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Balaramaiah, Y.
- Critical Aspects in Propellant Mixer Development
Authors
1 C M T I, Bangalore, IN
Source
Manufacturing Technology Today, Vol 7, No 11 (2008), Pagination: 12-14Abstract
Mixer is versatile equipment, finding application in diverse fields ranging from Household, Food, Pharmaceuticals, Chemical, Personal care industries, Construction, Rocket Propellant application and many others. To suit the requirement of individual applications, Mixers have been developed with different design philosophies-(a) horizontal and vertical versions with (b) single, dual, three and four blade configurations and (c) with and without planetary motion to the agitator system. Some mixers are of fixed bowl (Mix container) construction and some are rotating bowl type.... For Rocket propellant applications, considerations like stringent requirements of homogeneity and consistency of the product mix as well as the operational safety drive the choices in the Design Philosophy and various features. This paper attempts to focus on some of the salient features of the Solid propellant Mixers developed at CMTI.
- Process Capability (Cp and Cpk) Study of CNC Machines
Authors
1 Advanced Machine Tool Testing Facility, Bangalore, IN
Source
Manufacturing Technology Today, Vol 18, No 1 (2019), Pagination: 15-22Abstract
The accuracy of a machine tool is generally assessed in accordance with the relevant BIS/ISO standards, which serves mainly to provide information concerning the geometrical and other accuracies, as a rule with the machine in unloaded condition. Besides these tests, there are other factors important while assessing the quality and acceptance of the machine tool, based on of its capability in machining, which is considered effective and useful to the seller and buyer of the machine. BIS/ISO:230 standard define the machine tool acceptance based on its testing for geometrical errors and other performance parameters, whereas ISO:26303, ISO:22514 and VDI-DGQ:3441 standards provide a procedure for the acceptance of a machine tool based on of its capability in machining. The statistical verification process described in these standards is applicable to all machine tool categories, and it is necessary to follow typical test pieces and machining conditions, as per guidelines indicated in the VDI-DGQ standard.
ISO recommends to calculate Cp/Cs using standard deviation by normal method, whereas VDI-DGQ recommends use of Range method, and trend to be corrected to estimate for Cp, if observed. ISO standard defines Cpk, based on upper and lower tolerance limits, and also method for surface finish like errors, including the permissible values. This document intends to provide consolidated information how the Cp/Cpk is defined in ISO and also the method of calculation by an example. There is lot confusion in the minds of industry, to calculate the Cp/Cpk and the recommended permissible values for the machine performance. The purpose of this document is to make the industry people (Manufacturer’s and users) to understand the calculation of Cp, well talked by the people.
The purpose of this study is to bring out the differences defined between these various standards, explain the method of estimating the process capability index with an example, and also provide source for the recommended permissible values as per relevant standards, to help industry partners in understanding and the calculation of the process capability index.
Keywords
Cp, Cpk, Testing, Process Capability, Tolerance.References
- ISO:26303-2012: Short term capability of machining Process on metal cutting machine tools
- ISO 22514-4 2016: Process Capability estimates and Performance measures
- VDI/DGQ 3441: Statistical Testing of Operational and Positional Accuracy of Machine tools
- VDI/DGQ 3442: Statistical Testing of the Operational Accuracy of Lathes
- VDI/DGQ 3443: Statistical Testing of the Operational Accuracy of Milling Machines
- VDI/DGQ 3444: Statistical Testing of the Operational Accuracy of Drilling Machines
- VDI/DGQ 3445: Statistical Testing of the Operational Accuracy of Grinding Machines
- Sheet-1: Fundamentals
- Sheet-2: Plain Grinding Machines
- Sheet-3: Centreless Grinding Machines
- Sheet-4: Internal Grinding Machines
- Sheet-5: Surface Grinding Machines
- Thermal Behaviour of Machine Tool Spindle
Authors
1 Advanced Machine Tool Testing Facility (AMTTF), CMTI Premises, Tumkur Main Rd, Bengaluru, IN