Mechanical engineering
News Update
Loading...

Wednesday, April 15, 2009

E-BUSINESS and E-commerce

E-BUSINESS and E-commerce

DEFINITION

E-commerce (electronic commerce or EC) is the buying and selling of goods and services on the Internet, especially the World Wide Web. In practice, this term and a newer term, e-business, are often used interchangably. For online retail selling, the term e-tailing is sometimes used.


Timeline

* 1990: Tim Berners-Lee writes the first web browser, WorldWideWeb, using a NeXT computer.
* 1992: J.H. Snider and Terra Ziporyn publish Future Shop: How New Technologies Will Change the Way We Shop and What We Buy. St. Martin's Press. ISBN 0312063598.
* 1994: Netscape releases the Navigator browser in October under the code name Mozilla. Pizza Hut offers pizza ordering on its Web page. The first online bank opens. Attempts to offer flower delivery and magazine subscriptions online. Adult materials also becomes commercially available, as do cars and bikes. Netscape 1.0 is introduced in late 1994 SSL encryption that made transactions secure.
* 1995: Jeff Bezos launches Amazon.com and the first commercial-free 24 hour, internet-only radio stations, Radio HK and NetRadio start broadcasting. Dell and Cisco begin to aggressively use Internet for commercial transactions. eBay is founded by computer programmer Pierre Omidyar as AuctionWeb.
* 1998: Electronic postal stamps can be purchased and downloaded for printing from the Web.
* 1999: Business.com sold for US $7.5 million to eCompanies, which was purchased in 1997 for US $149,000. The peer-to-peer filesharing software Napster launches.
* 2000: The dot-com bust.
* 2002: eBay acquires PayPal for $1.5 billion [2]. Niche retail companies CSN Stores and NetShops are founded with the concept of selling products through several targeted domains, rather than a central portal.
* 2003: Amazon.com posts first yearly profit.
* 2007: Business.com acquired by R.H. Donnelley for $345 million[3].
* 2008: US eCommerce and Online Retail sales projected to reach $204 billion, an increase of 17 percent over 2007



Business applications

Some common applications related to electronic commerce are the following:

* Email
* Enterprise content management
* Instant messaging
* Newsgroups
* Online shopping and order tracking
* Online banking
* Online office suites
* Domestic and international payment systems
* Shopping cart software
* Teleconferencing
* Electronic tickets



Market Research

In early 1999, it was widely recognized that because of the interactive nature of the Internet, companies could gather data about prospects and customers in unprecedented amounts -through site registration, questionnaires, and as part of taking orders. The issue of whether data was being collected with the knowledge and permission of market subjects had been raised. (Microsoft referred to its policy of data collection as "profiling" and a proposed standard has been developed that allows Internet users to decide who can have what personal information.)


Electronic Data Interchange (EDI)

EDI is the exchange of business data using an understood data format. It predates today's Internet. EDI involves data exchange among parties that know each other well and make arrangements for one-to-one (or point-to-point) connection, usually dial-up. EDI is expected to be replaced by one or more standard XML formats, such as ebXML.


E-Mail, Fax, and Internet Telephony

E-commerce is also conducted through the more limited electronic forms of communication called e-mail, facsimile or fax, and the emerging use of telephone calls over the Internet. Most of this is business-to-business, with some companies attempting to use e-mail and fax for unsolicited ads (usually viewed as online junk mail or spam) to consumers and other business prospects. An increasing number of business Web sites offer e-mail newsletters for subscribers. A new trend is opt-in e-mail in which Web users voluntarily sign up to receive e-mail, usually sponsored or containing ads, about product categories or other subjects they are interested in.


Business-to-Business Buying and Selling

Thousands of companies that sell products to other companies have discovered that the Web provides not only a 24-hour-a-day showcase for their products but a quick way to reach the right people in a company for more information.


