030070104-Cebrail YILDIRIM-1st week answers

 

 Flushing (new&better) [Surface Finishing]

The main purpose of flushing is to force a circulation of the dielectric fluid and to clean the working gap from removed material particles, different flushing strategies are used. There are direct and indirect flushing strategies. Direct flushing , such as lateral flushing, pressure flushing, or suction flushing, is produced by a fluid pump. Flushing can also be pulsatory or intermittent.

Definition of flushing technology has been fortified through some visual items.

( Yi Quin, Micro Manufacturing Engineering and Technology, 2010, pg 42)

Flushing (previous)

The single most important factor in successful EDM work is flushing: the removal of metal particles from the gap. Good flushing provides a good machining conditions. If the flushing is poor, metal will be removed erratically, time to machine will increase, and costs will increase. Sometimes, when the overcut is 0.0015’’ or smaller, a vacuum flush will be used. Sometimes a combination methods will be used.
(Brown, J.A., Modern Manufacturing Processes,Industrial Press. Inc., pg. 74)

---------------------------------------------------------------------------------------------------------------



Graphite mold casting(new&better) [Manufacturing Technique]

Using graphite molds for zinc-aluminum casting is a little-known process with
significant benefits. Graphite, a form of carbon, is an excellent, yet largely unknown, mold
material. Every casting method has its niche with some overlap occurring between processes,
but it is safe to say that one process will be best for a given part. The prerequisites for
selecting the proper casting process will be guided by the casting’s material, size, design,
annual quantities, or application.
Being one of the “permanent” mold processes, the GPM process falls into the same
category as the more familiar diecasting process; one mold is used over and over during
production. This is in contrast to “disposable” mold casting processes, such as sand or
investment, whereby the mold is destroyed in order to extract the casting. The basic design of
the graphite mold is similar to diecasting molds, exhibiting a split or multi-piece mold, with
cavities to accept the molten metal. The metal is allowed to solidify, the mold is separated and
the casting is removed. The mold is then closed again and the casting process is repeated.
The one major difference between these two processes is the mold material, which for a
diecasting is metal, and for GPM, obviously, graphite.

( Article Jim Tenglin, President, Castechnologies, Inc. SEPTEMBER 2003)

Giving more detailed information has improved the definition.

Graphite Mold Casting (previous)

Graphite is used in making moulds to receive alloys such as titanium, which can be poured only into inert moulds. The casting process must be performed in a vaccum to eliminate any possibility of contaminating the metal. The graphite moulds can be made either by machining a block of graphite to create the desired mould cavityor by compacting a graphite base aggregate around the pattern and then sintering the obtained mould at a temperature 1800 to 2000 F in reducing atmosphere. In fact, graphite mould liners have found widespread industrial applications in the centrifugal casting of brass and bronze.

(Product design and manufacturing, Yazar: A.K. Chitale, R.C. Gupta, Page 93)




---------------------------------------------------------------------------------------------------------------
Kanban (new&better)  [Production Scheduling]


With Kanban scheduling, the operators use visual signals to determine how much they run and when they stop or change over. The kanban rules also tell the operators what to do when they have problems and who to go when these problems arise. Finally, a well-planned kanban has visual indicator that allow managers and supervisors to see the schedule status of the line at a glance.
We define kanban schedulind as demand scheduling. In processes controlled by kanbans, the operators produce products based on actual usage rather than forecasted usage. Therefore, for a scheduling process to be considered  true kanban,the production process it controls must:

*Only produce product to replace the product consumed by its customers

*Only produce product based on signals sent by its consumers 


(John Gross, K.R. Micinnis,Kanban Made Simple,2003, pg 2)

Giving more large-scoped explaination has more clarified the understanding to kanban




 Kanban (previous)
The implementation of JIT in Japan involved kanban, meaning visible record. These records originally consisted of two types of cards (called kanbans- now replaced by bar-coded plastic tags and other devices):
The production card which authorizes the production of one container or cart of identical, specified parts at workstation. The conveyance or move card, which authorizes the transfer of one container or cart of parts from that particular workstation to the workstation where the parts will be used.
The cards contain information on the type of part, the location where issued the part number of items in the container. The number of containers in circulation at any time is controlled completely and can be scheduled as desired for maximum production efficiency.
(Kalpakjian S., Schmid S.R., Manufacturing engineering and technology, p. 1226)





---------------------------------------------------------------------------------------------------------------
 Pultrusion(new&better) [Manufacturing Technique]

 Pultrusion is a process throug which high modulus, lightwight composite structural members such as beams, truss components, stiffeners, etc can be manufactured. The operation is simple in concept but complex in detail, basically consists of pulling  a number pf fiber tows, or mats through a termosetting resin bath and then through a heated die where the wetted fiber bunder cures, thus producing a structually sound part exiting the die , or, in case of the pultrusion of thermoplastic composites, the material enters the die in the form of impregnated rovings.

(Golam M Newaz,Advances in Thermoplastic Matrix Composite Materials, 1989, pg 62)

(İmage: M.Palabıyık, ITU Plastic Materials& Manuf. Lecture Notes )








Through visual illustration, it has became more effective to understand pultrusion process.

Pultrusion (previous)

In pultrusion, resin-soaked matting or rowings (along with other fillers) are pulled through a long die heated to between 120 and 150 oC [250 to 300 oF]. The product is shaped and the resin is polymerized as it is drawn through the die. Radio frequency or microwave heating may also be used to speed production rates. The process appears to resemble extrusion. In the extrusion process, the homogeneous material is pushed through the die opening. In pultrusion, however, resin-soaked reinforcements are pulled through a heated die where the resin is cured.

(Richardson T.L., Lokensgard E., Industiral Plastics: Theory and Applications, 4th edition, pg.232)


---------------------------------------------------------------------------------------------------------------

  


 Controlled atmosphere furnace(new)

The most common method is the control of furnace atmosphere by introducing gases
that are inert to the steel at the quenching temperature. Here the endothermic atmosphere shall
be used to prevent decarburizing or carburizing within normal treatment times by effective
techniques that measure times by effective techniques that measure either dew point, CO2 or
O2 potential.

( Hanbook of Heat Treatment of Steels, K.H Prabhudev)

 

Atmosphere Furnaces(Previous)

Atmosphere furnaces are characterized by their use of a protective atmosphere to surround the workload during heating and cooling. The most common furnace atmosphere, however, is air. Often times,nothing more is needed. When an air atmosphere is used, such as in a low temperature tempering operation, the final condition of the material’s surface (or skin) is not considered important. Furnace atmospheres play a vital role in the success of the heat treating process. It is important to understand why we use them and what the best atmosphere for a specific application is. There are many different types of atmospheres being used, and it is important to understand how a particular atmosphere is chosen as well as its advantages and disadvantages and to learn how to control them safely.The purpose of a furnace atmosphere varies with the desired end result of the heat treating process. The atmospheres used in the heat treating industry have one of two common purposes:

1. To protect the material being processed from surface reactions, i.e., to be chemically inert(or protective)

2. To allow the surface of the material being processed to change, i.e., to be chemically active(or reactive)

Some atmospheres such as argon and helium are often associated with vacuum furnaces and are used at partial pressure (pressure below atmospheric pressure). Others, such as sulfur dioxide are used for very special applications (Geng H., Manufacturing Engineering Handbook, p. 18.51)