Machining on CNC machines is controled by a NC code. NC code is a list of instructions for the machine and also for the operator. Instruction are executed in time order. NC code must have a specific format so that the control system of machine is able to read it.
The tool in machine is moving in workspace. The position of the tool is given by coordinates. We are using different coordinate systems. If we set some coordinates in NC code, the machine moves the tool to the specified place.
Basic is orthogonal system Z Y X
Z axis is usually axis of spindle a X axis is the working axis, or the longest! Z Y X
Z axis is usually axis of spindle a X axis is the working axis diameter!!! X Z
To set the position we can add rotation along the axes. C Z B Y Second set of coordinates U,V,W resp. P,Q,R etc. A X
Refernce point a specific point on machine with given coordinates. Not always in the workspace of machine. A special command G98
Tool is moving to specific coordinates with given speed. On its way it may enter the material and perform machining
Ways how to define a movement a) Absolute programing position is in all point expressed as a distance from zeropoint b) Incremental programing position is expressed as a change from last postion
2. 3. 1. 2. 3. 1. Absolut G90 X0 Y0 Z50 G0 X15 Y70 Z50 G1 X15 Y70 Z0 G1 X25 Y70 Z0 G0 X25 Y70 Z50 G0 X0 Y0 Z50 Incremental G91 G0 X15 Y70 Z0 G1 X0 Y0 Z-50 G1 X40 Y0 Z0 G1 X0 Y0 Z50 G1 X-45 Y-70 Z0
Structure and form of NC code is standardized by international standard - ISO 6983 Numeric control programs formating Differences between different control system manufacturers and differences between versions.
Lines (blocks) Words Word has a meaning and value part S 1500
ISO is standardized code (G code) Some manufacturers devoloped their own standard for NC code native standard Mazak Mazatrol Heidenhein itnc Siemens - Sinumeric
Heading lines Definition of relation between coordinate system of CNC machine and program, type of programing, work mode, working conditions Program body Cutting and non-cuting moves, main program and subprograms, tool changes Ending lines Tool return to home point, change to first tool, coordinates reconstruction
Subprograms A link to another then the following line is entered into main programm. This subprogram is executed. After finishing this program we return to main program a we contiue until end of main program(m30)
Manual/Hand programing Shopfloor programming Automated programing
Editors are used. Program is written manually (by hand) line after line. Used for simple parts (but complex too) Toolpath is exactly defined Program can be adjusted to save time Can use canned cyles Can be parametrized Used in mass production
We need to know the functions: (many more function exist) Movement functions: G00 rapid movement G01 linear interpolation/movement G02/03 circular interpolation G40 diameter compensation off G41 diameter compensation on /right handed G42 diameter compensation on /left handed Support and help functions: M06 tool change M03/04 spindle start CW/CCW M05 program stop M30 program end
Specilzed editors Predator G-code editor G Wizard Mikronex
Somewhere in between manual and automated Uses cycles with parameters We have to edit these parameters manually But the NC code is generated automatically No postprocessing
Control system use programming on machine - No costs (together with machine) - Fast use (macros) - Time waste (program x work) - Comfort (on machine x in office with PC) - Shape limitations Heidenhein
Work with the sequential NC code preparation Uses CAM (Computer Aided Manufacturing) software For all parts including complex shapes We dont need to compute the toolpath We need correct postprocessor
Partprogram workpiece, material, cutting conditions, tools Procesor according to technology CL data virtual toolpaths on virtual machine Postprocesor translator for the specific CAMcontrol systém-machine combination NC code toolpaths of a real tool on a real machine Partprogra m CL-data NC-kód Proces or Postproces or
is Computer Aided Manufacturing (machining) From simple 2-axis turning up to multiaxis machining Feature or technologically oriented Special types of CAM for special purpose Live presentation
2D just in two axis - turning 2,5D two axis, but in layers not simultaneously 3D three axes simultaneously multiaxis 4D four axis - one rotary axis (rotary table) 5D five axis - maching (two rotary axes)
CAM software uses Strategies Strategy is a general plan how to move the tool durign machining Continual development Roughing offset, raster (Zig-Zag method) plunging Finishing strategies pencil milling, streaming, rest material maching
NX (Siemens PLM software) Catia (Dassault systémes) both 10% market share PowerMill, FeatureCAM, ArtCAM (Delcam company),inventorcam (Autodesk) Wildfire Pro/Ingineer (PTC) 5% EdgeCAM, SurfCAM, SolidCAM, MasterCAM, OneCNC, ESPRIT, GibbsCAM
Simulation is used to control generated toolpaths for following reasons: - Colisions - Undercuts (or rest material) - Postprocesing check
NX
We can do complex shapes, no need to calculate control points We can use simulation and verification We can change the tool easily But We need postprocessor Expensive (SW, computer, learning ) Program is always longer (again expensive)
Projects - Common same tasks for all - Individual own selection of part and individual work on it. Evaluated. Test from theory of programming and use of CAM software