Experimental investigation of stereolithography and digital light processing additive manufactured pallets

Anil Bairapudi; C. Chandrasekhara Sastry; J. Krishnaiah; Dola Sundeep; KV Eswaramoorthy

doi:10.2478/msp-2024-0001

Figures & Tables

Depiction of printing (a) SLA: point-based approach; (b) DLP: area scanning

Surface morphology depiction of 1-mm printed parts at 1-mm tolerance resolution using (a) CAD geometry (b) DLP (c) SLA

SLA and DLP 3D printing of tensile specimen dimensions: ASTM D638

GUI type IV tensile specimen (a) Preform: SLA, (b) 3D sprint: DLP software

3D printing of coupons (a) SLA Form 3 (b) DLP Figure 4 Standalone (CITD additive lab facility, MSME Tool room facility, Hyderabad, Govt. of India)

Bottom-up approach 3D printing of pallet coupons in DLP method

3D printed ASTM D638 type IV pallet coupon using (a) SLA process: form 3 printer (b) DLP method: stand-alone printer

(a) Complete process for developing a commercial pallet tensile coupon replicator (CITD, Hyderabad facilities); (b) bottom half; (c) top half of injection mould die; (d) ABS pallet tensile specimen coupon prepared with gate and runner

Investigation of (a) uniaxial tensile test of SLA and DLP 3D printed ASTM D638 type IV samples; machine used: Instron 5966 model, (b) Shore A hardness durometer

Design of a four-way pallet as per the ISO MH1-2016 standard in CAD software

Pallet 3D printing in accordance with the ISO MH1-2016 standard for optimized values using (a) SLA (b) DLP

Finite element model of the ASTM D638 model in ABAQUS 6.14

Simulations of 3D-printed test coupons for pallets corresponding to ABS (commercial replication: injection molding) (1); Pro-BLK-10 (SLA process) (2); and GrayV4 (DLP method) (3) for (a) maximum stress, (b) maximum deformation

Experimental uniaxial tensile test results for ABS (commercial replication: injection moulding), Pro-BLK-10 (SLA process), and GrayV4 (DLP method)

Simulated, experimental, and analytical uniaxial tensile test results for ABS, Pro-BLK, Grey V4 for injection molding, SLA and DLP 3D printed samples corresponding to (a) deflection (displacement) (b) stress

Coupon pallet 100 mm × 30 mm cross section being considered for (a) side view representing UDL load and (b) top deck of pallet corresponding to five beam elements

Global stiffness matrix of a simple supported beam with five elements corresponding to coupon pallet design

Beam representation for (a) 3D FEA model with fixed ends, (b) displacement module

Basis of boundary conditions for pallet analysis

ISO Pallet CAD model and finite element model with load distribution

Displacement and stress contours: ISO pallet corresponding to ABS material

Displacement and stress contours: ISO pallet corresponding to DLP material

Displacement and stress contour: ISO pallet corresponding to SLA material

Comparisons of (a) von mises stress and (b) displacement on the basis of pallet supports

Comparisons of deflection and stresses for DLP-manufactured pallet

Comparisons of deflection and von mises stresses for SLA manufactured pallet

(a) CAD model (b) Finite element model for optimized pallet design

Displacement and stress contour: optimized pallet design (ABS material)

Displacement and stress contour: optimized pallet design (DLP material)

Displacement and stress contour: optimized pallet design (SLA material)

Optimized pallet analysis correlation to (a) von mises stress (b) deflection

Deflection and stresses for DLP-manufactured pallet

Deflection and von mises stresses for SLAmanufactured pallet

SEM images for additive-manufactured (a) DLP (b) SLA pallet

AFM plots of additive-manufactured (a) DLP (b) SLA pallets

XRD plots for 3D printed pallets availing (a) DLP (b) SLA

Roughness values obtained from AFM for DLP and SLA pallets

S. No.	Pallet-making process	Roughness factor (nm)
1.	DLP	95.18
2.	SLA	207.35

Simulated versus physical uniaxial tensile test for ABS, Pro-BLK, and Grey V4 for injection molding, SLA, and DLP 3D printed samples

Material	Parameter	Simulation	Analytical	Physical testing	Difference between simulation & testing (in %)
ABS	Stress (MPa)	37.78	43.33	40.19	6.37
	Displacement(mm)	1.80	1.88	1.62	10
GrayV4	Stress (MPa)	55.76	57.52	61.55	10.38
	Displacement(mm)	2.89	2.36	3.25	12.45
ProBLK-10	Stress (MPa)	51.31	54.37	57.34	11.75
	Displacement(mm)	2.88	2.69	3.19	10.76

3D printing machine details: SLA – Form 3 and DLP

Machine Name	Form labs 3	Machine Name	DLP Standalone System
Build	145 ×	Build	124.8 ×
Volume	145 × 185 cc	Volume	70.2 × 196 cc
Resolution	25 μ	Resolution	1920×1080
Laser power	250 mW	Wavelength	405 nm
Laser Spot size	85μ	Pixel pitch	65μ

