CNC Router Essentials (PREVIEW)

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

CNC Router Essentials

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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