IT 390 Midterm

Define Milling.

One of basic machining processes. Milling is a very versatile process capable of producing simple 2D flat shapes to complex 3D surface contours.

Impact of CAD/CAM

Part Geometry Complexity Variability part program Trigonometry Calculation 3D graphical display

What are some of the design considerations?

Part Size Part Shape Required Accuracy Material Type Locating Points Stability Clamping Surfaces Production Quantity Operator Fatigue Possible Automation Cutting Forces Clamping Location Efficiency

What are the types of Workholding Fixtures?

Permanent (special purpose) Modular Temporary (General i.e. vices, chucks) High Volume to Low Volume (Permanent --> Temporary)

Time to Setup Fixtures

Permanent -Fastest Modular - slowest (higher # of steps) Power fixture - moderate (requires assembly)

What are the types of Tool Holders

Pull Stud Taper V-Flange Nut

How do you calculate RPM?

RPM = C.S. x 4 / Diameter CS= cutting speed

The skill level required to operate a CNC machine is _______ compared to machinist skill for producing workpieces with conventional machine tools. a) increased b) reduced c) the same

Reduced

Rough Pass: Depth/Feed Finish Pass: Depth/Feed

Rough Pass Depth: Up to 50% of Tool Dia. Feed: Fast -.02 - .1 in/rev Finish Pass Depth:-.005" Feed: Slow - .002 - .015 in/rev

What's the difference between scallop vs stepover?

Scallop is with a ball end mill cutter

What is Manual CNC programming used for?

Simple Geometries (short 2.5D programs) Quick Modification of existing program

What are the types of Cutting Tools?

Single Point - For Turning Multiple Point - For Milling

What's the process of making a joystick?

Solidworks Mold Design Rough in SolidCAM Linear Finish in SolidCAM

Servo Control System has Two loops..what are they?

Speed Control Loops: Sensor (Tachometer) Position Control Loop: Position Sensor

Closed Loop System for Controlling Tool Movement

Speed of these motors are variable and controlled by the amount of current. The motors are connect to the spindle and the table. A position sensor continuously monitors the movement and sends back a signal to controller to make adjustments.

What are the milling cutting tool styles?

Square End Mill Ball End Mill Number of Flutes

What are the types of Vises?

Standard Swivel Angle

Machinist Vises

Standard Swivel Angle -Manual click clamping of standard shapes -special jaws for odd shape

Temporary Fixtures are used mainly for

Standard Stocks i.e. Vices, Chucks (Low Costs)

What are the types of clamps?

Strap Toggle Wedge Swing

Temporary Workholding Methods

Strap Clamps Step Blocks T-Nuts

What was the type of ATC shown in class on video?

Swing Arm

What are the three types of work holding methods?

Temporary Modular Permanent High to Low Volume (Permanent to Temp)

In CNC machine tools, the rotation of the drive motor rotates: a) the ballscrew b) the jackscrew c) the socket screw d) the set screw

The Ballscrew

What is the 3-2-1 rule?

The workpiece location must be constrained at least in three directions that are mutually perpendicular to each other. Primary Plane -Horizontal Plane Second Plane -Perpendicular to First Third Plane -Perpendicular to other two

What is 3D?

Three Dimensional Surfaces Curvatures 3 Axes may simultaneously move

Based on what was explained during demo (or from online sources), chip-to-chip tool changing time is the: Select one: a) time for a tool to remove material in form of metal chips b) time between a tool is removed from spindle and next tool is inserted in spindle c) time for a tool to move from a metal chip to another while spinning d) time between a tool leaves the part and the next tool returns to the part

Time between a tool leaves the part and the next tool returns to the part

What type of fixture is commonly used on the CNC?

Tombstone

What's the CNC Machining Anatomy?

Tool Center Large Work Envelope 3 to 5 Axes Cutting Fluid Circulating AC/DC Servomotors Enclosure Processor Network Communications

What are some benefits of ATC?

Tool Changing Speed -Less non-value added time//More productive time -Less Labor -Especially for Heavy Tools Better Organization of Tools

What are the benefits of an ATC?

Tool Changing Speed Less Labor Better Organization of Tools

What are two primary factors for CAD/CAM programs?

Tool Material Work Material Other factors: -#Flutes -Diameter of tool in milling -Diameter of workpiece in turning -Rough cutting or Finish Cutting

How do you set up Tool Length?

