APE August 2021 | Page 18

EXPERT ADVICE
Early milling machines were simply a mining mandrel attached to a mobile undercarriage . They were designed to remove a layer of old concrete or asphalt so that a new layer could be applied to a better-quality base than resurfacing over the old road surface .
From the start , the emphasis for milling machines was to place more power to the cutting drum , which is needed to remove more material . Thus , the cutter head itself and the cutting teeth designs became critical . The cutting teeth would dull fairly quickly and needed frequent replacement . The replacement process could cause enough downtime to greatly detract from the initial efficiency of the milling process itself . So , manufacturers worked on designs for quicker replacement , as well as increased durability of the cutting teeth . Different sized cutting drums were offered so that machines could mill at different widths .
“ Knowing your milling speed along with drum speed are the two keys to ensure the best performance ,” said Austin Miller , milling and paving business development for BOMAG Americas , Ridgeway , South Carolina . “ On thin lifts you want a higher ground speed because it is normally a mill and fill job and the paver will be on your tail . With a higher ground speed you will need a faster drum speed to maintain a quality pattern . On thicker or full depth milling it is just the opposite , you will slow the ground speed down along with the drum speed so you do not burn up the cutting tools .”
Milling machines feature conveyor systems to collect the material during the milling process , thus reducing the labor of picking the material up from the roadway . Newer machines require two or more people to operate safely and efficiently . The operator stands on the deck of the machine and controls most of the machine ’ s functions , while a worker on the ground controls the depth of the cut and keeps an eye out for obstructions in the roadway , such as manholes and / or water valves .
Today ’ s machines are bigger and more technologically advanced . They are designed to handle any asphalt aggregates in use today . Depending on the depth of the cut , some of the larger machines can cut close to 15,000 square yards ( 13,000 m ²) a day , at 75 feet per minute .
“ Understanding the newer technologies and how to use them to achieve performance and quality is important ,” stated Tom Chastain , milling product manager , Wirtgen America , Antioch , Tennessee . “ Operating systems that allow the operators to simply tell the machine through the display what they are trying to achieve . Whether this be efficiency , performance , or pattern . Let the machine do the heavy lifting .
“ Even with machine technology , it still takes quality operators to achieve quality results . Every milling job is not simply cut out the material . There needs to be some finesse on certain jobs . Quality crews and the latest technologies allow these quality operators to get an even higher quality they have achieved with less work .” In addition to faster speed , added precision to the milling process has become
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