USER’S GUIDE Machining carbon fibre materials
Content GENERAL COMPOSITE AREA INFO 3 MATERIAL AND COMPONENTS INFO 8 HOLE AND SURFACE QUALITY 23 MACHINING STRATEGIES AND MACHINES 28 APPLICATIONS 37 PRODUCT OFFER (GEOMETRY SELECTION) 49 Holemaking Milling Grades SOLUTION/PROBLEM SOLVING Sandvik Coromant - Precorp co-branded solutions for the machining of composites are aimed at giving a wide variation of competitive products and high technical service to our customers.
GENERAL COMPOSITE AREA INFO SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 3
Composites with a focus on carbon reinforced plastic (CFRP) • Carbon fibre is being utilized at a greater scale which is increasing the demands on automated production to improve productivity. • Carbon fiber can be made to become - stronger than steel - lighter than aluminium and as stiff as titanium • Carbon fibre is commonly used to reduce the weight of the structural components on aircraft and thereby improving fuel economy, reducing emmisions and increasing carrying load.
Business environment - carbon fibre • Composites and especially carbon fibre are being utilized at a greater extent due to its benefitial properties. • Driving forces taking advantage of composite material properties are cost, environmental and technology benefits. Various industries are now using composites at a greater extent, especially in the aerospace industry.
Composites in modern aircrafts • Benefits from composite materials are especially important where weight control is critical: Aerospace industry (main focus) Materials used in 787 body Fiberglass - New aeroplane models: >50% in weight from Aluminum composites! Carbon laminate composite Carbon sandwich composite • Materials depending on application.
MATERIAL AND COMPONENTS INFO SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 7
What is composite material? Definition: engineered materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct on a macroscopic level within the finished structure • Polymer Matrix Composites (PMC’s) -The most common. Also known as FRP - Fibre Reinforced Polymers - these materials use a polymer-based resin as the matrix, and a variety of fibres such as glass, carbon and aramid as the reinforcement.
Fibre properties • Carbon fibres are characterised by: - High strength difficult to cut - High elastic modulus abrasive IM Carbon 2500 Tensile Stress (MPa) HS Carbon 2000 S-Glass 1500 Aramid 1000 E-Glass 500 0 1 2 3 Tensile Strain (%) 4 Typical Cost of ~300g/m2 Woven Fabric (£/m2) • Can be in unidirectional tapes (UD) or woven fabrics 50 45 40 35 30 25 20 15 10 5 E-Glass Roving E-Glass Yarn 7781 S-Glass Yarn 6781 Aramid HM Style 900 HS Carbon IM Carbon SANDVIK COROMANT USER’S GUIDE -
Composition: matrices (resins) • Epoxy The high-quality standard • Phenolic Fire resistant • BMI, cyanate High temperature • Polyester, Vinylester Low cost • Thermoplastic (PEEK, PEKK) High impact resistance SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 10
Fiber Orientation and Structure • Unidirectional reinforcement (UD), in which maximum strength and stiffness are obtained in the direction of the fiber Properties: - highest strength in direction of fiber orientation - bad handling features - critical machining due to high delamination risk • Planar reinforcement, two‑dimensional woven fabric Properties: - uniform strength in all directions - better handling features - lower delamination risk SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 11
Machining composites • FRPs are not homogeneous, therefore several aspects affect their machinability: • Continuous Fiber Curing Stacked materials Resin Fibre fabric Fibres Fibres volume Processing Coating Continuous fiber can be combined with virtually all resins. They are used for weaving, braiding, filament winding applications, uni-directional prepreg tapes and prepreg tow for fiber placement.
