Multi-Axis CNC Operations 218

5-axis machines

A multi-axis CNC machine that has two rotational axes and three linear axes. 5-axis CNC machines are the most common type of multi-axis machining center.

axes

An imaginary straight line that describes the positions of objects in three-dimensional space. Axes refer to locations or movements along linear and rotational paths.

CAD

Computer-aided design. A computer software program that aids in the automated design and technical precision drawing of a part, product, process, or building. CAD models of a multi-axis part should account for the available tools and axes on the machine.

CAM

Computer-aided manufacturing. The use of a computer to assist in part manufacturing. CAM generates instructions for machining a part.

chucks

A device that holds a workpiece in place as it rotates on a conventional CNC lathe. A chuck commonly has three or four jaws that can be adjusted to fit parts of various sizes.

collisions

Undesired contact between the cutting tool and the workpiece or other machine components. Collisions are caused by tool interference and poorly designed features like high walls.

computer-aided design

CAD. A computer software program that aids in the automated design and technical precision drawing of a part, product, process, or building. Computer-aided design models of a multi-axis part should account for the available tools and axes on the machine.

computer-aided manufacturing

CAM. The use of a computer to assist in part manufacturing. Computer-aided manufacturing generates instructions for machining a part.

cutting speed

The rate at which a workpiece and cutting tool move past one another at their point of contact. Cutting speed determines how quickly unwanted material is removed from the workpiece.

deform

To change or distort in shape. Cutting tools can deform and become inaccurate or break due to speed or collisions during multi-axis cutting operations.

dovetail cutter

A mill cutter used to cut a dovetail angle into a workpiece. Dovetail cutters can produce raised surfaces that fit into angled slots on dovetail fixtures.

dovetail fixtures

A multi-axis workholding device with an angled slot, dowel pin, and screw that clamp the workpiece in place. Dovetail fixtures create the most downward force to keep a part still during cutting.

dowel pin

A cylindrical semi-permanent pin that has one chamfered end and one radius end. Dowel pins are mainly used to locate machine parts in fixed positions or to maintain alignment.

encoders

A device that translates mechanical motion into a digital signal. Encoders send information about spindle or table movement and location to the machine control unit that helps the machine make toolpath adjustments during cutting.

features

A defining characteristic on a component or part that influences both design and machining. Features include holes, threads, text, and walls.

feed rate

The rate at which the cutting tool and the workpiece move in relation to one another. Feed rate typically measures a linear movement.

geometric errors

An undesired shift in one or more of a multi-axis machine’s rotational components. Geometric errors are typically associated with 5-axis machines and cause inaccurate machining and uneven tool wear.

holemaking

A machining operation in which a single-point or multi-point cutting tool creates, sizes, or finishes a hole. Holemaking encompasses a number of operations, including drilling, boring, reaming, and tapping.

horizontal machining center

A machining center with a spindle that is parallel to the floor. Horizontal machining centers are less common than vertical machining centers.

human error

A failure or flaw in the machining process that occurs as a result of an operator being tired, lacking fine motor skills, or losing concentration. Human error is greatly reduced by multi-axis CNC machining because it requires little human intervention.

hydraulic press

A device that uses hydraulic power to generate compressive forces. Hydraulic presses are sometimes used to add serrations to workpieces for workholding with serrated jaws.

lathes

A machine tool commonly used to create cylindrical forms. A lathe holds a cylindrical workpiece on one or both ends while the cutting tool is gradually passed along the surface of the rotating part.

linear

Moving in a straight line along a single axis. Linear movement of an object is described by the X, Y, and Z axes.

linear axis

An imaginary straight line that describes side-to-side, front-to-back, or up-and-down machine movements. Linear axes include the X axis, Y axis, and Z axis.

machine control unit

MCU. A computer that controls and operates a CNC machine. Machine control units interpret the numerical data in the part program to guide machine movement.

machine zero

The default home position that acts as the origin for a CNC machine. Machine zero is a fixed location that is set by the manufacturer of each particular CNC machine.

machining

A manufacturing process that involves removing material to form an object. Machining includes methods such as milling, turning, and drilling that remove metal using cutting tools.

material

The substance out of which something is made. The material of a workpiece can change cutting speeds and how cutting tools behave on multi-axis machines.

milling

A cutting operation in which a rotating multi-point cutting tool is fed along the surface of a part to remove material. Milling operations generally produce flat surfaces.

mills

A machine tool that performs cutting operations on flat, square, or rectangular workpieces. On a conventional mill, the cutting tool can move only linearly.

misalignments

An undesired shift in one or more of a multi-axis machine’s rotational components. Misalignments produce geometric errors and cause inaccurate machining and uneven tool wear.

multi-axis CNC machines

A machining center that has four or more linear and rotational axes. Multi-axis CNC machines, or multitasking machines, combine the functions of a mill and a lathe.

origin

A fixed, central point in the Cartesian coordinate system where the three X, Y, and Z axes intersect. The origin has a numerical value of zero.

parallel

Extending in the same direction and equally distance from one another at all points. On a multi-axis machine with a fixed spindle, the spindle should be parallel to the Z axis.

part programs

A series of alphanumeric instructions that direct a CNC machine to perform the necessary sequence of operations to machine a specific workpiece. Multiple part programs can be stored in a CNC at one time.

