Milling Machines Bring It Together

Sept. 28, 2010

When the first milling machines made their debuts in the late '60s and early '70s, they were hailed as a major innovation in road reconstruction. The earliest milling machines were simply a mining mandrel attached to a mobile undercarriage. They were designed to efficiently remove a layer of old concrete or asphalt so that a new layer could be applied to a higher quality base than if the resurfacing simply went over the old surface.

An added benefit of the milling process was the creation of sized material that could be recycled. Recycling in all of its forms was becoming popular, and removed road material was no exception. As a result, DOTs across the nation were attracted to the milling machine because of what it could do. Some versions even evolved into machines that could remove the road surface, mix it with fresh binder and lay it down again in a continuous process.

From the start, the emphasis when developing a milling machine was power to the cutting drum, which was needed to remove more and more material. Additional emphasis was placed on the cutter head itself and the cutting teeth that really did the job. The cutting teeth would dull fairly quickly and needed replacement frequently. The replacement process could cause enough downtime to greatly detract from the initial efficiency of the milling process itself. So manufacturers worked to hasten the replacement process as well as the durability of the cutting teeth. Later, different sized cutting drums would be offered so that machines could mill at different widths.

Next to come were controls that added precision to the milling process—controls that could handle slope, depth and speed. Now much of that has been automated.

Power, durability and precision have been combined into a mix that makes today's milling machines reflect the years of development that have taken place. A closer look at what manufacturers now offer proves the point.

The most dramatic advances in milling machines might be the controls. Most construction machines now reflect the technological advancements made in microelectronics, and milling machines are no exception. For example, both of Caterpillar's milling machines, the PM-465 and the newer PM-565B, are equipped with electronics designed to improve performance. The PM-565B, a half-lane machine, features two electronic sensors and a built-in cross slope. The sensors can read a variety of references from 12 to 55 inches directly below the bottom of the sensor. Each sensor can be calibrated and adjusted from the ground level or at the operator's console.

The position of the rotor in relation to the grade reference is constantly displayed on each sensor and on the central controller. Changes to the elevation controls include the addition of an all raise/all lower switch that is used when milling around obstacles. As with other Cat equipment, the electronic control module monitors and regulates the performance of major machine systems, including speed, steering, rotor drive and other functions. If a problem occurs, a warning is issued.

The PM-465, designed for urban applications but capable of high-production work, has a simplified grade and slope control system that provides three operating menus. The system electronically controls the depth of cut to within 0.125 inches. Like the PM-565B, the PM-465 electronically regulates speed, steering and rotor drive, plus the self-diagnostic setup.

Wirtgen also employs several technological advancements to keep its milling machines precise. Leading the list is the Tempomat cruise control. Integrated into the machine's control system, the Tempomat feature stores the speed being traveled and restores that speed at a push of a button as would be the case when changing trucks. Further, an automatic leveling system ensures that a constant milling depth is maintained. A reference area is scanned by sensors registering any changes in depth of cut, with the machine quickly compensating without overshooting. Another feature is the Wirtgen Information and Diagnostic System, WIDIS 32 for short. It constantly monitors the status of the engine and hydraulic system, visually and audibly informing the operator if anything is amiss. A monitor displays current operating data.

Along with the electronic features that keep milling machines on track are the advances being made in the cutting end of the machines. Foremost among these is the ability to change cutting drums fairly quickly to achieve multiple cutting widths with the same machine. The payoff is that a contractor needs only one machine to accomplish multiple job requirements. Again, Wirtgen has come up with a system for doing so that it calls FCS, which stands for Flexible Cutter System. It is designed so that milling drums can be changed in as little as two to three hours, says Wirtgen.

Regardless of the machine's working width, the zero edge is always located on the right-hand side of the machine. Currently, eight drum widths are available, ranging from 300 to 2,000 millimeters. Regardless of width, all drums cut to a depth of 30 centimeters, about one foot.

Another part of the FCS system is the two-part scraper plate, which has a right-hand section that is located behind the drum and seals the working area while the left-hand part runs over the existing pavement during milling work. The scraper blade is adjusted to different working widths depending on the drum width being used. The system is designed in such a way that the two parts of the scraper blade can be lifted hydraulically independent of each other, controlling the amount of material being loaded.

Roadtec adds flexibility to its machines by manufacturing and assembling the milling tractors and cutters separately, allowing the contractor to choose from several cutter patterns and widths when ordering equipment. The cutter assembly is designed for quick changing of cutting pattern styles and widths. The company also offers a drum rental program for small or short duration projects.

Roadtec machines also have the ability to mill in two different directions to accomplish different results. Traditional milling is accomplished in an up-cut direction. But Roadtec's offerings also can down-cut. According to the company, down-cutting is best used to control slabbing, permit pulverizing and mixing, and is an effective way to remove material over wet base. It also permits rear loading. The down-cutting feature can be used to easily convert Roadtec milling machines into cold-in-place recycle machines.

To reduce the amount of material contained within the housing and left in the trench, CMI Terex has an inward slant at the bottom of the front and rear cutting housing doors. This reduces the amount of cleanup required and helps keep the cutting operation working at peak performance.

