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