CNC Terms

Question 1

CNC

Answer 1

Computer Numerical Control. The automated control of machining tools.

Question 2

CAM

Answer 2

Computer-Aided Manufacturing

Question 3

End Mill

Answer 3

The most basic milling cutter. It comes in a variety of diameters, cutter materials, coatings, and flute styles. The tool has a flat bottom and is useful in creating features with flat faces.

Question 4

Ball End Mill

Answer 4

A modified end mill that is characterized by a full radius at the bottom of the tool. It can come in the same varieties present in a flat end mill.

Question 5

Flutes

Answer 5

The grooves on the sides of a cutting tool (drill, end mill, etc.) that are used to eject chips from the cutting area. In and end mill, the flutes are sharpened and can be used for cutting operations.

Question 6

Tool Holder

Answer 6

The precision component that rigidly constrains the cutting tool into the spindle for cutting operations.

Question 7

Collet

Answer 7

The precision component that can adjust in a small range of sizes to grasp different diameter tools and locks them into the tool holder.

Question 8

Spindle

Answer 8

The part of the CNC machine that spins the cutting tools. RPM ranges from 0 to 10,000 for the CNC mill in the metal shop, and 0 to 20,000 for the CNC router in the wood shop.

Question 9

G/M code

Answer 9

The basic instructions that CNC machines execute.

Question 10

Block

Answer 10

one line of G/M code

Question 10

G00

Answer 10

Rapid move, one of the basic CNC motion commands where the machine moves at the fastest possible speed. Used for positioning moves only, never used for cutting movement.

Question 11

G01

Answer 11

Linear move, one of the basic CNC motion commands where the machine moves at a specified rate in a straight line along any combination of axes.

Question 12

G02/G03

Answer 12

Arc move, one of the basic CNC motion commands where the machine moves in an arc motion with a specified radium and feed rate.

Question 13

Toolpath

Answer 13

The path that the top of the tool follows as it machines the desired geometry.

Question 14

Machine definition

Answer 14

A collection of parameters that describe the actual machine performing of the CNC machining. It contains values such as the number and layout of the motion axes, max RPM of the spindle, and type/configuration of the tool changer.

Question 15

Control Definition

Answer 15

A collection of parameters that describe the CNC controller. The controller interprets the G-code and instructs the CNC machine on the motion commands. It contains values such as the format for arc commands, support for canned cycles, and instructions on tolerances and motion smoothing.

Question 16

Post Processor

Answer 16

The instructions to translate CAM machining steps to the G/M code that CNC machines require.

Question 17

Stock

Answer 17

The raw material that will be used to machine the desired part.

Question 18

WCS

Answer 18

Work Coordinate System. The set of X, Y, and Z axes/planes and the origiin where they all meet. This is typically used to change the way that MasterCAM defines the top/right/front planes where the planes internal to the desired part geometry differ.

Question 19

Origin

Answer 19

The point at which al the planes and axes intersect. Also called the zero-corner.

Question 20

C-Plane

Answer 20

Construct plane; the plane on which all geometry being created (within MasterCAM) will be created on.

Question 21

T-Plane

Answer 21

Tool plane; the plane on which all machining operations will happen. You can use T-plane to machine on multiple sides of a part.

Question 22

Transformation

Answer 22

The MasterCAM functionality associated with changing geometry size and positions. Commands include: move, copy, scale, mirror, project, stretch, and roll.

Question 23

Tolerance (CNC)

Answer 23

The machining parameter that dictates how close to the theoretical perfect shape that an individual toolpath will attempt to achieve. Lowering the tolerance (increasing the parameter value) will speed up rough machining steps, raising the tolerance (decreasing the parameter value) will slow down machining steps.

Question 24

Drive surface

Answer 24

The surfaces of a solid model that are going to be cut in the stock.

Question 25

Check surface

Answer 25

The surfaces of the solid model that will not be cut by the tool. These surfaces are sometimes called avoidance regions and they are not always used in each toolpath.

Question 26

Containment Boundary

Answer 26

A (usually) 2D loop of geometry that the toolpath will be confined to. It can be used to localize smaller tools into a set region requiring more detail while still selecting a large set of drive surfaces.

Question 27

Conventional milling

Answer 27

Milling style in which the rotating tool in combination with the direction of travel of the work piece causes the tool to rob across the surface of the work and then 'scoops' out the chip. This style of milling may result in work hardening of the stock surfaces, dulled tooling, and poor surface finish.

Question 28

Climb milling

Answer 28

Milling style in which the rotating tool in combination with the direction of travel of the work piece causes the tool to make initial contact in the maximum position and decreases as it travels through the work piece. There is no tool rubbing, which can lead to longer tool like. The style can result in larger loads to the machine and therefore requires a more rigid setup than is usually found in traditional manual machining steps.

Question 29

Canned cycle

Answer 29

A G-code that offers a convenient method to program repetitive CNC machine operations. Canned cycles are stores internally on a machine control and called by a program and fed the required parameters to complete operations like drilling, tapping, and boring.

Question 30

Roughing

Answer 30

One or more toolpaths whose function is to remove the bulk of the work material as fast as possible. Final geometry, surface finish, and aesthetics are not considered in the definition of these toolpaths.

Question 31

Finishing

Answer 31

One or more toolpaths whose function is to bring the work piece to the final desired geometry.

Question 32

Step down

Answer 32

The distance in the z-driection per pass that the cutting tool will be plunged into the work.

Question 33

Step over

Answer 33

The maximum distance in the X/Y direction that the cutting tool will engage with the work.