perpendicular

Intersecting another line or plane at a right angle. On a vertical machining center, the spindle is oriented perpendicular to the floor.

personal protective equipment

PPE. Any clothing or device used to minimize exposure to hazards and prevent injuries. Personal protective equipment for CNC machining includes eye protection to guard against flying chips.

post-processing

A procedure used to clean, improve, or otherwise finish a part after it has been manufactured. Post-processing procedures include abrasive finishing, heat treatment, and painting.

program zero

The position that acts as the origin for a specific part program. Program zero acts as a reference point for all part dimensions.

resolution

The degree of detail visible in a CAD design. High-resolution CAD designs are required to precisely machine parts with fine details like text.

rotate

Move around a circular axis. On a multi-axis CNC machine, rotating describes movement by either the spindle or the worktable around the C axis.

rotational

Moving in a circular path around an axis. Rotational movement of an object is described by the A, B, and C axes.

rotational axis

Each of three imaginary circles that describe rotation around a linear axis. The A axis rotates around the X axis, the B axis rotates around the Y axis, and the C axis rotates around the Z axis.

rotational misalignments

A misalignment that occurs when one linear axis shifts away from its zero position along a perpendicular linear axis and moves the rotational axis that rotates around it. The rotational misalignments that can occur on a vertical 5-axis machine are A axis misalignments in the Y or Z directions and B axis misalignments in the X or Z directions.

sensors

A device that detects the presence or absence of an object, or certain properties of that object, and provides feedback. Common sensor applications include part detection, counting, and positioning.

serrated jaws

A multi-axis workholding device with serrated teeth that dig into the workpiece on two sides to provide grip. Serrated jaws give the cutting tool more access to the part than a standard vise.

serrations

A series of ridges or grooves notched into a surface. Serrations improve gripping ability without restricting tool access on multi-axis machines.

simulations

Representations made with computer-driven technology used to duplicate real-world and real-time situations in order to evaluate behavior under real conditions. Simulations model the behavior of a manufacturing process to test its effectiveness before it is used to make an actual product.

slot

An angled channel in the surface of a dovetail fixture. Slots have the same shape and angle as the dovetail on the bottom of a workpiece.

spindle misalignments

A misalignment that occurs when the spindle meets the Z axis at an angle rather than being parallel. Spindle misalignments are especially serious on multi-axis machines with fixed spindles.

spindles

A rotating component of a multi-axis CNC machine that holds the cutting tool. The spindle can be oriented horizontally or vertically and can move along a combination of linear and rotational axes, depending on the configuration of the machining center.

stickout

The distance between the end of the toolholder and the tip of the cutting tool. Excess stickout can increase the risk of collisions or cause tools to bend, break, or shake undesirably.

table/spindle

An axis configuration in which one rotational axis is located in the table and the other is located in the spindle of a 5-axis CNC machine. Table/spindle machines are best for complex, large, or heavy parts.

threads

A long, spiraling groove or ridge on the interior or exterior of an object. Threads help fasteners such as screws transform motion, grip material, and hold components together.

tilt

Swing or change in angle. On a multi-axis CNC machine, tilting describes movement by either the spindle or worktable around the A or B axis.

tilt misalignments

A misalignment that occurs when a linear axis meets the intersecting linear axis at an angle and moves the rotational axis that rotates around it. The tilt misalignments that can occur on a 5-axis machine are A-Y, A-Z, B-X, and B-Z misalignments.

tolerances

An unwanted but acceptable variation or deviation from a desired dimension of a part. Tolerances indicate the allowable difference between a physical feature and its intended design.

tool interference

An undesirable operating condition for a multi-axis CNC machine that occurs when parts of the spindle or cutting tool come into contact with other machine components or undesired parts of the workpiece. Tool interference can damage the workpiece or misalign the spindle.

toolholders

A device used to hold a cutting tool in place. Toolholders for multi-axis machines come in a variety of shapes and sizes that are optimized to reduce interference.

toolpaths

The course followed by the tool as it creates the workpiece. Toolpaths are described by a series of coordinate positions.

touch trigger probes

A type of contact probe that detects a part and generates an electronic signal to record its dimension and location. Touch trigger probes help CAM automatically determine part offsets.

turning

A machining operation in which a single-point cutting tool passes along the outer surface of a cylindrical workpiece. In turning operations, the tool gradually removes a layer of material as the workpiece rotates.

vertical machining center

A machining center with a spindle that is perpendicular to the floor. Vertical machining center worktables are parallel to the ground.

vises

A workholding device with two jaws that grip and hold a workpiece in place. Standard vises keep parts in a fixed position on conventional CNC mills.

work offset

The distance between machine zero and program zero. Work offsets help CAM communicate the location of the part to the machine before cutting begins.

workholding devices

A device used to hold and locate a workpiece on a machining center. Workholding devices are used to keep the workpiece stationary.

workpiece

A part that is in the process of being machined. A workpiece may be subject to cutting, grinding, forming, welding, or other operations to produce a finished part.

worktables

The part of a multi-axis CNC machine that supports the workpiece. The worktable, or table, can move along a combination of linear and rotational axes, depending on the configuration of the machine.