Caterpillar PM620 and PM622 Cold Planers

Caterpillar’s PM620 and PM622 Cold Planers are half-lane milling machines that perform controlled full-depth removal of asphalt and concrete pavements in a single pass. They are powered by a Cat C18 ACERT engine, a turbocharged, 6-cylinder diesel engine that provides 470 kW (630 hp) of gross power, meets Tier 4 Final emission standards and is iso-mounted to reduce vibration and increase operator comfort. Turbocharged air-to-air aftercooling provides high horsepower with increased response time, while Automatic Engine Speed Control optimizes output to match the load, reducing excessive fuel consumption and wear on the engine. Approximate weights for the PM620 and PM622, respectively, are: operating weight of 33,330 kg and 33,900 kg; transport weight of 29,400 kg and 30,000 kg.

Undercarriage and drive system
The PM620 and PM622 use a four-post design with auto-levelling that provides smooth height adjustment without stepping.

They are hydrostatically driven by two variable-displacement propel pumps supplying oil to variable-displacement motors on each track. The drive motors automatically control displacement, providing maximum torque for work or greater speed for moving around the job site. A propel lever/steering joystick provides infinite control of the travel speed within the range.

The propel system uses a diagonal cross flow design that provides exceptional traction. The pumps drive opposing track motors, front to back and side to side, to ensure the machine has power across the centre of gravity of the machine. In extreme conditions, automatic traction control minimizes slippage by providing more power to tracks that grip.

Several automated functions simplify operation. A ‘hold’ button stops the machine and pauses various functions while making truck changes or job stops. It returns to previous working speed and functions when deactivated. The operating speed can be set to ensure consistent operation. Position sensing cylinders in the posts and hydraulic systems provide improved basic machine functions, such as service height indications and rear leg auto-stop, and enable the optional Cat Grade Control system to include additional capabilities.

The drive tracks are based on proven Caterpillar designs and components. Track tension automatically adjusts to ensure optimal operation. Track assemblies are 1788 mm long, 305 mm wide and feature replaceable, bolt on polyurethane track pads for long service life.

Four-mode steering is standard. An electronic control module processes inputs from the sensors on the front and rear tracks, along with input from the steering selector controls. It provides precise simultaneous track movement in the cab and coordinated steering modes. When the front-tracks-only steering mode is selected, it automatically realigns the rear tracks to centre. In coordinated mode, inside turning radius is a tight two metres, providing exceptional maneuverability in confined spaces.

For greater steering precision, smoother cornering and reduced track wear, Cat uses a true-tracking alignment function that makes small adjustments to the alignment of individual tracks to ensure that they are travelling in the correct direction to make the desired maneuver without dragging a track or shorting a radius. This extends track pad and undercarriage component life.

Operator’s environment
Dual operating controls include joystick steering/propel lever, upper conveyor controls and rear-track steering controls. 

The touchscreen display is visible in day or night conditions, and keypads are backlit for comfortable low light operation. The display provides easy-to-read gauges, function indicators and warning indicators to keep the operator informed of machine operation and vital systems. It also shows video from optional remote cameras that provide views to the front and/or rear of the machine. A second monitor can be added to display additional machine functions.

The computerized monitoring system includes several electronic control modules (ECMs) that constantly monitor system pressures and engine conditions and can provide self-diagnostics and fault codes to the touchscreen display.

The operator’s platform has floor lighting that activates upon button press from any control station to provide visibility when accessing the machine in low light conditions.

Options include suspension seats and a hydraulically operated canopy. The canopy can deploy and retract to a storage position without disrupting operation, and can be equipped with optional front and rear windscreens that protect the entire width of the operator station.

Cutting system
The cutting chamber’s design streamlines material flow, reduces wear, and improves flush cutting. 

Side plates are moved by independent hydraulic cylinders equipped with position sensors, ensuring that the side plates float at the proper level. This eliminates binding and the need for a wire (yo-yo) sensor as the entire length of the side plate functions as an averaging ski for grade matching. 

A hydraulically operated anti-slab device prevents slabbing of the road surface, protects the collecting conveyor, and ensures an optimum discharge opening to the rotor chamber. The moldboard, side plates and anti-slab device all feature raise, lower, float and hold functions.

The rotor drive system uses a dry clutch coupled to the engine and hydraulically actuated by the keypad controls on the operator’s console. It drives a planetary gear reducer, which applies rotor power to the pavement. Three cutting speeds, controlled from the operator’s keypad, allow rotor rpm and torque to match job site conditions.

