Ahmet Can OLDAÇ -030060098-week10

Curing (old) -none

Curing (new) [manufacturing process]

Matrices for polymeric composites can be either thermosets or thermoplastics. Thermoset resins usually consist of a resin(e.g. epoxy) and a compatible curing agent. When the two are initially mixed they form a low-viscosity liquid that cures as a result of either internally generated(exothermic) or externally applied heat. The curing reaction forms a series of cross-links between the molecular chains so that one large molecular network is formed, resulting in an intracable solid that cannot be reprocessed on heating. On the other hand, thermoplastics start as fully reacted high-viscosity materials that do not cross-link on heating. On heating to a high enough temperature, they either soften or melt.

For thermoset resins the cure time is the time it takes for the cross-linking reactions to take place. Epoxies generally have cure times of 2-6h at elevated temperatures. Very short cure times are desired for some processes, such as compression molding and pultrusion. Cure temperatures can range from 250 F to 350 D for epoxies.

(Manufacturing Processes for Advanced Composites Author: Flake C. Campbell p.9-10)

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Toyota sewing system (old) -none

Toyota sewing system (new) [manufacturing layout]


There are relatively few formalised 'standards' of teamworking in the apparel context. The Toyota sewing 

system (TSS) is one of them: it originated in the Toyota Group in Japan, the pioneer for the implementation 

of JIT concepts. The characteristics of a TSS production line are as follows:

• Thelineout is U-shaped with garments progressing around the line.
• Each operatior is cross-trained on a different portion of the line(i.e. contigious operations) depending on 
  skill and operation complexity. Idealyy all the operators are cross-trained on all the operations.
• Each operator is assigned at least one operation(normally more than one).
• Operators have pitches which overlap with their neighbours by one or more workstations.
• Work is carried out in batch sizes(lots) of one. 
• Operators will generally stand at all workstations.
• The first and the last operations are uniquely assigned to the first and the last operator respectively.
• Buffering between workstations is normally not permitted.

(Group Technology and Cellular Manufacturing: A State-Of-The-Art Synthesis of Research and Practice Author:Nallan C. Suresh, John M. Kay p.256-257)
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Takt time(old) -none


Takt time(new) [manufacturing]


The ideal output from synchorized production consists of meeting the market's needs exactly. The market thereby dictates the takt time of production.


Takt time is the timing basis for all activities in the company(production, information, kaized, etc). It determines the timeframe for the material flow and all actions connected with it.
Takt time is the timeframe dictated vy the downstream process(customer) which is available for producing a part. The stock in any individual line is minimized as much as possible, but it must be guranteed that the downstream process(the customer) recieves the necessary parts in the necessary quantity at the appropriate time.


The available production time divided by customer demand. For example, if a widget factory operates 480 minutes per day and customers demand 240 widgets per day, takt time is two minutes. Similarly, if customers want two new products per month, takt time is two weeks. The purpose of takt time is to precisely match production with demand. It provides the heartbeat of a lean production system. Takt time first was used as a production management tool in the German aircraft industry in the 1930s. (Takt is German for a precise interval of time such as a musical meter.) It was the interval at which aircraft were moved ahead to the next production station. The concept was widely utilized within Toyota in the 1950s and was in widespread use throughout the Toyota supply base by the late 1960s. Toyota typically reviews the takt time for a process every month, with a tweaking review every 10 days. 


(The Synchronized Production System: Going Beyond Just-In-Time Through Kaizen Author: Hitoshi Takeda,SPS Management Consultants p.106-107)
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Thread Rolling(old) -none


Thread Rolling(new) [manufacturing method]


Thread rolling is also a cold-forming process. The thread form is impressed in the screw shank by rolling it in a single operation under controlled pressure between two hardened dies having the reverse profile of the specified thread. the indentation of the die thread crests causes the metal to fill the area between the thread flanks by plastic deformation. Since it is displaced from the screw blank rather than removed, the blank diameter on which the thread is rolled must be slightly under-size, about equal to the thread pitch diameter.


There are three types of thread-rolling processes, the flat(reciprocating) die, the centerless cylindirical die, and the planetary rotary die. The first two processes have production speeds in the range 60 to 250 parts per minute, depending on blank diameter, while the plenatary type achieves speeds of between 60 and 2000 parts per minute.


In reciprocating die method, there are two flat dies, one of which is stationary while the other reciprocates, rolling the screw blank between them. With the centerless cylindrical dies, there are two or three round dies and the blank is rolled between them. In the plenetary-die method, the blank is held while the dies roll around it.


(How It Works: Science and Technology Author: Marshall Cavendish Corporation p.2034)

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Low-Pressure Permanent-Mold Casting(old) -none


Low-Pressure Permanent-Mold Casting (new) [manufacturing]


Permanent-mold casting uses a metal mold constructed of two sections that are designed for easy, precise opening and closing. These molds are commonly made of steel or cast iron. the cavity, with gating system included, is machined into the two halves to provide accurate dimensions and good surface finish. Metals commonly cast in permanent molds include aluminum, magnesium, copper-base alloys, and cast iron. 


Low-Pressure Permanent-Mold Casting is another variant of the permanent mold process. Here, the casting is done inside a pressure vessel, and an inert gas is used to apply 35 to 70kpa(5 to 10psi) pressure on the liquid material. This results in shorter cycle times and excellent mechanical properties.

(Elements of Metallurgy and Engineering Alloys Author: Flake C. Campbell p.112)