FANUC RoboDrill a-D21MiB

$30,000 - $65,000 (used market) Updated 2026-03-16

Key Specifications

X Travel

500 mm (19.7 in)

Y Travel

400 mm (15.7 in)

Z Travel

330 mm (13.0 in)

Spindle Taper

BT30

Table Size

650 x 400 mm (25.6 x 15.7 in)

Rapid Traverse

54 m/min (2,125 ipm)

Overview

The FANUC RoboDrill a-D21MiB is the previous-generation medium-bed RoboDrill that preceded the current iB5 models — and it remains one of the most sought-after used compact VMCs on the market. Thousands of D21MiB machines were produced during their production run, and they continue to deliver reliable high-speed machining in shops worldwide. For buyers looking for proven RoboDrill performance at used-market pricing, the D21MiB offers the same core capabilities that made the platform famous: ultra-fast tool changes, rapid axis speeds, and seamless FANUC robot integration.

The D21MiB features X/Y/Z travels of 500 x 400 x 330 mm with a table size of 650 x 400 mm. The BT30 spindle runs at 10,000 RPM standard with the high-speed option at 24,000 RPM, delivering 11 kW continuous power. The 21-position turret ATC achieves tool-to-tool changes in approximately 0.8 seconds and chip-to-chip in 1.4 seconds — slightly slower than the current iB5 generation but still dramatically faster than conventional VMCs. Rapid traverse is 54 m/min on all axes. The machine runs on the FANUC 31i-B control (predecessor to the 31i-B5).

The D21MiB generation established the RoboDrill as the standard platform for high-speed small-part production, particularly in the electronics, medical, and automotive industries. Apple's massive deployment of RoboDrills for iPhone machining began with this generation. The machine's compact footprint, reliability, and automation-friendly design made it the obvious choice for production cells requiring multiple machines in tight floor space. The 31i-B control, while older, remains fully supported by FANUC with parts and service readily available.

Used D21MiB machines from 2012-2017 typically price between $30,000 and $65,000 depending on condition, hours, and options. Machines with the 24,000 RPM spindle and DDR 5-axis table command the highest prices. For shops evaluating their first RoboDrill purchase, a well-maintained used D21MiB often represents the best value proposition in the compact VMC market. New machines are no longer produced — FANUC replaced the iB generation with the current iB5 models — but the used market is deep with availability.

Full Specifications

Parameter	Value
X-Axis Travel	500 mm (19.7 in)
Y-Axis Travel	400 mm (15.7 in)
Z-Axis Travel	330 mm (13.0 in)
Table Size	650 x 400 mm (25.6 x 15.7 in)
Max Table Load	200 kg (441 lb)
Spindle Speed	10,000 RPM (24,000 RPM optional)
Spindle Motor Power	11 kW (15 hp) continuous
Spindle Taper	BT30
Tool Magazine	21-position turret
Tool Change Time	0.8 sec (tool-to-tool), 1.4 sec (chip-to-chip)
Rapid Traverse Rate	54 m/min (2,125 ipm)
Positioning Accuracy	±0.004 mm (±0.00016 in)
Repeatability	±0.002 mm (±0.00008 in)
CNC Control	FANUC 31i-B
Machine Weight	3,800 kg (8,378 lb)
Floor Space Required	2,050 x 1,750 mm (80.7 x 68.9 in)

Specifications sourced from emastercam.com — verified 2026-03-28

Strengths & Limitations

Strengths

Excellent value on the used market at $30K-$65K — proven RoboDrill performance at a fraction of new machine cost
Sub-second tool changes (0.8 sec tool-to-tool) and 54 m/min rapids deliver dramatically faster cycle times than conventional VMCs on small-part work
Massive installed base means deep application knowledge, readily available spare parts, and a strong used market with consistent availability
FANUC 31i-B control is fully supported with parts, service, and software updates still available from FANUC
Compact footprint fits into tight shop layouts and enables high machine density in production cell configurations
DDR 5-axis table option (if equipped) provides simultaneous 5-axis capability on a used machine at used-market pricing

Limitations

No longer in production — all available machines are used, requiring careful inspection of spindle hours, ball screw backlash, and overall condition
0.8-second tool change is slightly slower than the current iB5 generation's 0.7 seconds — minor but measurable over high-volume production
BT30 taper limits cutting force — the D21MiB is not a heavy-duty steel or titanium roughing machine
31i-B control lacks some features of the current 31i-B5 including enhanced 5-axis functions and the Plus processing upgrades
200 kg table load and 500 x 400 mm travel constrain part size and fixture weight for shops with diverse work requirements

Best For

Budget-conscious shops looking for their first high-speed compact VMC at used-market pricing without sacrificing core RoboDrill performance Production shops expanding capacity with additional RoboDrill cells where the slightly older generation performs identically on existing jobs Startup machine shops and contract manufacturers that need production-class equipment at a capital cost that doesn't require major financing Training and educational environments where students can learn on an industry-standard FANUC platform at reasonable acquisition cost Automation integrators building robotic manufacturing cells who need a proven, automation-friendly VMC platform at competitive pricing

Frequently Asked Questions

01 What should I look for when buying a used D21MiB?

Key inspection items include spindle hours and runout (request a test bar runout check), ball screw backlash measurement on all axes, turret indexing accuracy, way condition and axis servo load readings, coolant system condition, and overall machine geometry (level check, squareness). Ask for the machine's maintenance history and any CNC alarm log data. A D21MiB with under 15,000 spindle hours and documented maintenance history is considered a safe purchase.

02 Is the 31i-B control still supported?

Yes. FANUC maintains parts and service support for the 31i-B control. Replacement boards, power supplies, servo amplifiers, and other control components are available through FANUC's parts network. Software updates are limited compared to current-generation controls, but all essential functions remain fully supported. FANUC typically supports CNC controls for 15-20+ years after production ends.

03 How does the D21MiB compare to the current D21MiB5?

The D21MiB5 (iB5 generation) offers slightly faster tool changes (0.7 vs 0.8 seconds), the updated 31i-B5 control with enhanced processing and 5-axis functions, improved servo tuning for better acceleration and surface finish, and updated thermal compensation. The mechanical platform dimensions are identical. For most applications, the performance difference is modest — perhaps 3-5% cycle time improvement on the iB5. The price difference between used iB and new iB5 is substantial.