Automatic Load Control is standard and improves productivity while milling. An ECM continually evaluates engine rpm and controls propel speed, as required, to maintain peak performance for maximum output.

The PM620 and PM622 are equipped with 2,010-mm and 2,235-mm-wide high-production rotors, respectively. The maximum cutting depth for both machines is 330 mm. The rotor is equipped with three-piece, quick release tool holders and carbide-tipped cutting bits in a chevron pattern for maximum breakout force. 

Cat Diamond Bits are available as an option. They last up to 80 times longer than conventional carbide bits, extending periods between stops for bit maintenance, and are sharper, reducing drag on the cutting system, which means that the machine can cut at a faster speed. Reduced drag also decreases fuel consumption, vibration to the operator and machine wear.

Cat Grade Control option
Another useful option is integrated Cat Grade Control. The 2D-capable/3D-ready grade and slope system automatically controls rotor depth and cross slope to a preset cutting depth. The base system is fully integrated with the machine, resulting in easier, more precise operation and better system protection. It can be configured with contacting or non-contacting grade sensors, including Cat sonic sensors and mounting hardware, side-plate position or optional inboard ski. The machine can be set up to control grade on both sides using any combination of sensors, or to control grade on one side of the machine and slope on the other. Sensor arrangement can be changed with simple commands during operation.

The position sensing technology, coupled with the Cat Grade Control system, provides the machine with functions such as an automatic plunge cut feature that eases the rotor into the start of the cut. The machines also have a ramp-in, ramp-out capability to provide a gradual, sloped entry or exit from the cut. An auto-jump feature allows the machine to exit a cut, clear an obstacle such as a manhole cover or grate, and re-enter the cut at the previously set depth with push of a single button.

A cross communication function allows the operator to view and change settings of control boxes located on the opposite side of the machine. This provides a means to control both sides of a job from a single location. 

The system also provides a cross-coupling function; when an adjustment is made to the grade or slope of one side of the machine, the opposite side will automatically adjust based on the command parameters. Continual read-out for rotor depth and cross-slope is displayed on each control box and is visible in light or dark conditions.

Sonic grade-control sensors can be easily positioned on each side and provide a consistent accuracy to ± 3 mm (1/8”).

Conveyor system
The collecting conveyor is driven by a high-torque hydraulic motor and a large chamber discharge opening clears out the cutter box quickly. The 850-mm-wide, seamless collector belt has 32-mm-high cleats to clear out the cutter box effectively and control fine particles. 

An optional grease tensioning system uses a grease cylinder, rather than an adjustable screw, to adjust tension and tracking on the belt. This makes adjustment easier and reduces exposure to the spinning belt. A traditional screw adjustment design is available.

A standard water spray system lubricates the conveyor belt and helps control dust. An additional water spray system can be fitted as an option for greater lubrication, cooling and dust reduction during heavy-duty applications. This system includes an additional water pump, a second spray bar located in the rotor chamber housing, and extra spray nozzles on the collecting conveyor.

An optional dust abatement system uses a vacuum that pulls dust from the collecting conveyor and the transitional zone between the collecting and loading conveyors. The dust is ejected through the loading conveyor, along with the discharge material.

The hydraulically controlled, front loading conveyor features height adjustment for raise and lower, and two cylinders for a 60-degree swing to the left and right of centre that can be controlled from the operator’s station or at two ground level control stations. The conveyor is equipped with upper aluminum covers for added protection against material spills and blowing of fine materials. It can also be hydraulically folded downwards, reducing machine dimensions during transportation.

Servicing
The computerized monitoring system includes Electronic Control Modules (ECMs) that continually monitor system pressures and engine conditions. It can provide self-diagnostics and provide fault code to the touchscreen display. Product Link streamlines diagnostic efforts, maintenance scheduling, and costs by providing communication flow of vital machine data and location information between the dealer and customer. Optional configurations are available.

An auxiliary electric pump drive provides an emergency hydraulic flow that allows a disabled machine to manage some machine functions and be towed away from the work area to ensure that the disabled machine will not disrupt the continuation of work.

The engine-mounted air compressor and cutting bit removal tools make changing cutting tools quick and easy. An optional rotor-turning attachment is available to turn the rotor during cutter bit replacement. HEG