Intro to Manual MachiningFEB 2016

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Contents Machining capabilities

Tools and Tool selection

Spindle speeds and feedrates

Conventional vs. climb milling

Material removal – depth of cut guidelines

Locating a geometric reference

Tolerance capabilities

Hands-on practice!

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Manual vs. CNC Machining What can be machined?

What materials can you machine?

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Tools Endmills

◦ # of cutting edges (flutes) 2 vs. 4

◦ Material High-speed-steel (HSS) vs. Carbide

◦ Center cutting vs. non-center cutting

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Tools Surface cutters

Side cuttersFly cutter Face mill

Slit cutter Slot cutters

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Tools Edge profile tools

◦ Chamfer

◦ Countersink

◦ Round-over tools

Other Tools◦ Drills, Taps, Reamers, Engraving tools, etc

Round-over

Countersink / Chamfer

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Tool Selection Process1. Select Cutter Type What feature do you need to cut?

2. Select Cutter Flutes What material are you cutting?

3. Select Cutter Size How big of a cutter can you use?

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Spindle Speed Spindle Speed Guidelines (RPM)

Examples: ◦ Cutting aluminum with ¼” endmill

◦ RPM = 250ft/min * 4 / 0.25” = 4000 RPM

◦ Cutting plastic with 10mm endmill◦ RPM = 75m/min * 318 / 10mm = 2380 RPM

◦ Drilling a 12mm hole in mild steel◦ RPM = 30m/min * 318 / 12mm = 795 RPM

Tool Diameter [in]

Material Cutting speed[meters/minute]

Cutting speed[Feet/minute]

Aluminum 75-105 250-350

Plastics 75-110 250-400

Mild steel 30-40 100-125

Hard steel 15-18 50-60

RPM = Cutting Speed [ft/min] * 4

Tool Diameter [mm]

RPM = Cutting Speed [m/min] * 318

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Feedrate Guideline:

Practical aspect when milling manually;◦ Often no way to quantify feedrate on manual mills◦ If in doubt; Start slow and adjust as you go

Feedrate = # of cutting edges * tool chip load * RPM

Material Chip load[in/rev]

Aluminum 1.5-2.5% of tool diameter

Plastics 2.5% of tool diameter

Mild steel 0.5% of tool diameter

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Conventional vs. Climb Milling

Conventional Milling Climb Milling

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Material Removal Depth-of-Cut (DoC) guidelines

◦ If radial depth of cut > 50% of endmill diameter;◦ Max recommended axial depth of cut: 25% of diameter

◦ If radial depth of cut is < 50% of endmill diameter;◦ Axial depth of cut * radial depth of cut < 20% of diameter

◦ Max axial depth of cut < 2-4x endmill diameter◦ Beware of tool deflection and/or vibrations!

Note: For smaller milling machines, power may be a limiting factor for material removal

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Finding a reference Locating an edge, line or center point (X/Y)

Locating a surface (Z) by touching

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Tolerances Achievable tolerances

◦ Easy: +/- 0.25mm (+/- .010”)◦ Common: +/- 0.15mm (+/- .006”)◦ Doable: +/- 0.05mm (+/- .002”)

Key factors to consider;◦ Fixture and tool rigidity◦ Feeds and speeds◦ Workpiece material◦ Temperature while machining◦ Machine rigidity setup and calibration

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Advanced Machining Topics Advanced tooling geometry for a optimized cut

Advanced fixturing considerations◦ Non-flat parts, vacuum, magnetics, etc

Squaring up the vise and mill (tramming)

CNC machining…

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Process Overview1. Decide on fixturing scheme

2. Select appropriate cutter◦ Type Flute count Diameter

3. Determine speed (RPM) based on tool diameter and material

4. Setup and locate physical reference features (edges/surfaces)

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Hands-on Project Read and understand design drawing

Position part in vise

Locate edges with edge finder

Install tool, set RPM, and machine features

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Morten Steen – Founderinfo@steensolutions.comhttp://steensolutions.comhttps://twitter.com/SteenSolutionshttps://www.linkedin.com/company/steen-solutions https://www.facebook.com/STEEN-Solutions-1020658094626106