Milling_Machine_Fundamentals - Use
Transcript of Milling_Machine_Fundamentals - Use
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Milling Machine Fundamentals
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Overview Safety
Shop Etiquette
Milling Machine 101
Basic Terminology
Fixturing - Work Holding
Before Machining
Indicating Calculating Feeds and Speeds
Machining
Maintenance Clean up
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Safety
Respect the machines
Common Sense
Wear safety glasses Avoid loose clothing
Restrain long hair
Never wear gloves
Never wear shorts or sandals Stay alert
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Shop Etiquette
COE Shop
Always leave machines cleaner
Ask for help, if needed
Come prepared
Tooling list
Plan of action
Dimensioned drawings Check out CNC machines in advance
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Milling Machine 101 - Introduction
The Basics
The vertical mill is one of the most commonmachines found in todays modern machine shop.
Used primarily to produce flat surfaces, they canhowever cut pockets and complex contouring.
Different from a lathe in that it cuts using arotating tool against a stationary work piece.Classified as a universal machine, in that they arecapable of a wide variety of machining operations- facing, side/end milling, drilling , boringand more.
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Milling Machine 101 - Introduction
Types Of Milling Machines
The three most common types of mills found in a machine shop of
today are: Vertical Mill Manual and CNC
The 4 mills in the Student Shop. On avertical milling machine, shown in Fig. 1,the column is the main vertical support of the machine.
The knee refers to the support underneaththe worktable. With this type of mill, a head,located at the top of the column, extendsover the workpiece. The head contains thespindle, which is perpendicular to the shopfloor. The spindle in turn holds and rotatesthe tooling.
Fig. 1
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Milling Machine 101 - Introduction
Types Of MillingMachines
Horizontal Mill
The horizontal millingmachine has a spindle that is parallel to the shop floorand an overarm that extends over the workpiece,as illustrated in Fig. 1.
The overarm supports thearbor, which holds themilling cutter. On thehorizontal mill, the arbor isthe component that rotatesthe milling cutter.
Fig. 1
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Milling Machine 101 - Introduction
Types Of Milling Machines
CNC Machining Centers The CNC machining center,
as shown in Figure 1. Thesepowerful, versatile machinesuse computers that control themovement of the tools andworkpiece. A single CNCmachine can perform multiple
cutting operations without unloading the part.
Fig. 1
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Basic Terminology Coordinates
With respect to workpiece
Digital Readout (DRO)
Displays coordinates Absolute or incremental,
standard or metric
absolute
incremental
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Basic Terminology
Mills in the shop Vertical Knee Mills(aka Bridgeport type) Quill
Worktable
Head
Spindle
Y-axis adjustment
X-axis
adjustment
Knee (z-axis) adjustment
Spindle variablespeed adjustment
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Basic Terminology Variable Speed Control
Adjust Only WhenRunning (Rotating)
Hi Low Speed Range Lever
Change Only When Off (Stopped).Rotate spindle by hand to verifythe lever is engaged before turningthe machine back on.
When operating in LOW range
the machine must be running in
Reverse so the cutter will
rotate clockwise
Quill Hand Feed Lever
Adjustable micrometerdepth stop
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Basic TerminologyOn Off
Feed Reverse SwitchForward clockwise
Reverse counter clockwise
Spindle Brake Lever
Power Collet Controls (In & Out)Draws The Tool Holder & ToolInto The Seated Position (tight)
Variable Speed Dial
Note: Make Sure Quill Is Up All The WayBefore Using The Power Collet Controls
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Basic Terminology
Power Collet ChangerMake Sure Quill Is Up
Before Using
Quill TravelDigital Readout
(DRO)
Spindle
Quill
Quill Jack (lock)
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Basic Terminology Tooling Holders
Collets R8 Split & Solid (end mill holder) End mill goes into collet, and then into themilling machine spindle.
Split Most common
Solid (end mill holder) Most Rigid
Drill Chuck
Mainly for drill bits
Usually not as accurate as a collet
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Basic Terminology
Tooling
Center Drill use first
Keeps holes accurately positioned
Twist Drill
Reamer
Usually pre-drill to 1/64th
under Adjustable Boring Head
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Basic Terminology Tooling
End mills Rouging End Mills (aka Rougher)
Finishing End Mills (aka Finisher)2 - Flute For Aluminum and Plastics4 - Flute For Steels
Ball End Mills For internal radii
And, many, many more
2 flute
4 flute
Center Cutting End MillCan Plunge Cut
Non Center Cutting End MillNO Plunge Cutting
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Basic Terminology Tooling
Face Mill or Shell Mill For the rapid removal of material on
large surfaces.
