Bore machining on NF metals and NF alloys

Bore machining on NF metals and NF alloys

In the manufacture of components made of NF metals and alloys, in particular in fully automatic operation, polycrystalline diamond cutting tools offer great economic advantages. Alternative conventional tool designs are being used less and less frequently in these applications. PCD tools have won through in particular because a change has occurred in the cost calculation for cutting tool materials. Previously, the costs of cutting (e.g. the insert price) were considered and compared independently, but today, with the use of different cutting tool materials, the cutting tool material costs per workpiece, i.e. the machining costs, are compared in relation to each other. The advantages of PCD tools, namely the high material removal rate, long service life and thus far less frequent tool exchange, as well as the high reproducibility of machining results, play a particularly important role here.

Bore machining on NF metals and NF alloys – examples

Bore machining on NF metals and NF alloys – examples

Fine machining of tappet bores

Material Al Si 12 Cu
Machine Transfer line
Diameter mm 24 H7
Coolant Emulsion 8% 20 bar / 15 l/min / central
Spindle speed n U/min 3700
Cutting speed v m/min 280
Cut depth a mm 0.1
Feed s mm/U 0.12
Service life Per PCD cutting edge 50000 parts

Fine machining of injection pump bores

Material Al Si 12 Cu
Machine Transfer line
Diameter mm 17 H12 / 22 H7
Coolant Emulsion 9% 30 bar / 30 l/min / central
Spindle speed n U/min 2500
Cutting speed v m/min 133 - 173
Cut depth a mm 0.2
Feed s mm/U 0.15
Service life Per PCD cutting edge 150000 parts

CBN – machining examples

Internal turning and facing on hard cast material

In addition to the performance of the cutting inserts used to achieve economical rate of metal removal, the good service life properties of the cutting edges is an important factor in ensuring they do not quickly blunt, which would result in a reduction in cutting force and a greater displacement of the drill spindle, which adversely affects the geometric precision of the bore surfaces to be created. These tasks are often made more difficult by the fact that the bore surfaces have cut interruptions in the form of radial bores or axial grooves, which cause high dynamic loads on the cutting edges as well as vibrations in the system. CBN cutting inserts have also proved their worth in these applications, thanks to their good performance and service life properties.
Internal turning and facing on hard cast material – examples for CBN machining

Bearing seat, cast steel roller sleeve ( 18% Cr )

Hardness Shore C 80 – 85
Inner diameter mm 855
Bearing surface width mm 55
Spindle speed U / min
Cutting speed m /min 60
Cut depth mm 0.5 - 1.0
Feed mm / U 0.4
Indexable insert used CBN RNMN 120300 T
Service life 12 to 14 complete seats ( ~ 700 mm bearing surface !)

Cast steel part, raw, with axial groove ( G-X 165 CrMoV 12 )

Hardness HRC 60
Inner diameter mm 430 / 220
Bearing surface width mm 110
Spindle speed U / min
Cutting speed m /min 60 - 120
Cut depth mm 0.05 - 0.5
Feed mm / U 0.3 - 0.4
Indexable insert used CBN RNMN 090300 T
Service life 10 complete machinings
( significantly interrupted cut ! )

 

CBN – technical information

Particular features

Unlike PCD and diamond, CBN does not react with the carbide-formers present in these materials. The cutting heat generated is similarly not a problem for CBN, as this cutting tool material only reacts with oxygen as of a temperature of approx. 1200° C and thus has unrivalled hot hardness.
"Super-alloys” used in the building of aircraft and reactors with a marked austenitic phase and at the same time high toughnesses are areas in which CBN tools currently reach their limits. A cutting test must be used here on a case-by-case basis to clarify the situation. Typical materials of this kind include high nickel alloy materials such as Inconel 718 or Nimonic.

Basic properties

CBN, which in hardness is only surpassed by diamond, was developed to cut materials that cannot be machined with PCD or monocrystalline diamond. The main application areas here are currently iron materials with a hardness as of approx. 45 HRC, grey cast iron, Cr chilled castings and and alloys for wear parts on a cobalt, nickel or iron basis.

Manufacturing process

Cubic boron nitride ( CBN ) is a high-performance cutting tool material made of a polycrystalline mass of cubit boron nitride grain. With its high-temperature, high-pressure, sinter method, the production of CBN matches that of PCD.