Tool placed in spindle. Tool tip is jogged down to the part datum Repeat for remaining tools

True or False. All cutting tools must be held in a holder that fits in the spindle.

True That's included Fixed End Mill Holders and Collet Holders.

What are the two methods for moving the axes of the machine manually? a) use of jog keys and handwheel b) use of feederate and spindle speed knobs c) use of MDI and jog keys d) any of the above

Use of Jog Keys and Handwheel

Name the type of power clamping systems.

Vacuum Magnetic Pneumatic Toe

The knowledge of conventional machining helps a CNC programmer to: a) visualize the movements of the CNC machine b) select less expensive material c) select less expensive machine d) any of the above

Visualize the movements of the CNC machine

A good analogy to what happens in a CNC program is to: a) visualize the path from the airport to a company b) visualize the mixing of chemicals in a tank c) visualize the heating of a facility d) visualize the assembly of a car e) any of the above

Visualize the path from the airport to a company

For milling machines, the axes are...

X,Y,Z linear axes X Longitudinal Move Y Move at Right Angle to X Z Tool moves Vertically

The tool is ALWAYS in the

Z-axis Around 2 to 5 axes (First 3 are linear)

The function of a tool engineer is to : a) Design Computer Software Tool b) Design Fixtures c) Design Cutting Tools d) b and c

b and c

Running M6 T8 command in MDI: a) loads tool#8 in ATC b) loads tool#8 in spindle c) loads tool#8 in spindle then in ATC d) any of the above depending on previous code

loads tool#8 in spindle

What's the formula for calculating Feed?

(in/min) F_ipm = RPM x N x F_ipr N = # of flutes F_ipr is inch/rev

To Reduce Fiction

--Use Sharp Tool w/ Proper angles --Use Coolant --Use proper speed, feed, D.O.C

What are the factors a production man must use for rating a CNC machine?

-Accuracy -Reliability -# of Controlled Axes -Ease of Maintenance -Convenient Graphical Interface -Spindle/Axis Motor Horsepower and Speeds -Dimension of Workspace -Repeatability

What are the steps of CAD/CAM-CNC Steps?

-Design Part (CAD) -Import Design to CAM -Define Stock/Setup -Create Machining Features -Simulate Toolpath -Generate NC Code

Tooling: Common Practices

-Match Tool Style with Job -Use right tool material -Use right size tool -Use right # of flutes -keep asst of tooling -use high speed steel tools -use carbide tools on difficult to cut materials -use cobalt or oxide coated tools for sp. alloys -use insert type tooling -be aware of flexing that occurs with long length tools

What are the parts of the servo motor control?

-Program -Computer -Servo Motor -Machine Movement -Feedback Loop (to the computer)

What are the Major Components of CNC Systems?

-Program -Machine Control Unit (MCU) -Machine Tool/Processing Equipment

Advantages of CAD/CAM

-Programming Complex parts in short time. -Less Human Error -Excellent 3D Graphical display -Quick Access to Tool Library -Updated Tool Crib -Automatic Operations Planning -Changing Sequence of Operations

What are some of the advantages of CAD/CAM

-Quick Access to Tool Library -Updated Tool Crib in Computer -Automatic Operations Planning/Selection --Changing sequence. -No Trig Calculation

Temporary Workholding Method

-Usually for General Purpose Applications -For immediate and short term needs -For non-repetitive low quantity orders i.e. Vises/Chucks

According to the following website, the positioning accuracy of this Haas machine is ±________. a) 0.00002" b) 0.0002" Correct c) 0.002" d) 0.020"

0.0002"

What are the objectives of using a fixture?

1. Ensuring that successive parts are held exactly and safely in the same location. (Accuracy & Safety) 2. Making operations more productive: Faster Loading/Unloading Multiple Part Holding

What is the 3-2-1 Rule?

1. Position Pin 2. Line up Pin 3. Locating Pin --for setting up a fixture

Reducing stopover by half will approximately _______ the total length of tool path.

1/2

What is the typical number of flutes? What's the difference?

