Equipment Type

New Dozer 30 Percent More Productive?

Komatsu makes big claims for the D155AX-6's Sigmadozer blade design, engine-optimizing transmission, and longer track

June 01, 2006

Komatsu D155AX-6 crawler dozer
Exhaust-gas recirculation allows the Tier-3 diesel to generate more power and low-end torque more economically than previous engines. Komatsu's automatic-lockup torque converter and auto shift transmission make the tractor 10 percent more fuel efficient while moving 15 percent more dirt.
Sigmadozer blade
Notches in the Sigmadozer bring cutting force to a sharper point for more efficient digging, and direct material flow back toward the center so the blade carries more and windrows less.

At Komatsu Field Days, where the manufacturer hosts customers who come to see its latest machines, the demonstration spokesman estimated "conservatively, the new D155AX-6 crawler dozer will deliver a 30-percent improvement in productivity compared to the D155AX-5."

Innovation supporting the claim starts with a redesign of the dozer blade. Komatsu's new Sigmadozer is like a semi-U blade, but with pockets near the outside edges. The design is said to reduce cutting resistance, roll material more effectively, and redirect flow toward the center of the blade. This produces noticeably less windrowing off the outside edges of the blade, and larger blade loads.

A new blade linkage with dual-tilt control is standard equipment with the Sigmadozer. It holds the blade closer to the tractor, improving the operator's view of the work, and enhancing digging force with reduced blade sway. And because the blade retains material better, it can be tilted back to carry a load like a U-blade with little spillage.

The Komatsu SAA6D140E-5 engine delivers 320 horsepower at 1,900 rpm. To meet the Environmental Protection Agency's Tier 3 exhaust limits, Komatsu applied cooled exhaust-gas recirculation (EGR), direct fuel injection, and air-to-air aftercooling to the turbo diesel. Komatsu claims a 10-percent improvement in fuel economy and more torque output at lower engine speeds.

Torque-converter lockup comes on automatically in the usual dozing speed range. Locking up the torque converter eliminates a 10-percent loss of horsepower between the engine and transmission.

The patent-pending, auto-shift transmission has a manual mode that offers operators control over upshifts. But the auto shift controller is constantly communicating with controllers in the engine, steering system and hydraulic system, so when it's in control, it can keep the engine operating at peak torque all the time.

Komatsu brought the K-Bogie undercarriage proven on its largest mining dozers to the D155AX-6. The K-Bogie oscillates more effectively so the roller follows the track link better on rough terrain to maintain alignment between rollers and links. An additional roller in the undercarriage puts more track on the ground.

The D155AX-6, like all of Komatsu's new construction-machine introductions, comes with the KOMTRAX wireless data system as standard equipment. KOMTRAX relies on the global positioning system (GPS) location and cellular data transfer to send location, hours, and error codes, cautions, maintenance items, fuel levels, and more information to a secure website that dealers and customers can access. Machines with standard KOMTRAX come with five years of free communication (service starts when the machine is delivered to dealer inventory).

Komatsu's suggested retail price for the D155AX-6, with dozer blade and ripper, is $537,000.

Competitive Dozers
(By horsepower)
Net HP Blade Capacity (cu. yd.) Operating Weight* (lb.)
* With blade, without ripper
Source: Xpanded Specs at
Komatsu's D155AX-6, with 320 net horsepower and operating weight above 87,000 pounds, is larger than the competitive models clustered around the Cat D8 at 310 horsepower. The Komatsu product manager says the SAE method for estimating semi-U blade load underestimates the Sigmadozer's capacity at 12.3 cubic yards.
Caterpillar D8T 310 11.4 75,845
Dressta TD-25M 320 12.5 79,829
Komatsu D155AX-6 320 12.3 87,100
John Deere 1050C 324 12.5 73,985
Liebherr PR 752 330 12.5 75,852
Caterpillar D9T 410 17.7 94,900


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