CBN technical properties, comparative table

CBN technical properties, comparative table

  • Typical areas of use and applications
  • Iron materials as of 45 HRC
  • Cast steels: grey cast iron, nodular cast iron, Cr chilled castings
  • Carbides: sintered carbide (different types, trial machining usually required)
  • Sintered steels
  • Cold- and hot-work steels
  • Ball bearing and spring steels
  • Surface-hardened parts, welded-on elements and hard-facings
  • Wear parts: cobalt, nickel and iron basis

Comparative table of technical properties


PCD Mono diamond Carbide ISO – K10 Al²O³
Young's Module [Gpa] 630 1045 615 372
Modulus of shear [Gpa] 279 401 258 147
Poisson's constant 0.22 0.20 0.22 0.24
Limit tensile strength [Gpa] 0.45 2.60 1.00 0.24
Compression strength [Gpa] 2.75 8.68 4.51 4.00
Flexural strength [Gpa] 0.75 - 1.70 0.26
Knoop hardness at 20 N load [Gpa] 30 – 40 56 – 102 17.9 17
Thermal conductivity [Wm-1K-1] 100 500 – 2000 100 – 110 8.2


CBN usage parameters

CBN usage parameters

Cutting speed Vc (m/min) during turning

Material Vc (m/min) Comment
Cold- and hot-work steel 60 to 200
Lower Vc with high proportions of alloy
HSS, martensitic stainless steels 80 to 180
55
Ball bearing steel, surface-hardened steels
80 to 200 Take account of edge geometry and CBN type
Cr – chilled iron
30 to 70

Ni alloys / Co alloys
120 to 220

Grey cast iron 220 – 260 HB
500 to 800
Vc also over 800 if conditions stable

Cutting speed Vc (m/min) during milling

Material Vc (m/min)
Comment
Inner diameter It is essential to take account of stability during milling!
Milling cutter, clamping system and workpiece !
Cold- and hot-work steel
80 to 400
Lower Vc with high proportions of alloy
HSS, martensitic stainless steels
120 to 300

Ball bearing steel, surface-hardened steels
80 to 400 Take account of edge geometry and CBN type
Cr – chilled iron
30 to 150

Ni alloys / Co alloys
120 to 320

Grey cast iron 220 – 260 HB
500 to 1200 Vc also over 1200 if conditions stable

Cutting speed Vc (m/min) during milling

Material Vc (m/min)
Comment
Inner diameter It is essential to take account of stability during milling!
Milling cutter, clamping system and workpiece !
Cold- and hot-work steel
80 to 400
Lower Vc with high proportions of alloy
HSS, martensitic stainless steels
120 to 300

Ball bearing steel, surface-hardened steels
80 to 400 Take account of edge geometry and CBN type
Cr – chilled iron
30 to 150

Ni alloys / Co alloys
120 to 320

Grey cast iron 220 – 260 HB
500 to 1200 Vc also over 1200 if conditions stable

Cutting speed Vc (m/min) during millingFeed speed S (mm/u) during turning or Sz (mm/tooth) during milling

Material S (mm/U) or Sz (mm/tooth)

Comment
Cold-work steel
0.05 to 0.25

Hot-work steel
0.05 to 0.20

HSS
0.05 to 0.20

Martensitic stainless steels
0.10 to 0.30

Ball bearing steel
0.05 to 0.25
Take account of edge geometry and CBN type
Surface-hardened steels
0.05 to 0.20

Cr – chilled iron   
0.10 to 0.30 

Ni alloys / Co alloys 
0.05 to 0.25

Grey cast iron    220 – 260 HB 
0.10 to 0.40 

 

Information on standard equipment

Information on standard equipment

Information on laser chip breakers and cutting tool material types

PCD

We use PCD types on a compound basis for equipping the ISO indexable inserts and fullface inserts. An approx. 0.5 mm thick diamond layer of medium grain size is sintered onto a carbide base. These compounds are hard soldered onto the carrier indexable insert or, in the case of fullface inserts, are processed further in their original state. The cutting edge length in PCD standard inserts is 4.0 mm in the reusable version and 2.5 to 3.0 mm in the disposable version. For details, please see the relevant article descriptions. PCD is suitable for both wet and dry machining, and if the tool is configured accordingly, minimal lubrication is required.

