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Subtractive Manufacturing ( CNC ) (Constrains of using CNC (Work holding…
Subtractive Manufacturing ( CNC )
Computer Numerical Control (CNC)
NC Program
Control the movement of the spindle unit and work table
Consists of Alpha-Numeric code ->
G- Code
X, Y , Z values dictates the cutter location with respective to the work piece zero reference
Machining path is pre-programmed
What is it?
A manufacturing process in which pre-programmed computer software dictates the movement of factory tools and machinery
Parts of CNC
Control Panel
Starts the machining program
Spindle Unit
Holds cutter
Travels in X and Z direction
Rotates the cutter when cutting
Work Table
Holds the work piece
Travels in Y direction
How it works?
Remove material from a raw material until the desired shape
The process is programmable
Tool movement is controlled by NC program
Machining path is pre-programmed (NC Program)
Advantages of using CNC
Can cut on
hard-metallic
material
product a
fine surface finish
Process is
programmable
more
accurate
Constrains of using CNC
Work holding Device
Can only machine the top-half
need to hold the piece tightly
5-axis Machining Center
More expensive and complex
Post-processing needed
Might require post-processing such as gluing together
Limitation of cutter size
requires minimum diameter size of machining cutter
Limit cutter size
CAM Programming Skill
Special training required
Trained Machinist
Must have knowledge and skills of machining process
Work Flow
CAD Model
CAM
CNC
How does CAM system works
Step depth
define how deep can the cutter plunge
depends on work piece material
Step over
how far the cutter can progress when moving zig zag
better surface finish
longer machining time
Sindle Speed
feed rate, spindle speed
machining speed defined by spindle speed and cutter forward movement
Roughing and Finishing
Roughing
remove bulk material at a shorter time
ignore surface finishing
Finishing
cut the part to accurate dimensions
good surface finish