Chapter 21 and 22 Processes
The least expensive type of turning center is the _____. A. basic CNC lathe B. gang-tool lathe C. turret lathe D. swiss-type turning center
A
Unassigned Code
A code that can be assigned to different functions on different types of machine controllers for specialty purposes
Assigned Code
A code that has the same application or function on all machine controllers
Word Address Format
A style of programming that uses groups of letters and numbers referred to as words to program instructions for a CNC machine tool
Closed-Loop System
A system in which feedback is provided to the controlling mechanism
Open-Loop System
A system in which no feedback is provided to the controlling mechanism
Encoder
A transducer in the motor that drives a CNC axis that measures the position of the moving axis and provides electronic feedback to the controller
A basic CNC milling machine has _____ axes of movement. A. one B. two C. three D. four
C
Block
Groups of words taht are written on a single line and are meant to be executed together
M-Codes
Miscellaneous codes that control machine functions in CNC programming
Circular Interpolation
Movement in a circular or radial pattern
G-Codes
Preparatory codes that position the machining cutter
List three advantages of gang-tool lathes compared to basci CNC lathes.
Produce more parts per hour Cost is within the range of most manufacturers Allows for rapid tool changes
In CNC codes the number following the letter _____ determines the rpm of the spindle. A. G B. F C. M D. S
S
Why are the raw materials for swiss-type turning centers more expensive than for other types of turning centers?
The stock must be ground to a precise diameter before machining with the swiss-type turning center can begin
Identify two disadvantages of using basic CNC lathes.
They are not suitable for high-volume production They cannot match the capabilities of more advanced CNC machines
Automatic Tool Changer
a device included on some CNC machine tools that automatically changes and stores the tools
G90
absolute coordinates
The only differnce between CNC machines and manually operated machines is that CNC machines are _____.
automated
Minimizing _____ is critical to all CNC machines to ensure precision positioning.
backlash
Machine Control Unit
called the control, the part of a CNC machine that reads the CNC program from memory and translates it into the electronic signals needed for machine operation
G02
clockwise circular interpolation
G33
constant pitch thread cutting
G03
counterclockwise circular interpolation
Cycling all programs during setup without a part in place is called a _____
dry cycle
G21
metric programming
Once they have been activated _____ commands remain activated until another command is activated.
modal
For a basic CNC lathe, tooling changes are done by the _____.
operator
Linear Interpolation
straight-line movement
Word
In a word address format programming language, a combination of letters and numerical data
Identify three methods used to transmit machining instructions to a CNC machine
Into computer memory by entering the information through the keypad on the control Portable storage devices Networked into a company's computer systems
The positioning of the machining cutter is controlled by _____. A. G-codes B. F-codes C. M-codes D. S-codes
A
The programming method that involves typing code directly into a machine's control is_____. A. manual data input B. offline programming C. conversational language programming D. CAM programming
A
Machining Center
A CNC milling machine equipped with an automatic tool changer
Polar Coordinate System
A coordinate system in which straight-line distance and travel angle are used to specify locations or movement
Cartesian Coordinate System
A coordinate system that specifies positive and negative movement along the X, Y, and Z axes
Modal Command
A g-code command that once activated remains activated until the machine encounters another modal command in the CNC program
Horizontal Machining Center
A machining center with a spindle oriented horizontally
Coordinate System
A method of locating specific points or positions in three-dimensional space
Manual Data Input
A method of programming CNC programs by entering the program codes at the machine control unit
Servomotor
A motor that can provide feedback to a controlling mechanism
Stepper Motor
A motor that moves in small steps, or increments and does not provide feedback
Absolute Positioning
A programming mode in which the coordinate values for any point are interpreted in relation to the X0,Y0 position
Incremental Positioning
A programming mode, in which the coordinate values for any point are interpreted relative to the location of the previous point
Lead Screw
A rotating screw that translates the rotating motion of an electric motor into straight-line motion
Lockout/Tagout Procedure
A series of steps to stop equipment and remove its energy source to prevent accidental injuries while the equipment is being serviced or maintained
What happens when the G00 command is activated?
Activates the rapid travel setting for all of the positioning axes on the machine
How does color-coding a print help a programmer develop a CNC program?
Allows the programmer to readily associate tooling and processes with the colors of the features on the drawing
Why is it important for an operator to know the sequence of operations by a CNC program?
