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Do you want to be a better CNC'er in 37 Seconds? Get Better Tool Life, Surface Finish, and Material Removal Rates Fast. It's that easy. You can install and get results now. |
| N-Code to PWM |
The N-Codes are the names or titles of a block of G-Code.
In other words, the line number.
Rake is the angle from the workpiece wall to the cutting
tool at the cutting edge. If it
is 90 degrees, the edge is perpendicular to the workpiece. Angles less than 90 degrees are negative rake
angles. Angles greater than 90
degrees are positive rake angles. Positive
rake is generally preferable to negative rake because it requires less
pressure to cut. Negative rake
has the advantage that it provides more edges on a carbide
insert (See Also Carbide Insert) that may be used, and may be more economical.
NEMA is the National Electronic Manufacturers Association.
It is a standard setting group.
The relevant standards for CNC purposes include NEMA enclosures,
which make suitable enclosures for CNC electronics and the standards for
motor mounting, which are what NEMA 23, NEMA 34, and NEMA 42 are.
In this case, noise refers to electrical noise. Machine tools are inherently high electrical noise environments. Noise can interfere with the proper operation of controls, so proper care must be taken to avoid it. Shielded cables and proper grounding practices are a good start along these lines. Twisted pairs are another wiring approach to fighting noise.
Imagine what could happen if a noise spike caused a false
signal such as a step command to a motor, an encoder value, or home or
limit switch triggering.
NURB is an abbreviation for Non-Uniform Rational B-Spline. This is a mathematical
concept used by nearly all CAD software to represent curves.
A pre-determined distance entered into and used by the
CNC controller.
See “Cutter Offsets”, “Cutter Radius Compensation”, “Tool
Length Offsets”, “Tool Nose Radius Compensation”, “Tool Offsets”, “Wear
Offsets”, “Workshift Offset”, and “Work Offsets”.
An
An open loop system employs no feedback—it assumes the
axes always move as they are commanded to without checking. Stepper based systems are usually open loop.
When the system doesn’t go where it is commanded to, this is referred
to as “Lost Steps”. See also Lost Steps.
A limit switch (See Also Limit Switch) that uses an optical
sensor, usually based on the principle of breaking a beam of light.
If the block contains an M1 code and
the Optional Stop control is on, the machine to pause for operator inspection.
An Opto Isolator is an electronic
component used to provide isolation between two circuits. This is done to promote noise immunity and to
protect the circuits from accidental bad connections and electrical surges
that might be damaging. For example,
if your parallel breakout board didn’t include opto
isolators, a voltage surge on the motor driver side could go all the way
back through the parallel cable and burn out your PC’s motherboard.
The origin is the point at which coordinate values (See Also Cartesian Coordinates) are measured. In absolute coordinate systems (See Also Absolute), this origin is in a fixed location. In relative or incremental (See Also Relative), the origin is usually the current location. Think of it in terms of specifying where you want to go in a room. You could specify relative to a fixed origin, for example, the center of the room, or you could specify relative to where you are standing. Both are convenient, depending on the circumstances.
The origin is also the point that defines when coordinate values change their sign. In one direction relative to the origin they will be positive. In the other, they will be negative. The value at the origin is zero. The right-hand rule is a convenient way to determine which directions are positive versus negative. See also Right-Hand Rule.
All of the axes or dimensions in a Cartesian coordinate system intersect at the origin.
A measurement of torque. See also "Torque".
A facility that allows one or workpieces to be loaded on pallets that are automatically
cycled through the CNC machine.
A pallet is basically a moveable table.
This allows the machine to just keep working uninterrupted as operators
load pallets while the machine works with raw material and offload pallets
containing the finished parts as they’re completed.
The parallel port is one means of connecting a PC to
the motor driver electronics. It
is a legacy interface that is slowly being phased out of PC’s in favor
of USB. It is the most common way to connect a PC running
Mach3 to the driver electronics.
| Pin Number | Function | Pin Number | Function |
| 1 | Strobe (Output) | 14 | Auto Feed (Output) |
| 2 | Data 0 (Input/Output) | 15 | Error (Input) |
| 3 | Data 1 (Input/Output) | 16 | Init (Output) |
| 4 | Data 2 (Input/Output) | 17 | Select In (Output) |
| 5 | Data 3 (Input/Output) | 18 | Strobe Ground |
| 6 | Data 4 (Input/Output) | 19 | Data 0 and 1 Ground |
| 7 | Data 5 (Input/Output) | 20 | Data 2 and 3 Ground |
| 8 | Data 6 (Input/Output) | 21 | Data 4 and 5 Ground |
| 9 | Data 7 (Input/Output) | 22 | Data 6 and 7 Ground |
| 10 | Acknowledge (Input) | 23 | Busy and Error Ground |
| 11 | Busy (Input) | 24 | Paper Empty, Select, and Acknowledge Ground |
| 12 | Paper Empty (Input) | 25 | Auto Feed, Select In, and Init Ground |
| 13 | Select (Input) |
In CNC, the term Parameters generally refers to settings
that are made in the machine's controller outside the part program.
Parametric drawing refers to a feature of CAD programs
that allows the dimensions of the parts to act as parameters. One can change a dimension and the part will
adjust its size accordingly. This
is very convenient for revising drawings. The feature does not exist in all CAD programs.
