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Hard TurningHard Turning
withwith CBNCBN
Advantages of replacing grinding
with Hard Turning
Reduction of Machine Tool Costs
Improvement of Productivity
Improvement of Machining Flexibility
Improvement of Machining ...
1. Reduction of Machine Tool
Costs
1)Lower Investment
2)Energy Savings
Lower Price of Equipment :Lower Price of Equipment ...
2. Improvement of
ProductivityHigh-Efficiency MachiningHigh-Efficiency Machining
Lathe = about 1/2 of grinding machine
2) ...
3. Improvement of Machining
Flexibility
1) Profile
Machining
Reduce Machining CostsReduce Machining Costs
for Various Kind...
4. Improvement of Machining
Accuracy
High Precision
Process
A
A B
B
A B
BA
Accuracy:
possible under 10µm
B
A
BA
Finishing ...
5. Reduction of Industrial Waste
Sludge to
Chips
(Environmentally-
friendly
production)
Grinding sludge disposal
Used grin...
Hard turning with CBN is a better, more cost effective solution.
FaceFace
TaperTaperSphericalSphericalI.D.(Step)I.D.(Step)...
Tooling
CBN Grinding
Roundness
Tool life
Cycle time
Tool change time
Tool cost
Labor wage
Equipment cost
Total cost
3.5µ
1...
Hard Turning withHard Turning with CBNCBN
The Characteristics of Hard Turned
Surfaces
Generally, CBN can succeed in Hard Turning in which the tolerance is
H7 and the Surface Roughness is Rmax 3.2~6.3µm [Ra 32...
Surface
Integrity*
A Typical Example
of Surface Profiles
2~12.5
[20~125]
Residual Stress
Compression
0.1mm2µm
Periodic fee...
Peak to Valley of
the Feed mark
Transcribed the shape of the cutting edge to the work.
Development of the notch wear at th...
0.2mm
0.1mm2µm
Work Chromium Molybdenum Steel
HRC60
Insert TNMA332
Conditions V=100m/min 328sfm
d=0.2mm,0.008inch
f=0.1mm/...
0.1mm[0.004inch]1m
f=0.03mm/rev.[0.0012ipr]
f=0.08mm/rev.[0.0032ipr]
f=0.12mm/rev.[0.0048ipr]
3
[30]
0.05
[0.002]
0.10
[0....
5
[50]
4
[40]
2
[20]
3
[30]
1
[10]
0 100 200 300 400 500 600
Work : O55,C55,Induction Hardened
Insert : CBN CNMA432
Condit...
The temperature
at the cutting edge of the tool is very important
After Machining
Residual Stress
Compression
Tension
Stru...
CBN can be used for hard machining without
coolant, but in grinding, the use of a coolant is
absolutely essential for tech...
The formation of tempered layers is greatly
restrained in hard turning with CBN when
compared with grinding.
Distance from...
Thermalconductivity(W/mK)
0
20
40
60
80
The thermal conductivity of CBN is much
higher than that of Ceramic & grinding too...
Work :
52100,100CrMn6(HRC60)]
Cutting Conditions :
V 120m/min (396sfm),
F 0.1mm/rev. (0.04ipr),
D 0.2mm (0.08doc), DRY
Les...
:As cut
:After cut Surfaceresidualstress
TensionCompression
Yield stress
0
A
B
A
B
displacement
Plastic deformation
Elasti...
Temperature
Distance
fromthesurface
0
Heat
Cool
Surfaceresidualstress
TensionCompression
Temperature
0
A
B
Yield stressHea...
