- Improves surface finish by eliminating the peaks and valleys.
- Create maximum bearing area between the mating surfaces.
- Improves service life of the moving parts which are subject to wear.
- Improves geometrical and dimensional accuracies.
- There is absolutely no distortion in the component after lapping since no clamping devices are used.
- Minimizes the necessity of re hardening hardened parts because of less heat generation.
- Accessible flat surfaces of parts of any shape and size and any type of material can be lapped.
- Simple carrier plate design is enough to accommodate the component for lapping (i.e.) complicated fixture is not required.
- Any unskilled operator can work on the machine.
3 Comments
Lapping is the process of rubbing two surfaces together with a lapping medium (Lapping fluid and Lapping Grit) between them. Lapping is a low pressure abrading process which is employed as a precision finishing operation tooling to achieve high dimensional accuracy, improve geometrical accuracy, fine surface finish and ensure close fit between mating parts. Peaks and valleys before lapping Peaks and valleys after lapping
Lapping is the process of rubbing two surfaces together with a #lappingmedium (Lapping fluid and Lapping Grit) between them.
Stone age man (fig-1) used the process of lapping in preparing their tool and implements to the extent that they drilled holes in a work piece by rotating sticks on it sand strewn surface. A sketch as shown above (fig-2) from the German Museum in Munich, which has illustrated a probable early “Lapping Machine” CMM TRAINING PROGRAMME
GMT training programme that is tailor made for your company. Our experienced instructor will use latest equipment and software to show what your CMM can and cannot do. We offer to train you with your own parts, drawings and inspection tooling to see how usage of CMM can be optimisied. TARGET AUDIENCE Inspection personnel, Engineering personnel, Production personnel who would like to enter into the field of dimensional measurement and CMM programming. Open to companies and and individuals. Prerequisites: Basic knowledge in the following areas: Knowledge of Print Reading of drawings with tolerances Knowledge of Geometric Dimensioning & Tolerancing Knowledge of Basic Dimensional Measurement Tools Basic knowledge of PC and Windows So if you're looking to train your personnel for a refresher/training course on operation of coordinate measuring machine email us at [email protected] with complete details of your company and existing CMM. SSK gripper are primarily designed for drawing in and ejecting steep taper tooling provided with retention knobs internationally standardized as per DIN, ANSI, MAS, JIS and ISO which allow fast automatic tool changes.
SSK gripper are not only suitable for clamping tools, but also workpieces or workpiece holders and pallets on machining centres milling machines boring machines grinding centres special purpose machines and handling systems Grippers in special designs are available for other shapes in addition to the types for standardized clamping bolts. Actuation is mechanical, hydraulic, electro-mechanical or pneumatic. Design features SSK gripper comprise four clamping segments which are captively connected to the draw bolt to ensure easy assembly. They transfer the clamping force positively from the draw bolt to the retention knob. It is possible to clamp tool shanks of the same steep taper with retention knobs of different standards using different gripper in a uniformly designed spindle. Refer to the following table detailing the assignments. The version SSKS.. was developed for very high spindle rotational speeds. Their external design is identical to that of the SSK version of the same type. Gripper of the series SSK..JBS I(II) are always designed for the high-speed version. In comparison to the very high clamping forces of the SSK, SSKE and SSKF series, the SSKE - KH series are designed in favour of a considerably shorter axial stroke according to the generally common values. For new spindle designs the gripper style SSKF is recommended. Application SSK gripper are primarily designed for drawing in and ejecting steep taper tooling provided with retention knobs internationally standardized as per DIN, ANSI, MAS, JIS and ISO which allow fast automatic tool changes. SSK gripper are not only suitable for clamping tools, but also workpieces or workpiece holders and pallets on machining centres, milling machines, boring machines, grinding centres, special purpose machines, handling systems Grippers in special designs are available for other shapes in addition to the types for standardized clamping bolts. Actuation is mechanical, hydraulic, electro-mechanical or pneumatic. Design features SSK gripper comprise four clamping segments which are captively connected to the draw bolt to ensure easy assembly. They transfer the clamping force positively from the draw bolt to the retention knob. It is possible to clamp tool shanks of the same steep taper with retention knobs of different standards using different gripper in a uniformly designed spindle. Refer to the following table detailing the assignments. The version SSKS.. was developed for very high spindle rotational speeds. Their external design is identical to that of the SSK version of the same type. Gripper of the series SSK..JBS I(II) are always designed for the high-speed version. In comparison to the very high clamping forces of the SSK, SSKE and SSKF series, the SSKE - KH series are designed in favour of a considerably shorter axial stroke according to the generally common values. For new spindle designs the gripper style SSKF is recommended. Electro-Mechanical Actuators – U are meant primarily for use on rotating work spindles where there are restrictions on the use of pneumatic or hydraulic rotating cylinders for the actuation of power chucks, expanding mandrels, collets etc.
