Ramazan Rıdvan SEKMEN, 030080083, 7th week words

1-Electrochemical Grinding

(Electro Chemical Grinding): (Group:

Manufacturing)
This modification of electrochemical machining has been widely used for grinding carbide tools, since conventional methods can produce burrs, poor-quality finish and even cracking. It is also used to grind stainless steel and titanium honeycomb material and other surfaces. In electrochemical grinding the tool is a rotating and conducting circular stone or wheel composed of diamond abrasive bonded to copper. The electrolyte is pumped more slowly than in machining over the whole surface of the wheel which is moved slowly across the surface of the workpiece with a gap as low as 0.025 mm. The workpiece is again the anode and the wheel, the catode.

Walsh F., Pletcher D., Industrial Electrochemistry, p.465

New and better answer

This process employs a grinding wheel in which an insulating abrasive is set in a conducting bonding material. The D.C. power is connected to the part and the conductive bond of the grinding wheel in such a way that the latter is at negative potential with respect to the component part. Brushes arc used on the grinder spindle for the supply of current into the spindle, from which it then flows to the grinding wheel. The region between the wheel and work piece is flooded with electrolyte. The schematic diagram of the process is shown in Fig. 3.10. When the work piece contacts the bed of the machine, an electrolytic cell is formed, with the work piece as anode and the body of the grinding wheel as cathode. The insulating abrasive particles in the grinding wheel protrude evenly above the wheel surface, and when the work piece is pressed into contact with these, the height of the abrasive particles above the wheel de-termines the effective gap between the anode and cathode. It is in this space that electrolysis actually takes place. A D.C. voltage of about 5-15 V is applied between the work piece and the grinding wheel. Current densities range from 2 &cm in grinding tungsten carbide to about

3-A/cm2 in grinding steels. The electrolyte used in this process does not differ from that employed in electrochemical machining.

(   Pandey, P. C., Shan,H. S. (1980). ELECTROCHEMICAL GRINDING (ECG). Modern MacHining Processes.(pp. 76,77).)

2-Specimen Grinding ( Group: Manufacturing)

The specimen is first ground on the '220' grade paper. Assuming that a stationary table is being used, this is achieved by rubbing it back and forth on the paper, in a direction which is roughly at right angles to the scratches left by the filling operation. In this way, it can easily be seen when the original deep scratches left by the file have been completely removed. If the specimen were ground so that the new scratches ran in the same diraction as the old ones, it would be virtually impossible to see when the latter had been erased. With the primary grinding marks removed, the specimen is now washed free of '220' grit. Grinding is then continued on the '320' paper, again turning the specimen through 90 degree and grinding until the previous scratch marks have been erased. The process is repeated with the '440' and '600' papers.

(Materials for Engineers and technicians Materials for Engineers and Technicians, Yazar: Raymond Aurelius Higgins, Page 121-122)

New and better explanation

Two alternative grinding procedures have been reported by Dingle and Moore [1962]. Me-chanical grinding through a series of abrasive disks with successively finer grit sizes gives satisfactory results. The specimen should be rotated 90^o between disks.

In one procedure specimens are ground successively on 120-. 240-, 400.. and 600-grit wet or dry metallographic discs. Depending on the initial condition of the specimen, the coarsest disk, 120 grit, may sometimes be omitted. In other instances, the grinding may be terminated after the 400-grit disk, thus eliminating the 600- grit operation. Water may be used on all but the final disk, which is best used dry. Kerosene lubrication may also be used. Pressures should be extremely light, barely enough to keep the specimen against the disk. Only sharp disks should be used. The abrasive discs are revolved at 1750 rpm on a conventional pedestal grinder. The coarsest disc  (120 grit) is used either wet or dry, and it can usually be eliminated from the procedure. Grinding on the two finer discs (240 and 400 grit) is accompanied by the application of kerosene. The technique consists of holding an oil can containing kerosene in one hand and the mounted specimen in the other hand. While the grinding is being done. setcral drops of kerosene are applied every few seconds close to the center of the disc. Light oils and water are not satisfactory for the finer grinding operations.

Wet rough grinding holds and carries away dust generated during operation. Disks of water-proof silicon carbide grinding paper ale mounted on a wheel rotating at approximately 1150 rpm. Grit sites of 120. 240. 320. 400.. and 600 are used. Care must be taken to prevent deformation twinning, and ample time must be allowed at each grinding step to remove damage caused by previous operations.

The second procedure is perhaps slightly slower than the first and requires a more careful technique, but it eliminates the use of kerosene. The specimen is first ground wet on a 240-grit disc, followed by dry grinding on a 400-grit disc.