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Replace grinding with CBN

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Economics of hard turning versus grinding

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Replace grinding with CBN

  1. 1. Hard TurningHard Turning withwith CBNCBN Advantages of replacing grinding with Hard Turning
  2. 2. Reduction of Machine Tool Costs Improvement of Productivity Improvement of Machining Flexibility Improvement of Machining Accuracy Reduction of Industrial Waste Reduction of total machining costs and ‘Environmentally-friendly’ production The Advantages of replacingThe Advantages of replacing grinding with CBNgrinding with CBN
  3. 3. 1. Reduction of Machine Tool Costs 1)Lower Investment 2)Energy Savings Lower Price of Equipment :Lower Price of Equipment : Lathe = 1/2-1/3 of a grinding machine High-Efficiency &High-Efficiency & High-Flexibility Machining :High-Flexibility Machining : Takes less machine tools Lower Electric Power ConsumptionLower Electric Power Consumption Lathe = 1/2-1/10 of a grinding machine The Advantage of Machining withThe Advantage of Machining with CBNCBN
  4. 4. 2. Improvement of ProductivityHigh-Efficiency MachiningHigh-Efficiency Machining Lathe = about 1/2 of grinding machine 2) Limited Space 1) Reduction of Cycle Time forging turning hardeninggrinding forging hardening turning grinding Grinding Allowance <<1>> <<1/3>> Productivity <<1>> <<3>> High-Flexibility Machining :High-Flexibility Machining : Reduction of tool change time Integration of several processes Reduction of machining time Reduction of Machining Space :Reduction of Machining Space : The Advantage of Machining withThe Advantage of Machining with CBNCBN
  5. 5. 3. Improvement of Machining Flexibility 1) Profile Machining Reduce Machining CostsReduce Machining Costs for Various Kind of Lots :for Various Kind of Lots : Complicated partsSmall-diameter parts Finishing for Various Kind of Parts :Finishing for Various Kind of Parts : 2) Machining for any lot size Amount of Products Machining Costs [$/pcs.] Small lot Middle lot Large lot 1000 100 10 1 Grinding Cutting The Advantage of Machining withThe Advantage of Machining with CBNCBN
  6. 6. 4. Improvement of Machining Accuracy High Precision Process A A B B A B BA Accuracy: possible under 10µm B A BA Finishing of Complicated PartsFinishing of Complicated Parts with One-Chucking :with One-Chucking : The Advantage of Machining withThe Advantage of Machining with CBNCBN
  7. 7. 5. Reduction of Industrial Waste Sludge to Chips (Environmentally- friendly production) Grinding sludge disposal Used grinding oil disposal Chip disposal (Recycle) Dry Machining with CBN:Dry Machining with CBN: Total Costs of Grinding Machine tool cost Labors wage Overhead Others Tool cost Coolant ‚q The Advantage of Machining withThe Advantage of Machining with CBNCBN
  8. 8. Hard turning with CBN is a better, more cost effective solution. FaceFace TaperTaperSphericalSphericalI.D.(Step)I.D.(Step) Grooving+Face+O.D.Grooving+Face+O.D. O.D.+FaceO.D.+Face Typical Applications of Hard Turning withTypical Applications of Hard Turning with CBNCBN
  9. 9. Tooling CBN Grinding Roundness Tool life Cycle time Tool change time Tool cost Labor wage Equipment cost Total cost 3.5µ 1000 pieces 0.17min 25min/month $0.01 piece $0.02 piece $0.02 piece $0.05piece 3.0µ 150 pieces 0.5min 231min/month $0.01 piece $0.07 piece $0.07 piece $0.15 piece An Example of Cost AnalysisAn Example of Cost Analysis for Face Machining of Hardened Steelfor Face Machining of Hardened Steel Tool Change Cost $60.00/Month $693.00/Month