The Security of Business Transactions

Security includes authenticating business transactors, controlling access to resources such as Web pages for registered or selected users, encrypting communications, and, in general, ensuring the privacy and effectiveness of transactions. Among the most widely-used security technologies is the Secure Sockets Layer (SSL), which is built into both of the leading Web browsers.















E-commerce MAN..











>
Drilling

Drilling

Drilling is easily the most common machining process. One estimate is that 75% of all metal-cutting material removed comes from drilling operations.

Drilling involves the creation of holes that are right circular cylinders. This is accomplished most typically by using a twist drill, something most readers will have seen before. The figure below illustrates a cross section of a hole being cut by a common twist drill:



The chips must exit through the flutes to the outside of the tool. As can be seen in the figure, the cutting front is embedded within the workpiece, making cooling difficult. The cutting area can be flooded, coolant spray mist can be applied, or coolant can be delivered through the drill bit shaft.

Drilling Characteristics

The characteristics of drilling that set it apart from other powered metal cutting operations are:
  • The chips must exit out of the hole created by the cutting.
  • Chip exit can cause problems when chips are large and/or continuous.
  • The drill can wander upon entrance and for deep holes.
  • For deep holes in large workpieces, coolant may need to be delivered through the drill shaft to the cutting front.
  • Of the powered metal cutting processes, drilling on a drill press is the most likely to be performed by someone who is not a machinist.
Drill Press Work Area

A view of the metal-cutting area of a drill press is shown below. The workpiece is held in place by a C-clamp since cutting forces can be quite large. It is dangerous to hold a workpiece by hand during drilling since cutting forces can unpredictably get quite large and wrench the part away. Wood is often used underneath the part so that the drill bit can overshoot without damaging the table. The table also has holes for drill overshoot as well as weight reduction. A three-jaw chuck is used since three points determine a circle in two dimensions. Four-jaw chucks are rarely seen since offset of the bit is not necessary.

























Twist Drill Bit


The figure below labels the important angles for a typical twist drill bit.












Drill Bit Variety

The figures below illustrate various drill bits and their cut hole configurations.







Drill Chucks

Drill chucks can be of several types, but are typically three-jaw since three points on the circumference define a circle in two dimensions. A standard three-jaw and a multi-jaw chuck are shown in the figures below.















































Turning: Chucks

The chuck is integral to a lathe's functioning because it fixtures the part to the spindle axis of the machine. Below is shown a three-jaw chuck with jaws that are all driven by the same chuck key. This arrangement provides convenience in that parts can be mounted and dismounted quickly.


Three-Jaw Chuck

The inner construction of the three-jaw chuck is shown below. A spiral gear meshes with cog teeth on the jaws to move all three jaws in or out simultaneously. Parts can be fixtured on outer or inner surfaces since there are gripping surfaces on the inner and outer surfaces of the chuck jaws.




Four-Jaw Chuck

If the part needs to be off center or is not a solid of revolution (axially symmetric), a four-jaw chuck with independently-actuated jaws needs to be used. Such a chuck is depicted below.





Drill Press Detail



A typical manual drill press is shown in the figure below. Compared to other powered metal cutting tools, a drill press is fairly simple, but it has evolved into a versatile necessity for every machine shop.





The most adjustable part of the drill press is the vertical movement of the drill bit, since this is the motion that is used in production.
  • The capstan wheel (A) moves the drill head up and down.

  • This movement can be locked (D)
  • and there are point-to-point stops (B) for maintaining a specific length of travel.
  • Gradations marked on the stationary part of the drill press (C) let the operator know where he is vertically.
  • Both the drilling head and table can move vertically and rotate about the vertical guide post (b).
  • The base of the drill press incorporates a work surface similar to the table's for oversize workpieces. The base can be bolted down, but often is not since forces on a drill press do not typically cause it to tip over.
    The drill is powered by an electric motor (I)
Drill Press Work Area Detail

A detail of the work area of the drill press is shown below.




Drilling can be accomplished more accurately on alath or mill , although drill presses are much cheaper and more accessible machines.