2 or 4 2-Flute cutters have deeper cutting edges, allows for deeper cuts in rough cutting 4-Flute cutters have shallower cutting edges, suitable for shallow cuts in finish passes

The tool changer capacity of this Haas machine is: a) 8 b) 12 c) 14 d) 20

20

Tool changing time (chip-to-chip) of this Haas CNC machining center is_________. a) 16 s b) 9.5 s c) 3 s d) 4.5 s

4.5 s

Maximum cutting feed rate of this Haas machine is: a) 700 rpm b) 650 ipm c) 550 rpm d) 400 ipm

650 ipm

The cost per part for modular, permanent and permanent hydraulic fixtures is $_____, $_____, $______ respectively, if the number of parts per production run is 4000. (use the graph or it's adjacent data table) a) 6.9, 5.50, 5.07 b) 7.28, 7.35, 8.50 c) 7.01, 5.75, 5.80 d) 8.20, 7.20, 6.01

7.01, 5.75, 5.80

Define Workholding (Fixture)

A device fixed to the worktable of a machine and locates the work in an exact position relative to the cutting tool.

In rough machining, the main purpose is to remove...

A large amount of material at a high rate

Define Leadscrew/Ballscrew

A mechanical linear actuator that converts rotational motion to linear motion

To make sure a part is accurately located in a vise through the application of 3-2-1 concept, the machine operator must use: a) parallel bars placed between jaws b) a vise stop on the side c) a V-clamp attached to the vise d) a strap clamp attached to the vise e) any of the above

A vise stop on the side

What are the factors a production manager must use for rating a CNC machine?

Accuracy Repeatability Reliability Spindle and Axis Motor # of controlled axes Dimension of workspace Convenient Graphical Int. Ease of maintenance

Accuracy vs Repeatability

Accuracy is how closely the average size of sample group of parts cut on the machine conform to a spec. Repeatability is being able to hit the same spot over and over again

What's the difference between Accuracy and Repeatability?

Accuracy is how closely the avg size of a sample group of parts cut on the machine conform to a specification. Repeatability is being able to hit the same spot over and over again.

Tool/Fixture design process usually interacts with_______: a) Marketing b) Manufacturing c) Product design d) all of the above Correct e) only b and c

All of the above

Which of the followings is programmable almost in all CNC machine tools? a) the motion type b) the axes to move c) the amount of motion d) the motion rate e) all of the above Correct

All of the above

Define Optical Encoder

An electro-mechanical device (sensor) that converts the angular position or motion of a shaft to digital code

Optical Encoder

An electro-mechanical device (sensor) that converts the angular position or motion of a shaft to digital code

What is an ATC?

Automatic Tool Changer

What does ATC stand for?

Automatic Tool Changer -Carousel/Chain Tool Changer

Concurrent Engineering

Better than Traditional because there isn't any barriers. It's all Face to Face.

Define CAD and CAM systems.

CAD ( Computer Aided Design ) - Use of computer systems to assist in the creation, modification, analysis, or optimization of a design. CAM ( Computer Aided Manufacturing ) - Use of computer systems to plan, manage, and control the operations of a manufacturing plant through direct or indirect computer interface with plant's resources. --Direct- equipment monitoring&control --Indirect - Support Apps - planning, MRP, inventory control

Define two types of ATCs and which is better?

Carousel and Chain Tool --Chain Tool can store more tools

Cutting Directions What's the difference with climb milling and conventional (up) milling

Climb Milling is the most common option. Produces the better surface finish. Table Feed <--- Cutter Rotation --> Table Feed and Cutter Rotation at the same direction

Define DC Servo-Motors

Commonly used for Motion Control in CNC/Robotics •Accurate Positioning Capability •Easy Speed Control •High Torque Capabilities to take heavy cuts at high speeds •Compact

Managers should understand/learn CNC to: a) gain higher salaries b) operate the machines c) communicate intelligently with others d) all of the above

Communicate intelligently with others

Hardware Inaccuracies

Component Wear Sloppiness Spindle Runout Leadscrew Backlash

Define CNC

Computer Numerical Control -An automation of traditional manual machine tools by using computer hardware/software control and electrical technology. -The automation involves controlling the motion of a tool relative to workpiece to perform some type of processing

CAD and CAM

Computer-Aided Design --Direct Applications Computer-Aided Manufacturing --Indirect (Support) Applications

Name the Parts of an Electrical Control System

Control Data Source Optical Encoder DC Servo-Motors

What is 2-1/2 D?