  10. 10. Hard Turning withHard Turning with CBNCBN The Characteristics of Hard Turned Surfaces
  11. 11. Generally, CBN can succeed in Hard Turning in which the tolerance is H7 and the Surface Roughness is Rmax 3.2~6.3µm [Ra 32~63µinch]. There are some customers using CBN for Hard Turning in which the tolerance is H6 and the surface Roughness is Rmax 2µm [Ra 20µinch]. 12.5 [125] 6.3 [63] 1.6 [16] 3.2 [32] 0.8 [8] H6 H7 H8 13 [0.0005] 21 [0.0008] 33 [0.0013] Cutting Grinding Tolerance when diameter is Ø30mm[1.2inch] . µm[inch] SurfaceRoughness Rmax[Ra(µinch)] Tolerance Class Tolerance and SurfaceTolerance and Surface Roughness on Hard TurningRoughness on Hard Turning
  12. 12. Surface Integrity* A Typical Example of Surface Profiles 2~12.5 [20~125] Residual Stress Compression 0.1mm2µm Periodic feed mark SNCM439[AISI4340] (HRC50) CBN SNG432 V=150m/min,492sfm d=0.2mm,0.008inch f=0.1mm/rev,0.004ipr DRY SNCM439[AISI4340] (HRC50) WA60K Wheel Speed 1450m/min,4756sfm Work Rotating Speed 30m/min,98sfm d=0.015mm,0.0006inch Water Soluble Grinding ~12.5 [~125] Irregular Peak- Valley CBN Surface Roughness Rmax/µm[Ra/µInch] *dependant on the machining conditions Structural Changes Re-Hardened Layers (White Layer) and/or Tempered Layers Residual Stress Tension Structural Changes Re-Hardened Layers (Grinding Burn) and/or Tempered Layers The Characteristics of Hard Turning SurfacesThe Characteristics of Hard Turning Surfaces Machined byMachined by CBNCBN and Grindingand Grinding
  13. 13. Peak to Valley of the Feed mark Transcribed the shape of the cutting edge to the work. Development of the notch wear at the end of the cutting edge makes the surface roughness worse. Waviness Dependant on the accuracy of the spindle, feed mechanism, chucking Dependant on the rigidity of the machine, chucking, holder, work. Maximum Height = Peak to Valley of the Feed Mark + Waviness Peak to Valley of the Feed Mark Waviness Rmax Factor of the Surface RoughnessFactor of the Surface Roughness
  14. 14. 0.2mm 0.1mm2µm Work Chromium Molybdenum Steel HRC60 Insert TNMA332 Conditions V=100m/min 328sfm d=0.2mm,0.008inch f=0.1mm/rev,0.004ipr DRY 0.2mm 50mm 50mm Development of the notch wear at the end of the cutting edge makes the peak to valley of the feed mark higher. Cutting Edge and Surface RoughnessCutting Edge and Surface Roughness
  15. 15. 0.1mm[0.004inch]1m f=0.03mm/rev.[0.0012ipr] f=0.08mm/rev.[0.0032ipr] f=0.12mm/rev.[0.0048ipr] 3 [30] 0.05 [0.002] 0.10 [0.004] 0.15 [0.006] Experimental Data Theoretical Surface Roughness Work 52100,100Cr6 HRC 60 Insert CBN, DNMA432 Conditions:V=100m/min, 328stm D.O.C=0.1mm,0.004inch DRY Feed Rate mm/rev.[ipr]) SurfaceRoughness Rmax(µm)[Ra(µinch)] The accuracy of the machine and the rigidity of the tooling effects the waviness 2 [20] 1 [10] Feed Rate and Surface RoughnessFeed Rate and Surface Roughness
  16. 16. 5 [50] 4 [40] 2 [20] 3 [30] 1 [10] 0 100 200 300 400 500 600 Work : O55,C55,Induction Hardened Insert : CBN CNMA432 Conditions V=150m/min d=0.05mm, [0.002inch] f= 0.06mm/rev,[0.0024ipr] f=0.08,0.07,0.06mm/rev [ 0.0032, 0.0028, 0.0024ipr] Changing by N/C program per 10 parts Required Surface Roughness Spec. Rmax 3.2µm ,Ra 32µinch. Changing the feed rate by the N/C program improves the surface roughness, because the location of the notch changes and the notch wear decreases f=0.06mm/rev. [0.0024ipr] Constant f=0.06~0.08mm/rev [0.0024~0.032ipr] Changing by N/C. program 20 min SurfaceRoughness Rmax[Ra(µinch)] Number of parts (pcs.) How to Improve the SHow to Improve the Surface Roughnessurface Roughness
