Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 1,687,641	$ 1,951,889
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	1,261,446	1,262,725
(Gain) Loss from disposal of equipment	17,504	(15,659)
Deferred income taxes	233,000	6,000
Changes in operating assets and liabilities:
Accounts receivable, net	231,322	(158,884)
Inventories, net	624,262	(281,686)
Other current assets	(134,996)	(226,548)
Accounts payable	(178,703)	(79,935)
Accrued wages and salaries	6,455	44,915
Other accrued expenses	(55,061)	(89,123)
Unearned revenue and customer deposits	397,323	(56,200)
Net cash provided by operating activities	4,090,193	2,357,494
Cash flows from investing activities:
Capital expenditures	(2,081,272)	(1,656,230)
Proceeds from the sale of equipment	4,869	19,100
Proceeds from certificates of deposit	7,303,000	4,133,348
Purchases of certificates of deposit	(7,810,000)	(3,984,000)
Net cash used in investing activities	(2,583,403)	(1,487,782)
Cash flows from financing activities:
Cash dividends paid	(937,148)	(1,082,068)
Net cash used in financing activities	(937,148)	(1,082,068)
Net increase (decrease) in cash and cash equivalents	569,642	(212,356)
Cash and cash equivalents at beginning of year	231,252	443,608
Cash and cash equivalents at end of year	800,894	231,252
Cash paid for income taxes	710,456	1,160,769
Supplemental schedule of non-cash investing activities:
Capital expenditures in accounts payable	$ 22,995	$ 78,811