1 / 21

CMM-PPT

coordinate measuring

Shantilal
Download Presentation

CMM-PPT

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CMM Coordinate-Measuring Machine By Prof. A.U.Awate Department of Mechanical Engineering PRMIT & R Badnera-Amravati

  2. CMM is a 3D device for measuring the physical geometrical characteristics of an object. • CMM is a machine which takes readings in six degrees of freedom and displays these readings in mathematical form. • CMM is a specialized form of  industrial robot

  3. Parts • CMM include three main components: • 1.Main Structure • which include three axes of motion • 2. Probing system • 3. Data collection and reduction system • Application software • Machine controller • Desktop computer

  4. 1.Main Structure • Gantry type • Advantage: • Measurement of large size parts • Disadvantage: • Geometric changes caused by non-uniform temperature distribution owing to their large size. • Application: • Heavy machine construction, • car body and mold making sectors • of the automotive industry, • measuring wind tunnel models.

  5. 1.Main Structure • Cantilever type • Advantage: • Large measuring range • Maximum accessibility • Disadvantage: • Bending of the cantilever above the measuring area • Application: • For checking sheet metal, cast iron and steel parts in the automotive industry, aircraft construction and shipbuilding.

  6. 1.Main Structure • Column type • (horizontal arm type) • Advantage: • High accelerations and speeds • owing to the large supporting base • of the column and its low weight • Disadvantage: • Suitable for small measuring ranges • only since the projecting part of the columnmust have short length due to its rigidity. • Application: • In precision measurements • on gages and master parts.

  7. 1.Main Structure • Bridge type • Advantage: • Most widely used • High rigidity  owing to compact bridge design and thus small measuring deviations. • Disadvantage: • Limited accessibility caused by the bridge. • Application: • For medium to large measuring range

  8. Portable CMM Have six rotary axes with rotary encoders, instead of linear axes. Less accurate than a bridge type CMM Use angular measurements taken at the joints of the arm to calculate the position of the stylus tip. Can reach the insides of complex parts Applications: Reverse engineering, rapid prototyping, and large-scale inspection of low-volume parts are ideally suited for portable CMMs

  9. CMM Features • Granite Table • Structurally and thermally stable material • Low porosity • Low moisture absorption • Low coeff. of thermal expansion • Superior strength • Uniformity of texture • Non-glaring surface • M8 threaded table inserts

  10. CMM Features • Air bearings • Provided for ensuring friction free travel to all axes • Compressed air is forced through a series of very small holes in a flat bearing surface to provide a smooth but controlled air cushionon which the CMM can move in a frictionless manner

  11. CMM Features • Each axis is fitted with a reference system and a linear measurement transducer for positional feedback. • (0.5 micron resolution) • Passive vibration damping system isolates external vibrations • FEA designed bridge beam extrusion provides optimum M.I. for minimum deflection when operating at high accelerations

  12. 2. Probing system • The touch probe forms the sensing device on the end of the quill • Mechanical probe • Contact type • Soldering a hard ball to the end of a shaft • No control on measuring pressure • Electronic touch trigger probe • Contact type • Stylus is spring-loaded with ruby ball at the tip • As the probe touched the surface of the component the stylus deflected and simultaneously sent the XYZ coordinate information to the computer • Optical probes and Laser probes • Non-Contact type • White light/ Laser beam is projected against the surface of the part • Better for scanning

  13. 2. Probing system • Pre-travel variation (PTV) • Pre-travel is the amount of stylus bending • at the point that a trigger occurs. • Pre-Travel depends on • Contact Force FCneeded to overcome • Spring Force FS • Length L and stiffness of the stylus • Direction of measurement R • Pre-travel in the Z direction tends to be small • despite the higher forces • Pre-travel can be compensated by probe calibration. • Adatum feature (of known size and position) is • measured to establish the average pre-travel

  14. 2. Probing system • Stylus modules

  15. 2. Probing system • Qualifying Probe Tips • Correction for Tip Radius • CMM detects dimension from and to the center of the tip (ruby ball) which calls for correction for tip radius. • Each recorded value is corrected for tip radius.

  16. 3. Data collection and reduction system • Application software • PC-DMIS CMM • Dimensional Measuring Interface Standardis the world’s leading metrology software • PC-DMIS PRO • Full-featured metrology software system • without CAD capabilities. • PC-DMIS CAD • It adds CAD capabilities to PC-DMIS PRO. • It allows import and export CAD modules • Possible to develop, test and debug part programs directly on CAD models • Compares the measured data directly to the CAD model • Lets graphically test and debug inspection routines • PC-DMIS CAD++ • Handles difficult scanning tasks (contact & non contact type) • and supports sophisticated scanning devices

  17. 3. Data collection and reduction system • Application software Modules • PC-DMIS CMM • PC-DMIS Planner • PC-DMIS Gear • PC-DMIS Blade • PC-DMIS NC • PC-DMIS Portable • PC-DMIS Vision

  18. 3. Data collection and reduction system • Application software • Alignment • PC-DEMIS mathematically relates the Part Coordinate Systemand Machine Coordinate System.

  19. 3. Data collection and reduction system • Application software • Measured and Constructed Features

  20. 3. Data collection and reduction system • CMM controller • Controller is the heart of CMM • Provides precise control of the • motion of the machine • Interfacing to sensors and • with the metrology software.

  21. CMM Applications • Metrology • Linear Measurement (Measured and Constructed Features) • Angular Measurement (Measured and Constructed Features) • Geometrical Features • Profile Checking • Stages of Inspection • Receiving • In-proses • Final • Mode of Inspection Operation • Manual • Automated (DCC) • Purpose of Inspection • First-piece approval • Process Control • Pre-assembly qualification of parts • Reverse Engineering • Location of Inspection • Standard Room • Machine Shop • on Site

More Related