DMG Mori Control Generation
Siemens 840D Repair on DMG Mori
Siemens 840D is the most common DMG Mori control. The original 840D shipped through the mid-2000s; 840D solutionline (sl) is the current generation. Service work splits between hardware repair on older builds (NCU and PCU boards, drive faults) and configuration work on solutionline.
Machines this control shipped on
840D ships on the NLX/ALX, CTX/CLX, NTX, NHX/NH, NVX/NV/NVD, CMX, DMP/Milltap, SPRINT/MULTISPRINT, and the DMC builds in the DMU/DMC family.
Common failures and fixes
- PCU (Panel Control Unit) board faults — battery, fan, or HDD failure.
- NCU (Numerical Control Unit) board issues — generally board-level repair.
- Drive amplifier faults on heavy production work.
- Memory battery loss leading to parameter and program memory loss.
- MMC (Man-Machine Communication) failures on older 840D.
Parts availability
Siemens 840D parts are still well supported through Siemens and authorized service partners. Original 840D (non-solutionline) boards are heading toward aftermarket and remanufactured-only over the next several years. Solutionline parts are fully current.
Battery, memory, and parameter recovery
Parameter backup on 840D is a documented Siemens process — back up via the operator panel before any battery or board work. We capture the parameter set at the start of every service visit and verify the restore at sign-off. CF card and HDD migration on older 840D PCUs is part of the same conversation.