Thermal Management — The Core of the L7 Design
The L7 series of linear motors was developed specifically with machine tool applications in mind, such as high-speed cutting (HSC), high-performance cutting (HPC) and various grinding applications. Sizeable feed forces must be generated with maximum efficiency and the resulting power loss dissipated efficiently in order to minimise heat introduction into the machine structure or adjacent construction.
The L7 series therefore comes with a cooling circuit for the primary part, which is also available as an optional extra for the secondary part. The primary part cooling circuit absorbs the majority of the heat flow and dissipates it into the cooling medium.
Secondary Part Cooling System
The secondary part cooling system absorbs and dissipates the residual radiant and convection heat from the underside of the primary part. This renders the complex process of installing cooling ducts in the machine bed (which weakens the structure) unnecessary.
Three Measures Against Thermally Induced Geometry Changes
To minimise thermally induced changes to the machine geometry, the L7 motor comprehensively supports the following measures:
1. Thermal insulation
Special spacer elements create an air gap above the primary part, thermally insulating the linear motor from the screw mounting surface.
2. Homogeneous temperature distribution
Thermally and symmetrically constructed primary parts and a main cooling system produced to a special design enable optimum homogeneous distribution of the temperature.
3. Active temperature control as a complete system
Secondary parts are optionally available with a cooling facility and can be easily incorporated into the existing cooling system of the primary part.
Construction Breakdown
L7 motor components exploded view (Source: PHL en-GB / DE / 2025-01, p.5)
- Primary part with integrated water cooling system — absorbs the majority of the heat flow
- Cover plate (optional) — protects against mechanical influences; particles such as swarf can be easily removed
- Secondary parts in encapsulated design (optional) — provides excellent protection against liquids; the reinforced insulation system prepares the motor for future electrical requirements
- Secondary part cooling system (optional) — absorbs residual radiant and convection heat from the underside of the primary part, eliminating the need for cooling ducts in the machine bed
Efficiency & Power Loss
By combining a highly compact cooling system with an optimised coil system, L7 achieves — compared to the current benchmark — either of the following improvements:
At the same drive force, power loss is reduced by up to 50%
At the same power loss, nominal force is increased by up to 40%
Pronounced advantage in oscillating motion
L7 demonstrates its strengths particularly in oscillating motion applications, where high acceleration is required and the motor is continuously heated. The high acceleration capability reduces cycle times and the energy reserves ensure high contour accuracy of the workpiece. As power loss is minimal, less heat is introduced into the machine bed.
Compliance & Durability
Ecodesign Directive 2009/125/EC
The L7 series of linear motors meets the energy-efficiency requirements of the EU Ecodesign Directive (2009/125/EC).
Durability
The secondary parts offer the following options to extend life and protection:
- Cover plate — effective barrier against mechanical influences; production particles such as swarf can be easily removed
- Encapsulated — excellent protection against liquids
- Reinforced insulation system — prepares the motor for stricter future electrical requirements
These optional combinations make the L7 series exceptionally durable and reliable.
Positioning vs. the L1 Series
For many years, Schaeffler Industrial Drives has supplied water-cooled, iron-core L1 series linear motors with peak forces of up to 5,171 N. The L7 series expands this range to 24,300 N, allowing Schaeffler linear direct drives to be used much more widely in handling systems and the main axes of machine tools.
| Item | L1 Series | L7 Series |
|---|---|---|
| Peak force ceiling | 5,171 N | 24,300 N |
| Typical applications | Automation, semiconductor, PCB, laser cutting, metrology | Milling, turning, grinding, HSC axes, oscillation / out-of-round machining |
| Water cooling | L1C optional | Standard on primary part |
| Secondary part cooling | Not applicable | Optional |
| Dielectric strength | — | 800 V |
| IP rating | — | Primary part IP65 |