Jig Boring

Jig boring is used to accurately enlarge existing holes and make their diameters highly accurate. Jig boring is used for holes that need to have diameter and total runout controlled to a high degree. Typically, a part has holes machined on regular equipment and then the part is transferred to a dedicated jig boring machine for final operations on the especially accurate holes. Jig boring can also maintain high accuracy between multiple holes or holes and surfaces. Tolerances can be held readily within ±.005 mm (±0.0002 inches). Dedicated jig boring machines are designed to machine holes with the tightest tolerances possible with a machine tool.

When designing a part with holes, it is important to determine what holes must be jig bored. The reason for this is that jig boring requires extra time and attention, and the jig boring machine at the machine shop may have a back log of jobs. Jig boring can therefore have a big impact on the lead time of a part. A cross section of a hole being jig bored is shown below.


















Standard boring can be carried out on a mill fitted with a boring head or on a lathe. Boring is most accurate on a lathe since a lathe is dedicated to solids of revolution (axially symmetric parts).

Gun Drilling


For long holes such as those found in gun bores, gun drills are used. The length of the hole requires that coolant be delivered through the shaft of the gun drill to the cutting front. The coolant also serves to eject chips from the cutting area and to move them back and out of the hole entrance. The figures below illustrate a gun drill and the cutting/cooling configuration.








Computer Numerical Control (CNC) Drilling


Computer Numerical Control (CNC) Drilling is commonly implemented for mass production. The drilling machine, however, is often a multi-function machining center that also mills and sometimes turns. The largest time sink for CNC drilling is with tool changes, so for speed, variation of hole diameters should be minimized. The fastest machines for drilling varying hole sizes have multiple spindles in turrets with drills of varying diameters already mounted for drilling. The appropriate drill is brought into position through movement of the turret, so that bits do not need to be removed and replaced. A turret-type CNC drilling machine is shown below.

A variety of semi-automated drilling machines are also used. An example is a simple drill press which, on command, drills a hole of a set depth into a part set up beneath it.

In order to be cost-effective, the appropriate type of CNC drilling machine needs to be applied to a particular part geometry. For low-volume jobs, manual or semi-automated drilling may suffice. For hole patterns with large differences in sizes and high volume, a geared head is most appropriate. If holes are close to each other and high throughput is desired, a gearless head can locate spindles close together so that the hole pattern can be completed in one pass. For further reference for CNC processes, please refer to the































The Computer Numerical Control (CNC) fabrication process offers flexible manufacturing runs without high capital expenditure dies and stamping presses. High volumes are not required to justify the use of this equipment.

Tooling is mounted on a turret which can be as little as 10 sets to as much as 100 sets. This turret is mounted on the upper part of the press, which can range in capacity from 10 tons to 100 tons in capacity.

The turret travels on lead screws, which travel in the X and Y direction and are computer controlled. Alternatively, the workpiece can travel on the lead screws, and move relative to the fixed turret. The tooling is located over the sheet metal, the punch is activated, and performs the operation, and the turret is indexed to the next location of the workpiece. After the first stage of tooling is deployed over the entire workpiece, the second stage is rotated into place and the whole process is repeated. This entire process is repeated until all the tooling positions of the turret are deployed.


Drilled Part Design

The following are guidelines for drilled part design.
  1. Advantages of drilled holes include accuracy and sharpness of edges. Since machining is expensive compared to other manufacturing processes, drilling to create a hole should be justified by looking at alternatives. Before adding drilled holes to a design, ask yourself whether the hole is needed and/or whether it can be cast, molded, or pierced with sufficient accuracy instead of drilled.

  2. Specify standard drill bit sizes. Unusual hole sizes bring up the cost of manufacturing through purchasing and inventory costs.

  3. Through holes are preferred over blind holes. This has to do with the fact that a blind hole does not provide as much leeway for chip exit and cooling. Operations such as reaming and threading after drilling are more easily conducted on a through hole.