AHP-TOPSIS methodology for 3D printed pallets using the SLA process

S. No.	Layer thickness (μm)	Material	Weighted matrix			Closeness to ideal solution		Closeness coefficient	Rank
S. No.	Layer thickness (μm)	Material	W_TS	W_%E	W_H	Si+	Si-	Pi	Rank
1	25	Grey V4	0.24	0.07	0.03	0.02	0.16	0.87	4
2	25	Clear v4	0.24	0.07	0.03	0.03	0.16	0.86	5
3	25	Model V2	0.23	0.06	0.04	0.03	0.17	0.86	6
4	50	Grey V4	0.23	0.07	0.06	0.01	0.16	0.92	1
5	50	Clear	0.23	0.06	0.06	0.01	0.16	0.92	2
6	50	Model V2	0.22	0.06	0.04	0.03	0.17	0.84	8
7	100	Grey V4	0.23	0.06	0.03	0.03	0.16	0.85	7
8	100	Clear	0.22	0.06	0.05	0.02	0.16	0.89	3
9	100	Model V2	0.22	0.05	0.03	0.03	0.17	0.83	9

Response variables for SLA 3D-printed pallet specimens

Experiment No.	Layer thickness (μm)	Material	Tensile strength (MPa)	Elongation in (%)	Hardness (Shore D)
1	25	Grey V4	65.00	6	50.00
2	25	Clear V4	63.05	5.87	48.50
3	25	Model V2	61.00	5	55.00
4	50	Grey V4	61.55	5.85	85.00
5	50	Clear V4	61.40	5.733	82.45
6	50	Model V2	59.48	4.89	53.35
7	100	Grey V4	61.43	5.67	47.50
8	100	Clear V4	59.97	5.59	80.75
9	100	Model V2	58.98	4.67	52.25

Orthogonal L9 array experimental runs for SLA 3D printing of pallet coupons

Experimental runs	Layer thickness	Material
1	25	Gray V4
2	25	Clear v4
3	25	Model V2
4	50	Gray V4
5	50	Clear
6	50	Model V2
7	100	Gray V4
8	100	Clear
9	100	Model V2

Orthogonal L9 array experimental runs for DLP 3D printing of pallet coupons

Experimental runs	Layer thickness	Material
1	30	FlexBLK-20
2	30	ToughBLK-20
3	30	ProBLK-10
4	40	ToughBLK-20
5	40	ProBLK-10
6	40	FlexBLK-20
7	50	ProBLK-10
8	50	FlexBLK-20
9	50	ToughBLK-20

Material properties of the industry grade pallet 3D printing materials—SLA

Materials	Grey V4	Model V2	Clear V2
Tensile strength (MPa)	65	42	65
Percentage of elongation	6.2	4.8	6.2
Izod notched impact (J/m)	25	24	25
Heat deflection temperature (°C)	73.1	75	73.1

Material properties of the industry grade pallet 3D printing materials—DLP

Materials	Flex BLK-20	Tough BLK-20	Pro BLK-10
Tensile strength (MPa)	35	42	56
Percentage of elongation	71	27	12
Izod notched impact (J/m)	105	35	22
Heat deflection temperature (°C)	41	55	70

AHP-TOPSIS method for 3D printed pallets using DLP method

S. no.	Layer thickness (μm)	Material	Weighted matrix			Closeness to ideal solution		Closeness coefficient	Rank
S. no.	Layer thickness (μm)	Material	W_TS	W_%E	W_H	Si+	Si-	Pi	Rank
1	30	FlexBLK-20	0.17	0.10	0.04	0.12	0.09	0.41	4
2	30	ToughBLK-20	0.22	0.04	0.04	0.10	0.06	0.37	7
3	30	ProBLK-10	0.29	0.02	0.04	0.09	0.13	0.60	3
4	40	ToughBLK-20	0.21	0.04	0.04	0.11	0.05	0.33	8
5	40	ProBLK-10	0.29	0.02	0.04	0.08	0.13	0.61	2
6	40	FlexBLK-20	0.17	0.10	0.04	0.13	0.08	0.39	5
7	50	ProBLK-10	0.30	0.02	0.05	0.08	0.13	0.61	1
8	50	FlexBLK-20	0.16	0.10	0.04	0.13	0.08	0.38	6
9	50	ToughBLK-20	0.20	0.04	0.04	0.11	0.05	0.30	9

Close to ideal solution for SLA and DLP 3D printed pallets: AHP-TOPSIS

Process	Layer thickness (μm)	Material
SLA	50	Grey V4
DLP	50	ProBLK-10

AHP pairwise computation matrix

Attributes	Tensile strength	% Elongation	Hardness
Tensile strength	1.00	5.00	4.00
% Elongation	0.20	1.00	2.00
Hardness	0.25	0.50	1.00