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Basic Terminology
Indicating
Dial indicator
Test indicator
Edge finder
Pointed edge finder forlocating a hole
Electronic Edge Finder
Plunger Back
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Basic Terminology
Tool Bin (Box) Ask For A Tool Bin Each
Time You Check Out Tooling.
Remember Many Of These Items Are PrecisionTools And Should Be Kept Free Of Oil And Chips Keep Them Safe And Clean
DO NOT SIT OR LEAVE Y OUR BIN ON A MACHINETO GET KNOCKED OFF.LEAVE THEM ON A BENCHOR CABINET
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Fixturing Work Holding
Various Methods Vise
Clamping Kit T-slot nuts
Flange nuts
Coupling nuts
Step blocks
Step clamps
Parallel Bars
1-2-3 & 2-4-6 Blocks
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Fixturing Work Holding Fixturing
V-blocks
Collet Fixtures
Rotary table
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Fixturing Work Holding Mill Vise
Most common method used. Primarily used for flat, square or
rectangular work.
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Fixturing Work Holding Parallels
Machine Ground, matched pairs. Used to raise the work above the
vise jaws for machining & drilling.Prevents damaging the vise.
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Fixturing Work Holding Super Spacer
Commonly used to hold round work. 2, 3, 4, 6, 8, etc increments
360 degree increments
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Fixturing Work Holding Strap Clamps
Commonly used for work to largefor a mill vise.
Mount work directly to table
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Fixturing Work Holding Strap Clamps
Various types
Double End Strap Clamp Heel Strap Clamp
U Strap Clamp Goose Neck Strap Clamp Edge Strap Clamp
Course Pitch Heel Strap Clamp
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Fixturing Work Holding Strap Clamps
Clamping Hardware Various Types
Step Block HD Flat Washer
Coupling Nut Clamping Stud T-Slot Bolt
Flanged Clamping Nuts
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Fixturing Work Holding Strap Clamps
Methods of use Correct & Incorrect
Finished Surface Finished Surface
Incorrect
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Fixturing Work Holding Strap Clamps
Methods of use Correct & Incorrect
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Before Machining
Squaring the vise1. Start at one end, lightly tighten the nut on the
same end, and zero indicator.
2. Move to other end, read indicator3. Tap one side of the vise with soft hammer until
the reading is zero.
4. Tighten nut on that side and loosen other nut.
Repeat 2 and 3. Do this until the indicatorreadout does not move.
5. Tighten both vise clamping nuts and checkagain.
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Before Machining Squaring the vise
Goal - .000 - .001movement, end to
end on back jaw Try to avoid
overcorrection:approach the goalslowly
Dial (test ) indicator
Smooth clean vise surface
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Indicating
Using an edge finder1. Insert edge finder/collet into spindle.2. Turn on mill (avoid high speeds use the 500 rpm
range).3. Approach edge of part slowly until the edge finder is
visibly concentric.4. Very slowly continue feeding the edge finder until it
just comes (breaks) off center, you have found the
edge.5. Remember You must compensate for the edgefinder tip radius when setting the DRO! Half thediameter of the edge finder tip.
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Indicating Using an edge finder
Useful for locating a straight edge
Remember to compensate for tool radius
(1/2 tool dia.)
Edge finder
Stock
Vise
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Indicating Using An Edge Finder Approach edge of part slowly until the edge finder is
visibly concentric
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Indicating Using An Edge Finder Very slowly continue feeding the edge finder until it just comes
(breaks) off center, you have found the edge Repeat and checkyour DRO Then compare to the first reading Should be the same
Remember Compensate for the tool radius (1/2 the dia. of tool)
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Indicating
Using a dial (test ) indicator1. Move stock so that axis is almost directly
under the spindle2. Ensure that indicator never loses contact
with stock or bottoms out (this involvesadjusting the indicator and holder)
3. Put mill in neutral and rotate spindle around
part slowly by hand machine off 4. Move x and y axes (split the reading) so that
indicator has consistent reading around part
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Indicating
Using a dial (test ) indicator
Useful for finding
the (.0 -.0) point of a cylindrical surface
Test indicator
Stock
V-block
Vise
NOTE: Never have a piece stick this far out of a vise For illustration only!
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Calculating Speeds and Feeds
Information Station
Use the milling machineprogram on the
Information Station Computer!
OR THE
Machinerys Handbook
Can use formulas from here tocalculate proper spindle speed andfeeds.
NOTE: Use Only As A Guide !!!!!
