can I add another SSD internally? (e.g., M2 port)?

The product has internal bays available for storage expansion, but it does not specify the presence of an M.2 port.

Questions & Answers: Refurbished: HP Z640 CAD Workstation PC Intel Xeon E5-1650 v3 3.5GHz 6-Core 32GB DDR4 RAM Quadro NVS 295 New 512GB SSD 2TB HDD Windows 10 Pro

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HP Z640 CAD Workstation PC Intel Xeon E5-1650 v3 3.5GHz 6-Core 32GB DDR4 RAM Quadro NVS 295 New 512GB SSD 2TB HDD Windows 10 Pro

HP Z640 Workstation Intel Xeon E5-1650 v3 3.5GHz 6-Core 32GB DDR4 RAM DDR4 Quadro NVS 295 New 512GB SSD 2TB HDD Windows 10 Pro
Built for professional work such as design, content creation, rendering, engineering, and data-heavy applications.
The Intel Xeon E5-1650 v3 (3.50GHz) 6-Core processor provides responsive performance for design, rendering, engineering, and other demanding professional tasks.
32GB DDR4 memory supports smooth multitasking and helps handle larger professional projects and files.
2TB HDD, 1x 512GB SSD provides quick access to applications and project files, with capacity for everyday professional work.
NVIDIA Quadro NVS 295 supports professional visual work such as CAD, content creation, rendering, and multi-display setups; Windows 10 Pro is preinstalled and ready for the out-of-box setup experience.
Stock photos are used in this listing and may differ depending on configuration. This Renewed product is tested and certified to look and work like new. The refurbishing process includes functionality testing, basic cleaning, inspection, and repackaging. The product ships with all relevant accessories and may arrive in a generic box.