Informatics Publishing Limited

T. Shravan Kumar ¹, T. S. R. Murthy ¹

Affiliations
1 Daimler Commercial Vehicles Pvt. Ltd., Chennai-600096, IN

Abstract

In many precision machines and equipment, there are two or three reference axes intersecting at a point theoretically as per the drawing. One example is gyro spin axes construction. The other examples are N/C machine tool spindle axis and table axis as reference axes. Yet another example is the three bevel gear reference axes of space equipment like helicopter, intersecting at a common point. In all the above examples, theoretically the axes have to meet at a common point. But at manufacturing stage one has to specify the acceptable deviation. Presently each axis is measured separately for its straightness or perpendicularity with some surface. Though the axes are measured separately one cannot say to what extent they are meeting or how closely they are approaching to the theoretical intersection point. Further there is no standard to specify this error. The authors have earlier established and published different ways of fitting axis. Some six methods of specifying the deviation/error were also defined. In this paper a method of specifying the error namely Maximum Throat Deviation (MTD) is discussed and an algorithm to compute it is explained.

Keywords

GD & T, Evaluation of Reference Axes, Error Evaluation.

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T. S. R. Murthy ¹, Y. V. Ramanamurthy ¹

Affiliations
1 Computer Aided Engineering Division, PDE Central Manufacturing Technology Institute, Bangalore-560 022, IN

Abstract

Hydrostatic slides are used on many machines with multiple hydrostatic supports. These supports are provided on top and bottom faces of the slide to take load in both upward and downward directions. Similar supports are given in the other guiding plane. In order to design the pocket sizes for these hydrostatic bearings, the expected reaction load at these points is required. When there are only three simple supports in a particular direction, and when the load passes through the base of these supports, these reactions cannot be obtained directly from the equilibrium equations. When there are more than three supports, one has to obtain reactions through Finite element analysis. Though FEA is the answer to find reactions with multi supports, it Is not straightforward, because the present slide arrangement of hydrostatic bearings is such that they can support in +Z and/or -Z directions along with similar support in one other direction X or Y). But in FEM analysis such partial directional constraints (i.e constrained in only +Z direction or only -Z direction) cannot be given. This leads to different trials in getting the required reactions. As there are no established methods to solve such problem, an attempt is made in this paper to find a solution to such problems. Different approaches are also given to solve such problems.

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T. S. R. Murthy ¹, Y. V. Ramana Murthy ¹, A. K. Saxena ²

Affiliations
1 Department of CAE/CIM, Central Manufacturing Technology Institute, Bangalore, IN
2 Indian Institute of Astro Physics, Bangalore, IN

Abstract

Metrology applications require surface plates of high accuracy and stability Surface plates are made in different sizes, shapes and with different materials. The most common shape is rectangular and the most common material is steel or granite. The accuracy of the surface is obtained by repeated measurements and by lapping the non-flat regions. In this paper, an attempt has been made to analyze the circular surface plates to reduce its weight and optimize the deflection by different support locations and different types of ribbing.

Keywords

Optimized Surface Plate, FEM Analysis of Surface Plates. Circular Surface Plates.

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T. S. R. Murthy ¹

Affiliations
1 Central Manufacturing Technology Institute, Tumkur Road, Bangalore, 560022, IN

Abstract

Manufacturing and evaluation of the quality of the manufactured components become complicated when the accuracy requirements are stringent. Consider the most common application where holes are drilled on the flanges of cylindrical shells on a pitch circle. These holes are supposed to be equispaced on the pitch circle. The axes of the bores are supposed to lie on the pitch cylinder and thus the axes have to be parallel to each other and also parallel to the axis of the cylindrical shell as per the design drawing requirement. In general, such holes are clearance holes and as such no measurements are made. But presently there is an application where there is a need for such evaluation which is detailed in this paper.

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T. S. R. Murthy ¹

Affiliations
1 Central Manufacturing Technology Institute, Tumkur Road, Bangalore-560022, IN

Abstract

Flatness evaluation of granite and other surface plates in rectangular form is well established and standards are available. There are situations where the large flanges of some of the cylindrical shells have to be evaluated for flatness of the large flange, in the form of a circular ring. The flange is of three meters size. This needs a measurement and evaluation technique for its application. This paper details such an application. Since the measured data on the surface are on a polar form, it requires polar grid to obtain measurements. Depending on the width of the ring the measurements may be available on just one circle, i.e the mean circle of the ring or on different circles on the ring. Since the data is on a circle the relative height deviations must sum up to zero on each circle. This paper details a measurement and evaluation technique for this application and there are no standards for the same.

Keywords

Evaluation of Flatness, Flatness of Large Rings, Polar Grid for Flatness Evaluation.

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