Optimizing cutting tool technology has a major influence on the productivity and economics of a process. Right cutting tool design and grinding or insert allow higher cutting speed, feed and depth of cut, produce parts of consistent quality and provide predictable long tool lives.
20% increase in the material removal rate could reduce the total cost per component in machining by 15%. Hence, industrial engineers in their productivity engineering of processes can develop and evaluate multiple alternative tool designs and materials to select the best material and tool design. Along with the tool design, tool holder design or selection is also important to use the higher speeds.
The issues of cutting tool materials are discussed in detail in:
Cutting Tools for Machine Tools - Cost Reduction Opportunities
At present, turning is most commonly carried out using indexable inserts. Proper selection of inserts and tool holder is required for the best performance.
The following parameters must be selected for inserts:
1. Insert material and grade
2. Insert shape
3. Insert size
4. Insert thickness
5. Corner geometry (nose radius or flat)
6. Groove (chipbreaker) geometry
7. Edge preparation
8. Edge clamping/holding method
9. Lead, rake, relief, and inclination angles
In selection of insert and toolholder for a given operation, the following factors determine technical feasibility and economic benefit.
1. Type of operation (roughing, finishing, etc.)
2. Continuous versus interrupted cut
3. Workpiece material and primary manufacturing. process used to produce the workpiece (casting, forging, etc.)
4. Condition of the machine tool
5. Required tolerance
6. Feeds and speeds
Insert Shape
The shape of an insert is specified by the first letter of the insert designation.
Available insert shapes include diamond (C), octagon, round (R), square (S), triangle (T), and trigon (W). SNGA-532 represents a square insert, and a TPGT-322 is a triangular insert.
Insert Shapes and Included Angle
https://www.sandvik.coromant.com/en-gb/knowledge/general-turning/pages/how-to-choose-correct-turning-insert.aspx
The shape of an insert largely determines its strength, its number of cutting edges, and its cost. Round inserts provide maximum edge strength and are therefore a good choice for roughing operations. They also provide a maximum number of effective cutting edges since they can be rotated (or indexed) through small angles when a given edge wears out. Round inserts thin the chip, however, and generate high radial forces; as a result, they should not be used when chatter or instability are expected, or when tight tolerances are required.
Square inserts are common in many applications because they provide good edge strength and a large number of cutting edges (8 for a negative rake tool, 4 for a positive rake). A 80° diamond insert is very versatile because it performs turning with 90° shoulder and facing operations. Generally, the largest included angle suitable for the workpiece geometry should be used. As a general rule, an insert becomes stronger and dissipates heat more rapidly as its included angle is increased. The selection of the included angle is limited by the part configuration, the required tolerances, the workpiece material, and the amount of material to be removed. Insert shape selection involves a trade-off between strength and versatility.
Round inserts offer advantages for the machining of cobalt chromium and titanium implants. In internal turning of the spherical cup in a ball and socket hip joint, round inserts offer a more productive roughing process. They double productivity and reduce tooling costs by a third.
In roughing applications the round shape imparts a strong cutting edge and excellent resistance to excessive notch wear. Choosing round inserts gives secure, quality, reliable machining. It increases life of tool, results in fewer tool changes and trouble free machining.
Applying a round insert with an approach angle of less than κr 45º significantly reduces notch wear, a common problem which leads to an inferior quality component and a reduction in productivity.
Increase feed and speed for maximum productivity: By using a round insert with the depth of cut below the radius, the chip thickness hex is reduced relative to feed and the cutting edge length increased. This results in lower temperatures being generated and the opportunity to increase both feed and speed for maximum production.
Machining specification
Operation: Internal sphere turning, dia = 35 mm
Material: Cobalt chromium F75
Machine: CNC Turning lathe
Cutting data: Current Round (Sandvik Coromant)
Toolholder: A20M-SRXDR 08-R
Insert: VBMT11T308 R300-0828E-PL
Grade: GC1030
Cutting speed: 30 50 (m/min)
Feed: 0.08 0.1 (mm/rev)
Depth of cut: 0.5 0.5 (mm)
Time in cut per comp: 9.29 4.46 (min)
https://www.sandvik.coromant.com/en-gb/industrysolutions/medical/advancesinmedicine/pages/default.aspx#:~:text=Key%20Benefits&text=Applying%20a%20round%20insert%20with,changes%20and%20trouble%20free%20machining.
https://azcarbide.com/advantages-of-round-carbide-inserts
Turning Tool
At present, turning is most commonly carried out using indexable inserts. Proper selection of inserts and tool holder is required for the best performance.