Common production methods • Prepregs - Fibres and resin come together as a “tacky” fabric - Are stacked up by hand • Injection - The dry fibres structure is injected with liquid resin - Benefitial on large components • Automatic placement: - Preimpregnated fibre tapes are placed by a CNC machine - Used on large structures SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 13
Additional features • Glass cloth - UV protection, paint preparation • Gelcoat - For surface finish, corrosion protection • Lightning strike protection (LSP) - Al or Cu mesh or foil • Paint - For aesthetics, corrosion protection, improved aerodynamics • Erosion-resistant neoprene, metal sheets • Hybrid cloth glass, Kevlar: white fibres SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 14
How to identify a material • Visual inspection: - can help to identify some features of the material Geometry Surface • Thickness • Application • Finish • Coating Resin • Colour • Appearance Fibres • Colour • Fabric SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 15
How to identify a material • Geometry can suggest the application Geometry - Thick component: - Thin component: primary structure interiors (some secondary structure, skin) From the application, composition can be predicted • Structural application Surface - High-Medium Temperature Epoxy, HS and IM fibres • Interiors - Phenolics, HS carbon fibres, Glass fibres, Aramid (Kevlar) • Non-structural applications - Low resistance resins: polyesters, vinylesters Resin Fibres SANDVIK COROMANT USER’S GU
Surface features The variation of surface layers and its properties will effect hole exit and edge quality. Therefore, the geometrical shape of the cutting tool is very important. Geometry • Glass cloth - a layer of white glassfibre - glassfibre layers can possibly generate break out problems such as splintering, although it can help limit the delamination when applied to carbon fibre exit face.
Resin identification Typically, most common composite materials, including fiberglass, carbon fiber, and kevlar, include at least two parts, the substrate and the resin. Epoxy resin is almost totally transparent when cured. In the aerospace industry, epoxy is used as a structural matrix material or as a structural glue.
Fibres identification Carbon fiber is a material consisting of extremely thin fibres about 0.005–0.010 mm in diameter. The carbon atoms inside the fibres are bonded together in microscopic crystals. There are also other fibres such as glass fibre and aramid fibres.
Stacks • FRPs are often used in stacks with aluminium or titanium - primary structural components - floor panels, for fastening • Typical compositions CFRP CFRP Al Ti Al CFRP Al CFRP Ti AL = Carbon fibre reinforced plastic = Titanium = Aluminium SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 20
Health & Safety spindel air suction • When machining, dust extraction is strongly required - For the operator safety - For the machine maintenance: carbon dust is electrically conductive: may affect electrical parts and increase wear on spindle SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 21
HOLE AND SURFACE QUALITY SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 22
Quality issues in CFRP • Quality is not easily assessed: - there is no chip to look at - roughness measurement is not significant - damage can be not visible (delamination) Tool wear on cutting edge • The main indicator is the hole quality (and tool conditions) • Delamination - Separation of the bottom layer(s) due to the “thrust” of the drill • Splintering - Residual fibres in the interior of the hole, due to poor cutting action Delamination Splintering/fraying SANDVIK COROMANT USER’S GUIDE - COMP
Hole requirements CFRP materials • In composite materials, there can be loss of hole quality long before tool failure • Therefore, the hole quality determines when the tool needs to be changed or indexed. • Typical hole quality demands Typical requirements in the aerospace field: - roughness Ra < 4.8 µm - delamination <1 mm over the diameter - no splintering - cp on hole size >1.
Hole requirements Stacked materials • Common demands - Cpk>1,33 - Ra<3,2 in carbon fibre - Ra<1,6 for Aluminium and titanium - Hole tolerance: +/- 20 µm to +/- 40 µm - No delamination or chipping in the hole exit - No chip erosion on the carbon fibre from the metallic stacked material • Dimension control - Holes are commonly pre-drilled - Finish hole size produced with one shot solution if possible - Reamer to be used when high demands on finish and size control 2 mm in from Entrance • Criteria - Chi
Increasing productivity • Increased feed and speed will improve productivity, but another more critical factor is hole quality.
MACHINING STRATEGIES AND MACHINES SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 27
Machining mechanism • Composites: brittle fracture • The fibres are shattered and cut - The force needed is much lower - The tool toughness can be lower - Coolant or lubricant are often not necessary • On the other hand, fibre hardness is extremely high - Highly abrasive • Resins are weak - Interlayer fracture → delamination - Elastic mismatch → irregular surface - Easy pull-out of fibres → enhanced splintering SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 28
Machining strategies • CFRP - Quality must be checked both at hole entry and exit: different cutting conditions may be needed. - Quality at exit is usually more difficult to achieve due to cutting forces. 10 • Stacked materials feed rate: 0.15 - Cutting speed on a stacked metallic material, such as titanium, usually needs to be lower than the CFRP. 10 - The best cutting condition, for the metallic material, may be too slow for good productivity on the composite material.
