NIU) Additive Manufacturing Lab Federico Sciammarella, Director Northwestern University Mechanical Engineering Department McCormick School of Engineering Jian Cao National Institute of Standards and Technology (NIST) Engineering Laboratory Kevin Jurrens, Deputy Division Chief This work was performed under the following financial assistance award 70NANB13H194 from the U.S. Department of Commerce, National Institute of Standards and Technology. The views expressed do not necessarily reflect the official policies of NIST; nor does mention by trade names, commercial practices, or organizations imply endorsement of the U.S. Government.