FANUC Robodrill α-D21SiB5 Plus
Key Specifications
X Travel
Y Travel
Z Travel
Spindle Taper
Table Size
Rapid Traverse
Overview
The FANUC RoboDrill a-D21SiB5 is the short-bed standard model in the current iB5 RoboDrill lineup, offering the smallest travel range and footprint in the family. With X/Y/Z travels of 300 x 300 x 330 mm, this is the machine FANUC designed for maximum throughput on small parts where every fraction of a second counts. The 'S' designation means short-stroke, and the shorter axis travel means less moving mass, faster acceleration, and quicker settling times than the medium-bed or long-bed variants.
The D21SiB5 shares the same core platform as its larger siblings: 21-position turret ATC with 0.7-second tool-to-tool change, 54 m/min rapid traverse, BT30 spindle with 10,000 RPM standard or 24,000 RPM high-speed option, and the FANUC 31i-B5 control. The table measures 500 x 300 mm with a maximum load of 100 kg. Positioning accuracy is ±0.003 mm with repeatability of ±0.002 mm. The compact footprint of approximately 1,750 x 1,600 mm is the smallest in the RoboDrill family.
The standard D21SiB5 (without the ADV Plus designation) represents FANUC's value offering in the short-bed segment. It's available with the standard 10,000 RPM spindle at a lower price point than the ADV Plus model, making it the most affordable current-production RoboDrill. For shops machining small aluminum and brass parts that don't require 24,000 RPM spindle speeds, the standard D21SiB5 delivers the same mechanical precision and tool-change speed at meaningful cost savings. The machine also accepts the DDR 5-axis table for shops that need simultaneous 5-axis capability.
New D21SiB5 standard machines price between $65,000 and $100,000 depending on spindle speed and options. This is the RoboDrill entry point — the most affordable way to get a current-generation FANUC compact machining center on your shop floor. Used D21SiB5 machines from 2018-2023 are available in the $30,000-$55,000 range. The machine competes with the Brother Speedio S300Xd2, Haas Mini Mill 2, and Kitamura Mycenter-1XiF. For production shops that need RoboDrill speed on small parts at the lowest possible capital cost, this is the model to evaluate.
Full Specifications
| Parameter | Value |
|---|---|
| X-Axis Travel | 300 mm (11.8 in) |
| Y-Axis Travel | 300 mm (11.8 in) |
| Z-Axis Travel | 330 mm (13.0 in) |
| Table Size | 500 x 300 mm (19.7 x 11.8 in) |
| Max Table Load | 100 kg (220 lb) |
| Spindle Speed | 10,000 RPM (24,000 RPM optional) |
| Spindle Motor Power | 11 kW (15 hp) standard |
| Spindle Taper | BBT30 / HSK-E32 |
| Tool Magazine | 21-position turret |
| Tool Change Time | 0.7 sec (tool-to-tool), 1.3 sec (chip-to-chip) |
| Rapid Traverse Rate | 54 m/min (2,125 ipm) |
| Positioning Accuracy | ±0.003 mm (±0.00012 in) |
| Repeatability | ±0.002 mm (±0.00008 in) |
| CNC Control | FANUC 31i-B5 Plus |
| Machine Weight | 3,500 kg (7,716 lb) |
| Floor Space Required | 1,750 x 1,600 mm (68.9 x 63.0 in) |
| X Axis | 300 |
| Y Axis | 300+100 |
| Z Axis | 400 |
| Tool Storage Capacity | 28 tools |
| 14 Tools | α-D14SiBADVPlus |
| 21 Tools | α-D21SiBADVPlus |
| Spindle Spec | Max. speed |
| Standard | 10000 min-1 |
| High Torque | Heavy machining of steel parts (Max. 100N·m) |
| High Acceleration | High speed and high efficiency machining of aluminum parts |
| Tapping | 12000 min-1 |
| High Speed | 24000 min-1 |
Specifications sourced from fanuc.co.jp — verified 2026-03-28
Strengths & Limitations
Strengths
- Most affordable current-production RoboDrill at $65K-$100K — genuine FANUC performance and reliability at entry-level VMC pricing
- Smallest footprint in the RoboDrill family at 1,750 x 1,600 mm enables highest machine density on the shop floor
- Fastest acceleration and settling times of any RoboDrill variant due to lowest moving mass on the short-bed platform
- Same 0.7-second tool changes and 54 m/min rapids as every other current-generation RoboDrill — no performance compromise on speed
- DDR 5-axis table compatible, providing an upgrade path to simultaneous 5-axis machining when needed
- FANUC 31i-B5 control provides commonality with the entire RoboDrill family and FANUC's CNC ecosystem
Limitations
- 300 x 300 mm X/Y travel is the most restrictive in the RoboDrill lineup — strictly limited to small parts and single-part fixturing
- 100 kg maximum table load constrains fixture weight and eliminates heavy steel fixture plates
- Standard 10,000 RPM spindle (base configuration) lacks the high-speed capability needed for optimal aluminum and brass machining — the 24,000 RPM upgrade adds cost
- BT30 taper provides limited rigidity for anything beyond light-duty cutting — this is not a steel roughing machine
- 21-tool turret is fixed capacity with no expansion option for complex parts requiring many tools
Best For
Frequently Asked Questions
01
The ADV Plus includes the 24,000 RPM high-speed spindle as standard, enhanced servo tuning for faster acceleration, AI contour control, fine surface finish mode, and the 31i-B5 Plus control. The standard D21SiB5 comes with a 10,000 RPM spindle and the base 31i-B5 control. The ADV Plus costs approximately $30,000-$50,000 more but is recommended for shops machining aluminum at high speed or requiring the best possible surface finish.
02
If your parts fit within 250 mm in X and Y, the short-bed D21SiB5 is the better choice — it's less expensive, has a smaller footprint, and provides marginally faster acceleration due to lower moving mass. If you machine parts over 250 mm in any direction or use multi-part fixtures, the medium-bed D21MiB5 with 500 x 400 mm travel is necessary. Most shops default to the medium-bed for flexibility, but dedicated small-part production shops benefit from the short-bed's advantages.
03
FANUC has shipped over 250,000 RoboDrills worldwide across all generations and models. The platform is the most widely installed compact machining center in history. This massive installed base ensures strong parts availability, widespread application knowledge, excellent resale value, and a deep pool of operators with RoboDrill experience.
04
Yes. The machine supports FANUC DDR (Direct Drive Rotary) 5-axis tables for trunnion-style A and C axis simultaneous 5-axis contouring. However, the 300 x 300 mm travel and 100 kg table load significantly constrain the practical workpiece envelope after accounting for rotary table weight. Most shops choosing 5-axis opt for medium-bed or long-bed models.
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