Peck cycle metalic structure Begin Cycle Begin cycle at fast approach level (FAL). Typically 2.5mm above material. Drill retracts fully to FAL between pecks. Drill CFRP until the drill point is 0.5mm (0.020”) above metallic material. Reduction of feed rate on exit reduces risk for delamination and splintering. Beging peck cycle, 1mm (0.040”) for titanium or 3mm (0.115”) for aluminium.
Machining strategies • Top and bottom surface are often different, hole quality can therefore depend on where the drill enters or exits. Hole quality issue • A coating or surface layer on the carbon fibre can change the output completely. For example: - Lightning Strike Protection (LSP): a fine or coarse copper mesh, allows for higher feed rate - Glass-cloth coating: increases the risk of delamination - Both materials can be more easily machined by chosing the correct geometry.
Machine types CNC and PKM (Parallel Kinematic Machines) • Facts - CNC controlled - Stable environment - Short tool overhang - High and stable RPM (20.
Machine types Robots • Facts - CNC controlled - Flexible solution - Short tool overhang - Holemaking primary focus - CFRP or stacked drilling - Machines with end-defector for tool localisation • Requirements - Drilling focus - Cylindrical tools possible - Carbide and PCD tooling • Common applications: - Holemaking: drilling, countersinking and reaming - Rivetting SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 33
Machine types Power feed machines • Facts - Electrical or pneumatic versions - Holemaking applications - Machinel adapted tooling - Low rpm (100-2000) - Limited flixibility in cutting data - CFRP or stacked drilling • Requirements - Drills with threaded back end - Cylindrical tools possible in tool adapters - Carbide or dedicated PCD tooling • Common applications: - Holemaking: drilling, reaming and countersinking.
Machine types Power feed and hand tools • Facts - Electrical or pneumatic versions - Holemaking - Machinel adapted tooling - Low rpm (100-2000) - Limited flixibility in cutting data - CFRP or stacked drilling • Requirements - Drills with threaded back end - Cylindrical tools - Carbide or dedicated PCD tooling SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 35
APPLICATIONS SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 36
Typical component features • Holemaking • Edging • Trimming Holemaking in carbon fibre Holemaking in carbon fibre, aluminium and titanium Surface machining Trimming Edging Edging • Faces SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 37
Application example Holemaking in CFRP • Facts and demands: - Fibre rich carbon fibre - Unidirectional - Minimal splintering of fibres - Good surface finish and dimensions - CNC machining centre • Solutions - CoroDrill 854 drill point, diameter 6.35mm - N20C diamond coating • Cutting data - VC: 150m/min - fn: 0.
Application example Holemaking in CFRP • Facts and demands: - Resin rich material - Electrical or pneumatic versions - Minimal delamination of fibres - Good surface finish and dimensions - CNC machining centre • Solutions - CoroDrill 856 drill point, diameter 6.35mm - N20C diamond coating CoroDrill 856 • Cutting data - VC: 130m/min - fn: 0.
Application example Holemaking in CFRP/AL stack • Facts and demands: - Carbon fibre and aluminium stack - Minimal splintering of fibres - Reduced burr on exit - Good surface finish and dimensions - Pneumatic power feed machine • Solutions - CoroDrill 854 drill point, diameter 9.525 mm - N20C diamond coating • Cutting data Powerfeed - VC: 60 m/min - Fn: 0.
Application example Holemaking in CFRP/Ti stack • Facts and demands: - Carbon fibre and titanium stack - Reduced burr on exit - Good surface finish and dimensions - Pneumatic power feed machine • Solutions - Sandvik Coromant - Precorp drill solution - 86PT point geometry diameter 9.525mm - CD10 diamond tipped drill CoroDrill 86PT • Cutting data - VC: 12m/min - fn: 0.
Application example Holemaking: hand drilling in CFRP • Facts and demands: - Carbon fibre - Reduced burr on exit - Good surface finish and dimensions - Hand held pneumatic machine design • Solutions - PHT hand held drill - Right hand cut drill point - Left hand helix for drill stabilization • Cutting data - VC: 60m/min - fn: 0.
