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High Speed Machining
April 24, 2015
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High Speed Machining
What is it?
Very high tool rpm, small depths of cut and high feed rates
Mostly used in milling hard mold and die steels (hence term “hard milling”)
Also appears in airframe work for different reasons
Different materials (aluminum)
Used to reduce heat and material stress during machining
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High Speed Machining
Purpose?
Increase MRR
By Increasing cutting speed
Higher productivity
Lower production cost
Mainly in Automobile and Aerospace industry
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Approximate Range of
Recommended Cutting speeds (For Turning) (For Carbides and Ceramic Cutting tools)
Workpiece Material Cutting Speed (m/min)
Al alloys 200-1000
Gray CI 60-900
Cu alloys 50-700
Steels 50-500
High Temperature alloys 20-400
SS 50-300
Thermoplastics and Thermosets 90-240
Tungsten alloys 60-150
Titanium alloys 10-100
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High Speed Machining
HSS tools, cutting speed lower
Higher ranges for coated carbides and cermets
Diamond cutting tools; cutting speed higher
Depth of cuts, d: 0.5 – 12 mm
Feeds, f: 0.15 – 1 mm/rev
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What is High Speed ?
Cuttings speeds @
High Speed : 600-1800 m/min
Very High Speed : 1800-18000 m/min
Ultra High Speed : > 18000 m/min
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High Speed Machining
Value
Maximizes overall productivity – fewer process steps, faster machining
Machining Mold and Dies made of very hard materials, deep cavities and fine details typically require time consuming EDM processes
HSM produces high quality finish on milling machine – reduces need for EDM electrodes, burning and hand finishing
Challenges
How to drive HSM machines to capacity without breaking tools
Tool makers cutting data ranges from very safe to highly optimistic - “what data do we use and why doesn’t this data always work for me?”
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HSM
The first definition of HSM was proposed by Carl
Salomon in 1931
Cutting speed is 5 –10 times higher then in
conventional machining
The chip tool interface temperature decreases at
these speeds
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HSM: Temperature versus cutting speeds
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Issues with HSM
1. Selection of proper cutting tools
2. Power of machine tool
3. Machine tool stiffness and damping capacity
4. Stiffness of tool holders and work holding devices
5. Design of special spindle for high power and high rotational speeds
6. Inertia of machine tool components
7. Fast feed drives
8. Level of automation
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Hard Milling
“It is only as good as the weakest link.”
HSM - High Efficiency Hard Milling
HSM Capable
Machine Tool Cutting Tool Controller HSM capable
CAM System
Programming
Know-how
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HSM
Increasing spindle speed and feed while decreasing chip load is just the beginning step of successful high speed programming
Further understanding of the cutting action is essential (chatter, vertical engagement angle, material removal rate, effect of surface speed on the finish, etc.)
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HSM - Machine
A stable machine capable of running at high speeds
and feeds without the machine dynamics coming into
the machining equation
The cutting forces and vibration caused by the actual
contact between the tool and the material becomes
the primary action
High Speed Spindle retrofits are not High Speed
Machines
HSM Capable
Machine Tool
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HSM – Cutting Tools
Tools capable of handling very high surface
temperature
Available High Length to Diameter ratios for reaching
into intricate cavities
Tool holders capable of very low run-out at high
spindle speeds and acceleration
Dynamic v/s static run-out
Cutting Tool
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Hard Milling - Chatter
Chatter is the second most important cause of tool failure in HSM applications
It is also the most overlooked
Process for avoiding chatter
Chatter Zone
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Case Study - HSM on Connecting Rod Die
Operations required 11 7
Rest mill path 4:30 1:30
generation time
Overall Programming 6 hr 2 hr
Time
Measurement #1 #2
Improved In-process work-piece performance
Automatic cut levels in cavity milling
New Z-level Plus path to contour floors while roughing
Holder checking for multiple tools