(1) Classification of mining methods and mining scale

The mining methods of bentonite ore are open pit mining and underground mining. Using open-pit mining method of Liaoning Montenegro bentonite mining, bentonite mine in Xinyang, Henan, Hebei Qinghe bentonite mine in Zhangjiakou, Xuanhua bentonite mining, mineral sika bentonite, bentonite mine in Gansu Jiuquan, Gansu Kim Chang Hung-chuen, bentonite mining, Shantai Bentonite Mine, Quxian bentonite mine, Fujian Liancheng bentonite mine, Hubei Zaoyang bentonite mine, Xinjiang Keke bentonite mine in Toksun County, Xiazizi bentonite mine in Buxel County, Xinjiang, Altayzaerba bentonite mine in Xinjiang, Shandong Weifang bentonite mine, etc. . Underground mining includes Lin'an bentonite mine in Zhejiang Province, Qiushan magnetic clay mine in Zhejiang, and Jiulong bentonite mine in Jilin. Open-pit mining accounts for 75% of production, and open-pit mining accounts for 90% of mines. The rest is underground mining.
There are two types of mining scale: one is based on ore production, and the other is based on concentrate production, see the table below.

From the current production situation, most of them are small mines. The division of mine size is usually based on ore production, but the calculation of output value, profit, etc. is based on the amount of concentrate, which is generally the case for joint ventures with mining and processing.

(2) Developing transportation

The development of open pit mining of bentonite mines generally uses road development, especially new mines. Liaoning Montenegro bentonite mine is the mid-1950s China's first batch of construction of the mine, the use of narrow roads and rail iron forge 14t motor vehicle, 762mm gauge, depression open pit mining, mine car using 3.5m 3 Dropside. Mining site geometry: surface length 900m, width 350m; bottom length 600m, width 30m; step height 10m.
The pioneering transportation of underground mining is divided according to the type of main roadway. At present, the bentonite mine has been built, and the ore body has a relatively low dip angle. It is a sloping or gently inclined deposit with a small burial depth and a scale of only 100,000 t/a. It is usually developed by inclined wells, such as Zhejiang Lin'an bentonite mine and Jilin Jiutai. Bentonite mine and Zhejiang Qiushan magnetite mine. Zhejiang Lin'an bentonite mine was developed with an inclined shaft on the upper plate. The wellbore was located at the west edge of the minefield with a dip angle of 25° and a single-wing diagonal ventilation system.

Are such issues only because of your cylindrical grinding machine?
Causes of geometry faults such as improper circularity and cylindricity as well as surface roughness could be the insufficient machine precision or the balance of grinding stones. However, in many cases, all those issues may be caused by the accuracy of the "Center Hole". 
If you feel something should be improved, please first check the accuracy of the center hole. Not only can the causes of accuracy failure be because of center hole, but the "Centering machine" and "Center Hole Grinding Machine" can be the causes, too. 

"2M8015" created by a highly precise Machining Center manufacturing technique
XINXIANG SUNRISE's machining center, well known for its excellent precision and long lifetime, is highly appreciated by world-class machine manufacturers. And "2M8015", SUNRISE's Center Hole Grinding machine, is developed by utilizing SUNRISE's designing philosophy and essences of the manufacturing technique.
2M8015 is a precise center hole grinding machine capable of grinding both center holes accurately without turning the work pieces. Delivery of 2M8015 into the market made a step forward to the future potential of extra precision cylindrical grinding machines. 

The accuracy of the center hole influences that of cylindrical grinding greatly. The grinding motion of the unique grinding stone of 2M8015 is capable of grinding the center hole into the super-accurate polygonal shape with a deviation of 2μm or less, and this can only be realized by the cutting edge technology of SUNRISE. The center hole, which is polygonal-shaped based on the three-point support principle, is in contact with the spindle stock of the cylindrical grinding machine and the center of tailstock at three points precisely and securely. This makes possible the further higher grinding accuracy using your currently available cylindrical grinding machines.

Center Hole Grinding Machine

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