Steel: Curves and Castings:

Curves:

There are about 3 ways to tackle curves. There are quite a few ways and methods to barge our way through these, quite technical aspects of design. Induction bending is an application of specific heat, and used for industrial pipes.

Ways to create curves are:

Bend the Steel. Use a 3 point smooth bending machine. Use a break press and heat applied bending. Now, facet the building to give the appearance of curves, and use straight members. Cut curved forms out of the plate material. Various bending steel issues are, Member type, orientation of member, length of member, shipping considerations, sourced out work, accuracy of curve, multiple curves.

Castings:

Contemporary castings are used for special connections and standard connections. Can be one of large pieces formed with expandable molds. They can be smaller die cast pieces made in great quantity. They are either solid or hollow. Its uses are: Architecturally exposed structural steel particularly for HSS or timber connections, complex connections, geometry, etc., fatigue critical connections, and functional applications.

Metal Cutting and Machine Tools:

Many components need machining to get final shape and accuracy.

Machining:

"Machining is an essential process of finishing by which jobs are produced to the desired dimensions and surface finish by gradually removing the excess material from the preformed blank in the form of chips with the help of cutting tools moved past the work surfaces.

Importance:

These objectives are to be achieved:

·         Quick metal Removal

·         High class surface finish

·         Less power consumption

·         Economy in tool cost.

·         Minimum lead time of machine tools

Cutting tools are classified into various types.

Relative motion between tool and work-piece is necessary. The cutting speed is the largest of relative velocities.  Feed and depth are other parameters we should consider.

As far as nomenclature is concerned, Rake angle, Relief, and cutting edge angle are significant.

Tool signature is the system of designating the principal angles of a single point cutting tool. ARA system and ORS system are widely used.  Types of chips are continuous, discontinuous and continuous chips with build-up edge.

Chip breakers are used to tolerate a high temperature and cutting speed. Orthogonal and Oblique cutting are the two basic methods of metal cutting using single point tool.
talking of forces, various forces act on the chip, including Shear force, normal force, etc.

Relation between the various forces is determined using Merchant's Circle Diagram.
A parameter that does not depend upon cutting process parameters is Specific cutting Energy.
Tool failure due to wear is quite common. Various factors including heat have a say.
Taylor, out of curiosity derived a formula for tool life.

High speed dry machining of cast iron is now possible. There are various methods of applications of cutting fluids. The economics of metal machining is quite clear as to what it depends on.  Various methods can be employed to improve economic efficiency. Cemented or sintered carbides have risen, thanks to the demand for higher productivity. Diamond, is probably the only substance stronger than these. Improving techniques and resources thus far, has made today's engineering possible.

akshay