It can rotate maximum upto 3000 rpm. Electro Mechanical Actuator - UF have been developed as a time saver for quick and efficient clamping and de-clamping of arbors on machines (milling machines, boring machines etc.) which have steep, self-releasing taper on the spindle. Where a number of tools are to be used for an operation, GMT EMA enables the work to be completed in a single set-up. Use of this Electro Mechanical Actuator ensures fast and quick change of tool and cuts non-productive time drastically. Since the operation on the work piece is finished in one set-up, in process inventory is reduced. ISO 9001 ISO 9001 certified organisations have to make decisions regarding where to send their measuring instruments for calibration. Nowadays, many calibration laboratories have ISO 17025 accreditation. But some are not accredited, but still doing calibration work for other organisations. Also, many accredited laboratories are not accredited for all the services they offer. The use of non-accredited calibration labs, or non accredited services of partially accredited labs, may reduce operating costs in the short term, but could turn out to be costly in the long term. Examination of ISO 9001 (2000) and ISO 17025 suggests that ISO 9001 certified organisations should select their calibration labs carefully and make sure that the labs they use are properly accredited for the services they provide.
Organisations certified to ISO 9001 are required to calibrate all their measuring equipment used to verify or control quality, and all such calibrations are required to be traceable to national or international standards (ISO 9001 1994 section 4.11, ISO 9001 2000 section 7.6). All the records of calibrations are required to be maintained properly and corrective action to be taken when measurement equipment is found to be out of specification. Some of the implications of calibration and traceability requirements for ISO 9001 certified organisations and for calibration and test laboratories begins with the investigation, regarding the meaning and components of the term `traceable'. Many calibration laboratories claim accreditation to ISO 17025. Here we go for NABL for accreditation and in Australia NATA is the accrediting body. Accredited labs are entitled to use the NABL logo on their documents and web pages. ISO 17025 is an international standard that specifies quality and technical competence requirements for testing and calibration laboratories. ISO 17025 replaced ISO Guide 25 in 1999. Hiring and keeping competent technical staffs, internal audits, maintenance of in-house quality checks and participation in proficiency testing programs will improves the likelihood of an error-free service but it alone can never guarantee complete absence of calibration or other errors. However, customers of reputable ISO 17025 accredited labs can expect to be informed promptly and fully of errors when they are discovered, and of the particular consequences related to the calibration of their equipment (as per sections 4.9, 4.10). Calibration, uncertainty and traceability The ISO 9001 requirement for traceable calibration of test and measurement equipment raises questions concerning the term `traceable'. When we examine definitions and components of traceability extracted from ISO 9001, ISO 17025 and other documents, we get the answer for it in clear way and along with that discussion regarding the implications were also made in following lines. Tractability is defined as, ‘the property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties....' The unbroken chain of comparisons is called a `traceability chain'. An unbroken chain of comparisons is a logical and easily understood component of traceability. The manager of a non-accredited lab might claim that his calibrations are traceable because he is able to trace only the calibration pedigree of the references and standards, which he uses. This aspect can be analyzed by an example. Assume we keep a set of weights which we use to check balances in a chemical laboratory. The balance should have a resolution and repeatability within the uncertainty required in the final result, when compared with a set of calibrated weights. It must be properly serviced and maintained, mounted on an appropriately rigid and vibration-free bench in a temperature controlled environment. Air movement around the balance may need to be restricted. If the weights to be compared are of different density, compensation for buoyancy might be necessary. Buoyancy compensation might require measurements of air temperature, humidity and barometric pressure. If the lab provides other calibration services then the presence of other equipment nearby may alter the environment in the vicinity of the balance, e.g. a temperature calibration oven might alter the mean radiant temperature in the vicinity of the balance. If we appreciate the potential complexity of the calibration process then we should require that the lab calibrating our weights employ a technician with sufficient competence and training to appreciate all the potential sources of error in the calibration. He should be capable of setting up the equipment properly and deciding which errors are significant and which can be ignored for a particular calibration. Competence as a component of traceability is addressed in ISO 17025 section 5.6. The Section 5.6.2.1.1 states that traceability of measurement shall be assured by the use of calibration services from laboratories that can demonstrate competence, measurement capability and traceability. The use of the word 'shall' in a standard usually means that there is no other way to achieve compliance. ISO 17025 further states that, any calibration laboratories fulfilling the requirements of this International Standard are considered to be competent . A calibration certificate from a calibration laboratory accredited to this International Standard for the calibration concerned is sufficient evidence of traceability. Uncertainty as an essential component of traceability No measurement is ever true. There is always a difference between the true value