CNC
Router Essentials Basics for Mastering the Most Innovative Tool in Your Workshop
Randy Johnson
CNC
Router Essentials Basics for Mastering the Most Innovative Tool in Your Workshop
Randy Johnson
Contents 1 2 3 4 5 6
CNC Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7
Practice Project 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
8
Practice Project 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
9
Practice Project 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
10
Gallery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
Design Essentials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Toolpath Essentials . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Machine Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Project Materials .. . . . . . . . . . . . . . . . . . . . . . . . . . . .
50
Practice Project 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Basic Drawing & Toolpath Techniques
3-D Carving & Raised Lettering
Bitmap Tracing & Texture Carving
Two-Sided Machining & 3-D Texturing
C H A P T E R
1
CNC Basics Let’s start your CNC journey by helping you understand a few key aspects of working with a CNC machine:
• CNC machine mechanics • CNC workflow • CNC software
1 : ďťżCNC Basics
Machine mechanics Basic CNC (computer numerical controlled)
but a spindle costs several times the price
routers operate on three axes: X, Y, and
of a similarly sized router. Some CNC tools
Z, Image 1.1. Think back to your days
allow you to start with a router motor and
of graphing in math class. The X and Y
later upgrade to a spindle. The bed or deck
axes move left to right and front to back,
of a CNC machine may be metal, plastic,
while the Z axis is vertical. The machine
or plywood, and is often covered with a
can move in all three directions at one
spoilboard, Image 1.3. The spoilboard is
time, which allows it to cut complex
usually a sheet of MDF or plywood. It is
shapes as easily as simple shapes. Most
a consumable item, since many projects
CNC routers use an industrial high-
require you to cut completely through
speed spindle, although some CNCs use
the project material and slightly into
woodworking-style router motors to hold
the spoilboard. Over time the spoilboard
the bit or cutting tool, Images 1.2. The main
will become grooved, but you can renew
differences are spindles run quieter and are
it by routing the surface flat. When the
more accurate than woodworking routers,
spoilboard becomes too thin, it can be
plus a spindle’s bearings last several times
replaced, or a new one can be glued on top
longer than those in a woodworking router,
of the old one.
Z
Y Z X
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CNC Router Essentials
Image 1.1: Threeaxis CNC machines move in three directions. The Z axis controls vertical movement. The X and Y axes control the left to right, and front to back movement. The X and Y are reversed on some machines.
2 : ďťżDesign Essentials
Using 2-D designs
2-D vector line drawing
2-D part
A wide variety of CNC work can be accomplished using just 2-D lines, Image 2.1. Any CAD program can be used to create a 2-D line design, but designs must be saved as or converted to a vector line format to be compatible with the CAM toolpathing software. A vector line is made up of points that represent the geometry of the line, Image 2.2. One big benefit of a vector line design is that you can scale it up or down
Image 2.1: A 2-D line design creates a part that looks like it has been cut out on a bandsaw.
without losing details or resolution. Most CAD programs can create vector line designs, Image 2.3. Common vector file formats include .dxf, .esp, .dwg, .ai, and some .pdf files. These various file formats
CAD drawing tools
Control point
Vector lines
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CNC Router Essentials
Image 2.2: The basis of all 2-D CNC design work is the creation of vector lines. Vector lines are made up of control points, and can be scaled larger or smaller without losing any detail. CAM programs use vector lines to create the toolpath cutting files. VCarve Pro (shown here) contains CAD drawing tools that create vector lines by default.
Design Essentials :
2
Part preview
External vector drawing
Import
Image 2.3: Most CAD programs are capable of creating the vector lines, which can easily be imported into a CAM program for toolpath creation. So, if you are currently using a CAD program that creates or exports vector line drawing (e.g., .dxf, .eps, .dwg) you can probably keep using it as your primary CAD design tool.
Vector lines
CNC Router Essentials
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C H A P T E R
4
Machine Setup We’re nearly ready to start cutting on the CNC machine! But before that can happen, we need to first set up and check a few things on the machine, so let’s take a look at:
• Job setup • Material hold-down methods • Zeroing the X, Y, and Z axes • Testing a cutting file • Spoilboard maintenance
4 : Machine Setup
Job Setup Machine setup actually starts in the CAD/ CAM software with Job Setup, Image 4.1. This includes entering the width, height, and thickness of your material, and the zero locations for the X, Y, and Z axes. This information carries through to the toolpath, so it’s important to understand how it relates to your material and machine, Image 4.2.
