Machining and joining Exam 2

Machining

The idea of cutting materials into desired shapes

Types of machining

Turning, Milling, routing, Cutting, Finishing

Soft materials

PE or PP

Hard Plastics

ABS or PC

Types of cutting

Sawing, Punching, Blanking, Die Cutting

Induced facture cutting

Scoring or blanking of material. Usually a thin sheet.

Thermal Cutting

Hot thin wire used for cutting the material

Example of what material works well for thermal cutting

foam core cutting

Water Jet (hydrodynamic Cutting)

usually water or possible or slurry at high velocity (45,000 psi)

Laser Cutting

produces cuts with complex geometry, and holes have a slight taper

what is a

disadvantages to laser cutting

some materials will burn or catch on fire

Finishing

sanding or polishing

what is the case with most plastics when sanding and why

Most plastics have low thermal conductivity and tend to burn

ways to help with sanding

use coolint, and open grit paper or wheel when sanding

What is tumbling

a way to polish a batch of parts at the same time

Spin welding

parts are rotated against each other, only for circular parts

ultrasonic

uses frictional heat produced from ultra sonic vibrations to melt the plastic

what is the amount of Hz used to melt the plastic using ultrasonic bonding

greater than 20 kHz

Vibration bonding

uses heat from friction produced by vibrations to melt the part

what is the amount of Hz used to melt the plastic using vibration bonding

90-120 Hz

Hot gas welding

uses heated gas directed into the joints of the plastics to weld

how much weld can it exceed during hot gas welding

85%

Laser welding

only one material gets hit by the laser absorbing the energy

Friction Fitting

Relies on the friction on the interface on two joints

Press fitting

one part is forced into the

shrink fitting

Part is placed into another part at an elevated temp. and cooled simultaneously

Snap Fitting

plastic forced over a lip or into a undercut retaining ring

self threading

process material with hole then place the screw

Example of ,material used with self threading

sheet metal

thread inserts

place parts with threads in the the hole in plastic

Type of material is Mechanical adhesion

Thermoplastic Resin

What is mechanical adhesion

bonds well to adherends but allows for extension and compression

Chemical adhesion

molecules of material flow together and forces it to hold together

when can chemical adhesion happen

it can only happen when materials flow into each other.

solvent bonding

monomeric cements solvent cements, dope cements,

solvent cements

dissolves the surface other plastics being joined

dope cements

contain solvents and small amounts of the polymer being joined

monomeric cements

based on the monomer of the plastics being used