Experimental investigation and parametric optimization of cryogenic abrasive water jet machining of nitrile rubber using Taguchi analysis

Figures & data

Figure 1. Organization of the paper.

Figure 2. Methodology of the current work.

Figure 3. Fourier-Transform Infrared (FTIR) spectra of NR.

Figure 4. (a) Schematic of cryogenic setup and (b) photograph of the custom-made suspension-type AWJ machine setup, along with the cryogenic setup.

Figure 5. Photographs of (a) machined NR under conventional condition, (b) machined NR under cryogenic condition, and (c) temperature measurement using an infrared thermometer gun during and immediately after the machining under cryogenic conditions.

Table 1. Fixed process parameters during the suspension-type AWJ machining of NR

Parameters	Values
Type of operation	Slot cutting
Length of cut	20 mm
Jet impingement angle	90°
Number of passes	2
Abrasive	Garnet
Abrasive particle diameter	150 μm
Abrasive material hardness	6.5 to 7.5 Mohs hardness
Orifice	Tungsten carbide
Nozzle orifice diameter	1 mm
Focusing nozzle	Stainless steel
LN2 jet pressure	0.6 bar
LN2 spray angle	80° (with nozzle axis)
LN2 flow rate	1.5 LPM
Mass percentage of Zycoprint polymer (ωp)	0.8%
Mass percentage of Garnet (ωa)	3%

Table 2. Variable process parameters during the suspension-type AWJ machining of NR

Symbol	Process parameters	Units	Levels
			1	2	3
WJP	Water jet pressure	Bar	150	200	250
Vf	Traverse rate	mm/min	40	50	60
SOD	Stand-off distance	Mm	1	1.5	2

Figure 6. Kerf width measurement using (a) Toolmaker microscope and (b) Optical microscope.

Table 3. Performance parameters and S/N ratios of KT_R and MRR under conventional and cryogenic conditions

Sr. No.	WJP (bar)	Vf (mm/min)	SOD (mm)	KTR		MRR (mm^3/min)		S/N ratios (KTR) (dB)		S/N ratios (MRR) (dB)
				Con.	Cryo.	Con.	Cryo.	Con.	Cryo.	Con.	Cryo.
1	150	40	1.0	1.79	1.44	795.12	801.09	−5.06	−3.17	58.01	58.08
2	150	40	1.5	1.71	1.48	856.80	884.16	−4.66	−3.41	58.66	58.94
3	150	40	2.0	1.69	1.52	918.35	947.82	−4.56	−3.64	59.27	59.54
4	150	50	1.0	2.20	1.77	995.72	934.95	−6.85	−4.96	59.97	59.42
5	150	50	1.5	2.21	1.80	1018.47	1025.55	−6.89	−5.11	60.16	60.22
6	150	50	2.0	2.28	1.82	1041.05	1091.85	−7.16	−5.21	60.35	60.77
7	150	60	1.0	2.13	2.23	1346.15	1132.43	−6.57	−6.97	62.59	61.09
8	150	60	1.5	2.28	2.24	1308.21	1225.17	−7.16	−7.01	62.34	61.77
9	150	60	2.0	2.54	2.26	1270.07	1288.80	−8.10	−7.09	62.08	62.21
10	200	40	1.0	1.57	1.25	926.09	969.90	−3.92	−1.94	59.34	59.74
11	200	40	1.5	1.47	1.29	973.92	1035.51	−3.35	−2.22	59.78	60.31
12	200	40	2.0	1.42	1.30	1021.61	1081.68	−3.05	−2.28	60.19	60.69
13	200	50	1.0	1.92	1.39	1141.22	1140.57	−5.67	−2.87	61.15	61.15
14	200	50	1.5	1.87	1.42	1146.65	1209.30	−5.44	−3.05	61.19	61.66
15	200	50	2.0	1.86	1.44	1151.90	1253.78	−5.40	−3.17	61.23	61.97
16	200	60	1.0	1.95	1.57	1498.89	1372.55	−5.81	−3.92	63.52	62.76
17	200	60	1.5	2.00	1.60	1440.17	1439.10	−6.03	−4.09	63.17	63.17
18	200	60	2.0	2.11	1.62	1381.24	1476.54	−6.49	−4.20	62.81	63.39
19	250	40	1.0	1.72	1.37	1018.87	1099.11	−4.72	−2.74	60.17	60.83
20	250	40	1.5	1.56	1.38	1052.85	1147.20	−3.87	−2.80	60.45	61.20
21	250	40	2.0	1.46	1.38	1086.68	1175.97	−3.29	−2.80	60.73	61.41
22	250	50	1.0	2.15	1.44	1238.99	1296.57	−6.65	−3.17	61.87	62.26
23	250	50	1.5	2.03	1.45	1227.10	1343.48	−6.15	−3.23	61.78	62.57
24	250	50	2.0	1.95	1.45	1215.03	1366.13	−5.81	−3.23	61.70	62.71
25	250	60	1.0	2.24	1.53	1594.36	1553.27	−7.01	−3.70	64.06	63.83
26	250	60	1.5	2.24	1.55	1514.85	1593.63	−7.01	−3.81	63.61	64.05
27	250	60	2.0	2.29	1.55	1435.14	1604.84	−7.20	−3.81	63.14	64.11

