Title: Coatings for 3D Printed Molds and Fixtures

Authors: Mark Adam, Rick Spears, John Miller, Richard Pauer, Ashley Duncan, Michael A. Mathews, Hunter Watts

DOI: 10.33599/nasampe/c.24.0273

Abstract: "Large Area Additive Manufactured (LAAM) articles often require milling of critical surfaces for dimensional tolerances, character lines, and surface profile. These objects may be molds, fixtures, or prototypes. It is not uncommon for non-coated milled surfaces to manifest imperfections such as porosity, bead gaps, surface roughness, print/mill line transfer. A few commercially available coatings exist for 3D printed thermoplastic and thermoset tools. These products exhibit excellent adhesion to a variety of plastic substrates and have been shown to improve molded part aesthetics and vacuum integrity up to 149 °C. However, some of these coatings were not designed for use with reactive monomer-based resins common to glass and carbon filled composites. In addition, their Tg may be lower than the operating temperature of the molding process resulting in surface hazing, micro crazing, and delamination. Companies performing LAAM can attest how post-finishing often adds significant cost. In some estimations, the time needed to mill (especially to low RA values) can be 4-5 times longer than the print-time itself. Therefore, being able to reduce the milling time using high-build primers and topcoats may be a cost-effective alternative, especially when a high-gloss appearance is required. In the FRP tooling industry, in-mold applied gelcoats provide both the chemical resistance and high gloss needed. With 3D printed molds, these same coatings are hard and difficult to sand/polish. Printed tools need coatings that can be post-applied, render Class-A aesthetics, provide durability for high-volume molding applications, and are easy to use. The research to be presented in this paper will evaluate a range of coating materials and how they perform over thermoplastic and thermoset 3D-printed molds. Data will be presented to assist the printing organization in selecting the best coating option for ambient molding and high-temp molding applications (<180°C).

References: 1. Krassenstein B, “ORNL 3D Prints Working Shelby Cobra Replica-President Obama Approves,” 3D Print.com, January 15, 2015 2. Cohen J, “Shelby Cobra Recreated using 3D Printing,” Machine Design, February 15, 2015, pp. 34-38. 3. See Hassen A, Springfield R, Lindahl J, Kunc V, Love L, et al, The Durability of Large-Scale Additive Manufacturing Composite Molds, CAMX-The Composites and Advanced Materials, Expo, Anaheim, CA September 2016. 4. See https://www.ornl.gov/news/3-d-printed-shelby-cobra-highlights-ornl-rd-detroit-auto-show 5. Schroeder J, “Coating Cost Advantages,” Internal Document, 3D Platform, Roscoe, IL 61073, 2017. 6. Wong K, The Hidden Cost of Post-Processing, Digital Engineering 247, May 2, 2023 7. Pauer R, Lindahl J, Hershey C, Adams M, Thermally Stable AM Printed Molds/Fixtures Using Ambient Cured, Thermoset Print Media, AMUG- Additive Manufacturing Users Group Meeting, April 5, 2022. 8. Numerous articles have been written on the subject. For one example see Cong Chen et al, “Studies on Protective Coatings for Molding Tools Applied in a Precision Glass Molding Process for a High Abbe Number Glass S-FPM3,” MDPI.com, Coatings, vol 13, issue 8, p 1438, 2023.

Conference: CAMX 2024 | San Diego CA

Publication Date: 2024/9/9

SKU: TP24-0000000273

Pages: 16

Price: $32.00