Image 4.1: The Job Setup in the CAD/ CAM software sets material parameters that carry through to the machine. Z-zeroing to the top of the material is common for V-carving and 3-D carving. Z-zeroing to the bottom of the material is useful when you’re cutting all the way through the material, because it is not affected by variations in material thickness. Setting the XY Datum Position to the lower left or the center of the material are the two most frequently used locations.
Image 4.2: Your material can be attached any place on the table, as long as the datum position for zeroing the XY matches the setting you chose in in the Job Setup.
XY datum center XY datum lower left
40 CNC Router Essentials
Machine Setup :
4
Material hold-down
wooden hold-down may still break the bit.
There are many ways to secure your
If you use metal hold-downs be sure they’re
material to the machine. The method you
aluminum, not steel. Aluminum will do less
choose depends on the machine you have,
damage to your cutter if they collide.
the material you’re using, the kind of work
Hot glue has plenty of holding power for
you’re doing, and what’s fastest for you. The
many types of CNC work, Image 4.4. Make
following methods are some of the most
sure your spoilboard is clean and relatively
common and simplest to use.
smooth. Dust on the spoilboard will
If your CNC machine has T-track, you
prevent the hot glue from bonding. Choose
can use hold-down clamps to secure your
an area on the spoilboard that doesn’t have
work to the table, Image 4.3. This is a fast
a lot of deep cuts from previous projects.
and easy way to get your stock on and
These cuts minimize contact between your
off the machine. As long as you properly
project and the spoilboard, weakening the
tightened them, they will solidly hold
glue bond.
the work in place. Some CNC users use
Apply the hot melt glue as a fillet along
shop-made wooden hold-downs, instead
the edge of the project. Hold your material
of metal hold-downs. This minimizes the
firmly to the CNC table while applying the
risk to your bit, although colliding with the
glue. Do not put hot melt glue between the
Image 4.3: T-track and hold-down clamps provide a very fast means of getting material on and off the CNC table.
CNC Router Essentials
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C H A P T E R
6
Practice Project 1:
Basic Drawing & Toolpath Techniques The instructions in this chapter will guide you through the steps of designing a V-carved plaque. The beauty of designing on a computer is that you can easily make changes , so don't be afraid to experiment with the design. In this project, you’ll learn how to:
• Set up a new project file • Draw rectangles and create offsets • Add text • Create toolpaths for pocketing, profiling, and V-carving
• Add tabs
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CNC Router Essentials
Practice Project 1: Basic Drawing & Toolpath Techniques :
Getting started
6
These are the tools that you will use to complete the CAD portion of this project.
You’ll learn a great deal about VCarve Pro and your CNC machine by creating and cutting the project in this chapter. If you’re new to CNC, spend some time getting familiar with your CAD/CAM software before you start cutting. Understanding how to use the various CAD tools is an important part of learning how to design
Save File
Job Setup
for CNC. Draw Rectangle A Auto Layout Text
B
C
D
E
The primary design elements for this project include: (A) Material size, (B) XY Datum Position, also called the XY-zero location, (C) an outer rectangle with round corners, (D) an inner rectangle made using the Offset Vector tool, (E) and the Auto Layout Text feature.
Offset Vectors
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61
WOODWORKING
$24.95
Maximize the Potential of Your CNC Machine
Today’s CNC machines are easier to use, less expensive, and will greatly increase your woodworking productivity. So, if you’re looking to buy one— or just wish the user manual actually made sense—CNC Router Essentials is for you. With expert woodworker Randy Johnson leading the way, CNC Router Essentials will guide you through each critical step in learning how to master this game-changing woodworking tool.
Inside CNC Router Essentials, you’ll find: ■■ Easy-to-follow basics on machine use
and project design ■■ Pro advice for selecting the correct bits
and understanding toolpath fundamentals ■■ Helpful practice projects in 2-D and 3-D ■■ An inspiring gallery of projects to fuel
your own original designs ■■ Everything you need to maximize your
CNC’s woodworking capacity