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Feeds and Speeds
Note:
When setting Mill speeds and feeds youmay not always want to follow the exact
recommended settings found on theInformation Station Computer or in theMachinerys Handbook.
Keep in mind that the recommendedsettings are not always the best settings.There is no exact cutting speed for millingany one material.
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Feeds and Speeds
The 3 Most Important Situational Variables That Affect The Speed andFeed Used For A Particular Job.
Set-Up Rigidity: fixturing and orclamping
Percent (%) of cutter engaged in thework, depth of cut and step over.
Chip removal and lubrication
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Feeds and Speeds
Determining Spindle Speed One of the first steps toward making a part is
determining the spindle speed for the particularoperation.
Cutting speed for milling is expressed in surfacefeet per minute (sfm).This is the distance that thecutting edge of a milling cutter travels in one minute.
When considering spindle speeds, you must also
determine the cutter's revolutions per minute(rpm). Cutting speed is affected by the cutter'sdiameter, but rpm measures the rotation of the cutterregardless of its diameter.
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Feeds and Speeds
Determining Tool Feed Feed is the most important factor used to
determine the rate of metal removal. Feed is the
rate at which the workpiece moves past the millcutter.
The depth of cut and the feed rate determinethe volume of metal removed per minute. Factorsthat determine the feed rate include the type of
cutting tool, the number of the cutter teeth, andwhether a rough cut or finish cut is required.
Machinists often take a heavy rough cut first followed at the end by a finish cut.
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Feeds and Speeds
NOTE:
Keep in mind that if you are manuallyfeeding the workpiece, you must find your
"sense of feel" for the correct feed. You should first start out slow until you
feel comfortable with increasing the speed.
Make sure the feed rate you select correctly accommodates the power of thespindle, the workholding method, and thetool diameter.
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Machining Load Tooling
End mills Spindle/Quill must be all the way
up. Insert collet line up detent screw
in spindle with collet groove. Insert end mill just past flat on end
mill shank fig. B. Push the IN collet control button
until collet draws up tight.
Fig. A
Fig. B
Collet groove
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Machining
Direction of Feed
Conventional Milling A major consideration during milling is the direction
of feed in relation to the direction of the cutterrotation.
The direction of cut is classified as eitherconventional milling or climb milling.Conventional milling feeds the cutter against the
cutter rotation. In conventional milling, the cutterscoops the material from the bottom upward in aheavier cut. This type of milling is typically used forroughing the part to size.
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Machining
Direction of Feed
Climb Milling Climb milling feeds in the same direction as the cutter
rotation. Because climb milling normally takes lightercuts when finishing, the speed is often increased andthe feed rate decreased. This causes the cutter to tryand "climb" over the top of the workpiece.
Climb milling is often used for finish cutting after a
workpiece has been roughed to size. This is thepreferred method used when milling a pocket. Most climb milling is done on CNC mills because they haverigid feeding components and no backlash as inmanual mills.
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Machining Cutting - Review
Conventional (up) milling On CNC mill, tool right
Climb (down) milling Preferred Method
On CNC mill, tool left
The cutter rotates clockwise for
both conventional and climbmilling, the difference betweenthe two has to do with how thework piece is moved withrespect to the mill bit
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Machining Cutting - Review
Conventional (up) milling For roughing cuts, or if work
piece cannot be positioned
securely On CNC mill, tool right
Climb (down) milling
For finishing cuts On CNC mill, tool left
Feed direction
Spindle rotation
Feed direction
Spindle rotation
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Machining
Make sure nothing is tangled in cutter
Always know locations of stop andEmergency (E) - stop buttons
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Maintenance Clean UP
Clean up Vacuum Chips
Vacuum (aka R2D2)
Note: Follow theonline video for more
details on cleaning themills !
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Maintenance Clean Up Clean up When Finished With The Mill
Vacuum and sweep up chips
Limit use of air hose Use only on your part whenneeded.
Never use an air hose for general cleaning of themachine or to blow under chip/way covers.
Always wipe up these
areas (ahead andbehind the worktablechip/way covers)
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Maintenance Clean Up
Clean up
Always OIL these areas (ahead and behind theworktable chip/way covers) Use only Way Oil
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Final Notes
Now, make some parts and learn to use theCNC mills in the COE shop
Ask someone who knows, or check out the user
manual Take some time and view the videos located on
our web site (www.coestudentshop.engr.wisc.edu) before starting, and then again on each mills owncomputer.
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Conclusion
College Of Engineering ShopsUniversity Of Wisconsin Madison
Never be afraid to ask for helpExperience is the best way to learn!