What is the maximum machining accuracy of a machine tool？
Machining accuracy is mainly used to characterize the fineness of the product and is a term for evaluating the geometric parameters of the machined surface. The standard for measuring machining accuracy is the tolerance grade, which is 20 in total, from IT01, IT0, IT1, IT2, IT3 to IT18. Among them, IT01 indicates that the part has the highest machining accuracy, and IT18 indicates that the part has the lowest machining accuracy. General factory and mining machinery belongs to IT7 grade, and general agricultural machinery belongs to IT8 grade. According to the different functions of product parts, the machining accuracy required is different, and the selected machining form and processing technology are also different.
Turning
The workpiece rotates, and the turning tool moves in a straight line or curve in the plane. Turning is generally performed on a lathe to process the inner and outer cylindrical surfaces, end faces, conical surfaces, forming surfaces and threads of the workpiece. The turning accuracy is generally IT8-IT7, and the surface roughness is 1.6~0.8μm.
- Rough turning strives to use a large cutting depth and a large feed rate to improve the turning efficiency without reducing the cutting speed, but the processing accuracy can only reach IT11, and the surface roughness is Rα20~10μm.
- Semi-finishing and finishing turning try to use high speed and small feed rate and cutting depth, and the processing accuracy can reach IT10~IT7, and the surface roughness is Rα10~0.16μm.
- Using a finely polished diamond turning tool on a high-precision lathe to high-speed finish turning of non-ferrous metal parts can achieve a machining accuracy of IT7~IT5 and a surface roughness of Rα0.04~0.01μm. This type of turning is called "mirror turning".
Milling
Milling refers to the use of rotating multi-edged tools to cut workpieces. It is a highly efficient processing method. It is suitable for processing planes, grooves, various forming surfaces (such as splines, gears and threads) and special surfaces of molds. According to whether the main motion speed direction during milling is the same or opposite to the workpiece feed direction, it is divided into forward milling and reverse milling.
The processing accuracy of milling can generally reach IT8~IT7, and the surface roughness is 6.3~1.6μm.
1) The processing accuracy during rough milling is IT11~IT13, and the surface roughness is 5~20μm.
2) The processing accuracy during semi-finishing milling is IT8~IT11, and the surface roughness is 2.5~10μm.
3) The processing accuracy during fine milling is IT16~IT8, and the surface roughness is 0.63~5μm.
Planing
Planing is a cutting method that uses a planer to make horizontal relative linear reciprocating motion on the workpiece, mainly used for the shape processing of parts. The planing accuracy can generally reach IT9~IT7, and the surface roughness is Ra6.3~1.6μm.
1) The rough planing accuracy can reach IT12~IT11, and the surface roughness is 25~12.5μm.
2) The semi-fine planing accuracy can reach IT10~IT9, and the surface roughness is 6.2~3.2μm.
3) The fine planing accuracy can reach IT8~IT7, and the surface roughness is 3.2~1.6μm.
Grinding
Grinding refers to the processing method of using abrasives and grinding tools to remove excess material on the workpiece. It belongs to finishing and is widely used in the machinery manufacturing industry.
Grinding is usually used for semi-finishing and finishing, with an accuracy of IT8~IT5 or even higher, and the surface roughness is generally ground to 1.25~0.16μm.
1) The surface roughness of precision grinding is 0.16~0.04μm.
2) The surface roughness of ultra-precision grinding is 0.04~0.01μm.
3) The surface roughness of mirror grinding can reach less than 0.01μm.
Drilling
Drilling is a basic method of hole processing. Drilling is often performed on drilling machines and lathes, but can also be performed on boring machines or milling machines. The processing accuracy of drilling is low, generally only IT10, and the surface roughness is generally 12.5~6.3μm. After drilling, expansion and reaming are often used for semi-finishing and finishing.
Boring
Boring is a cutting process that uses a tool to enlarge the inner diameter of a hole or other circular contour. Its application range generally ranges from semi-roughing to finishing. The tool used is usually a single-edged boring tool (called a boring bar).
1) The boring accuracy of steel materials can generally reach IT9~IT7, and the surface roughness is 2.5~0.16μm.
2) The processing accuracy of precision boring can reach IT7~IT6, and the surface roughness is 0.63~0.08μm.