PCD with lasered chip breakers

3 different lasered chip breakers are possible with PCD reusable inserts.
LWLS-01 F for finishing
LWLS-02 M for medium machining
LWLS-03 R for roughing

CBN

For the standard equipping of CBN cutting inserts, we use four different qualities, which differ in their application range.
Type 1: LWC – 100 This type is best suited for the roughing and medium machining of grey cast iron, nodular cast iron, singered steels, CrNi alloys and coating alloys. It is also still the first choice for all milling operations.

Type 2: LWC – 200 The first choice for fine and ultrafine machining of hardened steels, but also all other iron materials as of a hardness of approx. 45 HRC. Turning operations with a smooth cut and slightly interrupted cut.

Type 3: LWC – 250 The first choice for fine and medium machining of hardened steels, but also all other iron materials as of a hardness of approx. 45 HRC. Turning operations with slightly or averagely interrupted cut.

Type 4: LWC – 350 The first choice for fine and medium machining of hardened steels, but also all other iron materials as of a hardness of approx. 45 HRC. Turning operations with averagely or severely interrupted cut.

The cutting edge length in CBN standard inserts is 4.0 mm in the reusable version and 2.5 to 3.0 mm in the disposable version. For details, please see the relevant article descriptions.

The size of the cutting edge chamfer is 0.20 x 20° for reusable inserts and 0.15 x 15° for disposable inserts.

For both CBN types, dry machining should be aimed for to avoid heat interactions on the inserts and chemical effects from water or oil on the cutting edges.

Overmachining of steel roller

Overmachining of steel roller

The machining of rollers made of hard cast steel and cast metal materials frequently presents roller manufacturers and roller users with considerable problems, particular with regard to the removal of crusts or cast skin or surfaces with cracks, welded-on elements and hardening zones. While cutting ceramic inserts reveal their limitations in dealing with the dynamic cutting loads caused here from an interrupted cut, carbide tools permit only very slow cutting speeds to achieve realistic service lives. However, CBN cutting inserts are increasingly being used in machining tasks to ensure economical machining times on large rollers, i.e. high removal capacities coupled with a reliable machining process with as few cutting starts as possible during an overrun.

Overmachining of steel rollers – examples of roller machining

Machining of used steel rollers

Hardness Shore C 90
Inner diameter mm 420
Bearing surface width mm 1700
Spindle speed U / min 45
Cutting speed m /min 60
Cut depth mm 1.0
Feed mm / U 0.3
Indexable insert used CBN RNMN 120300 T
Service life 1700 mm in 126 min Ra = 0.6 – 1.2 µm

New chilled iron raw roller ( ~ 18 % Cr )

Hardness Shore C 80 - 85
Inner diameter mm 570
Bearing surface width mm 1700
Spindle speed U / min 17
Cutting speed m /min 30
Cut depth mm 2.7
Feed mm / U 0.3
Indexable insert used CBN RNMN 120300 T
Service life 1060 mm in 210 min


 

PCD – machining examples

PCD – machining examples

Machining of composite materials

Composite materials based on wood, plastics or fibre-reinforced materials and alloys are increasingly being used. Higher performance and quality requirements mean that tool design must also be continuously improved. These criteria are met through the more widespread use of polycrystalline diamond cutters.
The materials, fibres and fillers added during surface treatment and coating naturally result in properties that make the machining of these materials more difficult. The careful selection of the cutting tool material is an absolute prerequisite for creating an effective tool.

Machining of composite materials – examples

Milling of chamfered grooves

Material Chipboard/fibreboard Lacquered/veneered
Machine Door frame folder Special machine
Milling cutter diameter * width mm 200 * 21.5
Coolant Without
Spindle speed n U/min
Cutting speed v m/s 31.4
Cut depth a mm
Feed s mm/min 0.12
Service life Per milling cutter 320,000 linear m

Turning of GRP workpieces

Material HRC 60
Inner diameter GRP / 65% glass Filament winding
Machine
Diameter mm 54.0
Coolant Dry/air Dust suction
Spindle speed n U/min 750
Cutting speed v m/min 127
Cut depth a mm 3.0
Feed s mm/U
0.533
Removal rate 200 cm³ / min

 

PCD – technical information

Particular features

The hardness of the PCD layer is practically the same as that of monocrystalline diamond and is coupled with toughness, excellent mechanical wear resistance and high thermal conductivity. In addition, PCD is an isotropic solid with orientation-independent hardness and a wear property without cleavage planes.

Basic properties

The combination of the excellent hardness and wear properties of the diamond with the strength properties of the carbide makes PCD a cutting tool material that permits metal cutting performance up to the very limits of today's the machine tools and metal cutting systems.

