Milling_Machine_Fundamentals - Use

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Milling Machine Fundamentals



Overview Safety

Shop Etiquette

Milling Machine 101

Basic Terminology

Fixturing - Work Holding

Before Machining

Indicating Calculating Feeds and Speeds

Machining

Maintenance Clean up



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



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



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.




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




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




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



Basic Terminology Coordinates

With respect to workpiece

Digital Readout (DRO)

Displays coordinates Absolute or incremental,

standard or metric

absolute

incremental



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



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



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



Basic Terminology

Power Collet ChangerMake Sure Quill Is Up

Before Using

Quill TravelDigital Readout

(DRO)

Spindle

Quill

Quill Jack (lock)



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



Basic Terminology

Tooling

Center Drill use first

Keeps holes accurately positioned

Twist Drill

Reamer

Usually pre-drill to 1/64th

under Adjustable Boring Head



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



Basic Terminology Tooling

Face Mill or Shell Mill For the rapid removal of material on

large surfaces.



Basic Terminology

Indicating

Dial indicator

Test indicator

Edge finder

Pointed edge finder forlocating a hole

Electronic Edge Finder

Plunger Back



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



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



Fixturing Work Holding Fixturing

V-blocks

Collet Fixtures

Rotary table



Fixturing Work Holding Mill Vise

Most common method used. Primarily used for flat, square or

rectangular work.



Fixturing Work Holding Parallels

Machine Ground, matched pairs. Used to raise the work above the

vise jaws for machining & drilling.Prevents damaging the vise.



Fixturing Work Holding Super Spacer

Commonly used to hold round work. 2, 3, 4, 6, 8, etc increments

360 degree increments



Fixturing Work Holding Strap Clamps

Commonly used for work to largefor a mill vise.

Mount work directly to table




Various types

Double End Strap Clamp Heel Strap Clamp

U Strap Clamp Goose Neck Strap Clamp Edge Strap Clamp

Course Pitch Heel Strap Clamp




Clamping Hardware Various Types

Step Block HD Flat Washer

Coupling Nut Clamping Stud T-Slot Bolt

Flanged Clamping Nuts




Methods of use Correct & Incorrect

Finished Surface Finished Surface

Incorrect




Methods of use Correct & Incorrect



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.



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



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.



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



Indicating Using An Edge Finder Approach edge of part slowly until the edge finder is

visibly concentric



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)



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



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!



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 !!!!!



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.



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



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.



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.



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.



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



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.



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.



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



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



Machining

Make sure nothing is tangled in cutter

Always know locations of stop andEmergency (E) - stop buttons



Maintenance Clean UP

Clean up Vacuum Chips

Vacuum (aka R2D2)

Note: Follow theonline video for more

details on cleaning themills !



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)



Maintenance Clean Up

Clean up

Always OIL these areas (ahead and behind theworktable chip/way covers) Use only Way Oil



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.



Conclusion

College Of Engineering ShopsUniversity Of Wisconsin Madison

Never be afraid to ask for helpExperience is the best way to learn!

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