Curves Pockets Holes Straight Lines X,Y Vary Z Kept Constant

Permanent Workholding Method

Custom made to hold single type For repetitive production Low production volume Also called Fixture

Cutting Motion and Feed Motion

Cutting Motion is Rotary Motion- CS, RPM Feed Motion is moving forward motion- ipr, ipm

According to this article which of the followings is not considered in designing a tool/fixture? a) cutting speed b) material type c) machine horsepower d) operator fatigue e) product lifetime

Cutting Speed

Name the steps for Integrated CAD/CAM-CNC Systems

Design Part (CAD) Import Design to CAM Define Stock/Setup Create Machining Features Simulate Toolpath Generate NC Code Verify

Design vs Machining Features

Design are features made by the designer CAD Machining are features to be machined CAM

An important strategy for successful tool design is to ________: a. start with focusing on just one design idea for fixturing b. develop multiple options first c. none of the above

Develop multiple options first

What is a tool stopover?

Distance between adjacent tool passes Smaller the stopover, less of a cusp

What are the four types of Milling Operations?

Face Side Pocket 3D Contouring (Surface)

What do face mill cutters do?

Facemills flatten large surfaces quickly and with an excellent finish.

True or False. To stop the axes of machines during program run, either Feedhold button or Emergency button can be pressed. Either way, the program can be continued from the same line it was stopped.

False

True or False. During demo, it was shown that for each tool used in the program, its diameter must be entered in tool register.

False

True or False. In absolute mode, if a motion mistake is made in one command all motions from the point of the mistake will also be incorrect.

False

True or False. This articles is focused on a very specific and particular type of CNC machine.

False

F-Code S-Code T-Code

Feed Rate Spindle Speed Tool ID number Understand all Operating Codes!!

How do you set up Part Program Zero (PRZ)?

Finding Z Position then Finding X and Y positions with touch paper and edge finder.

What are the types of tool holders?

Fixed End Mill Holders Collet Holders Pull Stud Taper V Flange Nut

Servo Control System Has two loops. For what?

For Control. Speed - Sensor (Tachometer) Position - Position Sensor

Modular Workholding Methods

For low to med protection Holding simple to odd shapes Can be disassembled/Reused Constructed from standard fixturing aka Flexible Fixture

Friction between tool and material....

Generates Heat --Poor Surface Finish --Wasting Energy

A cutting tool must possess certain properties ... what are some of the mechanical properties?

High Strength Hardness Toughness Wear Resistance Low Frictional Resistance Chemical Stability and Inertness

Define Jig

Holds workpiece and guides the cutting tool

What's the difference between Home Position and PRZ?

Home position is zeroing out all axes so the control knows the location of the machine home position. Part Program Zero is the point located on the part

There is a trade off between surface finish spec and production speed. How?

If the tool path is high, the production speed is limited.

The largest cost elements of building fixtures is usually related to _______: a) labor b) material c) equipment d) overhead cost

Labor

Lead screw vs Ball screw

Lead/Ball screw is a mechanical linear actuator that converts rotational motion to linear motion. Lead Screws have high friction and no recirculating elements Ballscrew allows balls to roll between the screw shaft and the nut to achieve high efficiency. required driving torque is only 1/3 of a conventional lead screw

What are the two main functions of work holding?

Locating -Orientating the workpiece relative to cutting tool Clamping -Holding the workpiece ---to hold the part firmly against locating devices ---counteract cutting forces

The tooling tolerance for a fixture locator should be __________: a) same as workpiece's tolerance b) looser than workpiece's tolerance c) tighter than workpiece's tolerance d) none of the above

Looser than workpiece's tolerance

Jig is more used in _________ machining.

Manual

MDI key (function) in CNC machines such as Haas stands for: a) Machine Data Interpolation b) Machine Display Input c) Manual Data Input d) Manual Drive Interpolation

Manual Data Input

Define Control Data Source

Microprocessor translates the part program into the appropriate electrical signals for input to motors that run the CNC machine.

Clamping Devices

Must always position so their action presses and retains the workpiece against all locators

The first rule of economic design is _________: a) use cost estimate rather than using exact cost b) brainstorm for least expensive design c) browse through catalog to find most economical tooling parts d) never build any component you can buy

Never build any component you can buy