*Con. = conventional and Cryo. = cryogenic

Table 4. ANOVA results for KT_R and MRR under conventional and cryogenic conditions

Source	KTR				MRR
	Con.		Cryo.		Con.		Cryo.
	% contribution	P-value	% contribution	P-value	% contribution	P-value	% contribution	P-value
WJP	15.78	<1×10^−3	47.37	<1×10^−3	16.92	<1×10^−3	37.92	<1×10^−3
Vf	76.50	<1×10^−3	41.67	<1×10^−3	79.46	<1×10^−3	56.00	<1×10^−3
SOD	0.34	<1×10^−3	0.44	<1×10^−3	0.06	<1×10^−3	5.08	<1×10^−3
WJP × Vf	0.74	<1×10^−3	10.34	<1×10^−3	0.74	<1×10^−3	0.01	<1×10^−3
WJP × SOD	1.96	<1×10^−3	0.10	0.04	0.33	<1×10^−3	0.88	<1×10^−3
Vf × SOD	4.61	<1×10^−3	0.03	0.44	2.87	<1×10^−3	0.11	<1×10^−3
Error	0.07		0.05		0.02		0.00
Total	100.00		100.00		100.00		100.00

*Con. = conventional and Cryo. = cryogenic

Figure 7. Factorial effects plots for the mean of S/N ratios of (a) KT_R and (b) MRR under the conventional condition.

Table 5. Response table for the mean of S/N ratios for KT_R (smaller is better) and MRR (larger is better) under conventional and cryogenic conditions

Level	KTR						MRR
	Conventional			Cryogenic			Conventional			Cryogenic
	WJP	Vf	SOD	WJP	Vf	SOD	WJP	Vf	SOD	WJP	Vf	SOD
1	−6.33	−4.05	−5.80	−5.17	−2.77	−3.71	60.38	59.62	61.18	60.22	60.08	61.01
2	−5.01	−6.22	−5.61	−3.08	−3.77	−3.85	61.37	61.04	61.23	61.64	61.04	61.54
3	−5.74	−6.82	−5.67	−3.25	−4.95	−3.93	61.94	63.03	61.27	62.55	62.93	61.86
Delta	1.32	2.77	0.19	2.09	2.18	0.22	1.56	3.41	0.09	2.33	2.85	0.85
Rank	2	1	3	2	1	3	2	1	3	2	1	3

*Bold ranks indicate the most significant process parameters.

Figure 8. Factorial effects plots for the mean of S/N ratios of (a) KT_R and (b) MRR under cryogenic condition.

Table 6. Consolidated optimal parameters of the suspension-type AWJ machining of NR, obtained from the experimental runs of Table 3

Machining condition	Performance parameters	Levels	WJP	Vf	SOD
Conventional	KTR = 1.42	2 1 3	200	40	2.0
	MRR = 1594.36 mm^3/min	3 3 1	250	60	1.0
Cryogenic	KTR = 1.25	2 1 1	200	40	1.0
	MRR = 1604.84 mm^3/min	3 3 3	250	60	2.0

Table 7. Percentage reduction and improvement in the optimal experimental result of KT_R and MRR in cryogenic over conventional suspension-type AWJ machining of NR

Performance parameters	Condition		Percentage reduction in optimal experimental KTR	Percentage improvement in optimal experimental MRR
	Conventional	Cryogenic
KTR	1.42	1.25	11.97	0.65
MRR (mm^3/min)	1594.38	1604.84

Table 8. Predicted optimal levels of the suspension-type AWJ machining of NR obtained from Taguchi analysis

Machining condition	Performance parameters	Levels	WJP	Vf	SOD
Conventional	KTR	2 1 2	200	40	1.5
	MRR (mm^3/min)	3 3 3	250	60	2.0
Cryogenic	KTR	2 1 1	200	40	1.0
	MRR (mm^3/min)	3 3 3	250	60	2.0