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Additive Manufacturing - Cleaning: Guidance for Removing Residual Powders - OMTEC 2018


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The popularity of additive manufacturing in the medical device manufacturing industry is growing thanks to the ability to print solid substrate and lattice structure for implant fixation in a single step. Printing a lattice structure is not only a matter of design, but it also requires the ability to process the foam-like structure in a way that make it usable in the human body. Cleaning, in this specific case, removes loose particles and/or contaminants from such structures. To achieve this objective, a mechanical and dry step has been developed to remove the majority of loose particles without adding any substance to the lattice structure. Following steps based on chemical etching of the titanium surface on a lattice structure can be used to remove the remaining particles and to modify the structures’ surfaces to enhance osteoconductivity. Where machining lubricants must be removed, we are seeing promising results in developing a proper cleaning step with specific detergents, which avoids any detectable residual in the foam but is capable of completely removing contaminants.

Published in: Health & Medicine
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Additive Manufacturing - Cleaning: Guidance for Removing Residual Powders - OMTEC 2018

  1. 1. Mukesh Kumar Global Technology Director Business confidential 2 Cleaning and Surface Modification of Orthopedic Implants made via Additive Manufacturing
  2. 2. What does the Orthopedic Industry do In the business of alleviating pain and restoring mobility by replacing damaged bone (and cartilage) with metallic (and plastic) Implants that − Must survive in vivo for years (10+ years) − In a hostile (corrosive) environment (in vivo) − (osseo) integrate with the surrounding bone to transmit 5-8 X body weight − Function under fatigue conditions − Restore Mechanical Alignment
  3. 3. A lot to do with Porous Structure • Why do we need this porous structure − Bone – Implant Interface − Transmit load Animal Studies Human Retrieval Analysis
  4. 4. Additive Manufacturing in Orthopedics: Why? • The need for a Bone Ingrowth Surface − Which is usually porous (or at least roughened) − May be − “mathematically generated” or − Organic shaped (Biomimetic) AM in Orthopedics is gaining traction because AM can build the Solid and Porous region simultaneously & consistently without concern of line of sight (e.g. cutting tool movement) Eliminate the need for a secondary operation of Coating etc.
  5. 5. Business confidential MANUFACTURING FLOW Printer (manufacturing step) Furnace Cut from starting plate CNC machining Post processing (ex.: coating or surface modification) AM OPERATOR Design (customer/tech dept) Final cleaning Cleaning from residual powder Final controls Customized packaging In process controls after each step
  6. 6. Powder Characteristics Check raw material properties (incoming inspection) Check raw material processability Check printed material properties (tensile test) Process Monitor Validated equipment Validated powder ageing Daily verification of log files Periodic verification of energy source power Periodic maintenance and verification of the calibration of the optical path Product Verification Dimensional verification Microscopic lattice observation Destructive test on dummy parts to check lattice properties Destructive test on dummy parts to check material properties PROCESS MONITORING Business confidential
  7. 7. Design of an efficient process:  Benefits over costs optimization Design for Additive Manufacturing:  Over a decade of experience in exploiting peculiarities of technology (e.g., undercuts design, light structures etc.)  Design optimization for helping parts printing (Support strategy, orientation…) EASE OF MANUFACTURING Business confidential PROPERTY OF A CUSTOMER
  8. 8. 9 How Surface Dynamics sees the AM process AM – Surface Dynamics style  Advanced manufacturing process; there is no «magic» inside  Suitable for serial production and not only for prototyping or small series  Need of having it under control  Need to understand it and be able to manipulate it  AM is just a part of a wider manufacturing flow  Scientific approach  Continuous R&D activities  Continuous training of engineers and operators  Continuous technology update to stay “on the edge”  Equipment and process validation  Raw material incoming inspection with narrow specifications  No powder mixing  Machine dedicated to a single material  Co-design of the whole process with customer – DFAM  Oriented on serial continuous production MORE THAN 50K IMPLANTABLE DEVICES SUCCESSFULLY PRINTED EACH YEAR Business confidential
