Minostar MR75 Roadheader

Minostar MR75 – Operational Capabilities

The Minostar MR75 roadheader has been developed for driving underground roadways that require an extended cutting range, high power and excellent machine stability during operation. Its design enables the machine to cover a cutting cross-section of at least 34 m² from a single position. The exact value depends on the roadheader configuration selected by the customer.

The cutter-head motor, rated at 200–230 kW depending on the configuration, enables the machine to cut rock with a compressive strength of up to 100 MPa. Our proprietary MR75 roadheader can therefore be deployed in conditions where lighter roadheaders cannot deliver the required productivity or cutting range.

Efficient muck removal is provided by a wide loading apron working in conjunction with a centrally mounted conveyor. The material-handling system provides a capacity of up to 300 m³/h, which helps prevent excavated material from accumulating in the working area and keeps the roadway drivage process running smoothly.

The MR75 combines a wide cutting range with the ability to stabilise the machine during cutting. Its modular construction also facilitates preparation for transport and assembly at the operating site.

Applications of the MR75 Roadheader

The MR75 roadheader is primarily intended for the mechanised driving of underground mine roadways. It can be used wherever harder rock formations need to be cut, large-cross-section roadways need to be developed and substantial volumes of excavated material need to be removed efficiently.

Typical applications of the MR75 include:

• driving main mine roadways,
• developing haulage and ventilation roadways,
• driving mine-access and development workings,
• cutting coal and surrounding rock,
• operating in rock formations with a compressive strength of up to 100 MPa,
• developing roadways that require a large cutting cross-section,
• operation in configurations that require additional equipment for rock bolting or roadway support installation.

Depending on the selected version and certification scope, the Minostar MR75 can be configured for operation in both non-gassy and gassy mine workings, as well as in workings exposed to a coal-dust explosion hazard. The final configuration of the electrical system, protective systems and other equipment is determined according to the conditions at the intended operating site.

The Minostar MR75 roadheader has a modular design that combines the assemblies responsible for rock cutting, gathering and conveying excavated material, machine travel, stabilisation, power supply and control. This design facilitates the transport of individual modules through mine workings with limited clearances, followed by their efficient assembly at the intended operating site.

The machine layout provides convenient access to key components and service points. This facilitates inspections, maintenance and servicing, helping to reduce planned downtime. The MR75 is designed for efficient and reliable operation in a wide range of geological conditions, including the cutting of rock with a compressive strength of up to 100 MPa.

Cutting Unit

The main working assembly of the MR75 is a transverse cutter head driven by a motor rated at between 200 and 230 kW. The system is designed to cut hard rock formations effectively and perform operations that require high power and stable cutting parameters.

The cutter-head drive comprises a water-cooled motor and a gearbox that transfers torque to the cutter head. The cutter-head configuration, arrangement of the cutting tools and drive-system parameters can be tailored to the anticipated geological conditions and the characteristics of the roadway to be developed.

Cutting Boom and Cutter-Head Slewing Mechanism

The cutter head is mounted on a boom connected to the slewing mechanism. The hydraulic system moves the cutting unit vertically and horizontally, allowing the cutter head to be guided across the working face and the required roadway shape and cross-section to be achieved without frequently repositioning the entire machine.

The cutting boom works in conjunction with a hydromechanical collision-protection system. This solution prevents the cutting boom from colliding with the loading apron, reduces the risk of damage to machine components and improves operational safety.

Loading Apron and Gathering Elements

Material cut by the cutter head is directed onto a hydraulically raised and lowered loading apron. The appropriate apron width and the option to install extensions allow the material-gathering area to be matched to the cross-section of the roadway being developed.

The gathering elements move the excavated material towards the centrally mounted conveyor. Surfaces exposed to intensive contact with rock are protected with abrasion-resistant materials. The loading apron also helps stabilise the front section of the roadheader during cutting.

