Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 1,698,629	$ 1,309,112
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	973,182	922,347
Gain on disposal of equipment	(26,135)	(1,700)
Deferred income taxes	118,000	(70,000)
Changes in operating assets and liabilities:
Accounts receivable	(1,175,724)	(547,573)
Inventories	(726,233)	(550,424)
Other current assets and prepaid income taxes	(106,338)	98,977
Accounts payable	460,603	460,171
Accrued wages and salaries	221,074	199,981
Other accrued expenses	(54,780)	(131,262)
Unearned revenue and customer deposits	61,073	(45,282)
Net cash provided by operating activities	1,443,351	1,644,347
Cash flows from investing activities:
Capital expenditures	1,635,189	1,069,559
Proceeds from the sale of equipment	26,135	1,700
Proceeds from certificates of deposit	3,735,000	5,320,000
Purchases of certificates of deposit	2,739,000	4,573,000
Net cash used in investing activities	(613,054)	(320,859)
Cash flows from financing activities:
Cash dividends paid	898,503	917,825
Net cash used in financing activities	(898,503)	(917,825)
Net increase (decrease) in cash and cash equivalents	(68,206)	405,663
Cash and cash equivalents at beginning of period	1,152,569	353,475
Cash and cash equivalents at end of period	1,084,363	759,138
Supplemental schedule of non-cash investing activities:
Capital expenditures in accounts payable	$ 7,265	$ 1,487