  17. 17. The temperature at the cutting edge of the tool is very important After Machining Residual Stress Compression Tension Structural Changes Tempered Layers Re-Hardened Layers (White Layers or Grinding Burn) As Hardened Compression Residual Stress Better surface integrity can be attained by optimizing cutting conditions. Mechanical stress Thermal stress Re-Hardened Mechanical Factors Thermal Factors Tempered Factor of Surface IntegrityFactor of Surface Integrity
  18. 18. CBN can be used for hard machining without coolant, but in grinding, the use of a coolant is absolutely essential for technical reasons. If structurally changed layers appear, they often reach deep into the work piece in grinding. Tempered Layer 0.1mm 1mm 0.01mm 0.01mm Re-Hardened Layer VB=0.2mm 0.01mm VB=0.06mm 0.01mm 0.01mm 0.9%C0.3%Si0.93%Mn(HRC65) Wheels:WA60Lm(Al2O3), V2370m/min(7821sfm) Work piece:v6m/min(19.8sfm), d0.08mm(0.2doc),DRY 100Cr(HRC62) V120m/min(396sfm), F0.04mm/rev.(0.02ipr), D0.2mm(0.08doc), DRY Grinding(Example)PcBN Structural ChangesStructural Changes of theof the Machined SurfaceMachined Surface
  19. 19. The formation of tempered layers is greatly restrained in hard turning with CBN when compared with grinding. Distance from the surface (mm) Work : 4340 (HRC50) 450 500 0.2 0.4 0.6 0.8 1.0 WET DRY Vickershardness (kgf/mm2 ) Distance from the surface (mm) Wheels:WA60K(Al2O3), V=1450m/min(4785sfm) Workpiece:v80m/min(264sfm), D=0.015mm(0.006doc) Grinding Vickershardness(kgf/mm2 ) 300(990sfm) 150(495sfm) 0.2(0.08doc) 0.2 0.4 0.6 0.8 1.0 450 500 450 500 450 500 Cutting speed Feed Depth of cut 50(165sfm) V(m/min) 0.025(0.01ipr) 0.1(0.04ipr) 0.3(0.12ipr) F(mm/rev.) 0.025(0.01doc) 1.0(0.4doc) D(mm) CBN Hardness of Machined SurfaceHardness of Machined Surface
  20. 20. Thermalconductivity(W/mK) 0 20 40 60 80 The thermal conductivity of CBN is much higher than that of Ceramic & grinding tool materials. Vitrified bondAl2O3CeramicsCBN 100 Turning tool Grinding tool Thermal Conductivity of Various Tool MaterialsThermal Conductivity of Various Tool Materials
  21. 21. Work : 52100,100CrMn6(HRC60)] Cutting Conditions : V 120m/min (396sfm), F 0.1mm/rev. (0.04ipr), D 0.2mm (0.08doc), DRY Less flank wear leads to higher compressive residual stress. 0.20 Residualstress(N/mm2 ) Distance from the surface (mm) 0 0.05 0.10 0.15-600 -400 -200 0 200 400 600 VB=0.15mm VB=0mm VB=0.1mm Residual Stress Distribution of Machined SurfaceResidual Stress Distribution of Machined Surface
  22. 22. :As cut :After cut Surfaceresidualstress TensionCompression Yield stress 0 A B A B displacement Plastic deformation Elastic deformation compression Cutting direction PcBN Burnishing Work piece Surface layer The Mechanism of Residual StressThe Mechanism of Residual Stress (Mechanical stress)(Mechanical stress)
  23. 23. Temperature Distance fromthesurface 0 Heat Cool Surfaceresidualstress TensionCompression Temperature 0 A B Yield stressHeat Cool Temperature Distance fromthesurface 0 Plastic deformation Tension Elastic deformation Expansion Contraction :As cut :After cut A B The Mechanism of Residual StressThe Mechanism of Residual Stress (Thermal stress)(Thermal stress)

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