For an experimentation purpose, we designed a model. The general data like spindle speed, tool motion, offset position, Coolant on and Off status, total time for the machining process, total time for cutting process, how much energy has been used for the whole operation and energy consumption while turning or facing generated by the CNC machine. Then we performed theoretical energy calculations using some formulas. Then we did simulation in Autodesk fusion 360 to check what is the cutting time and other parameters and we got some data from that cad software.

Experimentation using CNC machine in which we will collect real time data through Thing Worx software and there will be some architecture connected between Thing Worx and CNC machine including various sensors and servers. The real time values will be shared in an application server where these servers will display the real time working of the CNC. Then with this data we will compare all the results and then change the values or parameters which we used in theoretical calculations, the type of equations we need to change, the values which we got from experimentation as discussed in Fig. 1

## 3.1 Theoretical Calculations:

Thus the first step for estimating the energy we will calculate the power consumption through the assumptions for normal calculations. The power of a motor is the product of the torque and the shaft’s velocity. In machining, this is equal to the torque acting on the spindle multiplied by the spindle speed:

In Non-Rotating applications (Turning and Grooving), it is the force acting on the workpiece multiplied by the workpiece’s radius times the workpiece rotation speed (the spindle speed). [18]

The method to calculate the power consumption is to multiply the Metal Removal Rate (MRR) by the Specific Cutting Force (K)

DEPTH OF CUT: Dc

FEED RATE: Fr

CUTTING SPEED: Vc

EFFICIENCY: η

Specific Cutting Force (K): A material property that indicates the required force needed to extract a chip out of the workpiece.

$$K=Ka\times C{T}^{-{\mu }}\times \left(1-0.01\times A\right)$$

1

…

Ka = NORMALIZED SPECIFIC CUTTING FORCE (FROM VALUE CHART)

µ = SLOPE OF KC GRAPH

A = TOP RAKE RANGLE (+ 7°)

CT = CHIP THICKNESS

CT = Fr = FEED

Ka:

Each material has a specific Cutting Force coefficient that expresses the force in the cutting direction, required to cut a chip area of one square mm that has a thickness of 1mm with a top rake angle of 0°

A:

Each cutting tool has a radial rake angle. We considered the default value as + 7o

CT:

It is calculated differently depending on the application.

When the approach angle is 90° (or more), the feed per revolution as the chip thickness, we use CT = µ

Metal Removal Rate (MRR): ): MRR is the quantity of material machined per unit time in seconds during various machining operations.

$$MRR=Dc\times Fr\times Vc$$

2

…

Assuming the input values are in mm and K in Mpa (N/mm2) the result should be divided by 60,000 to get the power in kW.

$$Power=\frac{MRR\times K}{60\times {10}^{3}}$$

3

…

## 3.2 Theoretical Calculations results:

The below table includes the theoretical calculation results we obtained from the equations (1), (2) and (3). From the assumptions that we made, we got power values slightly higher compared to simulation and experimentation results. This deviation is observed because of certain assumptions such as, feed rate, spindle speed, and the resulting cutting speed.

Table 1

Theoretical Calculations results

Model no. | Spindle Speed (rpm) | Feed (mm/ rev) | Depth of cut/ Width (mm) | Cutting Speed (m/ min) | Power (kW) |

**Model 1** | 1000 | 0.2 | 2.5 | 150 | 2.44 |

**Model 2** | 1000 | 0.2 | 2 | 150 | 1.95 |

**Model 3** | 1000 | 0.2 | 5 | 150 | 4.80 |

## 3.3 Simulation:

From the above results, we can study the three cases we have taken into consideration. With the following data, we can easily calculate the energy consumption for three different cases and compare them with the simulation results we will get from the Autodesk fusion 360 software. First step is to create the models for the three machining operations. The first case is the turning operation, the second is the facing operation, and lastly, it is the grooving operation. In all three cases, we have kept the dimensions of the part the same. We will be taking down the data from the setup sheet we will get from the CAD software (Autodesk Fusion 360) and calculating the power consumption for all three cases.

## 3.4 Simulation Results:

From the calculations using the (1), (2) and (3) equations we have calculated the power consumption for the simulation case. We kept feedrate and spindle speed constant as 0.127mm/rev and 1000rpm respectively. The above table includes the calculations of power consumption which we got with the help of Fusion 360 software and then calculated using the same formulas which we used in theoretical calculations. Also, we assumed the material to be mild steel. There is slight difference in power values of turning and facing operations. The simulation models are previously mentioned.

Table 2

Model no. | Spindle Speed (rpm) | Feed (mm/ rev) | Depth of cut/ Width (mm) | Cutting Speed (m/ min) | Power (kW) |

Model 1 | 1000 | 0.127 | 2.5 | 94.24 | 1.07 |

Model 2 | 1000 | 0.127 | 2 | 94.24 | 0.855 |

Model 3 | 1000 | 0.127 | 5 | 94.24 | 2.14 |

## 3.5 Experiment Working:

After the calculations we will compare the results with the actual CNC machining process using digital twin concept. Here we have discussed the working of the experiment which we carried out.

The general data like spindle speed, tool motion, offset position, Coolant on and Off status, the total time for the machining process, the total time for the cutting process, how much energy has been used for the whole operation, and energy consumption while turning or facing which will be generally generated by the CNC machine in which it will be connected to the Programmable Logic Controller (PLC). For the IoT device, we use KepServerEx as a medium. This KepserverEx medium is installed with the PLC so that the data which are acquired from the CNC will be collected and analyzed and sorted by PLC which will transfer to the server with the help of KepserverEx. This KepserverEx will be connected to the internet in which the data will be transferred to the cloud medium.

Here Thingworx cloud is the cloud medium for this project as we use Thingworx application for viewing the real-time running data to capture the real-time data and to give a command by assuming the time and energy to be consumed by the machine to do an operation by altering the working motion and speed accordingly. As we use a CNC machine that is embedded with sensors to detect the spindle speed, offset position, tool movement, product count, and more which will be connected to a PLC for collecting the data from the CNC. The PLC is connected with the CNC for collecting the real-time data of the working machine. Now the KepServerEX is connected to the PLC to sort out the data which will be collected by the PLC. The Kepserver will be installed in the PLC by using an installation medium. The sensor data acquired from CNC will be collected by the plc and then the kepware will help to sort out the data i.e., which data has occurred from which sensor this the work of plc which each sensor value and will transfer to the application medium where we can see the real-time working data which are occurred from the sensors connected in plc to detect and collect information of each part in the machine.

The real-time values will be shared in an application server where these servers will display the real-time working of the CNC. The Kepware will send the data to the cloud server where we can open the Thingworx with the same IP address which will be given to the Kepserver to view the real-time operating data. Multiple machines can be connected to the Kepserver to view the Realtime operation of all the machines connected to the single server.

When we give a time and energy level to do a work in CNC it will automatically do the calculation within that time period and by consuming the particular amount of energy it varies the working procedure by changing the speed of the spindle by changing the offset motion and by changing the movement of the tool the CNC will complete the operation within the given time period and amount of power consumed.