The PCD tool material has high hardness, good thermal conductivity and small friction coefficient, which makes the cutting force reduced, the tool wear is slow, the cutting process is more stable, and is conducive to reducing the surface roughness. High speed turning workpiece surface can achieve mirror effect, is currently the ideal turning aluminum alloy tool material. Attention should be paid to the surface roughness and cutting edge wear of the workpiece during use.
The influencing factors on the surface roughness of aluminum alloy workpiece are shown in Table 1:
|
Influence factors |
Change |
Roughness change |
|
Feed |
increase |
increase |
|
Cutting speed |
increase |
Decrease to a certain value and then stabilize |
|
Cutting depth |
increase |
Not obvious |
|
Diamond grit |
increase |
increase |
PCD tool processing aluminum alloy cutting edge wear forms are different from traditional tools, mainly manifested as bond wear, diffusion wear and polycrystalline layer damage, its characteristics are shown in Table 2:
|
Cutting edge wear form |
characteristics |
|
Adhesion wear |
When aluminum alloy is processed at different linear speeds, there is no stick-knife phenomenon and chip accumulation, which is not the main wear mode. |
|
Diffusion wear |
When cutting aluminum alloy, it has excellent anti-diffusion wear ability and is suitable for processing aluminum alloy, which is not the main wear mode. |
|
Destory of polycrystalline layer
|
Physical and mechanical damage, the impact of the cutting edge in the process of processing leads to fine collapse or the loss of binder resulting in the spalling of diamond particles to form a gap, the occurrence of polycrystalline layer damage will directly affect the machining accuracy and scrap the workpiece. At present, it is the main cause of PCD wear. |
Main measures for cutting edge wear:
(1) Reasonable selection of PCD brand
Finishing or superfinishing, should choose high strength, good toughness, good impact resistance, fine particle size PCD tool. Coarse particle PCD is generally selected for rough machining. The coarser the PCD particle is, the stronger the abrasion resistance of the tool is. On the premise of ensuring the machining accuracy and quality, the coarse particle size PCD is preferred.
(2) Reasonable selection of cutting edge form
|
Blade form |
Characteristics |
Suitable for processing aluminum alloy |
|
Sharp Angle |
Sharp edge, cutting light, can obviously reduce the cutting force, improve the quality of the machining surface, reduce the formation of burr. |
|
|
blunt |
Passivating the cutting edge to an R Angle can significantly reduce the risk of blade fracture.
Medium/high
|
silicon aluminum alloy
|
|
chamfering |
Increasing the edge and Angle of the blade makes it more stable, but the cutting pressure and cutting resistance of the blade will also increase. |
Heavy duty cutting of high silicon aluminum alloy |
(3) Reasonable selection of tool angle
The main deflection Angle of PCD tool mainly plays a role in increasing tool strength and distributing cutting force in aluminum alloy processing. When the main deflection Angle is small, the cutting width is long and the force on the unit cutting edge length is small. The main deflection Angle increases, the radial component force decreases, the cutting is smooth, the cutting thickness increases, and the chip breaking performance is good.
(4) Reasonable selection of tool fillet
Tool fillet is a fillet formed at the intersection of the main cutting edge and the secondary cutting edge. For processing, the fillet enhances the strength of the tool tip. Under the same feed, the larger the fillet, the better the surface roughness. With the same machining roughness, the large fillet blade can achieve low speed and high feed. In general, the bigger the fillet, the better, but by the cutting depth and workpiece, machine tool rigid restrictions need to have a matching value, not the bigger the better.
(5) Reasonable selection of processing parameters
In general, PCD tool processing aluminum alloy cutting speed is recommended within 4000m/min, hole processing speed is recommended within 800m/min. If the feed is too large, the residual geometric area of the workpiece will be increased, leading to the increase of cutting force; If the feed is too small, it will make the cutting temperature rise, reduce the cutting life, the general recommended feed is 0.08-0.15mm/r. Increasing the cutting depth of PCD tool will increase the cutting force and cutting heat, which will increase the tool wear and easily cause edge collapse. But cutting depth too small will cause work hardening, accelerate tool wear and even collapse.
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