December 2019 Design Notes

Hydraulics lets driverless trucksmove 2 billion tons

Komatsu’s 400-ton capacity 980E-4 mining truckis a workhorse in autonomous hauling operations.

Global heavy equipment manufacturer Komatsu America Corp., Rolling Meadows, Ill., announced that its FrontRunner Autonomous Haulage System (AHS) has achieved the unprecedented milestone of more than two billion tons of surface material moved in driveless operation. According to company officials, the FrontRunner system has now hauled more than all other commercial mining autonomous haulage systems combined.

Since its first commercial deployment in 2008 at CODELCO’s Gabriela Mistral (Gaby) copper mine in Chile, the FrontRunner AHS has experienced exponential growth in cumulative production, breaking the one billion tons mark in 2016 and the 1.5 billion tons mark in late 2017. This has been accomplished with more than 130 trucks in operation to date. An additional 150 trucks will deploy to the Canadian oil sands over the next seven years.

One of the keys to success has been the simple and efficient hydraulics used in ultra-class vehicles such as the 400-ton capacity 980E-4 haul truck. The rear-dump mining vehicle includes an 18-cylinder, 3,500-hp engine and ac-electric drive, and reportedly provides an optimal match in large-scale mining applications with big bucket shovels (55 to 99 yd 3 ) — loading out in three to five passes, depending on bucket size and material density.

The hydraulic system is a proven and reliable design with fewer parts than other OEMs, said Komatsu officials. The system uses a single 250 gal (947 l) tank, providing one common source of fluid for steering, braking and hoisting. In-line, replaceable filtration elements provide protection from hydraulic system contamination, making the system easier to service.

An accumulator-assisted circuit with twin double-acting cylinders provides constant-rate steering. Secondary steering is automatically supplied by the accumulators. Two 3-stage dual-acting outboard cylinders, with internal cushion valves and over-center dampening, hoist the bed and dump loads.

The system includes dual, in-line high-pressure pumps in a single package. Hoist and brake cooling are handled by a tandem gear pump with output of 246 gpm (931 lpm) at 1,900 rpm and 2,750 psi. A pressure-compensating piston pump with output of 65 gpm (246 lpm) at 1,900 rpm and 3,000 psi serves steering and brake functions.

To keep downtime to a minimum, Komatsu developed a sub-frame pump module that can be removed and replaced as a single unit. This reduces changeout time and allows easy access to the hydraulic pump module.

Working closely with customers, FrontRunner AHS’s ten-year zero-harm and productivity record, and unmatched ability to accommodate an array of mining environments, has let the company accelerate the pace of AHS deployment, said Komatsu officials. Today’s FrontRunner system operates around the clock hauling copper, iron and oil sands, at seven sites, across three continents. “The ongoing investment in technology and equipment by major mining companies in Chile, Australia and Canada underscores their belief in the value of autonomous haulage,” said Anthony Cook, Vice President Autonomous and Communications Solutions at Modular Mining Systems, a subsidiary of Komatsu.

“AHS continues to play an increasingly crucial role in effective mine management as more and more operations transition from manned to unmanned fleets,” said Dan Funcannon, VP/GM, Large Mining Truck Division, Komatsu America. “As the demand for autonomous systems grows, Komatsu will continue raising the bar in an effort to help mines provide safer working environments, maximize production, and reduce operating costs.”

To underscore the company’s commitment to progress, Komatsu plans to enhance the AHS’ mixed-operation functions, enabling manned trucks of any make to interoperate with Komatsu AHS trucks in a blended operation. Komatsu is also working with industry stakeholders towards standardization of interoperability between Komatsu and non-Komatsu autonomous vehicles, to improve safety and efficiency at customer operations. FPW

Komatsu America | komatsuameria.com

The evolution of dualcylinder actuation

Traditional clamp and press mode actuation applications have a rapid stroke at a low force while requiring a steep ramp-up to a high force for a short period.These demanding parameters typically result in the expensiveoversizing of the hydraulic infrastructure to meet speed andforce requirements.

Within this large machine footprint, position and force control goals present complex motion and expense variables. In addition to having too many overall pieces in the equation, other factors include: oversized and continuously running pumps, large hoses that often leak and require maintenance, and the energy consuming frequency of stopping/starting with valves repeatedly turning on/off, while transitioning from high speed (low force) to lower speed (high force).

