EXTRA Flashcards
Advantages and disadvantages of sand casting?
- Can produce and shape
2. More expensive than welding
Advantage of shell casting?
can produce any shape
shape of die casting?
can produce any SMALL shape
Advantages of investment casting?
good surface finish/detail and good dimensional accuracy, can make any shape
shapes of rolling?
flat/curved shapes
shapes of powder metallurgy?
any shape
shapes for photo-fabrication?
for machining thin shapes
Amorphous materials?
PS, acrylic, PVC, PC, ABS, HIPS (Police Constable Peter Simon with PVC HIPS and Acrylic ABS)
Semi-crystalline materials?
LDPE, HDPE, PET, CA, Nylon, PP, PEEK (HoPE caN LoPE PEEKy PETs PP)
Blow moulding materials?
semicrystalline
Shapes of blow moulding?
hollow shapes such as plastic bottles
Advantages of blow moulding?
low tool and die costs, high production rates, low scrap rates
Disadvantages of blow moulding?
restricted to hollow articles, essentially a two step process as a hollow tube is first needed, wall thickness is difficult to control
Materials for (plastic) casting?
liquid or pellet thermosets, nylon and acrylic
advantages of (plastic) casting?
large articles can be moulded, low mould cost, low finishing cost
disadvantage of (plastic) casting?
restricted to simple shapes
Advantages of compression moulding?
large components can be produced, low material waste
Disadvantages of compression moulding?
tooling cost can be high, close tolerances are hard to achieve
Materials and shapes of plastic extrusion?
semicrystalline (PP widely used), possibly hollow shapes, shapes with uniform cross section
Advantages of plastic extrusion?
low testing cost, high production rates, variety of complex cross sections
disadvantages of plastic extrusion?
close tolerances are hard to achieve, parts must have uniform, even section
Materials for injection moulding
semicrystalline or amorphous
advantages of injection moulding?
high production rates, good surface finish, complex shapes
Disadvantages of injection moulding?
high tool and die cost, large production runs necessary for economy, size of part is limited
vacuum forming materials and shapes?
amorphous materials. hollow shapes if combined with joining
advantages of vacuum forming?
low cost techniques, thin cross section parts can be made
disadvantages of vacuum forming?
restricted to article with low profile
pressure forming advantages?
for deep drawn articles, can be used on sheet metal too thick for vacuum forming, high production rates
disadvantages of pressure forming?
expensive, highly polished mould required
advantage/disadvantage of mechanical forming?
High production rates but restricted to simple shapes
can you draw the effect of temp on elastic modulus graph?
YES OR NO
What shape of product does rotational moulding create?
produces hollow plastic products
how can more complex shapes be made from rotational moulding?
post-moulding operations allow the production of more complex shapes
how does rotational moulding differ from other moulding processes?
the melting and moulding processes occur after the polymer is placed in the mould?
describe the first stage of rotational moulding?
CHARGING THE MOULD: a predetermined amount of polymer powder is placed in the mould. Once the mould is closed it is then placed into an oven.
describe the second stage of rotational moulding?
HEATING AND FUSION: in the oven the mould rotates around 2 axes, tumbling the powder. Rotation speed is relatively low (<20 revs per min). As the mould becomes hotter the powder melts and sticks to the inner wall of the mould, building up an even coating over the entire surface.
describe the third stage of rotational moulding?
COOLING: after sufficient time to evenly distribute the molten polymer the mould is cooled using either air or water or a mix of both. The polymer solidifies to the required shape.
describe the fourth stage of rotational moulding?
DEMOULDING: when the polymer has cooled sufficientlu to retain its shape the mould is opened and the part removed.
suitable materials for rotational moulding?
LDPE, PP, PVC, EVA
Examples of products made from rotational moulding?
Manhole inspection chambers, water and fuel tanks, canoes and kayaks, childrens slides and playhouses, pallets, traffic cones.
Advantages of rotational moulding?
- Large mouldings can be produced economically
- Minimum design constraints
- No weld lines
- Stress free products
- Comparatively low mould cost
Disadvantages of rotational moulding?
- Relatively long cycle times means higher part cost
- May need more than one mould to achieve desired output
- Material cost relatively high
- Labour intensive
Describe forging?
- A bulk forming, hot-working process (typically 0.7 Tmelt)
- Produces a stronger grain structure with anisotropy
- Has a better fatigue strength and hence thinner wall (compared to casting) is possible
- There are cavity limitations i.e. it is hard to forge hollow shapes in one stage. This also requires intensive machining
- If heat treatment is followed by forging the anisotropy of the grain may be lost due to recrystallisation
Describe spinning?
- Sheet forming, cold working process (usually < 0.3 Tm)
- Produces anisotropic structure but less elongated than hot working case
- Causes some springback behaviour and some strain hardening which in some cases requires heat treatment
- Quality of surface finish is limited
- Limited reduction in plate thickness
- It may be used for more complex shapes!
What is pultrusion? (DRAW)
Pultrusion is a continuous process for manufacture of composite materials with constant cross-section.
Can you draw the example of the bevel and seam weld symbols?
YES OR NO
Can you draw the example of the intermittent fillet weld symbols?
YES OR NO
can you draw RIVETED VS WELDED?
YES OR NO
Can you draw the example of the lap joint stress concentration and the undercut weld stress concentration?
YES OR NO
Can you draw the graph that compares series aluminium alloys with strength, extrudability index and min wall thickness?
YES OR NO
Can you draw examples of possible extruded structures/ microstructures?
YES OR NO
Do you know main requirements and sub requirements for each part in the product development checklist?
YES OR NO
Can you draw thickness transition design for welding: good and bad?
YES OR NO
Typical fabrication procedures for welding?
- Profile cutting from plate or tube. 2. Cleaning burnt edges. 3. Weld preparation. 4. Clamping individual pieces. 5. Welding procedures. 6. Weld inspection and approval. 7. Removal of residual or distortion stresses. 8. Machining.
