Mitsui Seiki GR504
Key Specifications
X Travel
Y Travel
Z Travel
Spindle Taper
Tool Capacity
Spindle Power
Overview
The Mitsui Seiki GR504 is a trunnion-type simultaneous 5-axis machining center that brings Mitsui Seiki's ultra-precision philosophy to complex multi-surface machining. Where most 5-axis machining centers target versatility and cycle time, the GR504 targets accuracy — delivering ±0.001 mm positioning on linear axes and arc accuracy measured in microns on the A and C rotary axes. It is the choice for aerospace impellers, turbine blades, precision molds with deep cavity contouring, and medical orthopedic implants.
The GR504 features a 400 mm trunnion table with ±110° A-axis tilt and full 360° C-axis rotation. The 20,000 RPM, 22 kW (30 hp) inline spindle accepts No. 40 taper tooling (HSK-A63 optional) and is oil-cooled for thermal stability. X/Y/Z travels are 500 x 450 x 450 mm, sized for complex medium-format workpieces up to 350 mm diameter and 300 mm height on the trunnion. Ballscrew cooling, linear scale feedback on all linear axes, and high-resolution angle encoders on A and C axes constitute the metrology foundation.
The FANUC 31i-B5 control provides RTCP (Rotational Tool Center Point) compensation, 3D tool radius compensation, and look-ahead interpolation for smooth 5-axis contour surfaces. Mitsui Seiki's own thermal compensation cycles integrate sensor data from the spindle nose, column, and ambient environment to correct axis positions in real time during extended machining operations.
The GR504 competes with the DMG Mori DMU 50, Makino D500, and Hermle C 400, but differentiates on guaranteed accuracy specifications rather than speed or flexibility. For aerospace impeller manufacturers and precision medical device producers, the GR504's accuracy certification is the purchasing criterion.
Full Specifications
| Parameter | Value |
|---|---|
| Configuration | Trunnion-type 5-axis (A+C trunnion table) |
| X-Axis Travel | 500 mm (19.7 in) |
| Y-Axis Travel | 450 mm (17.7 in) |
| Z-Axis Travel | 450 mm (17.7 in) |
| A Axis Range | ±110° |
| C Axis Range | 360° (continuous) |
| Table Diameter | 400 mm (15.7 in) |
| Max Workpiece Diameter | 350 mm (13.8 in) |
| Max Workpiece Height | 300 mm (11.8 in) |
| Max Workpiece Weight | 300 kg (661 lb) on table |
| Spindle Taper | No. 40 (CAT40 / BT40 / HSK-A63 optional) |
| Spindle Speed | 20,000 RPM |
| Spindle Motor Power | 22 kW (30 hp) continuous / 26 kW (35 hp) 30-min |
| Rapid Traverse Linear | 40 m/min (1,575 ipm) X/Y/Z |
| Rapid Traverse A | 30 rpm |
| Rapid Traverse C | 50 rpm |
| Feed Rate | 1–20,000 mm/min |
| Positioning Accuracy Linear | ±0.001 mm (±0.00004 in) full stroke |
| Repeatability Linear | ±0.0005 mm (±0.00002 in) |
| Positioning Accuracy Rotary | ±3 arc-sec (A and C axes) |
| Repeatability Rotary | ±1 arc-sec |
| Feedback | Linear scales (X, Y, Z); high-resolution angle encoders (A, C) |
| Thermal Compensation | Spindle oil cooling, ballscrew cooling, 3D thermal correction |
| Rtcp | Yes — Rotational Tool Center Point (FANUC 31i-B5) |
| Tool Capacity | 30 (standard) / 60 (optional) |
| Tool Change Time | 4.0 sec (chip-to-chip) |
| Way Type | Linear guides (X, Y, Z); direct-drive rotary (A, C) |
| Base Material | Meehanite cast iron |
| CNC Control | FANUC 31i-B5 |
| Machine Weight | 10,000 kg (22,046 lb) |
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Specifications sourced from machinetools.com — verified 2026-03-28
Strengths & Limitations
Strengths
- ±0.001 mm linear and ±3 arc-sec rotary positioning accuracy — one of the tightest guaranteed specs in the trunnion 5-axis class
- 20,000 RPM oil-cooled spindle with HSK-A63 option enables high-speed finishing of aerospace impellers and turbine blades
- RTCP with 3D thermal compensation maintains programmed tool center point accuracy during extended 5-axis contouring operations
- Trunnion configuration with ±110° A-axis provides excellent accessibility to complex undercut geometries on aerospace and medical parts
- Meehanite cast iron base with direct-drive rotary axes delivers rigid, chatter-free 5-axis cutting in difficult aerospace alloys
- Every GR504 ships with individual axis calibration certificates — required documentation for AS9100 and NADCAP approval processes
Limitations
- 300 kg maximum workpiece weight on the trunnion limits the machine to medium-format parts — not suited for large aerospace structures
- Price of $750K–$1.2M positions the GR504 above more production-oriented 5-axis centers from DMG Mori or Haas
- 30-tool standard ATC may be limiting for complex multi-operation aerospace parts; 60-tool option adds significant cost
- Mitsui Seiki's 5-axis application engineering support network is smaller than DMG Mori or Makino — complex 5-axis programming support may require factory involvement
- Trunnion configuration is less suited to very tall or asymmetric workpieces compared to rotary-tilting-table alternatives
Best For
Frequently Asked Questions
01
The DMG Mori DMU 50 is a versatile, production-oriented 5-axis center with a broad dealer network and strong automation options. The Mitsui Seiki GR504 prioritizes guaranteed accuracy over throughput — it delivers ±0.001 mm linear and ±3 arc-sec rotary specifications that the DMU 50 does not guarantee. For aerospace impeller work where dimensional certification is required, the GR504 is the defensible choice. For general 5-axis production, the DMU 50 offers better economics.
02
RTCP (Rotational Tool Center Point) is a control feature that automatically compensates for the offset between the tool tip and the rotary axis center points as the A and C axes move. Without RTCP, the CNC program must account for these offsets manually, which complicates programming and reduces accuracy. The FANUC 31i-B5 in the GR504 implements RTCP natively, allowing the tool center point to remain precisely on the programmed path regardless of rotary axis position.
03
The GR504 is optimized for precision work in aerospace alloys (titanium 6Al-4V, Inconel 718, aluminum 7075), hardened tool steels (H13, P20, S7), and stainless steels. The 20,000 RPM spindle also handles aluminum roughing efficiently. The machine's rigidity and thermal stability make it appropriate for difficult-to-machine materials where other 5-axis centers may compromise accuracy.
04
Yes. The GR504 supports robot loading through the front door and can be integrated with pallet buffer systems. Mitsui Seiki offers automation interface packages for common robot brands. For lights-out production of precision aerospace and medical components, robot-loaded GR504 cells are used in high-value manufacturing environments.
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