Excavated-Material Conveyor

The conveyor runs through the centre of the roadheader and collects the material gathered on the loading apron. It then transports the excavated material towards the rear of the machine, where it can be transferred to the next item of haulage equipment.

Conveyor components exposed to wear are protected with replaceable abrasion-resistant plates. The conveying system has a maximum capacity of up to 300 m³/h, ensuring efficient removal of excavated material while the cutter head is operating.

Main Frame and Modular Design

The main frame is the primary load-bearing component of the MR75. It connects the machine’s key assemblies and carries the loads generated during cutting, material gathering and roadheader travel.

The modular division of the machine allows its key assemblies to be transported separately, which is particularly important in underground workings with limited dimensions. This solution facilitates machine assembly and disassembly and provides more convenient access to components during maintenance.

Stabilisation System

Hydraulic stabilisers help maintain the correct position of the machine during cutting. Once lowered, they support part of the roadheader’s weight, reducing unwanted movement of the structure under the forces generated during the cutting process.

The stabilisation system works in conjunction with the main frame, crawler undercarriage and loading apron. This allows the MR75 to remain stable and the cutter head to operate consistently under demanding operating conditions.

Crawler Travel System

The crawler undercarriage allows the roadheader to travel along the mine floor and be positioned accurately in relation to the working face. The large contact area between the crawler tracks and the ground provides adequate traction and helps reduce the machine’s ground pressure.

Independent control of the crawler tracks facilitates roadheader manoeuvring within the mine working and allows the machine to be positioned correctly before the next cutting cycle begins.

Hydraulic System with Load Sensing

The hydraulic system is responsible for operating the cutting boom, changing the position of the loading apron, controlling the stabilisers and operating the machine’s other mechanisms. The MR75 uses a Load Sensing system that adjusts the hydraulic system’s output and operating parameters to the current demand of individual hydraulic functions.

The Load Sensing system provides:

• precise and smooth control of the roadheader’s hydraulic mechanisms,
• lower electricity consumption by adapting system operation to the current load,
• lower hydraulic oil temperature, helping to maintain the correct operating conditions within the system,
• reduced wear of hydraulic components and lower loads acting on individual system components.

Automatic Central Lubrication System

The MR75 is equipped with an automatic central lubrication system that delivers the correct amount of lubricant to the machine’s key lubrication points. The system simplifies routine maintenance, ensures regular lubrication of interacting components and helps prevent their premature wear.

Automating this process reduces the number of manual maintenance tasks and helps keep the roadheader in proper technical condition during intensive operation.

Water-Spray and Dust-Suppression System

The water-spray system suppresses dust generated during cutter-head operation and helps prevent ignition in mines where gas hazards are present. Depending on the selected configuration, the MR75 can operate with one of two variants:

• variant 1 – external water-spray system, using an external water-spray manifold;
• variant 2 – combined water-spray system, comprising internal after-tool sector spraying and an external water-spray manifold.

The variant combining internal and external spraying directs water both into the immediate vicinity of the cutting zone and into the area surrounding the cutter head. This effectively reduces the spread of dust around the working face.

Electrical System and Controls

The MR75 electrical system supplies power to the cutter-head motor, auxiliary drives, lighting, monitoring equipment and control components. Its configuration is selected according to the parameters of the power-supply network and the requirements applicable at the intended operating site.

The control system enables the operation of individual assemblies to be controlled and monitors selected machine parameters. The installed protective devices safeguard the electrical system and components against the effects of abnormal electrical conditions. The exact range of protective devices depends on the configuration and version of the individual MR75 unit.

Solutions Used in the Tunnel Version

The tunnel roadheader version of the MR75 – Minostar MR75-T – features an optimised water-cooling system that maintains suitable operating conditions for key components in a demanding tunnel environment. The system supports safe and efficient machine operation, including during prolonged operation under substantial loads.

This version of the roadheader is also equipped with a spacious, air-conditioned operator’s cab. The cab improves operator comfort during long working hours and provides protection against adverse conditions at the worksite.