The most common applications for wide grooves or turning between shoulders are multiple grooving, plunge turning or ramping. All three methods are roughing operations and have to be followed by a separate finishing operation.
A rule of thumb is that if the width of the groove is smaller than the depth – multiple grooving should be used and vice versa for plunge turning. However for slender components ramping may be used. |
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| Multiple grooving |
Geometry GM is the first choice in this type of operation. Best tool life and swarf is obtained by using an insert width to produce full grooves first and then remove the rings. This protects the corner radius and directs the swarf into the middle of the chip breaker.
Choose ring width 0.6–0.8 x width of the insert. |
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| Multiple grooving operations. |
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| Plunge turning |
Geometries TF and TM should be used for plunge turning and ramping operations as the inserts are made for both radial and axial feeds.
Axial turning depth should not exceed 0.75 x width of the insert. |
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| Plunge turning operation. |
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| Ramping |
The ramping method is recommended to avoid vibration and minimise radial forces when machining slender components. It also gives best swarf control and reduces notch wear in advanced materials.
By using a round insert, RO or RM geometry, the feeding can be done faster, giving an even and higher productivity.
Ramping, however, does double the number of cuts required. |
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| Ramping operation. |
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| Roughing – recommended machining sequence |
| In order to generate a flat bottom and high quality on the side of the groove the following machining sequence is recommended. |
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1. | Radially infeed to required depth + 0.2 mm (max 0.75 x insert width). |
2. | Retract radially 0.2 mm. |
3. | Turn axially to opposite shoulder position. |
4. | Retract radially 0.5 mm. |
| Continue cycle until required depth is achieved.
After the roughing operation a finishing cut is required to achieve good surface finish. |
| Cycle time comparison |
Multiple grooving |
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| Direction of feed
Feed 0.2 mm/r |
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Insert width 6 mm
Depth of cut 3 mm |
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| Direction of feed
Feed - radial - 0.2 mm/r |
| Direction of feed
Feed - axial - 0.3 mm/r |
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37 sec | 68 sec
(7 passes) | 44 sec
(3 passes) |
| Finishing of grooves |
Care must be taken when machining around the bottom radius of the groove. As the insert contours around the radius, most of the movement is in the Z direction. This produces an extremely thin chip along the front cutting edge and can result in rubbing and hence vibration.
To prevent this adopt the following machining sequence – axial and radial cutting depth should be 0.5–1.0 mm. |
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Case stories
| Machining specification
Operation: Grooving
Material: Stainless steel, CMC 05.2
Machine: CNC turning lathe
Toolholder: LF123K32-2525BM
Insert: N123K2-0600-0004-TF
Grade: GC1125
| Cutting data | Competitor | Sandvik Coromant |
| Cutting speed: | 120 m/min | 150 m/min |
| Radial/axial feed: | 0.15/0.2 mm/r | 0.2/0.3 mm/r |
| Time in cut: | 0.50 min | 0.298 min |
| Components: | 156 pcs | 183 pcs |
Tool life +15%
Productivity +68%
Annual time saving 91 hours |
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