Question 34

Facing (milling)

Answer 34

A machining operation that is used to reduce the thickness of the work over an entire face, It can be accomplished with an endmill, but is often done with a face mill, shell mill, or fly cutter.

Question 35

Contour

Answer 35

A machining operation that follows along the drive geometry (lines or surfaces). Generally used for a finishing operation, but with the use of multi-passes can be used as a roughing operation.

Question 36

Pocket

Answer 36

A machining operation that removes material within a defined region of geometry. Can be used as a roughing operation, or a finishing operation with the use of the options within the toolpath.

Question 37

Dynamic or Adaptive milling

Answer 37

A set of machining operations that utilize a modern scheme of tool motion that always maintains consistent cut loads. The tool moves in long, flowing motions that remove material in the mathematically optimal way. Falls under the umbrella of High Speed machining.

Question 38

Raster

Answer 38

A machining strategy where the tool moves back and forth along one axis. Each pass is shifted by the step over distance. The tool is moved up ad down to follow the drive surfaces, if appropriate.

Question 39

Scallop

Answer 39

The material left over between passes of a ball0 or bull-nose endmill. The passes, separated by the step over distance, will naturally leave a series of small hill-shaped sections of material.

Question 40

Changing

Answer 40

The method of selecting machining geometry within MasterCAM. 2D wireframe entities, surfaces, and solid model geometry may be used to define machining parameters.

Question 41

Feed rate

Answer 41

The rate that the tool moves through the work. Measured in IPM (inches per minute). There are general guidelines for feed rates, but specific values are provided by the tool manufactures depending on, among other parameters, the tool material, work material, and the type of cutting operation.

Question 42

Feed (chip) per tooth

Answer 42

The amount that the tool moves per rotation of each flute, or put it in another way, the size of each chip that is created by the rotating and feeding tool.

Question 43

Plunge

Answer 43

The movement of the tool in the negative Z (down) direction

Question 44

Spindle speed

Answer 44

The RPM that the machine is moving the tool holder.

Question 45

SFM

Answer 45

Surface feet per minute. The speed that the tool moves across the surface of a workpiece. The value depends on factors such as workpiece material, tool material, tool coating, and the type of machining operation. There are general guidelines for choosing SFM, but specific values are provided by a tool manufacturers.

Question 46

Retract

Answer 46

Tool movement in the positive Z (up) direction.

Question 47

Compensation

Answer 47

The set of parameters having to deal with using the CNC controller to automatically offset the tool to one side of the geometry to be machined. This is particularly useful when manually programming to machine simple and complex surfaces. It is also useful for ensuring that the machined geometry is accurate even when the tool diameters can vary due to wear.

Question 48

Stock to leave

Answer 48

The MasterCAM parameter that describes the amount of material that should be left on the drive geometry. This can be used in a roughing operation to ensure that the fast and (generally) less-accurate machining seps do not make contact with the desired final geometry.

Question 49

Depth cuts

Answer 49

The MasterCAM parameter that provides for machining all the drive geometry at varying Z levels. Used to limit the amount of tool engagement with the work piece. Useful in situations where the final depth of the machining operation is too deep to create in a single machining step.

Question 50

Lead in/out

Answer 50

The MasterCAM parameter that defines how the tool approaches and leaves the drive geometry. Usually the lead in/out moves follow an arc that tangentially contacts the final drive geometry. This parameter is useful in ensuring a perfectly clean surface. Disabling this parameter will result in the tool plunging and retracting while still in contact with the drive geometry which may result in minute surface variations at the point of contact.

Question 51

Entry Motion

Answer 51

The MasterCam parameter that produces motion in more than one axis as the tool descends along the negative Z-axis. This is used to reduce the cutting load during a plunge move as well as to clear area around the tool as it descends for non-center cutting tools.

Question 52

Break Through

Answer 52

The MasterCAM parameter that specifies the amount to overshoot the final depth of a cut. This is useful to ensure that feature like a hole cut completely through the workpiece. Used in conjunction with Tip compensation which factors in the size of the end of a tool like a drill to ensure that the desired geometry is achieved.

Question 53

Multi-passes

Answer 53

The MasterCAM parameter that creates multiple tool motions that are offset from the desired final geometry to remove material from the outside in a contour tool path.

Question 54

Tabs

Answer 54

Areas of unmachined material used to ensure that parts aren't completely cut out of the stock. Parts that lose contact with the stock may fall and could cause tool breakage as well as unintended contact with the finished geometry. Tabs are machined away as a secondary operation, usually done outside the CNC machine.

Question 55

Linking parameters

Answer 55

The parameters within MasterCAM that define the depth of machining steps, the top of the machining steps, the plane where the tool should retract to between machining steps, and other parameters relating to the Z (up/down) axis movement of the tool.

Question 56

Retract Plane

Answer 56

The plane, usually above the work piece, at which the tool will move to in between cutting operations. This allows for chip clearance and to reposition the tool to the entry point of the machining operation.

Question 57

Feed plane

Answer 57

The plane above the workpiece that the tool moves in the negative Z (down) direction at the specified feed rate.

Question 58

Rest material

Answer 58

A MasterCAM parameter that allows for remachining areas that weren't accessible due to the size of the previous operations tool. Usually used to get closer into internal corners.

Question 59

Spring Pass

Answer 59

A final pass machined at the exact same place as the previous pass. So named as it is intended to remove material that wasn’t removed by the previous pass because the machining loads can cause the tool to deflect away from the desired position.