CNC Flashcards
a method for automating the control of machine tools through the use of software embedded in a microcomputer attached to the tool.
Computer numerical control (CNC)
international standard language
G-code
were built in the 1940s and 1950s by Prof. John T. Parson
NC machines
a method of automatically operating a manufacturing machine based on a code of letters, numbers and special characters.
Numerical Control
converts written instruction into a corresponding hole pattern.
Tape punch
reads the hole pattern on the tape and converts the pattern to corresponding electrical signal code.
Tape reader
receives the electrical signal code from the tape reader and subsequently causes the NC machine to respond.
Controller
responds to programmed signals from the controller.
NC machine
It is a NC machine with the added feature of an onboard computer. The onboard computer is often referred to as the Machine Control Unit (MCU).
Computer Numerical Control
generates, stores and processes CNC programs.
Machine Control Unit
responds to programmed signals from the MCU and manufacture the part
NC machine
An alphanumeric character or punctuation marks
Programming Character
A letter that describes the meaning of numerical value following the address
Addresses
Composed of an address and a number
Word
Is a complete line of information to a CNC machine.
Blocks
Is a sequence of blocks that describe in detail the motions a CNC machine is to execute in order top manufacture a part. The MCU execute the program block by block.
Programs
Different types of system control
Fanuc
Allen-Bradley
GE
Okuma
Bendix
Mazak
Others
They cause the tool to move to a point on the part and execute an operation at that point only.
Point-to-point control movement
They cause the tool to maintain continuous contact with the part as the tool cut contour shape.
Continuous path tool movement
Is a mathematical method of approximating the true or exact position required to follow a pre-calculated path.
Interpolation
send electrical signals to drive motor controllers and receives some form of electrical feedback from the motor controllers.
loop system
utilizes stepping motors to create machine movements
open loop system
Special motor called servos are used for executing machine movements in __________
Closed Loop System
All ballscrews have some “slop” or _________ at assembly that causes errors when the screws reverses direction and the nuts lag behind.
Backlash
The location of CNC tool at any time is controlled by a XYZ coordinates
Cartesian Coordinates
executes machining operations by performing some form of sliding linear motion and rotary motion.
CNC equipment
EIA RS-267A standard
Right Hand Rule for Linear Motion
locate each new tool position by measuring from the last tool position established. if one ____________ movement is in error, all subsequent movements will be incorrect.
Incremental Positioning
is a machine tool used principally for shaping articles of metal (and sometimes wood or other materials) by causing the workpiece to be held and rotated by the lathe while a tool bit is advanced into the work causing the cutting action.
Lathe Machine
– are large lathe and is usually floor mounted. It can handle more machining jobs
Engine Lathes
are usually used in production or job shops for mass production and specialized parts.
Turret Lathes and Special Purpose Lathe
is the foundation of the working parts of the lathe to another
bed
is located on the operator’s left end of the lathe bed. It contains the main spindle and oil reservoir and the gearing mechanism
headstock
mounted on bearings in the headstock and is hardened and specially ground to fit different lathe holding devices.
main spindle
may be inserted into the spindle.
Centers, collets, drill chucks, tapered shank drills and reamers
may be screwed onto the spindle or clamped onto the spindle nose.
Chucks, drive plates, and faceplates
located on the opposite end of the lathe from the headstock
tailstock
includes the apron, saddle, compound rest, cross slide, tool post, and the cutting tool.
carriage
carries the cross slide and the compound rest.
saddle
mounted on the cross slide and can be swiveled and clamped at any angle in a horizontal plane.
compound rest
are secured in the tool post which is mounted directly to the compound rest
cutting tool and tool holder
mounted on the dovetail ways on the top of the saddle and is moved back and forth at 90° to the axis
cross slide
contains the gears and feed clutches which transmit motion from the feed rod or lead screw to the carriage and cross slide
apron
has a radius ground onto the nose of the tool bit that is smaller than the radius for a finishing
roughing tool
is shaped to be fed from right to left.
right-hand turning tool bit
is the opposite of the right-hand designed to cut when fed from left to right
left-hand turning tool bit
very versatile and can be used to turn in either direction for roughing and finishing cuts.
round-nose turning tool bit
is machining the ends and shoulders of a piece of stock smooth.
Facing
sometimes called cylindrical turning, is the process of reducing the work diameter to a specific dimension
Straight Turning
are machined to add strength for parts that are to be fitted together, make a corner, or improve the appearance of a part.
Shoulders
to add to the general appearance of the work. Common types of corners are chamfered, rounded, and square
Corners
Undercuts are the reductions in diameter machined onto the center portion of workplaces
Undercuts
(or necking) is the process of turning a groove or furrow on a cylinder, shaft, or workpiece.
Grooving
the process of machining radii and these irregular shapes.
Form turning
When the diameter of a piece changes uniformly from one end to the other, the piece is said to be tapered.
TAPER TURNING
is a uniform helical groove cut inside of a cylindrical workpiece, or on the outside of a tube or shaft.
SCREW THREAD CUTTING
(thread)
is a process of impressing a diamond shaped or straight line pattern into the surface of a workpiece by using The diamond
Knurling
is the enlarging and truing of a hole by removing material from internal surfaces with a single-point cutter bit
Boring
sometimes called channeling or cambering, is the process of cutting a groove inside of a drilled, bored, or reamed hole.
RECESSING
The address code G90 in a program
absolute mode.
The code G91
incremental mode.
The most common codes used when programming CNC machines tools are
G-codes (preparatory functions), and M codes (miscellaneous functions).
sometimes called cycle codes because they refer to some action occurring on the X, Y, and/or Z axis of a machine tool
G-codes
, containing codes G00, G01, G02, G03,
Group 1
includes either absolute or incremental programming
Group 3
deals with canned cycles.
Group 09
The _____ ______ ______ move the axes at a controlled feedrate.
G01, G02, and G03 codes
codes are used to either turn ON or OFF different functions which control certain machine tool operations, figure below.
M or miscellaneous codes
M-codes are not grouped into categories, although several codes may control the same type of operations such as
M03 turns the spindle on clockwise
* M04 turns the spindle on counterclockwise
* M05 turns the spindle off
machine tool that removes metal as the work is fed against a rotating multipoint cutter.
milling machine
rotates at high speed and it removes metal at a very fast rate with the help of multiple cutting edges.
milling cutter
Once or more number of cutters can be mounted simultaneously on the
arbor
Classification of Milling Machine
According to the nature of purpose of use
According to the orientation of the spindle
According to configuration and motion of the work holding table/bed
According to automation and production rate
Machining flat surfaces which are at right angles to the axis of the cutter,
Face milling.
Machining flat surfaces which are at an inclination to the axis of the cutter.
Angular milling
Machining surfaces having an irregular outline
Form milling
Different Milling Operations
Surface, slot, dovetail, T-slot, Form, Straddle, Angular, Boring, Drilling
Workpiece fed with Milling cutter
Climb Milling
Workpiece fed against Milling Cutter
Conventional Milling
