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File Preparations for the CNC Mill
File Format and Preparation
To use the CNC Mill, a user must first create a Computer Aided Design file using a CAD software packages such as Solid Works, IronCAD, AutoCAD, and ProEngineer or illustrator.
Next the tool selection and path must be programmed; the user needs to decides where the path followed by cutting tool (as well as the depth) , and which tool will be mounted and when to change tools. This process is described by the G and M codes.
There are several methods to generate G-code from a cad file or a drawing. We describe here the definition of a 2D tool path from DXF to gcode using the ACE converter.
Additional information on preparing G-Code files: VMC 4000 Information Page.
You can also program your own G-code and test it with the simulator below.
Preparing the CAD file:
When preparing your CAD file, you need to draw the exact cutting path for the tool, therefore, you need to consider the size of the tool.
Make sure you define your units in either inches or millimeters consistently (throughout the whole process) starting from the drawing or model file, the Gcode generator, and the Benchman operation software.
- Prepare a 2D drawing file using Autocad, Illustrator, or IronCAD
- Save this in DXF (version 12 or 13 work best).
Converting to G-code (using the ACE converter)
ACE converter is A free G-code generator that allows you to define tool paths in 2D. ACE will only read 2D dxf files.
It is located in the computer in the RP LAB. (downloads sources below)
- Open ACE converter software
- Load the DXF file
- Set properties for each layer
You can assign a depth of cutting for each layer of the file, therefore accounting for many cutting types and depths.
- Set the post-priority, the pre- priority and the release value (for the whole file)
- The pre-priority code is
Mcode to add in the begriming of the file,
usually to set the tool number and spindle speed.
Ex::
M06 T08 (tool change #8)
M03 S1000 (clockwise and speed 1000)
- The post-priority code is the
Mcode to add in the end of the file,
usually to end the program. Ex:
M05 stop
M02 end the program
- The release-value is for is for moving the tool above the material between cuts. Zero is where the material starts. Ex
(.25 inch above zero in the z-axis)
- After the setting is complete, click convert: it will convert the drawing to Gcode.
Save your file as a .txt or a .nc file
- You can test the Gcode generated in ACE using CNC simulator.
Free G and M Code Generators and Simulators
G and M Codes
G-Code is for describing the tool path by means of coordinates, while M-codes are for describing machine commands, such as tool types, speeds and starting the ending the program. Both are necessary to run the program.
Short introduction to G and M codes to know.
G00 positioning (rapid traverse) |
G54 work coordinate system 1 select |
G01 linear interpolation (feed) |
G55 work coordinate system 2 select |
G02 circular interpolation CW |
G56 work coordinate system 3 select |
G03 circular interpolation CCW |
G57 work coordinate system 4 select |
G04 dwell |
G58 work coordinate system 5 select |
G07 imaginary axis designation |
G59 work coordinate system 6 select |
G09 exact stop check |
G60 single direction positioning |
G10 offset value setting |
G61 exact stop check mode |
G17 XY plane selection |
G64 cutting mode |
G18 ZX plane selection |
G65 custom macro simple call |
G19 YZ plane selection |
G66 custom macro modal call |
G20 input in inch |
G67 custom macro modal call cancel |
G21 input in mm |
G68 coordinate system rotation ON |
G22 stored stroke limit ON |
G69 coordinate system rotation OFF |
G23 stored stroke limit OFF |
G73 peck drilling cycle |
G27 reference point return check |
G74 counter tapping cycle |
G28 return to reference point |
G76 fine boring |
G29 return from reference point |
G80 canned cycle cancel |
G30 return to 2nd, 3rd & 4th ref. point |
G81 drilling cycle, spot boring |
G31 skip cutting |
G82 drilling cycle, counter boring |
G33 thread cutting |
G83 peck drilling cycle |
G40 cutter compensation cancel |
G84 tapping cycle |
G41 cutter compensation left |
G85,G86 boring cycle |
G42 cutter compensation right |
G87 back boring cycle |
G43 tool length compensation + direction |
G88,G89 boring cycle |
G44 tool length compensation - direction |
G90 absolute programming |
G49 tool length compensation cancel |
G91 incremental programming |
G45 tool offset increase |
G92 programming of absolute zero point |
G46 tool offset decrease |
G94 per minute feed |
G47 tool offset double increase |
G95 per revolution feed |
G48 tool offset double decrease |
G96 constant surface speed control |
G50 scaling OFF |
G97 constant surface speed control cancel |
G51 scaling ON |
G98 return to initial point in canned cycle |
G52 local coordinate system setting |
G99 return to R point in canned cycle |
M00 program stop |
M21 tool magazine right |
M01 optional stop |
M22 tool magazine left |
M02 end of program (no rewind) |
M23 tool magazine up |
M03 spindle CW |
M24 tool magazine down |
M04 spindle CCW |
M25 tool clamp |
M05 spindle stop |
M26 tool unclamp |
M06 tool change |
M27 clutch neutral ON |
M07 mist coolant ON |
M28 clutch neutral OFF |
M08 flood coolant ON |
M30 end program (rewind stop) |
M09 flood coolant OFF |
M98 call sub-program |
M19 spindle orientation ON |
M99 end sub-program |
Cost
Cost is dependent on Material, Tolerance, and Size.
Material: certain stock materials are more expensive than others. Higher grades of stock take more time to cut and are therefore more expensive. Stronger materials cause more wear on the mill.
Tolerance: Tolerances using a CNC milling machine can be as tight as 1 thousandth of an inch. Production tolerances are sometimes acceptable because human error and machine deviance are inevitable. The tighter the tolerances needed, the higher the cost.
Size and complexity: Larger pieces lead to higher costs;
larger, more complex parts take longer to produce, and therefore, cost more.
You need to buy your materials (machine wax) from the Mechanical Engineering Workshop
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