## Class Details

- Class Name:
- Calculations for Programming the Mill 312
- Difficulty:
- Advanced
- Number of Lessons:
- 17

## Class Outline

- CNC Milling
- Cartesian Coordinates and Program Zero
- Coordinates for the Mill Review
- Face Milling
- Face Milling Calculations
- Pocket Milling
- Pocket Milling Calculations
- Cutter Radius Compensation
- Face Milling and Pocket Milling Review
- Spot Drilling
- Spot Drilling Calculations
- Twist Drilling and Trigonometry
- Twist Drilling Calculations
- Trigonometry and Drilling Calculations Review
- Bolt-Hole Patterns
- Full-Circle Calculations
- Final Review

## Objectives

- Describe CNC milling.
- Describe the coordinate system used for the mill. Describe program zero.
- Describe face milling.
- Calculate face milling cutting passes.
- Describe pocket milling.
- Describe calculations for pocket milling.
- Describe cutter radius compensation.
- Describe spot drilling.
- Explain how to calculate drill depth for a spot drilling operation.
- Explain how trigonometry is used in twist drilling operations.
- Calculate total drill depth coordinate locations.
- Explain the calculations necessary to drill a bolt-hole pattern.
- Describe full-circle calculations.

## Job Roles

## Glossary

Vocabulary Term | Definition |
---|---|

adjacent | In a triangle, a side that touches an angle. The adjacent sides form the angle. |

aeronautical | Having to do with airplanes or other flying craft. Aeronautical applications tend to require extremely precise tolerances. |

approach distance | A short distance added to the beginning of a toolpath. Approach distance helps to prevent damage to the machine and the workpiece. |

arc center method | A method for programming circular tool movements that indicates the location of the arc's center along the X and Y axes using I and J codes. The arc center method is usually used for full-arc motions. |

arc-in motion | A partial-arc motion that leads into a larger-arc motion. Arc-in and arc-out motions leave a smooth surface finish. |

arc-out motion | A partial-arc motion that exits from a larger-arc motion. Arc-out and arc-in motions leave a smooth surface finish. |

axes | Imaginary lines that pass through the center of a point or object. Axes are used to describe the positions of objects on the Cartesian coordinate system. |

bolt-hole pattern | A series of equally spaced holes around the circumference of a larger imaginary circle. Bolt-hole patterns are calculated with trigonometry. |

boxing routine | A series of toolpaths used to machine a rectangular pocket. A boxing routine starts in the center of the pocket and moves outward in a rectangular pattern. |

CAD/CAM | Computer-aided design/computer-aided manufacturing. The use of computers to aid in the design and manufacturing of a part. CAD/CAM makes it comparatively easy to machine complex surfaces, especially parts with three-dimensional contour features. |

calculator | A small, handheld device used to solve mathematical problems. Calculators can be useful for finding the sine, cosine, or tangent of an angle. |

Cartesian coordinate system | The system that describes the position of any point or object in three-dimensional space by expressing its distance from a fixed position along linear axes. The Cartesian coordinate system is used to describe measurements in CNC milling and turning. |

chamfer | An angled surface added to an edge of a workpiece. Chamfers replace a sharp edge with a 45° angle. |

chatter | The development of surface imperfections on the workpiece caused by vibrations of the cutting tool. Chatter can occur if step-over is either too little or too much. |

circumference | The distance around a curve or circle. The circumference is the circle's outer perimeter. |

clearance | Any useful space that is intentionally maintained between components. Clearance is often necessary to prevent machine damage. |

computer numerical control mills | CNC mills. A milling machine that makes precise cuts according to numerical data. Computer numerical control mills are much more precise than their manual counterparts. |

contour features | A curved part of a workpiece. Contour features are complex and generally calculated using CAD/CAM software. |

cosine | In a right triangle, the ratio of the length of the side adjacent to the angle and the hypotenuse. The cosine of a right triangle can be found by calculating the ratio as a division. |

cutter radius compensation | CRC. An offset that accounts for variations in tool diameter. Cutter radius compensation is necessary for tools that continuously cut in the X or Y axis. |

deflection | The unintended movement or repositioning of a component due to a mechanical force. Deflection of a cutting tool can cause poor surface finish and inaccurate dimensions. |

diameter | The distance from edge to edge of the widest point of a circle. The diameter of a circle is always twice its radius. |

end mill | A long, thin milling cutter with a flat bottom and cutting edges that wind up the sides. End mills have helical flutes and relatively small diameters. |

face mill | A flat milling cutter with multiple cutting teeth on its periphery. Face mills rapidly remove metal from the top surface of a workpiece. |

face milling | A milling operation in which the surface of the workpiece is perpendicular to the spindle axis. Face milling is primarily used to mill the top surface of the part. |

finishing pass | A cutting pass that produces the surface finish and brings a feature to its proper size. The finishing pass is typically the last operation in the part program. |

