Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 30, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (6,649)	$ (5,696)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,905	733
Share-based compensation expense	855	260
Amortization of debt issuance costs	58	9
Change in preferred and common stock warrant liabilities	759	129
Net change in operating assets and liabilities:
Accounts receivables	(3,568)	(991)
Inventories	(4,025)	(1,144)
Prepaid expenses and other assets	122	60
Accounts payable	(4,349)	1,845
Accrued expenses and other current liabilities	1,608	(133)
Long-term liabilities	4	40
Net cash used in operating activities	(13,280)	(4,888)
Cash flows used in investing activities:
Purchases of property, plant and equipment	(3,795)	(3,719)
Proceeds from sale of fixed assets	132	0
Purchases of property, plant and equipment held for sale	(829)	0
Payment of security deposits	(501)	(13)
Net cash used in investing activities	(4,993)	(3,732)
Cash flows from financing activities:
Proceeds from Series G preferred stock offering, net of offering costs	0	1,229
Repayments on revolving credit line	0	(2,500)
Repayments on term loan	0	(125)
Payments of capital lease obligations	(9)	(59)
Proceeds from exercise of stock options	366	87
Payments of deferred offering costs	(946)	0
Net cash used in financing activities	(589)	(1,368)
Net decrease in cash and cash equivalents	(18,862)	(9,988)
Cash and cash equivalents at the beginning of the period	54,271	39,035
Cash and cash equivalents at the end of the period	35,409	29,047
Cash paid during the period for:
Interest	715	38
Non-cash investing and financing activities:
Non-cash additions to property, plant and equipment	589	1,226
Deferred offering costs, accrued not yet paid	$ 69	$ 0