Design and Fabrication of Square Hole Drilling Machine
The mechanical design and of a square hole producing tool based on Reuleaux Triangle. The main aim of our paper is to investigate how the circular motion can be converted into a square motion by purely a mechanical linkages; an application of which is to construct a special tool that drills exact square holes. The geometrical construction that fulfils the laid objective is Reuleaux Triangle . Additionally, for this geometry to work like a rotating drive (such as a drill press) must force the Reuleaux triangle to rotate inside a square, and that requires a square guide to constrain the Reuleaux triangle as well as a special coupling to describe the fact that the center of rotation also in moves within in the constrain. The practical importance of this enhancement is that the driving end can be placed in a standard drill press; the other end is restricted to stay inside the fixed square, will yield a perfectly square locus and this can be turned into a working square-to drill hole.
Hole serves various purposes in all machine elements. These holes may be round, square, rectangular or any other shape depending on the requirement or design. For circular holes, the machines are available in the market. But for square or any other type of holes, the Methods currently used are broaching, electrode-discharge machine (E.D.M.), and electro-chemical machine. These are very much expensive and require special tools or machines. The reuleaux triangle is one example of a wide class of geometrical discovery by germam mechanical engineer Franz Reuleaux , discussed the famous curvy triangle that is started being used in numerous mechanisms Watts Brother Tool Works. Although Franz Reuleaux was not the first to draw and to consider the shape formed from the intersection of three circles at the corners of an equilateral triangle .But the use of this curve and its special properties for producing polygonal holes was given by Sir James Watts in 1914 and the geometry has been constantly evolving from day to day exactly reproduce the square in which it revolves.
Material removal in electrical discharge machining which involves the generation of debris in the working gap that comprises eroded with
electrode particles and by-products of dielectric decomposition. Uniformly distributed gap contamination of a certain thresholds is desirable in the interest of discharge .However excessive debris concentration confined to isolated domains in the gap because of insufficient flushing leads to repeated localization of the discharge in a particular location.
This will have unfavorable ramifications on process strength, stability, geometry and integrity of the machined surface. Adequate gap flushing is therefore significant in terms of both machining productivity and the quality of the machining surface. Flushing could be accomplished by forced flow of the dielectric fluids through holes in the tool, but flushing holes leaves their footprints on the machined surface, as the work shape produced in
EDM is complementary to that of the tool. Flushing could alternatively be through micro holes,which is specially fabricated in the tool . In the instance that it is infeasible to provide flushing holes in either of the electrodes, the dielectric could be directed and controlled at the gap in the form of a jet from outside the machining area. This technique is not effective when the machined depth or the frontal machining
area is large.
The main idea for manufacturing a special tool for fulfilling the laid objectives is to make a mechanism which will transform the rotational
motion of a shaft about its longitudinal axis to revolving motion around the same axis in a given profile which is confined by four governing ellipses at each corner ,having their centre at the vertices of confining square which will guide the tool in confined profile keeping the rotation intact. This will lead to the cutting of the square geometry as required for the purpose. The rotation of tool with the same rpm as that of the chuck , which is necessary to overcome a large amount of force to cut a metallic component. Revolution becomes an integral part so the Reuleaux triangle centre is not fixed and it has to moved in a profile which is made by those four ellipses. After following the basic principles a need arises to put the components together without compromising the working of each components .
i) 3- Point Cutting Tool The special tool mounted on RT which has 3 cutting edge in order to obtain the square hole.The tool is made up of EN36,which has high hardness strength. Predrilling is highly recommended, this reduces wear on tooling and the amount of swarf to be removed.it also relives some pressure on the tool
and hence has greater tool life.The tool is mounted on a Reuleaux triangle of 25mm , the tool is made of EN36.
ii) Supporting Member
Square guide is a stationary part that guides the Reuleaux triangle to move in square shape and also helps the RT to rotate in fixed plane ,square guide is connected to drilling machine using two steel rods , these rods are clamped to the drilling machine by using clampers. Clampers are provided to attach supporting member to portable drilling machine. In order to obtain the smooth running of RT inside the square guide, we made the square hole of size larger than the width of RT, hence we can ensure rotation of tool without jamming inside the square hole.
Size of square hole =30cm
Material: Mild Steel
Universal joint is used to connect two shafts at an angle for transmitting torque. The centre of RT must rotate itself and also revolves in a noncircular path ,by using universal joint RT can revolve in noncircular path. coupling or joint which can transmit rotary power by a shaft at any selected angle, coupling in a rigid rod that allows the rod to ‘bend’ in any direction, and is commonly used in shafts that transmit rotary motion. It consists of a pair of hinges located close together, oriented at 90° to each other, connected by a cross shaft. The universal joint is not a constant-velocity joint.
To provide rotating motion to RT and tool ,the impact drill is used .The end of universal joint is connected to tool holder of drilling machine. The spindle speed is constant for all operations, while the cutting speed varies all along the cutting edge.
Cutting speed is normally computed for the outside diameter. The center of the chisel edge the cutting speed is zero; at any point on the lip and it is
proportional to the radius of that point. This variation in cutting speed along the cutting edges is an important characteristic of drilling.
1. Chunk size: 13 mm
2. Power: 350 W
3. Frequency: 50 Hz
4. Current: 1.5 A
5. Speed: 0 – 2800 rpm
6. Voltage: 220 V
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