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## CLASS DETAILS

- Class Name:
- Milling Calculations 295
- Description:
- This class explains the common calculations necessary to plot the toolpaths for a basic milling program.
- Version:
- 1.0
- Difficulty:
- Intermediate
- Number of Lessons:
- 17
- Additional Language:
- Spanish

## Class Outline

- Objectives
- The Purpose of Toolpath Calculations
- Program Zero Location
- Face Milling Calculations
- The Face Milling Toolpath: Y-Axis
- The Face Milling Toolpath: X-Axis
- Pocket Milling Calculations
- The Pocket Toolpath
- Spot Drilling Calculations
- The Spot Drill Toolpath
- Drilling Calculations
- The Drilling Toolpath
- CRC on the Mill
- Full-Circle Milling Calculations
- The Full Circle Toolpath
- The Bolt Hole Pattern
- Summary

## Objectives

- Describe the basic elements of a toolpath.
- Identify the appropriate location for program zero on a part.
- Explain the general rules that govern face milling calculations.
- Calculate the Y-axis locations for a common face milling operation.
- Calculate the X-axis locations for a common face milling operation.
- Explain the general rules that govern pocket milling calculations.
- Calculate the initial coordinates to begin a boxing routine for a rectangular pocket.
- Explain the general rules that govern spot drilling calculations.
- Calculate the depth required to leave a chamfer with a spot drill.
- Explain the general rules that govern drilling calculations.
- Calculate the depth required to completely drill a hole.
- Explain a common method for removing ramping motions from a program’s toolpaths.
- Explain the general rules that govern full-circle milling.
- Calculate the starting locations for matching full radius and arc in motions.
- Calculate the coordinate location of a hole in a bolt-hole pattern.

## Glossary

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

approach | A slight distance added to a toolpath at the beginning of a cut for safety reasons. |

arc center method | A method for programming circular tool movements that requires an I code and J code to indicate the location of the arc's center along the X- and Y-axes. The arc center method is best 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 in and arc out motions leave a smooth surface finish. |

bolt-hole pattern | A common specification on milled parts that requires a series of equally spaced holes around the circumference of a larger imaginary circle. |

boxing routine | A series of increasingly larger rectangular toolpaths used to machine a rectangular pocket. |

CAD/CAM | Computer-aided design/computer-aided manufacturing. CAD/CAM is the use of software to aid in the design and manufacturing of a part. |

chamfer | A small, angled surface added to an edge of a workpiece. A chamfer removes the sharp edge and helps eliminate burrs. |

clearance | Any useful space that is intentionally maintained between components. |

contour feature | A part feature that is non-linear, or curved. |

coordinate system | The numerical system that describes the location of an object by numerically expressing its distance from a fixed position along three linear axes. The coordinate system consists of the X-, Y-, and Z-axes. |

cosine | In a right triangle, the ratio of the length of the side adjacent to the angle divided by the hypotenuse. |

cutter radius compensation | An offset used on the machining center that accounts for variations in tool diameter. CRC is only necessary for tools that continuously cut along a horizontal plane. |

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. |

end mill | A thin, tall mill cutter with a flat bottom and cutting edges that wind up the sides. Both the bottom and side of the end mill provide cutting surfaces during milling operations. |

face mill | A flat mill cutter with multiple cutting teeth surrounding the tool. The bottom of the face mill is primarily the cutting surface during milling operations. |

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

finishing pass | A final cutting pass that produces the necessary surface finish and brings a feature to its proper size. |

finishing stock | The small amount of material that is intentionally left for a finishing pass. |

hypotenuse | In a right triangle, the side located opposite the right angle. |

I code | For circular interpolation, the program code that indicates the location of the arc's center along the X-axis. I and J codes are used for the arc center method. |

J code | For circular interpolation, the program code that indicates the location of the arc's center along the Y-axis. I and J codes are used for the arc center method. |

length-to-diameter ratio | A ratio describing the length of a cylindrical tool or workpiece compared to its diameter. Higher length-to-diameter ratios offer less rigidity. |

milling cutter | Any multi-point tool that is used to remove metal from the surface of a workpiece. |

part program | A series of instructions used by a CNC machine to perform the necessary sequence of operations to machine a specific workpiece. |

An interior recess that is cut into the surface of a workpiece. Pockets may be round or rectangular. | |

program zero | The position that acts as the origin for the part program of a particular workpiece. This position is unique to each workpiece design, and it is selected by the part programmer. |

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

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

ramping motion | A linear motion of the tool that is required for a control to adjust for a particular tool offset. |

sine | In a right triangle, the ratio of the length of the side opposite the angle divided by the hypotenuse. |

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 size of the cutter's diameter that is engaged in a cut. The step-over should be 75% to 80% of the cutter's diameter. |

symmetrical part | A part that can be divided by a line into two equal halves, with identical features that are equal distances from the dividing line. Both sides appear as mirror images of each other. |

tangent | In a right triangle, the ratio of the length of the side opposite the angle divided by the adjacent side. |

toolpath | The series of coordinate positions that determine the movement of a tool during a machining operation. |

trigonometry | The branch of mathematics that addresses the measurements and relationships of a triangle and its parts. |

wear offset | An offset used on a turning center and some machining centers that allows for the slight adjustment of tool tip location. Wear offsets account for part deflection, tool wear, etc. |

X-axis | On the mill, the linear axis representing coordinate positions along the longest distance parallel to the worktable. |

Y-axis | On the mill, the linear axis representing coordinate positions along the shortest distance parallel to the worktable. |

Z-axis | On the mill, the linear axis representing coordinate positions perpendicular to the worktable. The Z-axis is always parallel to the spindle. |