Manufacturing with Plastics

• Overview of Processes of Manufacturing PlasticsOverview of Processes of Manufacturing Plastics-Calendering

-Extrusion

-Moulding-Compression Moulding-Transfer Moulding-Injection Moulding-Blow Moulding-Rotational Moulding

-Heat Forming

-Foaming-Laminatio

n-Machining-Welding

• Words in this processWords in this process-Polymer:Plastics-Thermoplastic Polymer : a plastics that become

s soft and bendable when heated OROR a plastics that are capable of repeatedly softened by heating and hardened by cooling.

-Thermosetting Polymer : a plastics that becomes hard and unbendable after having been heated and shaped, during which a chemical reaction happens.

Key factors:

-raw material: rubber

-key process parameter: the roller must be heated up to specified temperature

-the gap between rollers depends on thickness of the sheet

-the linear speed of the roller is controlled at specified value

Step1: make the machine be ready

Step2: put rubber into the roller

Calendering Process

Extrusion for PlasticsPrinciple of Extrusion MachinePrinciple of Extrusion Machine

-Driving System: Motor + Gearbox to produce specified rotation speed

-Feed System: Feed hopper + Screw to move plastic grains or granulated polymer forward (i.e. towards left in this example below )

-Heating System: Electrical Resistance wires to generate heat and make the plastic grains soften as them moving

-Die: it is with a reverse shape of final part to be extruded

Extrusion process is used to produce:

-Film (thinner than 0.76mm)

-Sheet(thicker than 0.76)

-Filament

-Tubes

This process is also used to coat cables, wires and metal strips.

-Cooling System: after the shape is extruded from the die, a cooling medium must put on it in order to cool the extruded one and make it harden.The cooling is usually through exposure to air at room temperature, passing through a liquid bath held at controlled temperature, or jetting compressed air on it.

Extruder

Molding plastics with thermosetting plastics

Types of Moulding Types of Moulding

-Compression Moulding

-Transfer Moulding

-Injection Moulding

-Blow Moulding

Raw Material:Raw Material: thermosetting plastics

Principle of the processPrinciple of the process

-Load raw material into mould

-heat the material to be plasticized

-the mould is closed and impose pressure on the plasticized material to form a desired shape

-The mould is still held closed under pressure sufficiently long.

-Eject the final part

Compression Moulding

Moulding Process:Moulding Process:

-Clean the mould for removing all flash and foreign matter

-Load the material (preheated)into the cavity

-Close the mould completely

-Complete the cure time under pressure (13.8-20 MPa for example) and temperature (140-200oC)

-Open the mould and activate the ejector

-Take the moulded part away from the cavity

-Clean the mould and new cycle starts

NOTE—Cure time:Plasticizing time, for example 30’’to 2’if thickness of the moulded part ranges from 3.18-12.7mm.

Raw material:Raw material: Thermosetting

Transfer Moulding

Process:

-Place the powder into a compartment

-Force the molten material (originally powder) into the cavity by piston (plunger)

-Open the mould and take the finished product apart.

Raw material:Raw material: Thermosetting

Injection MouldingWork with thermoplasticsthermoplastics

stop

Blow Molding—to Manufacture Bottles

(A thick wall tube)

Process:

-Extrude a thick wall tube (parison) down to the blow-moulding mould;

-Close the mould while the parison is still soft;

-Blow air inside the parison (i.e. tube) until the parison wall is full of the wall of the mould;

-Open the mould and take the bottle out.

Vacuum Forming

The pattern must be in a correct position relative to the workpiece,otherwise the desi

red shape cannot be formed.

Foaming

• A process which converts polymer or plastics into sponge-like materials is called foaming.

• Process description:– Prepare plastics, foaming agent and resin– Mix above items together– Put them into mould and heat them

Lamination

• Process description:– Prepare a paper or cloth and resin

– Spread plastics through the paper or cloth

– Make the bonding material (resin) solidify

– Put another layer onto existed one

Rotational Moulding—How a football is manufactured

• Process:-a measured amount of plastics is placed in mould, -close the mould and heat it,-rotate the mould in a specified way.-if the plastics lines the mould cavity, open the product and take it out.

Test one Review

Test one (10/09/2003)Manufacturing Technology

         

Instructions to candidates:

1.      Any candidate must write the test independently, any copying each other is NOT allowed.

2.        If any misconduct (particularly copying) is found, he/she will be given zero.

3.        Text can be as a reference during testing

4.        Time allowed is 2 hours

5.        Writing and illustration must be neat and clearly

6.        Any question must be answered fully through sufficient steps

7.        The test paper contains five questions, candidate must answer all of them

Continued

• Question 1(20 marks)• In terms of equipments used in production line and other relevant factors, the

manufacturing system can be categorized into two types: Advanced and Traditional manufacturing systems, based on this context, please answer following questions:

• 1. For any manufacturing task, an advanced manufacturing system must be taken. Is this statement correct? Please state your reasons. (5 marks)

• 2. Without computer system as a control unit of manufacturing equipments, an advanced manufacturing system cannot be built. Do you think the statement is correct? If it is, give your own reasons. (5 marks)

• 3. Traditional manufacturing system is almost useless we don’t need to learn it. Please present your opinion for the conclusion. (5 marks)

• 4. For manufacturing a car, there may be two production organization styles: one is to produce all parts by company itself, another is to try to purchase most parts from part manufacturers in the world market as many as possible. Which production organization style is more reasonable in terms of simplifying production organization and reduction of production cost? And why? (5 marks)

• 5. How do you understand the definition of manufacturing: “Manufacturing is a process which changes raw materials into useful products through easiest and least–expensive methods”. (5 marks)

Continued

• Answer to Q1-1:No

-Reasons:

-A big investment is needed if an advanced manufacturing system is built. Therefore a justification must be considered first for any task.

-If a traditional manufacturing system can meet the demands, it is not necessary to take advanced one in terms of production cost.

Continued

Question 2(20 marks)1. Illustrated on the right is a sand casting process, explain all indicated

terminologies(i.e. function of each of them).(10 marks)

2. The material of the part to be cast above illustrated is aluminum alloy and the thickness of all walls is 3mm. For casting this part what casting process is supposed to be chosen? and describe the process you are going to choose (the explanation of the process should be step-by-step style). (10 marks)

Figure for Question2-1

Figure for Question2-2

Continued

• Question 3(20 marks)

• A length of material with a constant cross section shown below is going to be produced, please answer following questions:

• A: if the raw material is thermoplastics, choose an appropriate process to manufacture it and describe the process in detail.(10 marks)

• B: if the raw material is aluminum, choose an appropriate process to manufacture it and describe the process in detail. (10 marks)

Figure for Question3

Continued

Question 4 (20 marks)

For producing part illustrated below, the first option is to use thermosetting plastics, in this case describe the processes in detail . (10marrks).

If thermoplastic plastics is chosen as raw material, how about its processes? (10 marks)

Continued

Question 5 (20 marks)1.A plastics bottle with wall thickness

0.3mm shown below(the illustration is a section view of the bottle) is to be produced, what kind of manufacturing process should be taken? Describe in detail for your process selected. (10 marks)

2.On page 213 of text, it shows three steps of vacuum forming process and says that only in the last step the vacuum cylinder valve is allowed to open, what if the valve has already been opened in second step? (10 marks)