Experimental investigation of stereolithography and digital light processing additive manufactured pallets

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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
			W_TS	W_%E	W_H	Si+	Si-	Pi
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
			W_TS	W_%E	W_H	Si+	Si-	Pi
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