To solve this problem, motion control/actuation specialists Kyntronics, Cleveland, have developed a patent-pending HSHF (High Speed/High Force) All-In-One Actuator. Combining technologies from its servo-based SMART Hydraulic Actuator (SHA), coupled with a high-speed actuator and a high-force pair of actuators — the HSHF is a solution in a scalable, modular, ‘power-on-demand’ machine platform. The design is selfcontained with no hoses that eliminates the expensive leaky infrastructure.

The dual cylinder system configuration delivers myriad benefits, resulting in lower operating costs and better performance across a wide range of OEM applications. This actuation technology is a step forward in modularity and takes advantage of hydraulics to overcome inherent issues with existing clamp and press mode technologies including:

HSHF single “high-load” cylinder

CLAMP MODE: In this mode, rapid cycling times are needed while holding a lot of force (170,000 lb-ft / 756 kN) going back and forth. This mode is predominant in injection and blow molding applications which require rapid back/ forth position and hold, which puts a lot of pressure on the actuator.

Traditional systems include hydraulics that feature check valves that lock in position. These types of systems require a large footprint and higher costs. Electromechanical is also an option but requires large and expensive components including motors, gearboxes, and roller screws/ball screws. Furthermore, the consistent metal-to-metal contact can result in reduced life.

PRESS APPLICATION: Typically, this mode is used for 20-80 ton presses which need to come down quickly, and do work within a small distance ( 1 ⁄4 - 1 ⁄2-in. [6-13 mm]) for short periods. This application is dominated by hydraulic systems with huge power units, and excessive pumps and hoses.

The HSHF system provides accurate force control for both clamping and press applications’ performance. This next generation of actuation has rapid movement with high force clamping and a high force press (small distance) — at a low cost, with no hoses, in a small envelope.

The simplicity of this design eliminates oversizing methods and solves several of the issues associated with current options in a cost-effective package — representing upwards of 50% savings in equipment and operating costs.

The reduced space and machine footprint are significant, as it eliminates the hydraulic infrastructure and all oversized elements — providing substantial cost savings. Because it only uses power-on-demand, energy savings are built-in. Because there is no cylinder or pump waiting for the cycle to start, the HSHF uses minimal energy for the long stroke and proportional energy for the load-stroke.

Ease-of-integration with machine control systems and versatile control is also an inherent benefit, as the HSHF Actuator is compatible with Fieldbus, I/O (selectable indexes), and Analog (0-10 Vdc or 4-20 mA).

The HSHF Actuator’s patent-pending concept mechanically connects a high-speed cylinder to a larger high-force dual cylinder. The dual cylinder combines a larger (high-speed zone) cylinder (e.g., a 6-in.) and a slightly smaller (high force zone) cylinder (e.g., a 5-in.) with a piston designed to seal in the smaller cylinder and move freely through the larger cylinder. The high-speed cylinder pulls (e.g., a 1-in.) the dual cylinder’s piston through the longer stroke, (e.g., oil flows freely around the piston) into the smaller cylinder, (high force zone) and seals the piston allowing for either the press or clamp mode.

HSHF two “high-load” cylinder combination

With SMART actuation, the system knows the exact position where the piston enters the smaller high force cylinder zone and creates a seal. As the smaller high-speed cylinder approaches the high force zone, the system slows down and seamlessly combines the fluid flow to both the high-speed cylinder (e.g., 1-in.) and the high-force cylinder (e.g., 5-in.) without stopping the motion. The system continues to press forward based on force or position. After the operation is completed, the high-speed cylinder retracts, pulling the unique piston back to the retracted position. The highspeed cylinder provides the speed to reduce the overall cycle times with minimal flow, force and heat reducing energy consumption.

During a press mode, maximum power is required for a short period of the cycle (slower speed with high force) — minimizing the motor and drive size along with the overall heat. During a clamp mode, minimum power is required to move the cylinder (extend/retract). During the clamping, zero power is required as the check valves in the HF cylinder lock the actuator in position, and the HS cylinder is placed in float mode to prevent cylinder damage.

The all-in-one operation provides an optimal servo-controlled, closed loop-controlled force, as well as a closed loop-controlled position solution. Vertical market industries such as automotive, aerospace, packaging, and plastics, along with unique applications including injection molding, blow molding, toggle/platen clamping, metal forming, injection carriage actuation, trim press actuation, thermoforming platen actuation, will benefit from HSHF Actuator’s lower costs and higher precision.

