FIGURE 1. The uncoated maraging steel (MS1) inserts are shown before testing.

Applications for additive manufacturing continue to increase, including in the production of automotive stamping dies. The main benefits of using 3D-printed tools in forming applications are shorter production times for die inserts and lower costs (if complicated geometries require substantial material to be removed from the initial forged billet stock).

Researchers at Oakland University’s Center of Advanced Manufacturing and Materials (CAMM) recently conducted a study to investigate die wear in 3D-printed tools during room-temperature stamping of aluminum alloy 5754 sheet, typically used for lightweight automotive structural parts. They used forming inserts that were 3D-printed with laser-based powder bed fusion from uncoated maraging steel (MS1) (see Figure 1), MS1 with Ionbond 42 coating, and H13 tool steel with Ionbond 42 coating. The researchers U-bent 2.5-mm-thick AA5754 sheet, forming 50,001 parts in uncoated configuration and 50,001 coated, using left and right inserts from different sides.

The strip was blanked from a 2.5-mm-thick and 151-mm-wide coil lubricated with 61AUS (mill oil) lubricant at 50 mg/ft.² average weight. The depth of draw of the U-bent part was 43.5 mm, and the inner radius was 5 mm. The blank holder was supported by gas springs charged from a nitrogen tank to predetermined pressure. (For information on the design of the progressive die used for U-bending coupons, see “Detecting the onset of galling in aluminum sheet stamping.”)

To evaluate die wear and surface condition of the samples, the researchers measured the tangent line with a Bruker optical profilometer; the results are reported using roughness Sa. It expresses, as an absolute value, the difference in height of each point compared to the arithmetical mean of the surface.

For each set of inserts, the researchers evaluated one sample from each 1,000 produced (samples 1; 1,001; 2,001; etc., to 50,001), for a total of 51 evaluated samples, measuring the Sa parameter in three areas on the wall of each sample and averaging the results.

Surface quality of the samples produced with the uncoated MS1 inserts decreased as the number of tests increased. Scratches on the wall of the sample started appearing from the first sample, and the surface got shinier with each next sample collected. The worst surface condition (most scratched) occurred on sample 50,001 on both the right and left side; that sample was produced with the uncoated MS1 inserts. Sa roughness increased more than 100% in sample 50,001 compared to sample 1 (see Figure 2).

The surface quality of the samples produced with the coated inserts was very good (see Figure 3). While they showed random, not repeatable, shallow scratches caused by aluminum flakes, they had no deep scratches and no significant change in Sa roughness. The samples formed by the coated MS1 inserts had very shallow, hairlike flow lines. Comparing the significant increase in roughness caused by the uncoated inserts to the very minor change caused by the coated inserts shows the positive effect of the Ionbond 42 coating (see Figure 4).

Next the researchers evaluated insert surface quality. Figures 5 and 6 show the condition of the right- and left-hand uncoated MS1 inserts, respectively, after 50,000 U-bends. The researchers measured the tangent lines with the optical profilometer, which detected significant wear. The changes in surface due to wear are shown in the 3D plots.

Figure 7 shows the condition of the right-hand H13 tool steel insert with Ionbond 42 coating before and after the 50,001 bends. No significant wear was observed on the surface of the insert. Measuring the tangent line with the optical profilometer, researchers saw a slight increase in roughness, and the top area of the insert was scratched.

Figure 8 shows the condition of the left-hand MS1 insert with Ionbond 42 coating before and after the 50,001 bends. Researchers observed scratching on the top side of the insert, but no significant wear. They measured the tangent line with the optical profilometer and discovered the Sa increased from 118 to 306 nm—a greater increase than for the coated H13 tool steel insert.

FIGURE 2. The surface quality of the samples produced with the uncoated MS1 inserts decreased as the number of tests increased.

Figure 9 shows the top side of the coated inserts. The MS1 coated insert shows more scratches than the tool steel coated insert, but neither caused any changes in sample surface quality.

This research project was funded in part by the United States Council for Automotive Research with contributions from Novelis Corp., which provided 5754 aluminum alloy coil; and Ionbond LLC, which performed coatings of the tested inserts. The authors would like to acknowledge Dr. Dajun Zhou from Stellantis for his very useful comments and suggestions on the project.

Research Engineer, Manufacturing and Metals Research

Ford Research & Innovation Center

Building R, Receiving R, Room 2012A 2101 Village Road

See More by Alan Gillard

General Motors’ Global Stamping Center

See More by Dr. Krishna Murali

Oakland University Center of Advanced Manufacturing and Materials (CAMM)

See More by Dr. Sergey Golovashchenko

Oakland University - Center of Advanced Manufacturing and Materials (CAMM)

See More by Dr. Srecko Zdravkovic

Oakland University - Center of Advanced Manufacturing and Materials (CAMM)

See More by Natalia Reinberg

Center of Advanced Manufacturing and Materials (CAMM)

See More by Weitian Zhou

Read more from this issue

Find STAMPING Journal on Twitter

STAMPING Journal is the only industrial publication dedicated solely to serving the needs of the metal stamping market. Since 1989 the publication has been dedicated to covering the cutting-edge technologies, industry trends, best practices, and news that help stamping professionals run their businesses more efficiently.

Easily access valuable industry resources now with full access to the digital edition of The FABRICATOR.

Easily access valuable industry resources now with full access to the digital edition of The WELDER.

Easily access valuable industry resources now with full access to the digital edition of The Tube & Pipe Journal.

Enjoy full access to the digital edition of STAMPING Journal, which serves the metal stamping market with the latest technology advancements, best practices, and industry news.

Easily access valuable industry resources now with full access to the digital edition of The Fabricator en Español.

© 2022 FMA Communications, Inc. All rights reserved.

Not yet registered? Sign up