Technical keys to understand 3D-printing. Lucile BONHOURE. Sartomer, Arkema

Transcription

1 RTE Conference & Exhibition 2017 Technical keys to understand 3D-printing Lucile BONHOURE Sartomer, Arkema Prague, October 19th, 2017

2 Agenda Introduction to 3D-Printing, stakes and technical challenges Printing process : how to adapt the formulation to any printer Towards rubber-like materials

3 Agenda Introduction to 3D-Printing, stakes and technical challenges Printing process : how to adapt the formulation to any printer Towards rubber-like materials

4 AM to drive innovation towards the future

5 AM to drive innovation towards the future Additive manufacturing, or 3D-printing: Process of joining materials to make objects from a 3D model data, usually through a layer-upon-layer process. Source :

6 AM to drive innovation towards the future MJP FDM SLS BJ SLA, DLP

7 Stakes and technical challenges Parts built through polymerization Parts built through bonding agent Parts built through melting Plastic SLA DLP MJP BJ FDM SLS MJF Metal LM EBM Ceramic SLA Accuracy Speed Details Mechanical Properties Material Availability Estimated characteristics comparison

8 Stakes and technical challenges Parts built through polymerization Parts built through bonding agent Parts built through melting Plastic SLA DLP MJP BJ FDM LS MJF Metal Ceramic Accuracy Speed Details Mechanical Properties Material Availability SLA In an oversimplified LM way, the choice EBM among the different technologies is made according to: the part size the performance/aspect required. Estimated characteristics comparison

9 Stakes and technical challenges Photopolymerization technologies Processability : Low viscosity Low odor Printing speed Low shrinkage High mechanical performance : Impact resistance HDT Elongation Durability : No yellowing High clarity No loss of mechanical properties over time Develop thermoset resins with thermoplastic properties

10 Agenda Introduction to 3D-Printing, stakes and technical challenges Printing process : how to adapt the formulation to any printer Towards rubber-like materials

11 Introduction to the working curve method The working curve Adapt a formulation to a given printer : Every printer is different No customizable printing parameters Set printing parameters for a given formulation : According to formulation reactivity Depending on wanted printing definition Explanation of the method

12 What is a voxel? Voxel = «pixel» Laser beam hitting a spot in the photocurable resin = voxel of cured resin Size of the voxel depends on : Photoinitiator amount Deepness of the laser penetration Speed of cure C d, D p : µm E, E c : mj/cm² Source : Rapid Prototyping & Manufacturing, Fundamentals of Stereolithography, Paul F. Jacobs (1992)

13 The working curve equation Cure Depth : - Physically measured when assessing new resins for printers using a calibration print - Printing definition along the z axis Depth of Penetration : - Proportional to formulation absorbance - Determined value from plotting Energy delivered : - Set value on some printers - E = Power x time Critical Energy : - Critical amount of exposure required to gel the voxel at a depth of 0. - Synonym of formulation reactivity Working curve plot C d vs ln(e c ) Generated with calibration print

14 Side view Top view Calibration print on open source DLP printer Calibration print Working curve plot C d (µm) 0.5 s 1.0 s 1.5 s 2.0 s Square thickness Exposure time Ln (E c ) E = Power x time Ln (E) Applicative examples

15 Example of working curve method : Influence of the additive package (PI) System PI (%) Ec (mj/cm²) Dp (µm) ND1 0, ND1 1, ND ND1 = Engineered solution by Sartomer C d, D p : µm E, E c : mj/cm² Excess amount of PI leads to E c plateau and loss of conversion

16 Example of working curve Influence of the additive package (UV Blocker) System UV-Blocker (%) Ec (mj/cm²) Dp (µm) ND1 0, ND1 1, ND ND1 = Engineered solution by Sartomer C d, D p : µm E, E c : mj/cm² UV blockers have a filtering effect

17 Limitation in DLP printing : the viscosity Higher mobility of monomers : low influence of temperature Low mobility of oligomers at RT, high 60 C : high influence of viscosity on conversion Monomer η = 7 25 C Oligomer η = C 2% TPO-L at 23 C 2% TPO-L at 60 C 2% TPO-L at 60 C 2% TPO-L at 23 C Need for innovative printers with heating platforms, vat, and overall precinct

18 Agenda Introduction to 3D-Printing, stakes and technical challenges Printing process : how to adapt the formulation to any printer Towards rubber-like materials

19 Towards rubber-like materials Natural rubber properties in a rubber watch bracelet Elongation (%) : Hardness (ShA) : Parameters of the tensile test : Test specimen type : dogbone (DIN EN ISO type 5A) Speed : 50 mm/min (Rubber standard) Compression set (%) : Breaking stress (MPa) : Aspect : Flexible, returns to it s original shape after being stretched Natural rubber and SBS tensile test Source :

20 Towards rubber-like materials : Influence of IBOA With increasing amounts of IBOA x (%) break (%) break (MPa) Formulation Product Viscosity Composition Urethane 1 34 mpa.s@25 C 44% Urethane Pa.s@25 C 55-x % IBOA 13 mpa.s@25 C x % PIs - 1% / /-? 4, /- 20 9,8 Tensile Contrainte strength (MPa) (MPa) Tensile test x = 10 % x = 25 % x = 35 % Elongation Déformation (%) (%) Rubber-like profile at 35% of IBOA

21 Towards rubber-like materials : Influence of IBOA Tensile strength (MPa) Tensile test for x=35 % Soft domains, Hard nodules of p-iboa p-iboa p-iboa Soft urethane p-iboa p-iboa Elongation (%) Reproducible rubber-like profile

22 RIGID Conclusion and future work The challenge to bring photopolymerisation AM from prototyping to production resides both in printing process and in material development Designed to Resist Hi Temp Many challenges still remain : Clarity and durability Ensure processability of solutions Easy-burning materials High impact resistance Designed for Clarity TOUGH ELASTIC Designed to Burn Casting

23 Thank you Questions? Come visit us on our stand on Booth B19

24 Thank you Back-up slides

25 Reminder of the SLA and DLP technologies Stereolithography process Top-Down Approach with laser based tracking system New layers are a result of fluid overflow, or use of re-coating blade Resin Handling often an issue Quenching of cationic initiators with ambient moisture Viscosity build/creep over time Fillers, Particles and Modifiers all need high degree of stability > 3 months Digital Light Projection process Bottom-Up approach using a DLP projection or SLA laser source Parts are limited in size, shape and design Vat and tray size limits square footage of part Fluid flow, and pressure limitation on area of print Peel and Recoat mechanisms provide differentiation between printers

26 Introduction to the working curve method Voxel Cure Depth : - Depth of the layer cured, or the depth of the individual laser cured section - Physically measured when assessing new resins for printers using a calibration print - Printing definition along the z axis Energy delivered : - Amount of energy delivered into the image as a function of intensity and time - Set value on some printers - Time exposure can be set on open sourced DLP printers - Hard to assess for SLA

27 Introduction to the working curve method Depth of Penetration : - The distance the light has penetrated into the resin - Determined value from plotting : Extrapolated from the Cd vs ln(ec) plot generated with the Cure depth measurements on the calibration print - This value can be used to directly assist in modeling software for printer resin integration - Direct control with use of additives : PI, absorbers, dyes, pigments, fillers Critical Energy : - Critical amount of exposure required to gel the voxel at a depth of 0. If the Ec value is below the Energy delivered (E) than you get gelation. - The X-intercept of the working curve - Direct influence by improving curing : addition of functionality or high Tg constituents, additives to accelerate reaction, more reactive PI