Allows you to recognize problems with the machine when it does something out of the ordinary
Conversational Language
An interface on CNC machines that allows the operator to select operations from menus
A _____ lathe has multiple tools mounted along the cross-slide. A. basic CNC lathe B. gang-tool late C. turret lathe D. machining center
B
A major drawback of the _____ is that it loses torque at high speeds A. encoder B. stepper motor C. lead screw D servomotor
B
All of the following programming methods are used to generate CNC machine code except _____. A. manual data input B. paper tape programming C. conversational language programming D. CAM programming
B
The cross slide travel on a gang-tool setup on a basic CNC lathe is usually limited to a distance of _____. A. 6" to 12" B. 12" to 18" C. 18" to 24" D. 24" to 30"
B
In addition to the pront, the programmer determines the necessary machining processes based on a review of the print and the _____. A. feed rate B. spindle speed C. condition and size of stock D. color-coding
C
Machines functions such as starting and stopping are controlled by _____. A. G-codes B. F-codes C. M-codes D. S-codes
C
The development of the minicomputer converted numerical control technology to ______. A. punched paper tape B. automated numerical control C. computer numerical control D. programmed codes
C
What are the three axes of movement in the cartesian coordiate system? A. A,B,C B. 1,2,3 C. X,Y,Z
C
Which of the following commands signals circular movement in a counterclockwise direction? A. G00 B. G02 C. G03 D. G20
C
Designed to machine cylindrical parts a _____ is basically a computer-controlled lathe.
CNC turning machine
Backlash
Clearance designed into mating threaded rods and nuts to allow movement
Dry Cycle
Cycling through all programs of a CNC machine once during setup wothoug a part in place to check for potential problems
A _____ requires an encoder to provide feedback about the position of the machine's axis to the control A. lead nut B. stepper motor C. lead screw D. servomotor
D
A major advantage of using CNC equipment of manual equipment is that it _____. A. duplicates its actions perfectly for every part B. costs less initially than the manual equipment C. is an option that can be used by even the smallest companies D. eliminates much of the variation caused by human interaction
D
Codes that have the same application no matter what control is being used are called _____. A. temporary codes B. permanent codes C. unassigned codes D. assigned codes
D
Offline Programming
Entering a program using a computer that is not currently being used to control the operation of a CNC machine
What is post-processing?
The CAM software converts the CAM program into a language that the CNC machine control unit can understand
Post-Processing
The process of translating a CAM program into a format the CNC controller can understand
Explain how a turret lathe's cross-slide and turret work together during the machining process.
The turret rotates the appropriate tool into plance and the cross-slide feeds the tool into the work piece
Identify and advantage of the advances in CNC programming
They enable machine shops to utilize CNC technologies accurately without requiring a long learning curve
Machining centers are equipped with an ______ that automatically changes and stores the cutting tools.
automatic tool changer
Least expensive to most expensive turning centers
basic CNC lathes Gang-tool lathe Turret lathes swiss-type turning centers
A single line of code is called a _____
block
G04
dwell
Every line of code that calls for a linear interpolation move should include a _____ specification.
feed rate
A swiss-type turning center uses a _____ to hold the workpiece tightly at the point of machining.
guide bushing
G20
inch programming
G91
incremental coordinates
What are the advantages of vertical machining centers compared to manual vertial milling machines?
it has the added benefit of computer control and automatic tool changing, can be equipped with additional axes of rotation
Motors drive the axes of a machine using _____.
lead screws
G01
linear interpolation
In CNC programming, straight-line movement is called _____.
linear interpolation
In order to develop a CNC program, a programmer needs a copy of a part's _____.
G00
rapid traverse
Homing
resetting to zero position
G81
simple drilling cycle
Why were many companies slow to develop numerical control technology in the 1950s?
the cost of the machines and the skills needed to operate them outweighed potential cost savings
Explain how an operator uses conversational language to create programs for a CNC milling machine.
the software converts the operator's input into standard programming code for the control, which then drives the equipment to machine the parts
If a 2D CAD file is used as the basis for programming, the programmer must specify the _____ of the part.
type and thickness
Describe one application in which using the polar coordinate system is preferable to using the cartesian coordinate system
when dimensioning a pattern of holes
What style of programming does the ANSI/EIA 274D code format use?
word address format