  4. Do not specify flat-bottomed holes. Twist drills create cone-bottomed holes and flat-bottom holes cause problems with reaming, etc.

  5. If possible, do not specify holes that are smaller than one-eighth inches in diameter. Drills for smaller holes tend to break and for convenient mass production, are not recommended.

  6. For large holes, try to cast in a preliminary hole that must only be bored out to specification. This saves material, transportation cost, and drilling cost.
  7. When dimensioning holes, it is better to use rectangular rather than angular (or polar) coordinates. Angular coordinates will require the machinist to set up a dividing head or to re-dimension the part, both of which take time.

  8. Minimize the number of drilled hole sizes so that tool changes are minimized.

  9. Minimize the number of directions on the part that holes must be drilled from.

  10. The entrance and exit surfaces of a drilled hole should be perpendicular to the hole axis. The reasons for this are as follows:

    1. Upon entrance of the drill, the drill tip will wander if the surface that the tip contacts is not perpendicar to the drill axis.
    2. Exit burrs will be uneven around the circumference of the exit hole. This can make burr removal difficult.


    Bad and good examples of entrance and exit lands are shown in the figure below.

  11. Intersections of drilled holes with other cavities should be avoided if at all possible. If interesection with a cavity is unavoidable, the drill axis should at least be outside of the cavity, as shown below.

  12. On drawings, multiple holes in a flat surface should be located from the same horizontal and vertical datums.

  13. If there are protrusions surrounding a drilled hole, it may be difficult to bring the drill press head close to the entrance surface, resulting in a drill bit that is prone to wandering, chatter, and other instabilities. This problem can be solved by providing a fixture with a drill bushing close to the drill bit. However, part design must allow for this fixture, as shown below.

  14. Drilled Hole Depth:

    Deep, narrow holes with length to diameter ratios of larger than three should be avoided. Deeper holes are possible but the drill will tend to wander and possibly break. One way to avoid a deep, narrow hole is to use a stepped entrance. Blind holes should be drilled to a depth 25% deeper than the actual hole in order to provide space for chips.

Reaming: Summary

Reaming is a process which slightly enlarges a pre-existing hole to a tightly toleranced diameter. A reamer is similar to a mill bit in that it has several cutting edges arranged around a central shaft, as shown below. Because of the delicate nature of the operation and since little material is removed, reaming can be done by hand. Reaming is most accurate for axially symmetric parts produced and reamed on a lathe.




Detailed Nomenclature for a Reamer


A more complete listing of reamer nomenclature is provided below.



Reamed Part Design

Reamed holes should not intersect with drilled holes, so the configuration below should NOT be implemented:



As with a drilled hole, clearance for chips is needed at the bottom of a reamed hole. This is illustrated below:





Reaming should not be relied upon to correct the location or alignment of a hole. Its primary purpose is to fine-tune the diameter of the hole.

Honing

Honing is a final finishing operation conducted on a surface, typically of an inside cylinder, such as of an automotive engine block. Abrasive stones are used to remove minute amounts of material in order to tighten the tolerance on cylindricity. Honing is a surface finish operation, not a gross geometry-modifying operation. Hones can be of the multiple pedal type (pictured below) or the brush type. Either type applies a slight, uniform pressure to a light abrasive that wipes over the entire surface.


The figure below illustrates the configuration of the abrasive stones of an external hone.


Honed Part Design

Below are illustrated bad and good honed part geometries. Both pairs of figures show that a through hole design is always best for coolant flow, etc. The upper pair shows that a certain portion at the end of a blind hole is not completely honed. The lower pair shows that a right circular cylinder is the easiest to hone.