Manufacturing process

Polycrystalline diamond (PCD) is a synthetically produced, extremely strong, coalesced mass of randomly oriented diamond crystals produced through the sintering of carefully selected diamond grain at very high temperatures and extremely high pressures. The sintering process, strictly controlled within the diamond-stable range, produces an extremely hard isotropic structure. PCD cutting inserts have a carbide base onto which the polycrystalline diamond layer is bonded during the sintering process.

PCD technical properties, comparative table

Typical areas of use and applications

  • Al and Al alloys
  • Non-ferrous metals: copper, brass, bronze, zink, magnesium alloys, silver, Carbide: presintered (green) carbide
  • Cast steels: grey cast iron, nodular cast iron, Cr chilled castingsPlastics and rubber
  • Plastics and rubber
  • Ceramic
  • GRP/glass fibre composite materials
  • CRP / carbon fibre composite materials

Comparative table of technical properties


PCD Mono diamond Carbide ISO – K10 Al²O³
Young's Module [Gpa] 815 1045 615 372
Modulus of shear [Gpa] 345 401 258 147
Poisson's constant 0.22 0.20 0.22 0.24
Limit tensile strength [Gpa] 1.29
2.60 1.00 0.24
Compression strength [Gpa] 7.61
8.68 4.51 4.00
Flexural strength [Gpa] 1.10 - 1.70 0.26
Knoop hardness at 20 N load [Gpa] 50 56 – 102 17.9 17
Thermal conductivity [Wm-1K-1] 560 500 – 2000 100 – 110 8.2


PCD usage parameters

PCD usage parameters

Cutting speed Vc (m/min) during turning

Material Vc (m/min) Comment
Copper
250 to 2500
Lower Vc with high proportions of alloy
HSS, martensitic stainless steels 250 to 2000
Strive for high cutting and clearance angle
Brass/bronze
200 to 1500
Strive for large wedge angle, cutting angle usually 0°
Plastics, CRP, GPR, ceramic
100 to 1200
If possible select PCD special types
Titanium
50 to 150
Take account of alloy components
Sinter – carbide
30 to 120
Dependent on carbide type and density

Cutting speed Vc (m/min) during milling

Material Vc (m/min)
Comment
Al alloys
500 to 2500
Take account of clearance angle è Feed values usually high!
Copper
200 to 2500
Strive for high cutting and clearance angle
Brass/bronze
200 to 1500
Strive for large wedge angle, cutting angle usually 0°
Plastics, CRP, GPR, ceramic
100 to 1200
If possible select PCD special types
Titanium
50 to 150
Take account of alloy components
Sinter – carbide
30 to 120
Dependent on carbide type and density

Cutting speed Vc (m/min) during milling

Material Vc (m/min)
Comment
Inner diameter It is essential to take account of stability during milling!
Milling cutter, clamping system and workpiece !
Cold- and hot-work steel
80 to 400
Lower Vc with high proportions of alloy
HSS, martensitic stainless steels
120 to 300

Ball bearing steel, surface-hardened steels
80 to 400 Take account of edge geometry and CBN type
Cr – chilled iron
30 to 150

Ni alloys / Co alloys
120 to 320

Grey cast iron 220 – 260 HB
500 to 1200 Vc also over 1200 if conditions stable
Chipboard and fibreboard
As of 2000 Take account of machine stability!

Feed speed S (mm/u) during turning

Material S (mm/U)

Comment
Al alloys
0.05 to 0.50

Copper
0.05 to 0.50

Brass/bronze
0.05 to 0.50
Bronze with max. 0.25 (tendency towards brittle fracture)
Plastics, CRP, GPR, ceramic
0.05 to 0.50 and more
Ceramic with max. 0.25 (tendency towards brittle fracture)
Titanium
0.05 to 0.25
Take account of edge geometry and CBN type
Sinter – carbide
~ 0.10

Feed speed Sz (mm/tooth) during milling

Material Sz (mm/tooth) 

Comment
Al alloys
0.05 to 0.50

Copper
0.05 to 0.50

Brass/bronze
0.05 to 0.50
Bronze with max. 0.25 (tendency towards brittle fracture)
Plastics, CRP, GPR, ceramic
0.05 to 0.50 and more
Ceramic with max. 0.25 (tendency towards brittle fracture)
Chipboard and fibreboard

Normally as of 1.0