This guide was born from the desire to be able to solve the biggest problems in turning processes, going against the operators in the sector who find themselves taken aback by some unpleasant inconveniences.
Keep reading.
Chip Management - Cause/Solution
Long chip control
Long tangled chips that wrap around the tool or workpiece. Generally due to low feed values and low and/or shallow cutting depths.
Cause
- Progress too low for the chosen geometry
Solution
- Increase progress
- Choose an insert geometry with better chip control characteristics
- Use a tool with precision coolant
Cause
- Cutting depth too low for the chosen geometry
Solution
- Increase cutting depth, or choose a geometry with better chip control characteristics
Cause
Solution
- Select a smaller nose radius
Cause
- Recording angle not suitable
Solution
- Choose an attachment with the widest possible recording angle (angle of attachment).
KAPR = 90° (PSIR = 0°)
Short chip control
Very short chips, often glued together, due to difficult chip breakage.
Difficult chip breakage often reduces tool life or results in insert breakage, due to the high chip load on the cutting edge.
Cause
- Progress too high for the chosen geometry
Solution
- Choose a geometry designed for higher feeds, preferably a single-sided insert
- Reduce progress
Cause
- Recording angle not suitable
Solution
- Choose an attachment with the smallest possible recording angle (angle of attachment).
KAPR = 45°–75° (PSIR 45–15°)
Cause
Solution
- Select a bigger nose radius
Surface finish
The surface has an irregular appearance, both to the touch and to the eye, and does not conform to the specified tolerances.
Cause
- The chips break against the component leaving marks on the finished surface
Solution
- Select a geometry which guides the chips away from the component
- Change entering angle
- Reduce depth of cut
- Select a positive tool system with a neutral angle of inclination
Cause
- Irregular surface caused by excessive notch wear of the cutting edge
Solution
- Select a grade with better resistance to oxidation wear, for example Cermet
- Reduce the cutting speed
Cause
- Feed is too high, in combination with a nose radius that is too small, a rough surface is generated
Solution
- Select a wiper insert or a larger nose radius
- Reduce feed
Burr formation
Burr formation on the workpiece when entering or exit of the workpiece.
Cause
- The cutting edge is not sharp enough
- The feed is too low for the edge roundness
Solution
- Use insert with sharp edges, PVD coated inserts or ground inserts at small feed rates, < 0.1 mm/rev
Cause
- Notch wear at depth of cut, or chipping
Solution
- Use a holder with a small entering angle
Cause
- Burr formation at the end or start of cut
Solution
- End or start the cut with a chamfer or a radius when exiting/entering the workpiece
Vibrations
High radial cutting forces due to vibrations or marks produced by vibrations caused by tools or tool assembly. Typical problems of in-house machining with boring bars.
Cause
- Unsuitable entering angle
Solution
- Select a larger entering angle (lead angle). KAPR = 90° (PSIR = 0°)
Cause
Solution
- Select a smaller nose radius
Cause
- Unsuitable edge rounding, or negative chamfer
Solution
- Select a grade with a thin coating, or an uncoated grade
Cause
- Excessive flank wear on the cutting edge
Solution
- Select a more wear resistant grade or reduce speed
Vibration
High tangential cutting forces.
Cause
- Insert geometry creating high cutting forces
- Chip breaking is too hard, producing high cutting forces
Solution
- Select a positive insert geometry
- Reduce the feed or select a geometry for higher feeds
Cause
- Cutting forces vary or are too low due to small depth of cut
Solution
- Increase the depth of cut to make the insert cut
Cause
- Tool is incorrectly positioned
Solution
Cause
- Instability in the tool due to long overhang
Solution
- Reduce the overhang
- Use the largest possible bar diameter
- Use Anti-vibration tool or a carbide bar
Cause
- Unstable clamping leads to insufficient rigidity
Solution
- Extend the clamping length of the boring bar
Insert wear
To work with optimized cutting data, obtain the best possible quality components and safeguard tool life, always check the insert/cutter after machining. For successful turning, refer to this list of causes and solutions of various forms of insert wear.
Flank wear
Preferable wear type in every application. Offers predictable and stable tool life.
Cause
- Cutting speed too high
- Too tough grade
- Insufficient wear resistance
- Hard inclusions in workpiece material
Solution
- Reduce cutting speed
- Select a more adequate quality in terms of toughness or wear resistance
Notch wear
Cause
- Sticky and/or work-hardening materials
- Use a ~90° entering angle
(~0° lead angle)
- Geometry is too negative
Solution
- Select a sharper edge
- Decrease entering angle
- Vary depth of cut
Crater wear
Cause
- Too high cutting speed and/or feed
- Chip breaker too narrow
- Chemical dissolution or abrasive wear
- Wear resistance too low
Solution
- Reduce cutting speed or feed
- Select a more wear resistant grade
- Select a more open/positive geometry
Plastic deformation
Depression Impression
Cause
- High heat load and pressure, cutting temperature too high
- Grade too tough/soft
- Lack of coolant supply
Solution
- Reduce heat and pressure load by reducing cutting speed and/or feed
- If edge depression, reduce feed first
- If flank depression, reduce speed first
- Select a more wear/heat resistant grade
- Select a more open/positive geometry
- Improve coolant supply
Built-up edge (B.U.E)
Cause
- Too low cutting temperature
- Sticky/smeary material
- Geometry too negative
- Coating too thick
Solution
- Increase cutting temperature by increasing speed
- Select a PVD-coated grade (less T. D. R. on PVD-coatings)
- Select a more positive geometry
Flaking
Cause
- Smeary material
- Cutting speed too low
- Intermittent machining with coolant
- Coating too thick
Solution
- Increase cutting speed
- Turn off coolant
- Select a grade with thinner coating and better edge line security (PVD)
Chipping on edge
Cause
- Unstable conditions
- Grade too hard/brittle
- Coating too thick (CVD, leading to edge line flaking)
Solution
- Make the machine conditions more stable
- Select a tougher grade
- Select a stronger geometry
- Select grade with thinner coating (PVD)
Thermal cracks
Cause
- Varying cutting edge temperatures
- Intermittent cuts and coolant
- Grade is sensitive to heat shock variations
- Use of grade with thicker coating (CVD)
Solution
- Switch off coolant or apply coolant copiously to obtain an even temperature level
- Decrease cutting speed
- Select grade with thinner coating (PVD)
Breakage
Cause
- Excessive wear
- Wrong choice of grade (too tough/hard)
- Wrong cutting data
Solution
- Run shorter (time in cut) operations: check how wear begins and the dominant wear type
- Change cutting data
- Select a more suitable insert grade/geometry
Slice fracture - ceramics
Cause
Solution
- Reduce feed
- Select a tougher grade
- Select an insert with a smaller chamfer, or use another geometry to change cutting force direction
Chipping outside the cutting zone
Cause
- Chip jamming because of facing towards shoulder
- The chips are deflected against the cutting edge
- Not optimized feed or feed direction
Solution
- Change operation path (to avoid facing towards shoulder)
- Change feed
- Select a PVD-coated grade
- Select an insert geometry that alters the chip flow
Conclusions
Sau with its forty years of experience can solve your problems and provide you with considerable technical support. Thanks to all this and the advanced technologies that enable its continuous growth and the possibility of offering solutions tailored to every need, it makes SAU the ideal partner for those who want to achieve excellent results in every situation.
To learn more about how to best manage your chip and how Sau can improve your manufacturing processes, contact us today.
Sau Team
SAU - Quality Tools Engineering since 1982.