# Mechanics of CNC 110

This class describes the mechanical systems involved in CNC axis movement, as well as how feedback is used for tool location.

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## Class Details

Class Name:
Mechanics of CNC 110
Description:
This class describes the mechanical systems involved in CNC axis movement, as well as how feedback is used for tool location.
Version:
1.0
Difficulty:
Beginner
Number of Lessons:
17
Spanish, Chinese
Related 2.0 Class:
Introduction to CNC Machines 201

## Class Outline

• Objectives
• CNC for Modern Manufacturing
• Movement of CNC Machines
• CNC Coordinates
• The Axes and Origin
• Plus and Minus Directions
• Rotational Axes
• Machine Control Unit
• Point-to-Point Positioning System
• Continuous Path System
• Open-Loop Systems
• Closed-Loop Systems
• Servomechanisms
• Feedback Devices
• Input Methods
• Control and Operation Features
• Summary

## Objectives

• Describe how CNC machines have impacted modern manufacturing.
• Identify machine components that move during CNC machining.
• Explain the role of axes in the Cartesian coordinate system.
• Identify axes on a CNC machine.
• Identify positive and negative movement along machine axes.
• Identify rotational axes.
• Describe the role of the machine control unit.
• Define point-to-point positioning.
• Define continuous path movement.
• Define open-loop system.
• Define closed-loop system.
• Describe the role of servomechanisms.
• Distinguish between different feedback devices.
• Describe various input methods.
• Describe different control and operation features available to the CNC machine.

## Glossary

Vocabulary Term Definition
A-axis A rotational axis describing motion around the X-axis.
AC servo A type of servomechanism that is more reliable and less energy consuming than the DC servo.
ASCII American Standard Code for Information Interchange. It is a standard for information exchange.
axes An imaginary line that passes through the center of an object. Axes are used to measure the distances of objects in the Cartesian coordinate system.
ballscrew A long, threaded device that rotates to move the worktable of a CNC machine. The ballscrew is powered by a motor.
B-axis A rotational axis describing motion around the Y-axis.
canned cycle A predetermined machining sequence used to simplify programming.
Cartesian coordinate system The numerical system that describes the location of an object by numerically expressing its distance from a fixed position along three linear axes.
C-axis A rotational axis describing motion around the Z-axis.
closed-loop system A control system that provides feedback to the controller.
CNC lathe A lathe that is controlled by a computer running programs driven by numerical data.
CNC milling machine A milling machine that is controlled by a computer running programs driven by numerical data.
computer numerical control The use of a computer with numerical instructions and program codes to carry out various machining operations.
continuous path A type of control system where cutting can take place as the tool moves from one position to the next.
contouring Tool movement along two or more axes at the same time.
control system A method of tool and part movement in CNC machining. Point-to-point and continuous path are the two main control systems.
cutting tool A device made of hard, tough material that is used to remove metal by creating chips.
DC servo A common type of servomechanism.
drill A machining tool used to penetrate the surface of a workpiece and make a round hole.
dry run A trial run of the part program without any parts or cutting fluids.
EIA Electronics Industry Association. It publishes Recommended Standards (RS) for transmitting data between devices.
feed rate The rate at which the cutting tool and the workpiece move in relation to one another.
feedback A return signal that confirms the position of the tool or worktable.
feedback device A device that sends information back to the controller in the closed-loop system.
floppy drive A device that reads magnetic data from a floppy disc.
hardware The physical components of a CNC machine.
horizontally Parallel to the horizon, like a table top.
hydraulic servo A type of servomechanism that is driven by fluids.
linear axes The axes that describe movement along a straight line.
linear scale A device that relies on the size of an electrical current to convey the position or distance on a CNC machine. A linear scale is one of the most accurate feedback devices.
lot A group of similar parts created during the use of a particular tooling setup.
machine control unit A small, powerful computer that controls and operates a CNC machine.
machining center A sophisticated CNC machine that can perform multiple machining operations at the same location with a variety of tools.
mylar tape A thin, yet strong polyester film that was used to transmit programs to numerically controlled machines.
open-loop system A control system that does not provide feedback to the controller.
optical encoder A type of feedback sensor that records light reflections and converts the reflections into feedback signals.
origin The fixed, central point in the Cartesian coordinate system. The origin has a numerical value of zero.
paper tape A way of transmitting programs to numerically controlled machines. This is a somewhat older method.
part program The instructions for the CNC machine about how to create a part.
point-to-point positioning A type of control system where no cutting takes place during the movement of the tool from one position to the next.
punch presses A machine that uses force to either cut or form a workpiece.
rectangular coordinate system Another name for the Cartesian coordinate system.
right-hand rule A quick reference that shows the X-, Y-, and Z-axes. A person displays his or her right hand, and the first three fingers from the right each represent the X-, Y-, and Z-axis in order.
rotary resolver A device that sends signals back to the CNC controller to indicate position or speed.
rotational axes The axes that describe turning or spinning movement.
RS232 A standard that defines a computer's serial port and interaction with other devices.
servomechanism A special motor used in CNC machines that moves with precision.
signal A message sent electronically.
slide The part that moves and holds a tool.
software The coded instructions, formulas, and operations that structure the actions of a computer.
spindle speed The rate that the cutting tool or workpiece moves at the point of contact.
stepper motor servo A servomechanism that generates steps to move the tool and the worktable.
turning center A sophisticated CNC machine that specializes in turning, boring, drilling, and threading operations, all at the same location.
vertical line A line that travels up and down.
workpiece A part that is being worked on. It may be subject to cutting, welding, forming, or other operations.
worktable The table that supports a workpiece during a manufacturing operation.
X-axis The linear axis that represents motions and positions to the left or right of the operator.
Y-axis The linear axis that represents motions and positions both toward and away from the operator.
Z-axis The linear axis that represents motions and positions both up and down. The Z-axis is always parallel to the main cutting device.