Please enable JavaScript.
Coggle requires JavaScript to display documents.
Subtractive Manufacturing (Parts (Spindle unit: Holds cutter. Moves in X…
Subtractive Manufacturing
Definition: Manufacturing process where cutter movement is controlled by NC program
Parts
Spindle unit: Holds cutter. Moves in X and Z direction. Also rotates cutter
Work table: Holds product, travels in Y direction
Control Panel: Starts machine program
Program: Has Alpha-numeric code. XYZ dictates cutter location with respect to zero reference (Top left)
Pros and Cons
Pros
Programmable
Can cut on hard metal
Fine surface finish
Accurate
Cons
Need post processing
Sometimes half of the parts are made separately then glued tgt
Cutter size limitation
Cutter has minimum diameter size, not possible to machine sharp edges
Cutter length short, cutter holder cannot collide with part
Work holding device
Can only move cutter in XYZ direction
Product need to be held tightly as cutting force is strong
Flip over product manually when top half is done
Can only shape design's top half
CAM programming skill
Need to use CAM software. Need skill
Trained Machinist
Need skill to operate CNC machine
5 axis machining center
Has two rotational axes but more expensive & complex
Work flow
CAM
Tool path programming
Toolpath & tool definition
Optimize toolpath and CNC
Part & Assembly design
program drives CNC
CNC
Program drives cutter movement to shape material
CAD
Product modelled and converted to STL
Terminology
CNC- Computer Numeric Control
CAM-Computer Aided Manufacturing
Parameter for CAM
Step depth
How deep cutter can plunge into product
Depends on material; softer material deeper cut faster material removal
Cutter plunge down more times for hard material cuz smaller depth of cut
Step over
How far apart cutter progress when zigzagging
Narrow when shaping curved surface
Spindle speed/feedrate
Spindle speed: RPM rotation
Feedrate: Feed direction mm/min
Roughing and Finishing
Cut part to accurate dimension + good surface finish
Roughing: Remove bulk material at shorter time