Cutting speed and feed changes on ocm

OBJECTIVES
To observe the surface of the material, when it is cut by a cutting tool, so it includes to see the various combination about the feed and cutting speed.
To observe how a CNC lathe work.
To conclude about what will happen if we change some parameters, such as the feed and cutting tool.
To obtain the next graphs: (logPu vs log v; logr vs log v; logτ vs log v; logPu vslogto;log r vs logto and logτ vs logto) and to conclude base on obtained results.
INTRODUCTION
THE CUTTING SPEED.
Cutting speed may be defined as the rate (or speed) that the material moves past the cutting edge of the tool , irrespective of the machining operation used — the surface speed.

THE FEED

Feed rate is the velocity at which the cutter is fed, that is, advanced against the workpiece.It is expressed in units of distance per revolution for turning and boring (typically inches per revolution [ipr] or millimeters per revolution). It can be expressed thus for milling also, but it is often expressed in units of distance per time for milling (typically inches per minute [ipm] or millimeters per minute), with considerations of how many teeth (or flutes) the cutter has thendetermining what that means for each tooth.

FORCE AND POWER RELATIONSHIP IN LATHE
To cut a material by a cutiing tool, it must have a good sharp which could cut the material easily, so that force is colled cutting force.

The necessary cutting force that we need to remove some extra material in the workpart should be highert than than the resistance of the material, because if it isn’t, the cuttingwill break quickly.

We can find three form to fed the cutting tool before to begin a work:
Tangencial direction
Axial direction
Radial direction

PRINCIPLES AND PRACTICE

A Lathe is used for shaping metal (or other materials) round by holding and rotating the workpiece while a carbide tool bit is advanced into the work causing a chip removing cutting action. Holding the part isnormally done with a chuck that has jaws to grip the part at one end and a pointed center to support the center of the part at the other end.

Lathes may also be able to produce screw threads, tapered work, drilled holes, knurled surfaces, and crankshafts depending which tooling is used and options are chosen. Slight differences in the various engine lathes make it possible to group them into fourcategories: lightweight bench type, precision tool room type, gap type and big bore. Precision tool room lathes are used for all operations, such as turning, boring, drilling, reaming, producing screw threads, taper turning, knurling, and radius forming.

For measure the effects produced by changes in cutting speed and feed are necessary the following parameters which are function of the same.Chip Thickness ratio [r].- The relation between the thickness of chip before and after cut.

r=t_o/t_c

Shear stress [τ] .- Is produced in the machining process.

τ=(F_c cos⁡(φ)-F_t sin⁡(φ))/((t_o w)/(sin⁡(φ)))

Unit power Pu=Fc/(to*w) / v=(pi*D*N)/1000 (m/s)
Experimentally will be of more benefit to select individual speeds on geometric progression andgraph the final results on a logarithmic scale. This way the results will be obtaining equally space.

In order to observe the effects in feed and initial chip thickness it is desirable to cover a range as wide as possible; maybe the best procedure will consists in select equally space increments from the lower to the higher feed velocity, all this, with the higher cutting speed.
PROCESS OFTHE PRACTICE

For each data of cutting speed we will work with four feeds, in total we will work with four different cutting speeds, it means that in total we will have sixteen measurements. For doing the respective calculus we need some values, these are cutting force and thrust force which will be given by the instructor during the practice, these values are:

Cutting force [Fc] = 1535 N...