PSI - Issue 66

Mohammad Jameel Ziedan et al. / Procedia Structural Integrity 66 (2024) 229–246 Author name / Structural Integrity Procedia 00 (2024) 000–000

231

SPIF process at room temperature (Clavijo-Chaparro et al., 2018a; Le et al., 2008). Using a factorial design of experiments (DoE), the concentrations of these additives were optimized, see Table 1. The researchers found that the plasticizer and nanoclay worked together, with the nanoclay enhancing the plasticizing effect and improving stress transfer within the material. This allowed them to create PMMA composite sheets with improved formability, making them suitable for manufacturing customized cranial implants by SPIF. Table 1. The compositions of the PMMA-based samples added with plasticizer and C-30B, and the corresponding codified matrix for the DoE (Clavijo-Chaparro et al., 2018a).

Samples

Weight percent (wt%)

Codified matrix

PMMA

Triacetine

Cloisite

Triacetine

Cloisite

T15-C1 T15-C3 T25-C1 T25-C3 T20-C2

84 82 74 72 78

15 15 25 25 20

1 3 1 3 2

-1 -1

-1

1 1 1 0

1 1 0

Table 2. Taguchi DoE (orthogonal array selected is L16 ) (Karthik et al., 2019)

Exp. No.

Tool diameter (mm), Φ

Step size (mm)

Sheet thick (mm)

Spindle speed, ω (rpm)

Table feed (mm/min), υ

1 2 3 4 5 6 7 8 9

10 10 10 10 12 12 12 12 14 14 14 14 16 16 16 16

0.25

1

1000 1500 2000 2500 1000 1500 2000 2500 1000 1500 2000 2500 1000 1500 2000 2500

600

0.5

1.5

1000 1400 1800 1800 1400 1000

0.75

2

1

2.5

0.25

1

0.5

1.5

0.75

2

1

2.5

600

0.25

1

1000

10 11 12 13 14 15 16

0.5

1.5

600

0.75

2

1800 1400 1400 1800

1

2.5

0.25

1

0.5

1.5

0.75

2

600

1

2.5

1000

SPIF for thermoplastic sheets has been explored (Michael Rabinovich et al., 2008). The cone-shaped part was used with varying wall angles to assess formability of the thermoplastic sheets, focusing on the maximum wall angle reached without tearing and/or failure. To optimize the process, a (2 4-1 ) fractional factorial design of experiments were employed, with four parameters; step size, tool size, feed rate, and spindle speed. The results indicate that these factors, and their interactions, have an important impact on formability. Specifically, smaller tool sizes and higher spindle speeds resulted in better outcomes. The Taguchi design method was employed to optimize and analyze the impact of process parameters such as tool diameter, step size, spindle speed, and sheet thickness on formability, surface roughness, and depth of failure. The depth of failure is influenced by the sheet thickness and the thinning of the