CNC machining custom prototype surface roughness

CNC machining custom prototype surface roughness

shiny steel component rapid prototype

What is the surface roughness of CNC machining?


The surface roughness is generally formed by the machining method and other factors, such as the friction between the tool and the surface of the part during CNC machining, the plastic deformation of the surface metal during chip separation, and the high-frequency vibration in the process system. Due to different CNC machining methods and workpiece materials, the depth, density, shape and texture of the marks left on the machined surface are different.


CNC turning machining roughness

stainless steel bearing component

CNC turning is through the workpiece rotation, turning tool in the plane for linear or curved motion, in order to process the internal and external cylindrical surface, end face, conical surface, forming surface and thread of the computer CNC processing process.

(1) General CNC turning surface roughness is 1.6-0.8μm.

(2) rough turning: in the case of cutting speed without reducing the use of large cutting depth and large feed to improve efficiency, surface roughness requirements for 20-10μm.

(3) Semi-finishing turning and finishing turning: the use of small cutting speed and high speed feed, surface roughness requirements of 10-0.16μm.

(4) for high precision CNC lathe: fine grinding diamond turning tool can be high-speed precision turning non-ferrous metal workpiece, surface roughness of 0.04-0.01μm, also known as “mirror turning”.


CNC boring machining roughness

steel threaded rod

custom Stainless steel turning lathing threaded rod
Boring is an internal cutting technique that uses a boring tool to enlarge a hole or other existing circular profile. The tool used is usually a single edge boring cutter (boring bar). Suitable for semi-rough machining to finish machining.

(1) The boring accuracy of steel can reach 2.5-0.16μm.

(2) The precision of fine boring can reach 0.63-0.08μm.


CNC milling machining roughness

steel threaded custom part

CNC milling refers to the machining of stationary workpiece with rotating multi-point cutter on a computer controlled machine tool. It is suitable for machining grooves, planes, gears and special features.

(1) The general surface roughness of milling is 6.3-1.6μm.

(2) rough milling accuracy: 20-5μm.

(3) Semi-finishing milling: 10-2.5μm.

(4) Finish milling: 6-0.63μm.


Grinding CNC machining roughness

turning stainless steel drilling component

Grinding is an abrasive processing technology that uses the grinding wheel to cut off the excess material on the workpiece. It is widely used in the machinery manufacturing industry, usually for semi-finishing and finishing, and can achieve finishing and accurate cutting. The grinding can be controlled to move around the fixed workpiece.

(1) The surface roughness of grinding is generally 1.25-0.16 μm.

(2) The surface roughness of precision grinding is 0.16-0.04 μm.

(3) The surface roughness of ultra-precision grinding is 0.04-0.01μm.

(4) The surface roughness of mirror grinding is less than 0.01μm.

The surface roughness of CNC machining is closely related to the matching properties, wear resistance, fatigue strength, contact stiffness, vibration and noise of mechanical parts, and has an important influence on the service life and reliability of mechanical products. We usually label it with Ra.

Surface roughness has a great influence on the use of parts. Generally speaking, the surface roughness number is small, it will improve the quality of fit, reduce wear, prolong the service life of parts, but the cost of parts will increase. Therefore, the surface roughness should be chosen correctly and reasonably. When designing parts, the choice of surface roughness number is determined according to the role of parts in the machine.

How can we improve the surface roughness, visual performance and wear resistance of CNC machining parts?

turning milling CNC stainless steel 304 prototype

Generally speaking, IT6 is widely used in CNC machining fit index, according to the international precision tolerance division. IT6 indicates that the matching surface has high uniformity requirements, can ensure a very high matching performance, stable and reliable use, machining center can complete drilling, milling, boring, expanding, reaming, tapping and other processes.

Drilling is an important process of machining center, drilling is the basic method of processing holes, generally in the drilling machine, lathe drilling, some precision requirements are relatively high, can also use CNC machining center to complete. The drilling accuracy is not high, generally only 12.5~6.3μm, the workpiece surface roughness is generally only 12.5~6.3μm, but the subsequent semi-finishing and finishing are generally completed by reaming and reaming.

Milling is the most important machining process of CNC machining center, we can even say that all the processing of CNC machining center is carried out with milling cutter. Milling can be divided into reverse milling and forward milling according to the different feed. Cutting workpiece with rotary multi – edge tool is an efficient and common machining method. It is used for machining surface of various complex shapes such as plane, groove, etc., such as surface die. The surface roughness of the workpiece is between 0.63 and 5 microns. The precision tolerance of precision milling can reach IT16-IT8 level in general.

Boring is usually used for inner diameter machining. A CNC machining method that uses a tool to enlarge the aperture or trim the circumference of the circle, usually used to convert semi-rough machining to finishing. For steel structural parts, the boring accuracy error level can reach IT9-IT7, and the surface roughness is 2.5~0.16 micron.

Therefore, generally speaking, the surface roughness of CNC turning is 1.6-0.8μm, the surface roughness of grinding is 1.25-0.16μm and the surface roughness of milling is 6.3-1.6μm.

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