BASIC PRINCIPLES OF CONVENTIONAL AND HIGH SPEED MACHING
Conventional machining, one of the most important material removal methods, is a collection of material-working processes in which power-driven machine tools, such as lathes, milling machines, and drill presses, are used with a sharp cutting tool to mechanically cut the material to achieve the desired geometry.
The basic principles of conventional machining involve feeds and speeds. Speed in case machining means speed of spindle that carries the work piece in a lathe machine, the speed of tool in the simple milling machine, or the speed of the drill spindle carrying drill bit in case of conventional drilling. Feed is referred to the movement of cutting tool towards the work piece machined in a lathe or a milling machine and the movement of drill bit into the work piece in case of drill machine. These feeds and speeds depend usually on the material type to be machined and type of shape to generate and shape of tool and inserts, etc. Usually these are the main principles on which the whole mechanism of machining depend whether it's conventional or High Speed Machining. In spite of these two parameters one other important factor considered in machining is "finishing". The smoother the surface of the machined part, the higher is the finish. In case of higher material removal rate we give high feed rate that is called "roughing". For the fine finish the tool feed rate should be low such that the machined part has fine grooves which are invisible to the naked eyes.
HIGH SPEED MACHING:
The basic principle of High Speed Machining is same as that of conventional machining. But the addition of some special features has made HSM demanding in the market. The high speed machines are usually multiple axis machines and can perform almost all operations on a single machine which is not possible in any conventional machine. All the tools are mounted on a single machine and operation like turning, boring, milling, drilling and other machining operation can be easily done by a simple program which is written on computer and fed into Computer Numerical Control (CNC) machine. Here the ratio of speed and feed is high which leads to high surface finish and better accuracy than conventional machining.
The difference in conventional and high speed machining is that, in conventional machining accuracy depends on the skill and experience of the person handling the job. Also it requires lot of brain effort to analyse the things. But in 21st century high speed machining has taken over conventional machining mainly in the large scale sector.
ADVANTAGES OF HIGH SPEED MACHING OVER CONVENTIONAL MACHINING:
- The accuracy of HSM is 100% if programmed correctly.
- HSM gives good repeatability and is simple to use then conventional.
- Parts can be produced to maximise accuracy and it also provides excellent positional accuracy unlike conventional machining.
- Less skilled trainer can operate the machine whereas conventional machining requires highly skilled person.
- Tooling cost is comparatively low than conventional.
- There is no need of complex fixtures as that in conventional.
- HSM reduces time of manufacturing the product.
- Complex machines operations can be done with lot of ease and at a single machine itself.
- There is no need to change tool for different operations as in conventional machining.
- Can be operated for almost for very long hours say almost 24 hrs and can be left operated for months.
- Latest design software's are available these days and HSM operator can design his own new ideas.
DIS-ADVANTAGES OF HIGH SPEED MACHING OVER CONVENTIONAL MACHINING:
- High speed machines are more expensive as than manually operated machines.
- Tools used for high speed machines are quite costly.
- A part of machine which includes machine and tooling are expensive and requires extensive justifications.
- Repairing is expensive too.
- High speed machines do not eliminate all the error.
- Internal shapes cannot be machined in High speed machining.
- Size limitations depend on the size of machine.