Today's milling machines also reduce the time required to change the all-important cutting teeth. Early machines had the teeth welded on, so tooth replacement required a fair amount of downtime as each had to be rewelded to the drum. Now, teeth are held in variously designed bolt-on housings that permit faster changing.

Cat's PM-465
Cat's PM-465 has simplified grade and slope control system that provides three operating menus.
Cat's PM-465 has simplified grade and slope control system that provides three operating menus. On-board electronics also regulate speed, steering and rotor drive, plus self-diagnostics.
Milling machines come in various sizes, including smaller units such as this Wirtgen W 600, shown here equipped with the Rumbler II, an attachment that speeds the installation of rumble strips.
Roadtec manufactures milling tractors and cutters separately, allowing the contractor to choose from several cutter patterns and widths.
The CMI Terex PR-600 Roto-Mill features front and rear cutting housing doors that slant inward to reduce the amount of material contained within the housing and left in the trench.
Manufacturers at a Glance



Number of models: 2.

Recent changes: Higher-power engine, new elevation controls, new control console layout, modifications to hydraulic system.

Noteworthy features: PM-565B is fully hydrostatic with track system, automatic load sensing, two-speed propel, standard rubber tracks.

CMI Terex

Number of models: 8.

Noteworthy features: Inward angle of front and rear moldboards helps deliver optimum horsepower to the cut, electronically controlled engine, good weight to power ratio, electronically controlled load sensing ground drive.


Number of models: 3.

Noteworthy features: Programmable Logic Control, Cummins engines. Models range from 60 to 600 horsepower.


Number of models: 6.

New models: RX-500.

Noteworthy features: Wide range from utility to full lane, optimum balance of horsepower, productivity and economy of operation, interchangeable cutter heads for various cutting widths.


Number of models: 12.

Recent changes: W2200 has 12-foot-wide drum option, flexible cutter system.

Noteworthy features: Durability, application of horsepower to drum, application of high technology.

$231,000  Average base price, wheel-mounted milling machines.$551,700  Average base price, crawler-mounted milling machines.$196/hour  Average ownership and repair cost, wheel-mounted milling machines.$403/hour  Average ownership and repair cost, crawler-mounted milling machines. Source: "Contractors' Equipment Cost Guide," published by EquipmentWatch - 800/669-3282
Basic Specifications: Milling Machines
Manufacturer/Model Max. Width of Cut (in.) Max. Depth of Cut (in.) Crawler Or Wheel Gross Engine Power (hp) Working Speed (ft./min.) Operating Weight (lbs.)
Specifications shown here are based on information provided by Spec Check and are given here for comparison only. Specifications are subject to change and manufacturers or their distributors should be contacted for the most current information.
PM-465 79 12 CR 500 120 57,959
PM-565B 83 12 CR 625 132 85,100
CMI Terex
PR-100 14 12 WH 100 360 18,900
PR-1050 150 12 CR 800 280 120,500
PR-1200 150 15 CR 1200 264 160,300
PR-160 24 12 WH 152 360 20,000
PR-205 30 12 WH 200 360 21,400
PR-525-7 84.4 12 CR 525 106 66,750
PR-600 86 14 CR 600 158 84,000
PR-800-7 84 12 CR 800 250 76,000
PR-800-7/12 144 12 CR 800 250 83,050
PR-860 84.375 12 CR 860 308 87,500
PL 2000 S 79 12.6 CR 600 13 173,870
PL 2100 S 83 12.6 CR 600 131 74,740
PL 350 S 14 4 WH 60 82 6,174
RX-10 12 6 WH 108 95 15,900
RX-20B 40 10 WH 230 264 32,440
RX-25 52 8 CR 250 12 42,000
RX-50B 98 12 CR 600 160 74,800
RX-60B 86 12 CR 750 160 91,800
RX-60C 150 12 CR 800 155 106,720
RX-68B 98 12 CR 750 160 109,000
RX-70B 150 8 CR 800 120 110,220
RX-500  86  13  CR  500  150  58,000 
1900 Combo 48 12 CR 400 102 51,000
1900 DC 86 12 CR 400 102 54,672
1900/52 52 12 CR 400 102 52,908
1900/60 60 12 CR 400 102 53,349
2100 DC 87 12 CR 601 130 77,000
W 1000 F 40 12 WH 248 108 38,140
W 1000 FT 40 12 CR 248 108 40,785
W 1000 L 40 10 WH 164 104 31,195
W 1000 R 40 10 WH 199 96 38,802
W 1200 F 48 12 WH 248 108 41,557
W 1200 FT 48 12 CR 248 108 44,203
W 1900 86 12 CR 430 116 54,850
W 2000 86 13 CR 565 180 65,131
W 2100 86 12 CR 630 275 82,010
W 2200 87 14 CR 860 275 101,851
W 2200/3.8 150 14 CR 860 180 110,550
W 350 14 4 WH 47 66 9,700
W 500 20 6 WH 105 66 16,314
W 600 24 12 WH 164 104 27,226
Web Resources
CMI Terex