MIL-STD-1916 DOD Preferred Methods for Acceptance of ProductThe purpose of this standard is to encourage defense contractors and other commercial organizations supplying goods and services to the U.S. Government to submit efficient and effective process control prevention procedures in place of prescribed sampling requirements.

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MIL-STD-1916

APPENDIX

30.4 Continuous sampling. A visual inspection of stamped metal parts for the presence of a spot weld will be performed immediately after units pass through a spot welding station. Verification level II (VL-II) has been specified. The product will be submitted for continuous attributes sampling inspection. The production interval size is an 8-hour shift, which initially will consist of between 700 to 800 welded parts. With VL-II and code letter C (CL-C) from Table I, the "i" and "f" values (Table IV) are found to be 116 and 1/48, respectively. A segment of sampling experience is shown in figure 4.

Product 1tem Number	Code Letter	Frequency or 100%	Stage T/N/R	Event/Action
1	C	100%	N	Start production: Begin screening phase with i = 116.
8	C	100%	N	Find a defective unit: Reset counter.
124	C	100%	N	i =116 consecutive conforming units cleared: Begin sampling phase with f = 1/48.
170	C	1/48	N	First random sample selected: Found it to conform.
9697	C	1/48	N	200 consecutive conforming sampled units observed: Switch to reduced inspection with f = 1/68. Here, 200 equals 10 times the Table 11 sample size entry for CL-C and VL-11.
9769	C	1/68	R	Next sample randomly selected with f = 1/68.
13982	C	1/68	R	Production interval size tripled (2100 to 2400 units): End CL-C and begin CL-E sampling phase, f = 1/136, since VL-11 and reduced sampling inspection are in effect.
14121	E	1/136	R	First random sample taken with new f = 1/136: Found it to conform. Continue random sampling.
16290	E	1/136	R	A nonconforming unit observed: Switch to normal inspection. 1nitiate screening phase with i = 228, since CL-E and VL-11 are in effect.
16518	E	100%	N	i = 228 consecutive conforming units cleared: Begin sampling phase with f = 1/96.

FIGURE 4. Continuous sampling inspection log.

30.5 Continuous sampling - plan tailoring. The producer may opt to use another continuous sampling plan instead of the one specified in Table IV. The only restrictions are that such a change is not allowed while inside a screening sequence and that the new plan be derived in accordance with the procedure described below.

Certain circumstances make such choices desirable. Sometimes the selection of a clearance number or frequency is application dependent, e.g., if it matters that i or 1/f be a