Comprehensive Investigation. Surface Characterization Methods. Laser Sintered Parts

Transcription

1 Comprehensive Investigation of Surface Characterization Methods for Laser Sintered Parts Marc Vetterli INSPIRE AG irpd Sankt-Gallen, Switzerland DDMC14, March 13, 2014 Berlin

2 AGENDA: 1. Introduction 2. Methods 3. Results 4. Conclusions 5. Outlook 2

3 Introduction So far: The human hand is the best characterization method for the roughness of SLS parts à Surface state of SLS-produced subject to different default patterns: - Part orientation - Scan lines - Powder material à Many papers have identified the reasons for such surface state and characterized the surfaces mainly with profilometer à But how effective and representative are they? 3

4 Introduction Filtered out using a CUT OFF value λ c = 0.8 mm Source: ASME B46.1. Surface texture (surface roughness, waviness, and lay),

5 Introduction Arithmetic average of absolute values Average distance between the five highest peaks and five lowest valleys Source: DIN EN ISO Jul 2010, Mahr Federal 5

6 AGENDA: 1. Introduction 2. Methods 3. Results 4. Conclusions 5. Outlook 6

7 Methods Cube sintered on EOS P760 machine Dimensions: 15X15X15mm Parameter Value Unit UP Face Laser power 38 [W] Outline laser power 5.5 [W] Scan spacing 0.25 [mm] Layer thickness 0.1 [mm] Z SIDE Face Laser speed 6 [m/s] UP Face parallel to building platform X Y DOWN Face 7

8 Methods: Profile Investigation 1 2 1) Cube 2) Embed and polish 3) Micrograph of profile 4) B/W image processing 5) Interface recognition 6) Roughness calculation um 4 Side Face 5 6 Cutoff 0.8 mm Total measurement length 4 mm 8

9 Methods: Profilometers - Measurement length: 5.6 mm - Cut-off filter: 0.8mm - Scanning speed: 0.5 mm/s Mahr Perthometer à Tip radius of 5µm, angle of 90 Veeco Dektak 150 à Tip radius of 2.5µm, angle of 45 R a and R z(iso) are directly calculated by the integrated software. Source: Veeco Dektak 150 User s Manual à 4 measurements per direction at equidistant intervals 9

10 Methods: LEICA DCM 3D Interferometry + Confocal Microscopy: - Measurement area: 3.406x2.529 mm - Objective: 10X - Cut-off filter: 0.8mm - Resolution: 20 µm per data point R a and R z(iso) for both directions of the surface à Each pixel line is considered as a single surface profile in both X and Y directions Source: Leica DCM 3D User s Manual 10

11 Methods: GelSight GELSIGHT Elastomeric sensor covered with reflective skin 1) Sensor is pressed onto surface; its reflective skin conforms closely to it and lends it its optical properties. 2) Area is successively illuminated and photographed from six directions. 3) Pictures are computed with algorithm creating a surface normal map of the area. Optimal size of measured features: µm 11

12 Methods: GelSight GELSIGHT - Measurement area: 4x4mm - Objective: 1X - Cut-off filter: 0.8mm - Resolution: 4.2 µm/pixel R a and R z(iso) for both directions of the surface. à Each pixel line is considered as a single surface profile in both X and Y directions 12

13 Methods: GelSight GELSIGHT Inc. - Measurement area: 4x4mm - Objective: 1X - Cut-off filter: 0.8mm - Resolution: 4.2 µm/pixel R a and R z(iso) for both directions of the surface. à Each pixel line is considered as a single surface profile in both X and Y directions 13

14 Methods: GelSight GELSIGHT Inc. - Measurement area: 4x4mm Objective: 1X Cut-off filter: 0.8mm Resolution: 4.2 µm/pixel Ra and Rz(ISO) for both directions of the surface. à Each pixel line is considered as a single surface profile in both X and Y directions 14

