Condensed Statements of Cash Flows - USD ($)	6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (16,090,000)	$ (13,092,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,957,000	1,620,000
Share-based compensation expense	2,678,000	710,000
Amortization of debt issuance costs	78,000	35,000
Change in preferred and common stock warrant liabilities	12,503,000	259,000
Net change in operating assets and liabilities:
Accounts receivables	(21,762,000)	(2,788,000)
Inventories	(12,438,000)	(6,178,000)
Prepaid expenses and other assets	(2,131,000)	(154,000)
Accounts payable	9,799,000	6,623,000
Accrued expenses and other current liabilities	1,028,000	259,000
Long-term liabilities	12,000	39,000
Net cash used in operating activities	(22,366,000)	(12,667,000)
Cash flows used in investing activities:
Purchases of property, plant and equipment	(7,502,000)	(9,973,000)
Proceeds from sale of fixed assets	232,000	0
Purchases of property, plant and equipment held for sale	(3,121,000)	0
Payment of security deposits	(487,000)	(60,000)
Net cash used in investing activities	(10,878,000)	(10,033,000)
Cash flows from financing activities:
Proceeds from issuance of common stock pursuant to the initial public offering, net of issuance costs	255,448,000	0
Proceeds from Series G preferred stock offering, net of offering costs	0	1,350,000
Proceeds from bank term loan borrowing	0	10,000,000
Repayments on revolving credit line	0	(2,500,000)
Repayment on term loan	0	(1,000,000)
Repayment of Missouri Note	0	(1,450,000)
Payments of capital lease obligations	(21,000)	(117,000)
Proceeds from exercise of stock options	533,000	871,000
Net cash provided by financing activities	255,960,000	7,154,000
Net increase (decrease) in cash and cash equivalents	222,716,000	(15,546,000)
Cash and cash equivalents at the beginning of the period	54,271,000	39,035,000
Cash and cash equivalents at the end of the period	276,987,000	23,489,000
Cash paid during the period for:
Interest	1,445,000	63,000
Taxes	21,000	3,000
Non-cash investing and financing activities:
Capital lease obligations for the purchase of property, plant and equipment	0	85,000
Issuance of convertible preferred stock warrants in connection with debt	0	248,000
Non-cash additions to property, plant and equipment	1,003,000	1,656,000
Deferred offering costs, accrued not yet paid	578,000	64,000
Non-cash additions to property, plant and equipment held for sale	646,000	0
Reclassification of warrant liability to additional paid-in capital in connection with the initial public offering	14,421,000	0
Issuance of common stock upon conversion of convertible preferred stock	$ 199,540,000	$ 0