Weights disguised for each response variable

Variable	Weight
Tensile strength	0.687
% Elongation	0.186
Hardness	0.127

Process parameters corresponding to SLA 3D printing of pallet coupons

Layer Thickness (μm)	Material
25	Gray V4
50	Model V3
100	Clear V4

Process parameters corresponding to DLP 3D printing of pallet coupons

Layer thickness (μm)	Material
30	FlexBlack-20
40	ToughBlack-20
50	ProBlack-10

Simulation and analytical values for displacement for a coupon sample

Parameter	Simulation	Analytical	Difference between (percentage) simulation and analytical
Displacement (mm)	7.29	7.8	6.5

Response variables for DLP 3D-printed pallet specimens

Experiment No.	Layer thickness (μm)	Material	Tensile strength (MPa)	Elongation (%)	Hardness (Shore D)
1	30	FlexBLK-20	33.25	71.25	68.75
2	30	ToughBLK-20	41.75	28.50	77.00
3	30	ProBLK-10	56.05	11.4	75.53
4	40	ToughBLK-20	40.50	27.65	74.69
5	40	ProBLK-10	57.23	11.64	77.12
6	40	FlexBLK-20	32.25	69.11	66.69
7	50	ProBLK-10	57.34	12	79.50
8	50	FlexBLK-20	31.59	67.69	65.31
9	50	ToughBLK-20	39.66	27.08	73.15

Comparison of rack support vs_ floor support, rack support vs_ forklift support, and rack support vs_ conveyor support for DLP

Comparison for deflection			Comparison for von mises stress
Rack vs. floor	Rack vs. forklift	Rack vs. conveyor	Rack vs. floor	Rack vs. forklift	Rack vs. conveyor
90.89	61.80	37.97	48.55	64.59	9.69
90.82	61.86	37.88	48.52	64.58	9.72
90.88	61.85	37.87	48.56	64.59	9.76
90.81	61.84	38.01	48.53	64.58	9.76
90.89	61.82	38.00	48.52	64.60	9.81
90.78	61.92	37.88	48.54	64.66	9.81
90.89	61.92	37.85	48.53	64.68	9.89
90.76	61.90	38.10	48.47	64.69	9.92
90.88	61.75	37.89	48.44	64.74	10.06
90.65	61.68	37.85	48.46	64.77	10.31
90.91	62.24	37.76	48.39	64.91	10.78
90.14	61.97	38.03	47.96	65.16	11.76

Comparison of rack support vs_ floor support, rack support vs_ forklift support, and rack support vs_ conveyor support for SLA

Comparison for deflection			Comparison for von-misses stress
Rack vs. floor	Rack vs. forklift	Rack vs. conveyor	Rack vs. floor	Rack vs. forklift	Rack vs. conveyor
90.33	61.21	37.88	46.65	64.64	9.22
90.34	61.24	37.87	46.64	64.63	9.23
90.35	61.28	37.85	46.65	64.65	9.23
90.36	61.33	37.83	46.63	64.64	9.23
90.24	61.25	37.94	46.64	64.60	9.29
90.23	61.24	37.83	46.62	64.59	9.25
90.24	61.30	37.79	46.64	64.60	9.33
90.24	61.17	37.96	46.61	64.59	9.27
90.24	61.25	37.94	46.62	64.60	9.39
90.25	61.37	37.91	46.56	64.58	9.47
90.22	61.41	37.50	46.58	64.61	9.59
90.22	60.87	38.04	46.36	64.55	10.00

Residual stress values obtained from XRD

S. No.	Pallet-making process	Residual stress (MPa)
1	DLP	338.23
2	SLA	122.6

Experimental investigation of stereolithography and digital light processing additive manufactured pallets

Figures & Tables

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Roughness values obtained from AFM for DLP and SLA pallets

Simulated versus physical uniaxial tensile test for ABS, Pro-BLK, and Grey V4 for injection molding, SLA, and DLP 3D printed samples

3D printing machine details: SLA – Form 3 and DLP

AHP-TOPSIS methodology for 3D printed pallets using the SLA process

Response variables for SLA 3D-printed pallet specimens

Orthogonal L9 array experimental runs for SLA 3D printing of pallet coupons

Orthogonal L9 array experimental runs for DLP 3D printing of pallet coupons

Material properties of the industry grade pallet 3D printing materials—SLA

Material properties of the industry grade pallet 3D printing materials—DLP

AHP-TOPSIS method for 3D printed pallets using DLP method

Close to ideal solution for SLA and DLP 3D printed pallets: AHP-TOPSIS

AHP pairwise computation matrix

Weights disguised for each response variable

Process parameters corresponding to SLA 3D printing of pallet coupons

Process parameters corresponding to DLP 3D printing of pallet coupons

Simulation and analytical values for displacement for a coupon sample

Response variables for DLP 3D-printed pallet specimens

Comparison of rack support vs_ floor support, rack support vs_ forklift support, and rack support vs_ conveyor support for DLP

Comparison of rack support vs_ floor support, rack support vs_ forklift support, and rack support vs_ conveyor support for SLA

Residual stress values obtained from XRD