Two-Sided Machining & 3-D Texturing
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CHAPTER
CNC Basics
Let’sstart your CNC journey by helping youunderstand a few key aspects of working with a CNC machine:
• CNC machine mechanics
• CNC workflow
• CNC soware
8CNC Router Essentials
1 : CNC Basics
Machine mechanics
Basic CNC (computer numerical controlled) routers operate on three axes: X, Y, and Z, Image 1.1. Think back to your days of graphing in math class. The X and Y axes move le to right and front to back, while the Z axis is vertical. The machine can move in all three directions at one time, which allows it to cut complex shapes as easily as simple shapes. Most CNC routers use an industrial high-speed spindle, although some CNCs use woodworking-style router motors to hold the bit or cuing tool, Images 1.2. The main differences are spindles run quieter and are more accurate than woodworking routers, plus a spindle’s bearings last several times longer than those in a woodworking router,
but a spindle costs several times the price of a similarly sized router. Some CNC tools allow you to start with a router motor and later upgrade to a spindle. The bed or deck of a CNC machine may be metal, plastic, or plywood, and is oen covered with a spoilboard, Image 1.3. The spoilboard is usually a sheet of MDF or plywood. It is a consumable item, since many projects require you to cut completely through the project material and slightly into the spoilboard. Over time the spoilboard will become grooved, but you can renew it by routing the surface flat. When the spoilboard becomes too thin, it can be replaced, or a new one can be glued on top of the old one.
Image 1.1: Three-axis 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.
Z
X
Z
Y
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CNC Router Essentials
CNC Basics : 1
Images 1.2: An industrial spindle (left) or woodworking router (right) is used to hold the router bit on a CNC machine. Spindles run quieter than routers and last longer, but cost several times more. Spindles are available as either fan-cooled or water-cooled. Water-cooled spindles are often less expensive, but water-cooled spindles require a reservoir and pump to circulate the water.
Image 1.3: A spoilboard usually covers the machine bed to protect it during cutting, since many CNC operations involve cutting slightly through the project material. The spoilboard is considered a consumable and replaceable part of the machine.
Spoilboard
Bed/deck
0CNC Router Essentials
1 : CNC Basics
The brain of a CNC consists of onboard electronics connected to an external computer or control pendant, Images 1.4. Together these are referred to as the control system. The control system automatically moves the machine during operation, but can also be used by the operator to manually move the spindle along the machine axes during tool setup.
CNC workflow
The workflow for CNC projects consists of three primary steps: designing, toolpathing, and machining, Image 1.5. Each of these has several sub-steps that we’ll discuss in later chapters, but the important thing to know is that they are each associated with a particular kind of soware. CAD (computer-aided drawing) for drawing; CAM (computer-aided machining), which converts the CAD drawing to toolpaths and machine code; and the Controller soware that communicates the code to the CNC machine and tells it where to move during the machining process. Don’t let that alphabet soup of leers intimidate you. Using today’s CNC machines has been simplified by advances in CNC soware that automates much of the complex processes of the past. With a lile practice, it will start to make sense, but first, let’s take a quick look at each type of soware.
Images 1.4: CNC machines connect to either a control computer or a control pendant. These allow the operator to control the movements of the CNC machine automatically and manually.
Image 1.5: A specific type of software is associated with each step of the CNC workflow.
CNC Router Essentials
CNC Basics : 1
CNC