>
Machining: An Introduction

Machining: An Introduction


In terms of annual dollars spent, machining is the most important of the manufacturing processes. Machining can be defined as the process of removing material from a workpiece in the form of chips. The term metal cutting is used when the material is metallic. Most machining has very low set-up cost compared to forming, molding, and casting processes. However, machining is much more expensive for high volumes. Machining is necessary where tight tolerances on dimensions and finishes are required.
The Machining section is divided into the following categories:


drilling:


  1. Turning:


  2. Milling:


  3. Grinding:


  4. Chip formation:






>

Monday, April 13, 2009

Gearbox

Gearbox

Volkswagen Direct Shift Gearbox



3-speed auto transmission



Compact 6-Speed and Reverse Gearbox


>
Forge Welding

Forge Welding



Forge Welding - 1904




Forging Vine Picketts part 1



The Marsi Chandelier Part 2 - Hot Forging & Forge Welding



Blacksmithing Forge-welding a branch



Twisting a big bar



Resistance Seam Welding

Resistance Seam Welding


لحام المقاومة

ويسمى بالإنجليزية: (Resistance Welding)، هى إحدى طرق اللحام التي تستخدم فيها الحرارة والضغط وتتولد الحرارة نتيجة لمرور تيار كهربي له شدة عالية وفولت منخفض لفترة زمنية قصيرة محددة في الموضع المراد لحامه من الجزء. وتمم عملية اللحام في النقطة أو المكان الذي ارتفعت حراراته وذلك بالضغط بواسطة قطبية.

تعتبر هذه الطريقة في اللحام من اطرق السهلة في إتمامها وكذلك لها قدرة إنتاجية عالية لذا في تعتبر طريقة اقتصادية بالنسبة لسعر التكلفة لو قورنت بالطرق الأخرى بالرغم من ارتفاع سعر ماكينات اللحام بالمقاومة وتمتاز أيضا أن في هذه الطريقة إمكانية لحام المعادن الغير متشابهة.

تستخدم هذه الطريقة عادة في لحام الألواح الصغيرة السمك للمعادن المختلفة سواء كانت حديدية أو غير حديدية

.



أنواع لحام المقاومة الكهربية


اللحام النقطي (لحام البقعة)

و يسمى بالإنجليزية(Spot Welding)، وهو أحد الطرق الشائعة في عمليات اللحام بالتلامس وينقسم لحام البقعة إلى مجموعتين:

  • لحام البقعة المفردة من جهة واحدة أو من الجهتين.
  • لحام البقعة المتعددة، حيث يتم عمل بقعتان أو أكثر في نفس الوقت أثناء تدفق التيار.

اللحام الدرزي (اللحام الخطي)

و يسمى بالإنجليزية (Resistance Seam Welding)، يستعمل هذا النوع في لحام خزانات الزيت والبنزين والماء والمواسير وعدد من الأجزاء المصنوعة من الصلب والمعادن غير الحديدية ويتراوح سمك المعدن الذي يمكن لحامه بهذه الطريقة بين 25-30 مم.

وينقسم هذا النوع من اللحام إلى مجموعتين:

  • لحامات التدريز التركيبية.
  • لحامات التدريز التقابلية.

Resistance Seam Welding is an extremely efficient joining technique ideally suited for high-volume manufacturing, adaptable for most metals and their alloys.

Resistance welding uses the application of electric current and mechanical pressure to create a weld between two metallic parts. Copper electrodes conduct a current through the work pieces, generating enough local heat from the electrical resistance and the thermal conductivity of the metal to create a small molten pool. The metal then cools while under pressure, forming a weld nugget with adequate strength to hold the parts together. The process requires the application of external force, but no fluxes, filler metals, or external heat sources are necessary

Resistance Seam welding is a high-speed resistance welding process that produces leak-tight, continuous joints for sheet metal applications. In seam welding, the sheet metal parts are clamped between rotating wheel electrodes that transmit continuous pulses of electrical current while advancing the work piece, forming a series of overlapping weld nuggets.

Resistance Seam Welding Benefits

  • Efficient energy use, with little pollution
  • Fast processing times
  • Easily automated
  • No required filler materials
  • Economical
  • Adaptable to a variety of electrically conductive materials
  • Ability to produce leak-tight welds

Resistance Seam Welding Limitations

  • Applications may be limited by component shape and wheel access

Vollrath, a full-service, ISO 9001:2000 certified company, has the manufacturing strength, technical knowledge, and experience to hold the leading edge in welding services. Our attention to process control eliminates common production problems and ensures the delivery of consistent quality for every welding application.

