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Tuesday, 27 January 2015

CNC CYLINDRICAL GRINDING MACHINE

Cylindrical grinding machines are basically used for producing work pieces with non circular or cylindrical contours and on increasingly basis. Hence it was very important for monitoring on route or process and measurements in-process as surface or shape is not circular but also its shape is cylindrical. 

The cylindrical grinding machine i.e. CGM faces a no. of various types of disturbances for example; temperature drifts, tool wear, path control deviations and much more factors and due to these factors there will be losses in productivity as well as there will be dimensional deviations also in work piece.  

In order to achieve the right quality there are various types of tools for monitoring the correct operation and these monitoring tools can help in order to amend the process of grinding.  

Measurement controls could also be utilized in order to compensate for the most various types of disturbances during process of cylindrical grinding. This is done by the concept of measuring & positioning the tools during process of machining in remote way or in the way of automation. Now these days the measurement controls tools are used widely and also well established. 

These are very - very important in case of securing high for an efficient as well as for robust manufacturing processes. It could be concluded that the intelligent monitoring facilities in CNC cylindrical grinding processes will play very important role. 

The modern cylindrical grinding machine of these days could also be utilized for the higher precision grinding process of non-circular or cylindrical contours and for this purpose the cylindrical grinding machine has path control continuous in the X- & C-axes, for example in case of for eccentric grinding. 

Objective
  1. We have to search, understand and to implement the following techniques in cylindrical grinding machines for better productivity.
  2. Parameters which must be measured on the cylindrical ground components for ensuring geometrical and dimensional accuracy.
  3. Show how our experience and knowledge, on Cylindrical grinding process, could be utilized in order to predict the behaviour of grinding and securing optimum operating processes- parameters.
  4. List of instruments for monitoring the process during cylindrical grinding.
  5. Different types of sensors used for efficient operation of cylindrical grinding machine.
  6. Importance of sensors for cylindrical grinding machine.
  7. Location of sensors for efficient operation CGM.
  8. Feedback or compensation system for CGM sensors


Fig: 1 cylindrical grinding machine

Parameter which must be measured on the cylindrical ground

Cylindrical grinding process is a process of giving final finishing of product or component required for smoother surfaces as well as with close tolerances. We must understand that in case of cylindrical grinding process a very small size of chips will be produced. It is mostly used in industrial areas.

The bigger operating I/P parameters which influences the output response of the surface - roughness are as mentioned below.
  1. Machine parameter
  2. Process parameter
  3. Grinding wheel parameter
  4. Work piece parameter
  5. Static tests, such as local reproducibility, repeatability, reproducibility over
  6. Measuring range
  7. Slope limit as well as point to point inspection
  8. Dynamic tests inspection of scanning probing error on sphere

There will be some important input processed parameters also and these are as Feed rate, Cutting Speed and depth of cut. 

This knowledge is basically in the form of empirical models and physical models that will describe different characteristic of cylindrical grinding process. Taguchi method now utilized that integrates these empirical models and physical models to replicate what happens during the process of cylindrical grinding processes. 

Anticipation from the simulation is analyzed further b y calibration along with actual data’s. There are various factors those are involved for securing the optimal values such as grinding wheel Chemical composition, Abrasive, feed rate, Cutting Speed and Depth of Cut. Surface finish is very important output feedback in production w. r. t quality & quantity.

List of instruments for process monitoring of cylindrical work piece diameter and surface finish

There are some important facilities are provided to be control or monitor the operation during grinding operation. 

The distance measurement sensor is installed on wheel head in cylindrical grinding machine and it could be automatically put in place for measuring, as alternative to the wheel head, otherwise it was located in rear portion of cabin. 

Chromatic confocal distance sensor was selected in order to measure the head. The sensor employs one polychromatic point-source. As chromatic aberration will be used, each focal-point relates to a particular wavelength or the distance between the sensor and the surface of the work piece, corresponds to a particular wavelength. 

A spectrometer is basically utilised for measuring the wavelength of reflected light and the most important and considerable advantage of such type of principle of measuring over other various types of principles is it’s insensitivity to various surfaces along with various reflectivity and noted also that it is also beneficial for shiny surfaces. 

As sensor is fixed on wheel head, it will move along the direction of X-axis just like grinding wheel. It only requires a smaller measuring range of the order of 1 mm for highly precision measuring over a big working distance.

The optical sensor is also utilized for this purpose and this type of sensor will be completely integrated with the CNC unit of Cylindrical grinding machine. It will allow information from sensor, the X-, Z and C- axes to be noted as well as linked simultaneously. 

List of sensors used for intelligent operation of CGM and their importance

There are various types of sensors used in cylindrical grinding machine for different purpose, let us understand each sensor and its importance in efficient working of cylindrical grinding machine

Contact displacement sensors

This type of sensors are used for measuring outer diameter of cylindrical work piece such as ingot. 
               Fig2: Contact displacement sensors

Optical sensor

The optical sensor is also utilized for this purpose and this type of sensor will be completely integrated with the CNC unit of Cylindrical grinding machine. It will allow information from sensor, the X-, Z and C- axes to be noted as well as linked simultaneously. 
                      Fig3: optical sensors

Distance measurement sensor

The distance measurement sensor is installed for controlling or monitoring the operation during grinding operation.
    Fig4: Simulator of arrangements coordinates transformations and tests

Proximities sensors

This type of sensors are basically used for detecting metal parts & objects

Location of sensors

Location of sensors, we may understand in above figure the location of sensors, for location of optical sensors we may refer following figure for better understanding.

Conclusion

We have concluded that it is really possible and quite beneficial for using optical sensors in cylindrical grinding machines; however it is not easy to measure directly during operation of grinding. With new possibility of monitoring the process of grinding, such type of metrology will lead for additional values for the complete manufacturing process. 

We also concluded that we will have ability for detecting contour- errors and to rejecting work pieces those are not in allowable range of tolerance as well as we will also have opportunities for securing useful knowledge about cylindrical grinding machine.

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1 comment:

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