Application example Holemaking: hand drilling in CFRP/AL and CFRP/Ti stack • Facts and demands: - Carbon fibre and metal stacks - Reduced burr on exit - Good surface finish and dimensions - Hand held pneumatic machine design • Solutions - CMD: drilling of CFRP and metallic stacks - CMDP: drilling of pre drilled CFRP and metallic stacks CMD • Cutting data CFRP/Aluminum - VC: 118m/min - fn: 0.05mm/rev CMDP CFRP/Titanium - VC: 20m/min - fn: 0.
Application example Edging of carbon fibre • Facts and demands: - Primary structure carbon fibre - High material removal rates - Minimal splintering of fibres - Good surface finish and dimensions • Solutions - CoroMill 390 - Cutter: R390-032A32-11H - Diamond coated inserts (enginnered solution) • Cutting data - VC: 200m/min - Fz: 0.
Application example Sturtz milling: profiling of carbon fibre • Facts and demands: - Tilting of tool 2-10 degrees - High rpm and feed rate - Primary structure carbon fibre - Hand held pneumatic machine design - 2D and 3D feature solutions - Good surface finish and dimensions • Solutions - CoroMill 390 - Cutter: R390-032A32-11H - CD10 PCD inserts (3mm modied radii) • Cutting data - Vf: 1800 mm/min - 2mm depth of cut. - 5 degree sturtz angle. - fz: 0.
Ball end scanning Vs Sturtz • 32mm diameter tools used with the same cutting data. Tool 32mm Ball Surface Speed (M/min) RPM Feed/ Tooth (mm/min) Table feed (mm/min) No of flutes Step over (mm) Passe / Sq Metre Time for 1 Sq Metre 32mm Sturtz 2011 2011 20000 20000 0.12 0.12 12000 12000 5 5 3.52 11 284 91 23.7 7.6 Over 3 times faster generating the surface. • Typical to use smaller ball end tools resulting in even greater productivity when switching to Sturtz techniques.
Application example Surface machining of carbon fibre CoroMill Century • Facts and demands: - Primary structure carbon fibre - Minimal splintering of fibres and delamination - Good surface finish and dimensions • Solutions - CoroMill Century with PCD inserts - Cutter: R590-04C3-11M - Inserts: R590-1105H-PS2-NL CD10 • Cutting data - Cutting speed: 300m/min - Fz: Roughing: 0.16 / Finishing: 0.1mm/tooth - Ap: Roughing: 2.5mm / Finishing: 0.
Application example Edging of carbon fibre • Facts and demands: - Carbon fibre skin - Minimal splintering - Good surface: Ra value of 1.25 μm • Solutions - CoroMill Plura engineered solutions - 1: Diamond coated carbide cutter - 2: PCD brazed cutter - Cutter diameter 10mm with 2 cutting edges • Cutting data - Speed: 10.000 rpm, tabel feed: 3200mm/min - Fz: Roughing: 0.03 – 0.08mm/tooth - Fz: Finishing: 0.02 – 0.
PRODUCT OFFER SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 49
Product solutions Machine type Operation Material Solution Hand drill Drilling CFRP PHT Hand drill Drilling CFRP/AL/Ti CMD-P Hand drill Chamfer CFRP Countersink Power feed Drilling CFRP CD 854, 856, 85 Power feed Drilling CFRP/AL/Ti 86PT CNC machine Drilling CFRP CD 854, 855, 856, 85 CNC machine Drilling CFRP/AL/Ti 86 CNC machine Edging CFRP Plura PCD/N20C CNC machine Surface machining CFRP CM 590/390 PCD SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 50
CoroMill Century Product solutions • Standard products Holemaking - CoroDrill 854 and 856 composite geometries - Milling CoroMill Century and CoroMill 390 CoroDrill 854 CoroDrill 856 • TailorMade products - Holemaking CoroDrill 854, 855 and 856 (dimensions, grades) CoroDrill 854 CoroDrill 855 CoroDrill 856 • Engineered solutions Holemaking - PCD drills, reamers and countersink tools - Milling PCD milling cutters Diamond coated milling cutters CoroDrill PCD SANDVIK COROMANT USER’S GUIDE - COMPO
Product offer drilling CNC – automated machine • CFRP - Fibre rich material - Allround geometry - Resin rich material CoroDrill 854 CoroDrill 855/85 geometry CoroDrill 856 Carbide / PCD Carbide / PCD Carbide / PCD CoroDrill 854 86A geometry Carbide / PCD PCD 86B geometry PCD • CFRP/Aluminium - Carbon fibre stack - Carbon fibre stack • CFRP/Titanium - Carbon fibre stack *Carbide tools available as uncoated or with N20C, diamond coating.