For more information about our resistance welding capabilities or to request a quote for your specific application, please contact Vollrath. We’d enjoy hearing from you.



Resistance Seam Welding

by Steve Westgate


Description

The seam welding process is an adaptation of resistance spot welding and involves making a series of overlapping spot welds by means of rotating copper alloy wheel electrodes to form a continuous leak tight joint. The electrodes are not opened between spots. The electrode wheels apply a constant force to the workpieces and rotate at a controlled speed. The welding current is normally pulsed to give a series of discrete spots, but may be continuous for certain high speed applications where gaps could otherwise occur between individual spots. Seam welding equipment is normally fixed and the components being welded are manipulated between the wheels. The process may be automated; it is illustrated in Fig.1.

Conventional wide wheel seam welding

Fig.1. Conventional wide wheel seam welding

Current status

There are a number of process variants for specific applications:

Wide wheel seam

  • Wheel contact width normally 5 roott mm flat (where t is single sheet thickness in mm).
  • General purpose welding (domestic radiators up to about 6 m/min).
Wide wheel seam

Fig.2a) Wide wheel seam

Narrow wheel seam

  • Wheel contact shape typically 6mm radius.
  • Knurl drive on wheel edge with contact surface continuously planished.
  • Controls electrode contamination when welding coated steels, such as for vehicle fuel tanks.
Narrow weld seam

Fig.2b) Narrow weld seam

Consumable wire seam welding

  • Shaped, consumable copper wire fed between the wheels and sheets to be joined to give consistent clean contact.
  • Used for welding coated steels such as tin cans and vehicle fuel tanks.
Consumable wire seam

Fig.2c) Consumable wire seam

Mash seam welding

  • Narrow overlap of sheet edges, which are partly crushed together during welding.
  • High speed welding of tin cans and drums (0.2mm tinplate up to 100m/min).
  • Wide wheel or consumable wire processes used.
Mash seam welding

Fig.2d) Mash seam welding

Foil butt seam welding

  • Foil welded on to each side of the butted edges of the sheets to be joined.
  • Typically 4mm wide stainless steel foil used to preserve corrosion resistance on coated steel.
  • Virtually flush finish with no crevice and used to produce wide panels.
Foil butt seam welding

Fig.2e) Foil butt seam welding

Important Issues

The main issues concerning seam welding are in weld quality control and welding speeds.

  • High speed welding of coated steels is of particular importance in manufacture of tin cans. Specialist consumable wire seam welding machines are used. Quality monitors have been developed for these applications and welding speeds up to about 100m/min are possible. Steels with alternative coatings to tin, for canning applications, present difficulties due to their high surface resistance.
  • Weld quality is controlled mainly by tight process control together with periodic testing of samples. Factors such as material and pressing quality, and alignment of the electrodes to the material, are critical to achieve high speed, quality welding, for example in coated steels for fuel tanks.

Benefits

Seam welding enables high welding speeds to be obtained compared with many other techniques, but can be limited by component shape and wheel access.

Risks

There are some limitations on material weldability but attention to correct setting up and good process control can solve most production problems. The main hazards are: (i) the risk of crushing fingers or hands; and (ii) burns or eye damage from splash metal. Little fume is produced but may need attention when welding coated steels or when oils or organic materials are present.




Sunday, March 15, 2009

Sand Casting

Sand Casting

Sand Casting at School

Sand casting an Aluminium PC Mouse using School Equuipment







Engine block casting



Cylinder Block Machining Video - Engine Building DVD




Sand Casting Mould Making - no sound



Featured

[Featured][recentbylabel]

Featured

[Featured][recentbylabel]
Notification
This is just an example, you can fill it later with your own note.
Done