of a measurand and the output of an instrument. Measurement uncertainty is a quantitative statistical estimate of the limits of that difference. The measurement uncertainty is ' a parameter associated with the results of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand'. Uncertainty estimates document the rationality and consistency of the comparisons. A traceability chain is a documented set of comparisons between consecutive pairs of instruments or measurement systems: A-B, B-C, C-D, etc. Usually instrument A is compared with instrument or standard B for the purposes of calibrating A, and the uncertainty estimated is that associated with that calibration process. The contribution of instrument or standard B to the overall calibration uncertainty is typically 4-10 times smaller than the contribution of A. Similar process to be handled between C & D also. Properly calculated and documented uncertainty estimates in a calibration chain indicate the `direction' of traceability. Everyone should view uncertainty estimates as confirmation that his instrument is calibrated against a reference of adequate performance and that all-potential sources of error are under control during the calibration process. The essential component for traceable calibration is stated as below, Traceable calibration involves comparisons with traceable standards or reference materials. Only laboratories, which demonstrate their competence can perform traceable calibrations, by accreditation to ISO 17025. A traceable calibration certificate must contain an estimate of the uncertainty associated with the calibration. Organizations using non-accredited calibration labs do not conform to ISO 9001 and should not claim conformance. At the same time, some calibration laboratories offer a wide range of calibration services but are accredited for only a subset of those services. In some cases labs claim `ISO 17025 accreditation' but are vague about exactly which services are accredited and which are not. ISO 9001 organizations should be careful to select calibration labs that are explicitly accredited for the services they are using. NABL keeps an up-to-date ,publicly available list of accredited labs with details of the calibration services for which they are accredited and their least uncertainties of measurement. In a manufacturing environment it is often the case that more than one measurement system is used to monitor or control the quality of the product, and inevitably some measurements contribute more than others to uncertainty in product quality. ISO 9001 does not require all measurement systems to be rigorously calibrated - only those that contribute significantly to the control or verification of the quality of the product. One approach to this problem might be to perform uncertainty analyses on quality-related measurements using techniques similar to those outlined in the ISO to determine which measurement systems require calibration and the maximum associated uncertainties. Thus, an ISO 9001 certified organization should analyze the measurement systems it uses to verify or control quality, make informed decisions on which instruments require calibration, and have these instruments calibrated by selected ISO 17025 accredited labs. SYSTEMS OF MEASUREMENT
Errors in Measurements There is a true fact that, no measurement is exact. All measurements are subject to some error. It is therefore necessary to state not only the measured dimension, but also the accuracy of determination to which the measurement is made. As for as possible the errors inherent in the method of measurement used should be kept to a minimum, and having minimized the error, its probable magnitude, or accuracy of determination should be stated. Along with the actual gauge block size details, there should be details regarding the measured error in the block and the accuracy of determination with it enclosed. The accuracy of determination can be improved by repeating the measurement a number of times and stating the mean value. Types of errors: There are two types of errors, • Those which should not occur and can be eliminated by careful work and attention. • Those which are inherent in the measuring process. Misreading an instrument, arithmetic errors, alignment errors, parallax error, errors due to temperature were some of the errors that we can eliminate on proper procedural handling of the system. When we can truly believe a measurement? We can never have 100% confidence in a measurement. No measurement is ever correct. There is always an unknown, finite, non-zero difference between a measured value and the corresponding true value. Most instruments have specified or implied tolerance limits within which the true value of the measurement should lie if the instrument is functioning correctly. One can never be 100% sure that an instrument is operating within its specified tolerance limits. There are steps we can take to minimize the probability of a measurement falling outside specified tolerance or uncertainty bands. Regular traceable calibration is a method for gaining quantifiable confidence in a measurement system. For example, if we consider about the pressure transducer, there are a number of modes in which electronic circuitry and the digital display can fail or malfunction. Most of the faults and malfunctions would not be visible to an operator therefore it is impossible to verify the absence of faults and electronic drift by simple inspection. We cannot tell by inspection if the instrument has recently been dropped, subjected to an over-range pressure or otherwise mistreated. When we make a measurement in the field we are forced to trust the instrument. The only way we can gain confidence in the electronic manometer is by regularly comparing its response with another similar or preferably superior instrument in which we have a high level of confidence. A quantitative comparison or verification of the performance of an instrument is called a calibration. |
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AuthorNarendran Somadev - I work for Guindy Machine Tools, India as a webmaster |