  9. 9. Technical Considerations for Additive Manufactured Medical Devices Guidance for Industry and Food and Drug Administration Staff Document issued on December 5, 2017. • Manufacturing material removal processes (cleaning) should ensure that residues are removed to the level where they do not impact the safety or effectiveness of the product (see Section VI.E Removing Manufacturing Material Residues and Sterilization) • additively manufactured devices are expected to increase the difficulty in removing manufacturing material residues (cleaning) and in sterilization due to the likelihood of increased surface area, generation of extensive tortuous pathways, and creation of internal voids with limited or no access. FDA and Additive Manufacturing Business confidential 10
  10. 10. • Porous Structure − Development Engineers + Biomaterials Scientists − Organic Shaped (Biomimetic) or Lattice (ordered) shaped • Raw Materials − Size of powder • Energy Source − Laser Based followed by heat treatment − Electron Beam in Heated Chamber (~750C) Porous Structure Design, Raw Materials and Technology Business confidential 11 Tortuosity is better for biological fixation Larger the particles, the harder it is to remove from porous structure Incipient Sintering at elevated temperatures leads to clustering i.e. increased “effective size”
  11. 11. Experience in design of lattice structure suitable for 3D printing using specific software developed for this technology Process and melting strategy specific for lattice structure (DFAM):  Selection of the most effective laser path  Know how of the effects of the key parameters on the melted material  Optimization of the component design to match with the specific melting strategy POROUS STRUCTURES ENGINEERED FOR AM Business confidential
  12. 12. Cleaning process Target • Get different surfaces finishing on the same part • Roughness – reduce if needed • Remove loose particles • Preserve the lattice structure • Leave the part clean • Must use mass production process(es)
  13. 13. • “Cleaning” step(s) to remove weak particles • Wet and Dry • Mechanical process to reduce roughness • Parameters are determined by DOE • Initial cleaning step in dry condition • Possible chemical/mechanical smoothing of lattice struts surface • Possible tumbling with proper selection of abrasive agent (shape and chemistry) to have smooth substrate surfaces • Final cleaning customized to remove residuals without modification of the substrate Cleaning/surface finishing processes Approach Solution 0.00% 0.01% 0.02% 0.03% 0.04% 0.05% 0 1 2 3 massloss% number of cycles dry cleaning a dry cleaning b wet cleaning c wet cleaning d
  14. 14. Original surface - Ra≈20µm Treatment step 1 - Ra≈8µm Treatment step 2 Ra<2µm Advanced treatment Ra<1µm Finishing: macroscopic/surface effect
  15. 15. Mechanical Chemical (may be used also to apply functional features to the surface) Lattice • Several different kinds of lattice structures with different pore size, strut shape and geometry • Wide range of possibility depending on the desired target
  16. 16. Lattice: cleaning effect Original state after printing and finishing: some particles sticking on the surface and processing residuals Just after cleaning: remaining particles are well attached to the substrate, no more process residuals Possible additional processing to further modify the surface
  17. 17. 18 Post AM treatments CaP coating Coatings, Calcium Phosphate based, can be applied (Eurocoating processes) to modify the struts surface morphology and chemical nature CaP coatings used: Hydroxyapatite (HA) Brushite (BR) Untreated HA coated BR coated
  18. 18. 19 Post AM treatments Surface modification Business confidential • Electrochemical surface modification  Enhance osteointegration  Can act as antibacterial treatment (doped)
  19. 19. Business confidential 20 THANK YOU FOR YOUR ATTENTION Surface Dynamics Memphis 3110 Stage Post Drive, Suite 101 38133 Bartlett, TN, USA tel. +1 (901) 326 0168 fax +1 (901) 377 6688 Surface Dynamics Cincinnati 231 Northland Blvd. 45246 Cincinnati, OH, USA tel. +1 (513) 772 6635 fax +1 (513) 772 0825 Eurocoating SpA Via al Dos de la Roda, 60 38057 Pergine Valsugana, Trento, Italy tel. +39 0461 538901 fax +39 0461 518902 Anteco Srl Via Maestri del Lavoro, Lotto D 29, Loc. Pezzagrande I 84025 Eboli, Salerno, Italy Tel.: +39 0828 366156 fax.: + 39 0828 364 802 @PEC: Eurocoating Medical Technology (Wuxi) Co., LTD 30 Wanquan Road, Yunlin, Xishan District 214192 Wuxi, Jiangsu, China tel. +86 158 6246 7089