The surface roughness we often say is the micro-geometric features composed of small spacing and tiny peaks and valleys on the surface of the designated CNC machined parts. Surface roughness has an impact on the coefficient of friction, airtightness, wear resistance, corrosion resistance, fatigue strength, contact stiffness, mating properties, and thermal and electrical conductivity of custom CNC machined parts, so we need to understand the surface of custom CNC machined parts The cause of roughness and improvement measures can better improve the performance of customized CNC machining parts.
Causes and effects of surface roughness
The surface roughness of common custom CNC machined parts is mostly caused by physical factors and abnormal reasons. The irregular nicks and attachments on the surface of the custom CNC machined parts during the processing are caused by the following points :
a. Scale spines: Scale spines refer to scale-like burrs on the surface of customized CNC machined parts.
Impact: Intensified the plastic deformation of the metal layer, and reduced the surface roughness level by 2 to 4.
b. Vibration: If there is vibration during the cutting process, vibration lines will appear on the surface of the customized CNC machined parts, and the surface roughness will increase significantly.
Impact: It has a great impact on tool wear and deteriorates the surface quality of customized CNC machined parts.
C. Chip buildup: The buildup buildup is caused by the plastic flow of the chips and the external friction between the tool and the chips surpassing the internal friction during the cutting process. The cutting bottom layer and the tool are caused by the large pressure between the tool and the chips. Cold welding occurred in front.
Effects: ①It can mark longitudinal grooves; ②It will stick to the surface of customized CNC machined parts when it breaks off.
D. Other factors in addition to the above, the reasons for the rough and uneven surface of the custom CNC machined parts include: the squeeze and friction marks caused by the wear of the tool flank; the defects on the blade are reflected on the surface of the custom CNC machined parts. ; Scrap marks and scratches etc. by cutting chips.
Influence: uniform influence on coefficient of friction, airtightness, wear resistance, corrosion resistance, etc.
If you need to better understand the quality system of your partners, then you can try to find out whether they have the relevant certification of the quality system. For example: ISO9001 quality system and SGS on-site factory audit and other certifications. Because a Chinese CNC machining manufacturer does not pay attention to quality control, it is definitely not a qualified CNC machining supplier. After identifying these, you may wish to ask them to provide you with a test report before shipping, which will help you better understand whether the product meets your CNC machining requirements.
Measures to improve the surface roughness of customized CNC machining parts
1. Choose the right tool material
Due to the high affinity of the tool material and the metal molecules of the material to be processed or the material to be processed is easy to bond with the tool, built-up tumors and scales are generated, and the metal bonded on the blade is separated from the surface of the customized CNC machined part. Create additional roughness.
Therefore, the surface roughness is large if the bonding situation is serious and the friction is serious; on the contrary, the surface roughness is small.
2. Reasonable choice of cutting amount
(1) Cutting speed. Cutting speed v is an important factor affecting the surface roughness of custom CNC machined parts.
(2) Feed amount. The smaller the feed f, the lower the height of the residual surface area of ??the customized CNC machined part, and therefore, the smaller the surface roughness.
3. Improve the performance of customized CNC machining parts materials:
Generally speaking, the strength, hardness and thermal conductivity of the materials of customized CNC machining parts have a great influence on the cutting temperature. Because the unit cutting force is an important factor affecting the cutting temperature, and the strength and hardness of the customized CNC machining parts directly determine the unit cutting force, so when the strength and hardness of the workpiece material are high, more cutting heat is generated and the cutting temperature rises. high.
The better the material toughness, the greater the plastic deformation tendency, and the greater the surface roughness during cutting. Therefore, if necessary, normalizing and quenching and tempering of custom CNC machined parts should be carried out to increase the hardness, reduce plasticity and toughness. During the cutting process, the impact of built-up edge and sticky chips is small, so as to improve the material performance of the custom CNC machined parts. Effective measures to reduce the surface roughness value.
4. Reasonable selection of tool geometry parameters
(1) Front and rear corners. Appropriately increasing the rake angle of the tool makes it easy for the tool to cut into customized CNC machining parts, and the small plastic deformation is beneficial to reduce the surface roughness value.
(2) The main and auxiliary deflection angles and the radius of the tool nose arc. Reducing the tool’s main deflection angle Kr and secondary deflection angle Kr’ and increasing the tool tip arc radius rε can reduce the residual cutting area and reduce the surface roughness of customized CNC machined parts.
(3) Blade inclination. Large blade angle λs tool can significantly reduce the surface roughness of customized CNC machining parts. As the cutting edge angle λs increases, the actual working rake angle also increases.
5. Choose the right cutting fluid
The correct selection of cutting fluid can significantly reduce the surface roughness of customized CNC machining parts. Due to the cooling and lubricating effect of the cutting fluid, the interface friction during the cutting process can be reduced, and the temperature of the cutting zone can be reduced, thereby reducing the plastic deformation during the cutting process and inhibiting the growth of built-up tumors and scales. Therefore, the reduction of customized CNC machining The surface roughness of the parts is favorable.
Summarize
In this article, we briefly introduce and improve the basic knowledge of the surface roughness formation of customized CNC machining parts. The basic exploration and improvement of surface roughness are carried out, and measures and methods for customizing the surface roughness of CNC machining parts are provided.