Indexable Inserts
The following parameters must be selected for inserts:
1. Insert material and grade
2. Insert shape
3. Insert size
4. Insert thickness
5. Corner geometry (nose radius or flat)
6. Groove (chipbreaker) geometry
7. Edge preparation
8. Edge clamping/holding method
9. Lead, rake, relief, and inclination angles
In selection of insert and toolholder for a given operation, the following factors determine technical feasibility and economic benefit.
1. Type of operation (roughing, finishing, etc.)
2. Continuous versus interrupted cut
3. Workpiece material and primary manufacturing. process used to produce the workpiece (casting, forging, etc.)
4. Condition of the machine tool
5. Required tolerance
6. Feeds and speeds
Insert Shape
The shape of an insert is specified by the first letter of the insert designation.
Available insert shapes include diamond (C), octagon, round (R), square (S), triangle (T), and trigon (W). SNGA-532 represents a square insert, and a TPGT-322 is a triangular insert.
Insert Shapes and Included Angle
https://www.sandvik.coromant.com/en-gb/knowledge/general-turning/pages/how-to-choose-correct-turning-insert.aspx
The shape of an insert largely determines its strength, its number of cutting edges, and its cost. Round inserts provide maximum edge strength and are therefore a good choice for roughing operations. They also provide a maximum number of effective cutting edges since they can be rotated (or indexed) through small angles when a given edge wears out. Round inserts thin the chip, however, and generate high radial forces; as a result, they should not be used when chatter or instability are expected, or when tight tolerances are required.
Square inserts are common in many applications because they provide good edge strength and a large number of cutting edges (8 for a negative rake tool, 4 for a positive rake). A 80° diamond insert is very versatile because it performs turning with 90° shoulder and facing operations. Generally, the largest included angle suitable for the workpiece geometry should be used. As a general rule, an insert becomes stronger and dissipates heat more rapidly as its included angle is increased. The selection of the included angle is limited by the part configuration, the required tolerances, the workpiece material, and the amount of material to be removed. Insert shape selection involves a trade-off between strength and versatility.
Round Inserts - Benefits
Round inserts offer advantages for the machining of cobalt chromium and titanium implants. In internal turning of the spherical cup in a ball and socket hip joint, round inserts offer a more productive roughing process. They double productivity and reduce tooling costs by a third.
In roughing applications the round shape imparts a strong cutting edge and excellent resistance to excessive notch wear. Choosing round inserts gives secure, quality, reliable machining. It increases life of tool, results in fewer tool changes and trouble free machining.
Applying a round insert with an approach angle of less than κr 45º significantly reduces notch wear, a common problem which leads to an inferior quality component and a reduction in productivity.
Increase feed and speed for maximum productivity: By using a round insert with the depth of cut below the radius, the chip thickness hex is reduced relative to feed and the cutting edge length increased. This results in lower temperatures being generated and the opportunity to increase both feed and speed for maximum production.
Doubling of Productivity by Using Round Inserts - An illustration
Reduction in tooling costs by a third.Machining specification
Operation: Internal sphere turning, dia = 35 mm
Material: Cobalt chromium F75
Machine: CNC Turning lathe
Cutting data: Current Round (Sandvik Coromant)
Toolholder: A20M-SRXDR 08-R
Insert: VBMT11T308 R300-0828E-PL
Grade: GC1030
Cutting speed: 30 50 (m/min)
Feed: 0.08 0.1 (mm/rev)
Depth of cut: 0.5 0.5 (mm)
Time in cut per comp: 9.29 4.46 (min)
https://www.sandvik.coromant.com/en-gb/industrysolutions/medical/advancesinmedicine/pages/default.aspx#:~:text=Key%20Benefits&text=Applying%20a%20round%20insert%20with,changes%20and%20trouble%20free%20machining.
https://azcarbide.com/advantages-of-round-carbide-inserts
News Related to Cutting Tools
2016
Insert ISO nomenclature - the details, and what's important
01 April, 2016
This blog is written by Dasarathi GV, Director-Applications, Cadem Technologies Pvt. Ltd.
https://www.cnctimes.com/editorial/insert-iso-nomenclature-the-details-and-whats-important-1
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