G code | A code that determines the type of operation performed on the machine. G codes select the type of motion, speed or feed mode, etc. |

geometry | A branch of mathematics that involves the measurements, properties, and relationships of dimensional objects. Geometry is used in CNC machining. |

hypotenuse | In a right triangle, the side located opposite the right angle. The hypotenuse is the longest side of the triangle. |

I code | The program code that indicates the location of an arc's center along the X axis. I and J codes are used for the arc center method. |

isosceles right triangle | A triangle with one 90° angle and two 45° angles. The two 45° sides of an isosceles right triangle are always equal in length. |

J code | The program code that indicates the location of an arc's center along the Y axis. J and I codes are used for the arc center method. |

length-to-diameter ratio | A ratio comparing the length of a cylindrical tool to its diameter. Higher length-to-diameter ratios offer less rigidity. |

machine control | A computer that directs a CNC machine. The machine control interprets the part program and relays its instructions to the CNC machine. |

milling cutter | A multipoint tool that removes metal from the surface of a workpiece. Milling cutters can create parts with complex shapes. |

offset | A fixed adjustment that moves the tool to compensate for the tool's length, width, or another factor. Offsets help to ensure that finished parts are to specifications. |

origin | The fixed center point of the Cartesian coordinate system. The origin has a numerical value of zero for any axis. |

part program | A series of instructions used by a CNC machine to perform the necessary sequence of operations to machine a specific workpiece. Part programs are written in G code. |

An interior recess that is cut into the surface of a workpiece. Pockets can be circular, rectangular, or a combination of the two. | |

program zero | The position that acts as the origin for the part program of each particular workpiece. Program zero is selected by the part programmer. |

programming language | A language used to program or provide directions to a computer or machine. The programming language used by CNC machines is called G code. |

R code | The program code that indicates the length of an arc's radius. In certain canned cycles, an R code indicates the R level for tool return. |

radius | A straight line extending from the center point to the periphery of a circle. The radius of a circle is always one-half of its diameter. |

radius method | A method for programming circular tool movements that indicates the size of the arc's radius using an R code. The radius method is best used for partial-arc motions. |

right triangles | A triangle that includes a 90° angle as one of its three angles. Right triangles are often used in drilling calculations. |

sine | In a right triangle, the ratio of the length of the side opposite the angle and the hypotenuse. The sine of a right triangle can be found by calculating the ratio as a division. |

spot drill | A short, sturdy drill used to start a hole and accurately locate it. Most spot drills have a 90° tip. |

step-over | The amount of the cutter's diameter that is engaged in a cut. Step-over is generally 75% or less of the cutter's diameter. |

symmetrical parts | A part that can be divided into two equal halves with identical features that are equal distances from the centerline. Symmetrical parts typically have program zero placed in the center. |

tangent | In a right triangle, the ratio of the length of the side opposite the angle and the side adjacent to the angle. The tangents of a right triangle can be found by calculating the ratio as a division. |

three-dimensional | Having length, width, and depth. Three-dimensional parts can be machined with CNC machines. |

through holes | A hole that passes completely through a workpiece. Through holes require that the depth of the hole, the length of the drill tip, and a small amount of additional clearance all be calculated. |

toolpaths | The series of coordinate positions that dictate the movement of a tool during a machining operation. Toolpaths are programmed using G code. |

trigonometry | A branch of mathematics that addresses the measurements and relationships of triangles and their components. Trigonometry is often used in milling calculations. |

twist drill | A common drill characterized by helical flutes along its length and two cutting edges at the drill point. Twist drilling is usually preceded by spot drilling. |

X axis | The linear axis representing the longest distance of travel parallel to the worktable, or left to right on a vertical mill. The X axis is perpendicular to the Y and Z axes. |

Y axis | The linear axis representing the shortest distance parallel to the worktable, or towards and away on a vertical mill. The Y axis is perpendicular to the X and Z axes. |

Z axis | The linear axis that represents motion towards and away from the worktable, or up and down on a vertical mill. The Z axis is perpendicular to the X and Y axes. |