In a third procedure, rough polishing is performed using a 550 rpm Wheel, a chemo-textile cloth with adhesive backing, and a mediumlight concentration of 8 to 22μm diamond compound. The specimen should be frequently rotated counter to the direction of wheel rota-tion. Heavy pressure is used to maximize material removal, although excessive pressure may introduce mechanical twins. Polishing time is approximately 2 min.

( Walsh, K. A. (2009).Grinding Procedures. Beryllium chemistry and processing (pp.199,200). )

3-Vibratory Casting ( Group: Manufacturing)

The same conventional castables , made up and placed in the same way , may be vibratory cast. The consistency may be exactly the same or a little drier, but not much. The apperiance of small nodulus , in a wad of material sparated by cracks, signifies that it is too dry.

Recalling that castable mixes are thixotropic, they can be kept fluid more or less throughout by been kept in constant shear throughout.This end is achiaved by the use of >= 10 kilohertz vibrators, working either on the forms or in channal geometry via the top surface of the fill. Wheather this techniques is better than those of conventional manual placement, above, may be matter of geometry and size of casting or to some degree one of the local preference and style. Where it is feasible vibratory casting gives superior density and strenght

Stephen C. Carniglia, Gordon L. Barna Handbook of industrial refractories technology: principles, types, properties, and applications, P. 564

New and better explanation

Cast vibrating became popular in the mid- to late I980s and is the greatest development in castable placement during the past 20 years. This technique of refractory is much more complex than other installation methods and requires considerable expertise and coordination. Forming is critical to the procedure and must be designed to withstand the force from the hydrostatic head of the castable and force produced by the vibrators. In parts such as elbows, curved pipe, and Wye sections, buoyancy must be considered. The buoyancy of a 165 Ib/ft³ (2,640 kg/m3) castable is sufficient to "warp” or "bend" poorly supported or reinforced forms. The cast vibration process appears simple enough. Font, vibrate, pour, and then strip the fonns. As simple as it appears. the procedure will likely cause more trouble and lost resenue than any other installation technique. due to the cost of removing a cast-vibrated lining and performing a repair.

( Sadeghbeigi, R. (2000).Cast vibrating. Fluid Catalytic Cracking Handbook. (p.214). )

4-Rolling Through Time  ( Group:

Management)

In requirements planning environments, as a result of the limited visibility into the future, the manufacturers often plan their replenishment schedules on a rolling horizon basis. Using the currently available data, they determine their best replenishment quantities over a specified planning horizon and implement a subset of the earlier replenishment decisions. After rolling through time, the schedules are updated utilizing recently collected data.

Application of rolling schedules is common in industry; however, appropriate use of rolling schedules requires careful consideration as it poses many challenges for channel integration. First of all, one needs to be aware of the limitations of rolling schedules. Even if the best possible replenishment schedule is determined in each planning cycle, the long-term replenishment schedule may not necessarily represent the best possible schedule. This is usually the result of the length of each planning cycle. If each cycle is not long enough, it is not possible to determine the best replenishment schedule that would be found knowing demand beyond the end of the planning cycle.

(Supply Chain Coordination Through Schedule Integration, Sahin F., 2008, Page #1)

New and better explanation ( here I found a case study to explain )

Let's say that you received an order for 100 gizmos from one of your regular customers on June 15. You have no materials in stock. You order the materials from your various vendors, and you receive them on July 12. The money clock has started ticking. You will have to pay for these materials thirty-seven days from now (usually calendar days, not business days; let's call it August 19). You have to pay the people who are building this product (your employees) every Friday. You schedule and build the product over the next six weeks (a six-week lead time is fairly common in a conventional batch manufacturing company) and ship the product to your customer—let's call it August 23. Your customer receives the product on August 25 and will pay you in fifty-seven days—on October 21. Here's the math: You paid your people in July and August. you paid for your materials in August, and your normal running expenses are paid monthly. You do not receive any money from your customer until the end of October. You have spent a big chunk of your money (or your bank's money—remember the interest you're paying) a cou-ple of months before you receive your return. That's negative cash flow. If you look at this as a rolling-through-time exercise, you are paying for today's expenses with money you received from past or-ders shipped.

( Carreira, B. (2005). Case in Point 1. Lean Manufacturing That Works (p.20)

5-FDL (First Day Load) (Group: Schedule

Management)

There is no old explanation.

New and better explanation

To get FDL figure is quite essential for capacity adjustment, and this function is included in the system [8]. However, the time figure is just the accumulated overload volume on the first day of planning. The more important data requested are on which day, in which particular process and how much the production capacity should be increased for minimising the total lead time. The system does not exactly give these data.

( Fukushima, K. . 2) Effectiveness of checking FDL (First Day Load) peak. Pull Scheduling System – A Conceptual Algorithm. Josai University, Faculty of Economics.)