SolidWorks and Alibre
3D have it, while Rhino 3D does not.
Parametric programming is the practice of designing a part program so that it has parameters that may be varied without having to rewrite the program. This is useful, for example, when a single part program is used for families of parts, or when some characteristics of a part must change from time to time on different production runs.
Parametric programming tends to be a proprietary feature
that differs from one CNC controller to the next.
A part chute is a component of a CNC lathe that provides
a convenient way to gather parts as they are sliced off and place them
in a bin.
What you’d call a G-Code program. Part Program is a more proper and less confusing
term than “G-Code” because G-Codes are only one type of word that can
appear in a part program.
A word that indicates the name of a
subprogram to execute.
A type of drilling or canned cycle (See Also Canned Cycle)
in which the bit is advanced into the hole a
short distance and then withdrawn repeatedly to facilitate chip evacuation.
A handheld control for a machine tool.
Any milling that uses the edge of the milling cutter that is parallel to the axis of rotation instead of the end of the cutter, as in Face Milling (See Also Face Milling).
PID is a type of servo or feedback tuning system which
stands for Proportional, Integral, and Derivative.
Usually, the number of turns the leadscrew must make
to travel a standard distance. For
Imperial screws, the standard distance will be an inch and the unit of
measure would be TPI or Turns Per Inch.
A gantry style (See Also Gantry) machine used to move
a plasma cutting torch over sheets of metal under CNC control.
To cut straight down, similar to drilling
with a twist bit.
An interior recess that is cut into
a part.
Rake is the angle from the workpiece wall to the cutting
tool at the cutting edge. If it
is 90 degrees, the edge is perpendicular to the workpiece. Angles less than 90 degrees are negative rake
angles. Angles greater than 90
degrees are positive rake angles. Positive
rake is generally preferable to negative rake because it requires less
pressure to cut. Negative rake
has the advantage that it provides more edges on a carbide
insert (See Also Carbide Insert) that may be used, and may be more economical.
The “Post” is the set of G-Codes or part program generated
by the
The act of sending the G-Code program to the CNC machine,
usually from a
A powered drawbar typically uses an air or electric impact wrench to operate the drawscrew mechanism under power. It’s advantages over a manual drawbar include much faster operation together with more repeatable torque on the drawbar.
A powered drawbar is a much simpler way to speed up tool
changes than an automatic toolchanger (See also
Toolchanger)
Preload is a mechanism used to eliminate backlash by
tensioning a bearing or leadscrew to take up the slack that causes backlash.
Some typically ways in which preload can be achieved include using
a threaded screw that is torqued down to create a load, using spacers or shims, using
springs, wavy (Belleville) washers, or using oversized balls in a ballnut.
As in "blueprint" or drawing. Refers to the drawings that define what the part should be. Once upon a time all prints were "blueprints", which were made with a photo-chemical process. They smelled strongly of ammonia and were a deep purple blue in color with white lines. This was before laser printers and the like, and the blueprint process was a fast way to copy hand drawn prints of any size.
Sliding ways are used by many machine tools so that their
axes may slide against one another. There
are four prominent designs:
-
Dovetail Ways: Very
common on mills, dovetail ways look like the dovetails used in wood joinery.
-
Box Ways: Box Ways
are rectangular cross section, as opposed to the angular shape of dovetail
ways. Box ways are very strong,
but they suffer from two shortcomings.
First, they involve a lot of surface contact area, so managing
friction is key. Second, in order
to slide at all, some clearance is required, which results in some slop
in their travel. They are the strongest
and most rigid design, but they are difficult and expensive to manufacture.
-
-
A proximity switch is a type of sensor that responds
to metal being nearby. They operate
on a variety of principles such as capacitance and are commonly used for
home and limit switches because they are relatively robust. One issue is that they may be triggered by an
errant chip. See
also Home and Limit Switch.
PTFE is the scientific name for the material whose trademark
is Teflon. It stands for Poly Tetra
Flouro Ethylene, and is an extremely slippery low friction
compound. See also Acetal for machine
tool uses.
The speed at which signals are being sent over a digital circuit. For example, the number of steps being sent to a stepper motor during a fixed period of time, or the number of steps coming out of an encoder.
In systems that use a parallel port to communicate between
the PC and the driver electronics, the pulse rate will be limited. Typically the limitation will be somewhere from
20,000 to 45,000 pulses per second, or Hertz. 1 Herz
(abbreviated Hz) = 1 pulse per second.
This limitation can limit the speed at which you can drive stepper
motors, or the amount of resolution from an encoder or spindle index sensor
that your system will handle. Higher
pulse rates are possible with devices like the GRex
that use either the USB port or a LAN connection instead of the PC parallel
port.
PWM is a technique to vary the average current sent to a device by varying the number (or frequency) of pulses or their duration. Chopper supplies work through PWM.
PWM can also be a mechanism used to communicate analog
information using a digital circuit. For
example, PWM could be used to convert a single output pulse line from
a CNC controller to an analog voltage needed to control spindle speed
using a VFD.
| N-Code to PWM |
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Do you want to be a better CNC'er in 37 Seconds? Get Better Tool Life, Surface Finish, and Material Removal Rates Fast. It's that easy. You can install and get results now.
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