Studied by 2 people
cutting
reduce length of material
remove section
sawing
a type of cutting
each saw tooth cuts a small groove in the material
teeth angled out from the blade so the cut groove is wider than the blade (so the blade doesn’t get stuck)
debris is deposited as the saw emerges from the other side
can only cut as fast as the material is removed, adding extra force won’t make it cut faster
harder material = smaller saw teeth
different types of saws
hacksaw - fine teeth for metal/polymers
junior hacksaws - smaller, for cutting thinner sections of metals/polymers
mechanical saws - big hacksaws for metal bars/rods
coping saw - narrow blade for cutting curved shapes in polymers
tenon/rip/sheet saw - straight cuts for structural timber, with larger teeth than saws used to cut metal
jigsaw - a motor moves the blade. there’s a wide variety of these
shearing
a type of cutting
applying force from opposite sides of a metal sheet
sheet separates in a line between the two points where the force was applied
tin snips/shears cut thin sheet
guillotines cut thick sheet
industrial guillotines push a blade made of tool steel
laser cutting
thin sheets of polymer/metal
material along cut line is vaporised, and the vapor is sucked from the machine
controlled by a computer, as it’s unsafe to control by hand
expensive, but flexible
accurately makes small quantities of parts
turning
uses lathe
parts/features with a round profile
workpiece held by lathe and rotated
tool pressed into workpiece to remove material
facing off: creates a flat face, at right angles to the axis of rotation
cylindrical/parallel turning on a lathe
uniform shape, same diameter along the turned length
taper turning on a lathe
diameter larger at one end and keeps reducing, making a tapered shape
drilling/boring on a lathe
make holes through round workpieces
centre drilling: drillbit pushed to the end to make a hole
boring: produces an internal hole
you can adjust internal diameters, produce internal tapers/steps, cut internal threads, etc
CNC lathes are computer programmed, and fitted with tools so you can do all of the above
milling
rotating tool removes metal one layer at a time
can face (make slots/grooves)
the axis which the milling tool rotates about can be horizontal or vertical
can make PCBs (can also be made with a computer controlled milling machine)
CAD drawing of PCB & a strip of insulating material with a layer of copper
tool cuts a groove into copper layer around the outside of the tracks of the PCB design
doesn’t use hazardous chemicals (chemical etching)
copper tracks are a bit bigger to let the tool access to remove extra copper, so PCB is bigger
Drilling
makes holes using a rotating tool
not centre drilling, which uses a lathe
hand drill is manual
portable/battery powered drills use electricity, reducing effort
pillar drills are used if the part can be moved
part held in vice, jig, g-cramp
different materials, different cutting speeds
chemical etching
uses chemicals to remove materials
photo-etching
1. PCB material coated with light-sensitive film over copper
2. transparent material with the PCB design is printed (mask)
3. mask placed over light-sensitive film
4. film exposed to UV. The mask protects the design from light
5. The image of the PCB design appears on the board
6. placed in chemical bath (with ferric chloride), which eats away at areas that were exposed to light, and the copper that is in these areas
7. board rinsed with water, and holes drilled
