Lecture 6: Joining

Question 1

What is joining in manufacturing?

Answer 1

Joining refers to processes that bring all components together into one assembly.

Question 2

Why is magnetism important in joining?

Answer 2

Magnetism is important because components may stick together during the assembly process.

Question 3

What is detachability in assembly?

Answer 3

Detachability refers to the ability to take apart an assembly without damaging the components.

Question 4

What are the principles of joining?

Answer 4

Geometry, force, material.

Question 5

What are the three geometric types of joining?

Answer 5

Point, line, face.

Question 6

What is fusion welding?

Answer 6

Fusion welding involves melting materials to join them with materials of similar compositions and melting points.

Question 7

What are the advantages and disadvantage of oxyfuel-gas welding?

Answer 7

Advantage – we don’t need electricity ➔
thermochemical welding process
* Disadvantage – not a subtle process because
we are burning gas ➔ flame cannot be small ➔
doesn’t work with thin materials, but it can be quite
good for construction work beams etc.

Question 8

What are the advantages of shielded metal-arc welding?

Answer 8

Free hand for the operator, higher accuracy in positioning the workpiece. Big
advantage, we do not need additional filler rods or gas storage places
Disadvantage – operator
has to control the
distance between the
electrode and the
workpiece quite
accurately ➔ process is
difficult to be done by
robot because it can’t
accurately predict when
the electrode is wearing away

Question 9

What is Gas Metal-arc Welding (GMAW)?

Answer 9

GMAW involves using an electrode made of consumable material. This material is fed through a wire, continuously replacing the electrode as it wears away. The process uses active gas, such as CO2, which contains oxygen. . There are two types of gas metal-arc welding: MAG and MIG

Question 10

Active gas → MAG (Metal Active Gas), CO2

Answer 10

▪ Electrode is metal, not tungsten
▪ active gas – contains oxygen ➔ it starts to burn when it comes in contact with the base
material
 oxygen ➔ more heat ➔ material burns away quicker
 oxygen ➔ risk of rust, corrosion, oxygenation in the base material

Question 11

Inert gas →

Answer 11

MIG (Metal Inert Gas)

Question 12

What are some examples of beam welding?

Answer 12

Electron-beam welding, laser-beam welding.

Question 13

What distinguishes Plasma-arc welding from Tungsten-arc welding?

Answer 13

In Plasma-arc welding, the electrode is positioned within the torch body, separating the plasma arc from the shielding gas envelope.

Question 14

There are two main types of
fusion welding:

Answer 14

1. Oxyfuel-gas welding. Method that uses only gas to weld.
2. Arc welding. Method that uses gas AND
   electricity to weld.

Question 15

Friction welding means that there are two components
to connect. What do these components do?

Answer 15

one component that rotates, and
one component that doesn’t rotate. When the
components touch, the materials will kind of melt together, because of the enormous friction that has a lot of energy.

Question 16

Ultrasonic Welding (other welding processes)

Answer 16

high-frequency ultrasonic acoustic vibrations are locally applied to workpieces being
held together under pressure

Question 17

what is Friction Welding and its two main characteristics?

Answer 17

in Friction Welding we connect two components by keeping one of them steady and rotating the other one,
while pushing them together
* Strong connection – when rotating, all grains will be pushed to the outside ➔ clean weld, no air traps
* We have to rotate on of the components ➔ difficult with bigger parts

Question 18

in Resistance welding

Answer 18

In resistance welding, we do not need any gas. We
simply have two electrodes again. We place the
material between two pieces of material, and forces and electricity is added to push the material
together. Normally nothing will happen because everything is made out of metal, but because there is
electrical resistance, there will be enough heat to melt the materials together.

Question 19

4 characteristics of resistance welding

Answer 19

1.Surface of the material is not perfectly smooth ➔
o The smoother the surface ➔ the lower the resistance
2.Non-detachable process – once done, the process can’t be undone
3.Fast process
4.We know where we are going to weld between the two electrodes ➔ we can use automation

Question 20

3 Types of resistance welding

Answer 20

o Projection welding – connect two materials in multiple
spots in one go
o Flash Welding – pushing together two materials that are not rotating, we add a lot of force until they are welded together
o Stud Welding

Question 21

Seam welding

Answer 21

using electrode wheels to “roll”
the products together and thus weld them
▪ continuous AC (alternating current)
▪ electrically conducting rollers

Question 22

in Fastening and bonding we have process such as riveting. describe this process

Answer 22

• The rivets that connect the components have to be made of a softer material than the materials
  o Softer rivets allow a bit of movement, unlike welding which makes the joint pretty sturdy
• permanent or semi-permanent mechanical joining

Question 23

Describe joining faces with glue

Answer 23

Two components are connected with an intermediate layer of adhesive, typically weaker than the components themselves.

Question 24

What are some common materials used as adhesives?

Answer 24

Glues are often organic materials like resin, suitable for bonding porous materials, plastics, and metals.

Question 25

what do we do in Brazing, soldering?

Answer 25

– we heat up the components and add a
softer material in order to have cohesion between all the
materials, the softer material will melt and perfectly fill the
space between the components (capillary effect)

Question 26

in Seaming –

Answer 26

– the two components are rolled together and thus locked

Question 27

in Crimping

Answer 27

• joining (ductile) components by deforming one or both of them to hold the other