Analysis of Surface Roughness and Edge Wear of Aluminum Alloy Machining by PCD Tool

03 April 2023

PCD tool material has high hardness, good thermal conductivity, and a small friction coefficient, which reduces cutting force, slow tool wear, and a more stable cutting process, which is beneficial to reduce surface roughness. The surface of the workpiece can achieve a mirror effect during high-speed turning, and it is an ideal tool material for turning aluminum alloys. During use, attention should be paid to the surface roughness of the workpiece and the wear of the cutting edge.


PCD Inserts


The factors affecting the surface roughness of aluminum alloy workpieces are shown in Table 1:


Influencing Factors Changes Roughness Change
Feed Increase Increase
Cutting Speed Increase Stabilize after decreasing to a certain value
Depth of cut Increase Not obvious
Diamond grain size Increase Increase
The wear form of the aluminum alloy cutting edge processed by PCD tools is different from that of traditional tools, mainly manifested as adhesive wear, diffusion wear, and polycrystalline layer damage.
The characteristics are shown in Table 2:
Edge wear form Features
Adhesive wear The aluminum alloy is processed at different linear speeds, and no sticking phenomenon and built-up edge are seen with the naked eye, which is a non-main wear mode.
Diffusion wear It has excellent resistance to diffusion wear when cutting aluminum alloys, and is very suitable for processing aluminum alloys. This is a non-primary wear mode.
Polycrystalline layer damage Physical and mechanical damage, the cutting edge is impacted during the processing process to cause fine chipping or the loss of the binder causes the peeling of diamond particles to form gaps, and the damage of the polycrystalline layer will directly affect the processing accuracy and make the workpiece scrapped. Currently the leading cause of PCD wear.
PCD Tool
The main countermeasures for cutting-edge wear:
(1) Reasonable selection of PCD grades
For finishing or ultra-finishing, PCD tools with high strength, good toughness, good impact resistance, and fine particle size should be selected. Coarse-grained PCD is generally selected for rough machining.
The coarser the PCD particles, the stronger the wear resistance of the tool. On the premise of ensuring processing accuracy and quality, PCD with coarse particle size is preferred.
(2)Reasonably choose the cutting-edge form
Edge form Features Suitable for processing aluminum alloy types
Sharp angle The cutting edge is sharp and the cutting is brisk, which can significantly reduce the cutting force, improve the quality of the processed surface and reduce the formation of burrs. Low-silicon aluminum alloy finishing
Passivation Passivating the cutting edge with an R angle can significantly reduce the risk of breaking the cutting edge. Medium/high silicon aluminum alloy
Chamfer Increasing the edge angle of the blade makes it more stable, but the pressure and cutting resistance on the blade will also increase during cutting. Heavy duty cutting of high silicon aluminum alloy
PCD Insert
(3) Reasonably choose the tool angle
The leading angle of the PCD tool mainly plays the role of improving the strength of the tool and distributing the cutting force in aluminum alloy processing.
When the leading angle is small, the cutting width is long, and the force per unit cutting edge length is small; The force is reduced, the cutting is stable, the cutting thickness is increased, and the chip-breaking performance is good.
(4) Reasonable selection of tool fillets
The rounded corner of the tool is a rounded corner formed at the intersection of the main cutting edge and the secondary cutting edge of the tool.
For processing, the rounded corner enhances the strength of the tooltip. Under the same feed, the larger the fillet, the better the surface roughness.
In the case of obtaining the same processing roughness, the large radius insert can achieve low speed and high feed.
In general, the larger the fillet, the better, but due to the depth of cut and the rigidity of the workpiece and the machine tool, a matching value is required, not the bigger the better.
(5) Reasonable selection of processing parameters
In general, the cutting speed of PCD tool processing aluminum alloy is recommended to be within 4000m/min, and the hole processing speed is recommended to be within 800m/min.
If the feed rate is too large, it will increase the remaining geometric area on the workpiece, resulting in increased cutting force; if the feed rate is too small, it will increase the cutting temperature and reduce the cutting life.
Generally, the recommended feed rate is 0.08-0.15mm/ r. Increasing the depth of cut of the PCD tool will increase the cutting force and heat, which will increase tool wear and easily cause chipping.
However, too small a depth of cut will cause work hardening, accelerate tool wear, and even chipping.
In summary, when processing aluminum alloy workpieces, PCD grades should be reasonably selected, the knife type should be reasonably designed, and the correct processing parameters should be reasonably selected to make the surface finish of the processed workpieces good, reduce the wear of the tools, prolong the service life of the tools, and reduce production costs.
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