Product offer drilling Power feed machine • CFRP - Fibre rich material - Allround geometry - Resin rich material CoroDrill 854 CoroDrill 855/85 geometry CoroDrill 856 Carbide* / PCD Carbide* / PCD Carbide* / PCD CoroDrill 854 86PT geometry Carbide* / PCD PCD • CFRP/Aluminium/ Titanium - Carbon fibre stack - Carbon fibre stack *Carbide tools available as uncoated or with N20C, diamond coating.
Product offer drilling Hand tool • CFRP - Fibre rich material PHT geometry Carbide* CMD geometry CMDP geometry Carbide* Carbide* Counter sink PCD • CFRP/Aluminium/ Titanium - Carbon fibre stack - Carbon fibre stack • CFRP/Titanium - Carbon fibre *Carbide tools available as uncoated or with N20C, diamond coating.
Product offer edging/slotting CNC – automated machine • CFRP - Carbon fibre CoroMill Plura Carbide* - Carbon fibre CoroMill Plura PCD - Carbon fibre Compression router Carbide* - Carbon fibre CoroMill Plura - ball nose PCD *Carbide tools available as uncoated or with N20C, diamond coating.
Product offer edging/slotting CNC – automated machine • CFRP - Carbon fibre CoroMill 590 PCD - Carbon fibre CoroMill 390 PCD *Carbide tools available as uncoated or with N20C, diamond coating.
CoroDrill grades Grade comparison • N20C, Solid Carbide with Diamond coating - Low friction coefficient - Stable hole dimensions - Cost efficient - Not regrindable • N30C, Solid Carbide with Diamond like carbon coating - Thin wear resistant coating - Limited life, lower tool cost.
Geometry selection guidelines Material usage & curing temperature CFRP Material CD 854 CD 855 or 85/85C CD 856 Cutting conditions Primary 0 0 0 0 X - X X X MS LF MS MF MS LF Thermoplastic - X X LS MF With glass skin - X MS LF With LSP X X MS HF - (medium-high T epoxy) - Low temperature Epoxy - Non structural skin (Epoxy-Phenolic) X X = recommended 0 = acceptable - = not recommended MS = medium speed LF = low feed MF = medium feed HF = high feed SANDVIK COROMANT USER’S GUIDE - COMPO
Geometry selection guidelines CFRP stacked material Material CD 854 86PT* CD 856 (for power feed and unstable CNC) (For stable CNC) Aluminium stack X X X Titanium stack - X X - X X Ti/AL stack X = recommended 0 = acceptable - = not recommended SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 59
SOLUTION/PROBLEM SOLVING SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 60
Cutting data • Tipycally: - speed 60-120 m/min - feed rate 0.02-0.15 mm/rev • PCD allows for higher feed and sometimes speed • With positive geometries high feed rate must be avoided (>0.1mm/rev) • Low feed rate reduces delamination, especially at the hole exit • High speed can melt/damage the resin (especially thermoplastics) • Diamond coated and PCD drills have a higher thermal conductivity, which results in reduced effects on hole dimension variation.
Machining strategies Problem Solution Delamination • Reduce feed rate • Consider a change in geometry Splintering • Consider a more positive geometry • Increase speed • Increase feed rate Poor tool life • Consider a different grade • Consider a less positive geometry Poor quality on a coated material • Consider drilling from the opposite side Disparity of quality on entry and exit • Consider variable feed rate SANDVIK COROMANT USER’S GUIDE - COMPOSITE SOLUTIONS 62
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