Forest-Line Horizontal Machining Centers

Forest-Line Modumill

$2,000,000 - $5,000,000 Updated 2026-03-16

Key Specifications

X Travel

Customer-configurable, typically 6,000 - 20,000 mm

Y Travel

3,000 - 5,000 mm (portal width dependent)

Z Travel

1,000 mm (39.4 in)

Max Spindle

24,000 RPM

Spindle Taper

HSK-A63

Rapid Traverse

30 m/min (1,181 IPM)

Overview

The Forest-Line Modumill is a portal horizontal machining center designed for the high-precision machining of large aerospace structural components, wing ribs, spar assemblies, and fuselage frames from aluminum alloy and titanium billet. Forest-Line, a French machine tool builder based in Capdenac-Gare with strong ties to the Airbus and French aerospace supply chain, developed the Modumill platform to address the structural machining requirements of large commercial aircraft programs where workpiece lengths routinely exceed 5,000 mm and dimensional accuracy demands are stringent.

The Modumill uses a traveling gantry (portal) structure in which the bridge traverses the length of the fixed workpiece in the X-axis, while the crossrail-mounted spindle head moves in Y and Z. This configuration allows unlimited workpiece length (theoretically) by extending the portal rails, and accommodates very wide, flat structural workpieces that would not fit in any conventional HMC. The machine is typically configured with a high-speed spindle delivering 24,000 RPM at 35 kW (46.9 HP) through an HSK-A63 interface for high-speed aluminum roughing and finishing. Feed rates exceed 30 m/min on all linear axes for rapid traverse.

Forest-Line configures the Modumill with a Siemens SINUMERIK 840D sl or NUM control. The machine's portal structure is constructed from steel weldments with finite-element-optimized ribbing to minimize structural deformation under dynamic loads. Active thermal compensation corrects spindle growth and structural drift during production runs. For aerospace customers requiring 5-axis machining of compound-angle rib features, an optional 5-axis universal head providing A-axis tilt and C-axis rotation is available.

Pricing for the Forest-Line Modumill is application-specific and configured to customer requirements, typically ranging from $2,000,000 to $5,000,000 depending on machine width, rail length, spindle configuration, and automation.

Full Specifications

Parameter	Value
Machine Type	Traveling gantry portal HMC
Max Spindle Speed	24,000 RPM
Spindle Motor Power	35 kW (46.9 HP)
Spindle Taper	HSK-A63
X-Axis Travel	Customer-configurable, typically 6,000 - 20,000 mm
Y-Axis Travel	3,000 - 5,000 mm (portal width dependent)
Z-Axis Travel	1,000 mm (39.4 in)
Rapid Traverse Rate	30 m/min (1,181 IPM)
5 Axis Option	Universal head, A-axis ±110°, C-axis 360° continuous (optional)
Positioning Accuracy	±0.006 mm (±0.00024 in)
Repeatability	±0.003 mm (±0.00012 in)
CNC Control	Siemens SINUMERIK 840D sl or NUM

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

Strengths & Limitations

Strengths

Traveling gantry architecture imposes no practical workpiece length limit — rail extensions allow machining of wing panels, spars, and fuselage sections exceeding 15,000 mm that no conventional HMC can accommodate
24,000 RPM high-speed spindle provides the surface speeds required for efficient aluminum aerospace roughing and finishing with high material removal rates
Forest-Line's deep expertise in the French and European aerospace supply chain means the Modumill's design has been validated on actual Airbus-class programs, with application support specific to aerospace structural machining
Optional 5-axis universal head enables compound-angle machining of complex rib and frame geometries without manual workpiece repositioning

Limitations

High capital cost ($2M-$5M+) limits the Modumill to large aerospace prime contractors and Tier 1 suppliers with sustained large-structure machining workloads
Long machine footprint and site preparation requirements (foundation, coolant system, enclosure) add significant installation time and cost before production can begin
Highly application-specific machine that excels at large aerospace structural parts but is overbuilt and poorly suited for general job shop or mixed-workpiece environments

Best For

Aerospace prime contractors and Tier 1 suppliers machining large aluminum wing panels, spars, ribs, and fuselage frames for commercial and military aircraft programs Defense manufacturers producing large structural components for military aircraft, rotorcraft, and unmanned aerial systems from aluminum and titanium billet Space launch vehicle manufacturers machining large propellant tank sections, adapters, and structural rings from high-strength aluminum alloys Advanced composite tooling manufacturers producing large aluminum and Invar layup tools and autoclave tooling for aerospace composite structures

Frequently Asked Questions

01 What makes the Modumill a portal machine rather than a conventional HMC?

A portal (gantry) machine places the workpiece on a fixed table or floor, and a bridge structure straddles the workpiece and moves over it in the X-axis. The spindle head is mounted on the bridge crossrail and moves in Y and Z. This architecture allows machining of workpieces much longer and wider than any conventional HMC pallet system could hold, making it the standard configuration for aerospace structural machining centers that process fuselage panels, wing spars, and similar large-format parts.

02 Is the Forest-Line Modumill used on Airbus programs?

Forest-Line has a long history of supplying portal machining centers to the French aerospace and European Airbus supply chain. While specific program details are confidential, Forest-Line machines are used by major Tier 1 aerospace suppliers in France, Germany, and the UK processing structural components for the A320, A330, A350, and A380 family aircraft. Forest-Line's proximity to the Toulouse aerospace cluster and its application focus on large aluminum structural machining aligns closely with Airbus supply chain requirements.

03 Can the Modumill be configured for titanium machining?

Yes. While the standard high-speed spindle (24,000 RPM / HSK-A63) is optimized for aluminum, Forest-Line offers alternative spindle configurations with lower maximum RPM and higher torque suited for titanium machining. The 5-axis universal head option also enables compound-angle titanium machining on complex structural parts. Customers machining mixed aluminum and titanium programs should discuss spindle selection with Forest-Line applications engineering.

04 How is the Modumill's portal structure optimized for aerospace accuracy requirements?

The portal bridge and column structures are designed using finite element analysis (FEA) to minimize dynamic deformation under the accelerations and cutting forces generated during high-speed aerospace machining. Steel weldment construction with optimized ribbing provides high stiffness-to-weight ratio. Active thermal compensation monitors temperature at multiple points on the machine structure and corrects axis positions in real time to maintain ±0.006 mm accuracy over long production runs.

05 Where is Forest-Line based and what other machines do they make?

Forest-Line is based in Capdenac-Gare in the Aveyron department of south-central France, approximately equidistant between Toulouse and Clermont-Ferrand. The company produces a range of large portal machining centers and specializes in aerospace structural machining applications. Their product range includes the Modumill portal HMC, the Ulysse large gantry milling machine, and various bespoke large-format machining systems built for aerospace prime contractors.