15 Methods: GelSight GELSIGHT Inc. - Measurement area: 4x4mm Objective: 1X Cut-off filter: 0.8mm Resolution: 4.2 µm/pixel Ra and Rz(ISO) for both directions of the surface. à Each pixel line is considered as a single surface profile in both X and Y directions 15

16 AGENDA: 1. Introduction 2. Methods 3. Results 4. Conclusions 5. Outlook 16

17 Results: UP Face RaX RaY RzX RzY Ra (um) Rz (um) 17

18 Results: DOWN Face RaX RaY RzX RzY Ra (um) Rz (um) 18

19 Results: SIDE Face RaX RaZ RzX "RzZ" Ra (um) Rz (um) 19

20 Results: Efficiency Time needed to measure a surface: t Veeco < t Perthen < t GelSight < t Leica Amount of information obtained surface: INFO Perthen < INFO Veeco < INFO Leica < INFO GelSight All in all, the information ratio from GelSight overrides its longer processing time. 20

21 Results: How representative? Perthen stylus tip Gelsight data points mapping Leica data points mapping à based on relfection of light: SLS surface is shiny and rough very high scattering of light leading to information loss 21

22 AGENDA: 1. Introduction 2. Methods 3. Results 4. Conclusions 5. Outlook 22

23 Conclusion à Every method subject to important variations à Measured values vary from method to method à However Gelsight enables a rapid and good reproduction of the surface state qualitatively as well as quantitatively à Qualitatively the impressions obtained by stroking SLS parts by hand are confirmed: - UP and DOWN Faces are smoother than SIDE Face 23

24 Conclusion DF PA12 sand-blasted DF PA12 vibratorygrinded 24

25 Conclusion Orgasol, Magnification 10X, spatial resolution 0.43 µm/pixel 25

26 AGENDA: 1. Introduction 2. Methods 3. Results 4. Conclusions 5. Outlook 26

27 Outlook With help of GelSight - Comparison between vibratory-grinded and conventional surfaces including the material ratio, height and wavelength parameters à Get a benchmark for optimizing the surface and making vibratorygrinding obsolete - Application of roughness surface areal parameters - Determination of factors being able to characterize and identify orange peel 27

28 Thank you for your attention! Questions? 28

29 Introduction SLS surfaces are subject to many different default patterns Source: Tumer,Thompson,Crawford 29

30 Introduction From Mitutoyo adapted from DIN EN ISO 4288:

31 Methods: Mahr Perthometer à Tip radius of 5µm, angle of 90 - Measurement length: 5.6 mm - Cut-off filter: 0.8mm - Scanning speed: 0.5 mm/s R a and R z(iso) are directly calculated by the integrated software. à 4 measurements per direction at equidistant intervals 31

32 Methods: Veeco Dektak 150 (New generation profilometer) à Tip radius of 2.5µm, angle of 45 - Measurement length: 5.6 mm - Cut-off filter: 0.8mm - Scanning speed: 0.5 mm/s - Resolution 1.7 µm R a and R z(iso) are directly calculated using Veeco s software. à 4 measurements per direction at equidistant intervals Source: Veeco Dektak 150 User s Manual 32

33 GelSight Benchtop Beta System n n n n n Canon T3i 18 Megapixel Camera 5202 x 3465 pixel Canon MP- E 65mm macro lens Spa:al Resolu:on: 1X: 4.3 µm per pixel 2X: 2.2 µm per pixel 3X: 1.5 µm per pixel 4X: 1.1 µm per pixel 5X: 0.9 µm per pixel The first two images were captured at a spa:al resolu:on of 3.8 µm per pixel. The 10X image was captured at a spa:al resolu:on of 0.43 µm per pixel. 33

34 Outlook - Use of the most reliable method to determine the impact of particle size distribution on surface roughness for SLS-produced parts - Comparison of DuraForm PA and Orgasol from Arkema Same basis material (nylon polyamide 12) The accuracy of Orgasol parts is much higher and surface smoother than DuraForm FUTURE: Obtaining similar surface characteristics with DuraForm PA 34

35 The Surface Roughness Issue If you cannot measure it, you cannot improve it. Lord Kelvin Source 35