According to Kyntronics’ President, Wayne Foley, “The HSHF Actuator is a production enhancing product via cycle time reduction at a lower cost versus current alternative hydraulic and electromechanical options. Accurate position, force, and speed control move quickly under the low load, then the balance of the cycle (5-10%) retracts/ repeats quickly like nothing else on the market.”

Kyntronics | kyntronics.com

Hydraulic control block ensuressafety in marine winches

Winch systems on ships are used to wind up orwind out cables of wires when anchoring ships,depositing cargo on the bottom of the sea andmore. Hydraulic control blocks from Rexrothensure safety and reliability in these systems.

Winches are used for many applications on vessels both large and small,such as anchor hoisting, mooring of the vessel, and subsequent holdingof the ship against the quay. To this end, Bosch Rexroth introduced theHIWCB, a control block developed specifically for high-pressure hydraulicwinches, intended for deck mounting. Its modular design enablesinteroperability with almost any type of winch.

The new control blocks for high-pressure hydraulic marine winches build on the developments underlying Rexroth’s existing control blocks. What sets them apart is that they are entirely assembled from standard components. In other words: because they employ proven techniques and technologies, reliability is guaranteed. This is further underlined by the fact that these blocks come from a production line which is also used to manufacture products for the mobile industry. All components are carefully documented, and parameters such as tightening torques are measured, evaluated and documented. The incidence of component failure in the field is reduced to a minimum by this approach. And of course, standard components are less expensive than non-standard variants.

What makes the HICWB unique is its modular design, which enables it to be combined with virtually any winch. This enables the vessel’s owner to hold fewer spare control blocks and offers more options for dealing with changes. This is an improvement over control blocks designed specifically for a certain application or winch. Moreover, the new blocks can be combined with both axial and radial piston motors, and with their light weight of just 44 kg, they can even be directly motor-mounted.

In addition, each complete control block undergoes a specific treatment for maximum resistance to the extreme conditions offshore. The blocks themselves are galvanized and chrome-plated, and stainless steel is used for external moving parts such as the control lever and bushes. All adjustment elements have weatherproof covers. And as a final protective barrier, a triple coating is applied in layers of each 80 µm thickness.

The modular HIWCB control block for high-pressure hydraulic winches is intended for deck mounting, and can operate with almost any type of winch.

Besides the required standard functions like counterbalance, relief and anti-cavitation valves, these lightweight and compact control blocks offer a range of additional features. To start with, they can proportionally control the winches or capstans used to raise or lower the anchor. The so-called anchor break-off function of the block, in combination with a variable displacement motor, enables the anchor to be broken free in a controlled manner. A threeposition hand lever valve is used for this function: in the breakoff mode, up to 1.5 times the maximum rated load is permitted. The second position of the valve allows the operator to select minimum speed (which can be pre-set) at maximum rated load, followed by maximum speed with minimum load at the third valve position.

A second important feature of the control block lies in the ability to maintain a constant tension on the mooring lines when the vessel is berthed. When the mooring lines slacken due to vertical movement of the vessel, e.g. during tide, wave motion or loading/unloading, the winches will wind in to maintain line tension. When the lines are tightened by vertical movement in the opposite direction, the winches will pay out line. The system’s high responsiveness means that tension in the lines remains constant, avoiding overload and shock forces, and keeping the vessel firmly and securely moored against the quay.

Lastly, a number of safety features are integrated into the control blocks. An extreme situation can potentially occur when the hydraulic supply is cut off (for whatever reason) to a winch holding a suspended load, and without a brake applied. Oil can then leak via the motor drain circuit back to the tank, resulting in insufficient hydraulic pressure to continue holding the load. Ultimately, the motor will cavitate, and the load will drop uncontrollably.

To ensure a safe situation even in cases such as this, an extra valve is incorporated that responds to falling pressure by holding the oil in the motor, and blocking leakage to the tank. The motor will slow down, but will not cavitate, and the holding power remains assured.

Integrating the various features into the control block has made it possible to assemble a block that is highly compact. Not only does it require minimal space on deck, it also simplifies the integration of functionality in the installation, since it requires considerably less piping, and with fewer external couplings, the risk of leakage is even further reduced. This approach also drives down maintenance costs over the long term.

Bosch Rexroth | boschrexroth-us.com