Problems Encountered and Remedy Action
Problems in Control Aspect
Lack of Sustainability
Because of the requirement of the client, the robot should be sustainable. To increase the sustainability of the system, the wiring of the PLC and the peripherals should be flexible. Also, the location of the PLC, terminals and the other equipment should be confirmed before mounting. Moreover, the wiring method of the devices mentioned above should tidy, clear and systematic.For example, we have set the color of the wires with difference types. For the power supply, the black color wire has set for the - 24 V and the red color wire has been set for +24V. For the wiring method of the PLC, the blue color wire has set for input and green wire has set for the output. By the result, the customer can maintenance the control system more easily since the technician of the company can check the circuit more consistent and it is a superiority for the further development.
Besides of the wiring method, the location of the devices is also a important element. In the very begin of the summer project, we just mount the PLC, terminal and other devices without any rule. We found that this method is not benefit for the further development. After consideration with this issue, we have mounted all the devices near the left part of the circuit board. After the change, the right section of the circuit board can be used for the further development and increase the sustainability of the system.
Because of the requirement of the client, the robot should be sustainable. To increase the sustainability of the system, the wiring of the PLC and the peripherals should be flexible. Also, the location of the PLC, terminals and the other equipment should be confirmed before mounting. Moreover, the wiring method of the devices mentioned above should tidy, clear and systematic.For example, we have set the color of the wires with difference types. For the power supply, the black color wire has set for the - 24 V and the red color wire has been set for +24V. For the wiring method of the PLC, the blue color wire has set for input and green wire has set for the output. By the result, the customer can maintenance the control system more easily since the technician of the company can check the circuit more consistent and it is a superiority for the further development.
Besides of the wiring method, the location of the devices is also a important element. In the very begin of the summer project, we just mount the PLC, terminal and other devices without any rule. We found that this method is not benefit for the further development. After consideration with this issue, we have mounted all the devices near the left part of the circuit board. After the change, the right section of the circuit board can be used for the further development and increase the sustainability of the system.
The Installation of the Software
The installation of the software is also a big problem when we try to starting the programming process. The software for the PLC is called FPWin GR. The software for the HMI is called EasyBuilder Pro. In the beginning of the programming process we just assume that both of the software will be provided by the SMC Company. Unfortunately, we know that we need to search for the recent software on the internet. The product number of the HMI is MT6071iE. We found two version of the software when we try to find out the corresponding software for the HMI, one of the software is for MT type HMI and the other one is for the iE type HMI. Thus, we are confused with these two versions and waste many times in this process. To solve for this problem we try to install both of the software and we found that the EasyBuilder Pro can fulfill the requirements of the HMI.
The installation of the software is also a big problem when we try to starting the programming process. The software for the PLC is called FPWin GR. The software for the HMI is called EasyBuilder Pro. In the beginning of the programming process we just assume that both of the software will be provided by the SMC Company. Unfortunately, we know that we need to search for the recent software on the internet. The product number of the HMI is MT6071iE. We found two version of the software when we try to find out the corresponding software for the HMI, one of the software is for MT type HMI and the other one is for the iE type HMI. Thus, we are confused with these two versions and waste many times in this process. To solve for this problem we try to install both of the software and we found that the EasyBuilder Pro can fulfill the requirements of the HMI.
The Connection Between PLC and HMI
The connect method of the PLC and the HMI is the main problem in the control part. After we chose the right version of the software, we try to design the layout and interface of the touch panel (HMI). When we tried to connect the HMI with the PLC, the screen of the HMI has shown that the PLC No Response. We confused about this phenomenon since we have wired all the input and output of PLC and connect the cable between the PLC and HMI. We have tried to solve the connect problem by re-install the HMI and PLC software but the problem is persist. Moreover, we dissect problems and question the reason. After trial and error, we think the wiring method of the 9 Pin Cable may be having some error. By double check the manual of the touch panel, we found that we have confused with the Male Port and Female Port of the Cable. Thus, the wiring method of the cable for the connection is incompatible.
The connect method of the PLC and the HMI is the main problem in the control part. After we chose the right version of the software, we try to design the layout and interface of the touch panel (HMI). When we tried to connect the HMI with the PLC, the screen of the HMI has shown that the PLC No Response. We confused about this phenomenon since we have wired all the input and output of PLC and connect the cable between the PLC and HMI. We have tried to solve the connect problem by re-install the HMI and PLC software but the problem is persist. Moreover, we dissect problems and question the reason. After trial and error, we think the wiring method of the 9 Pin Cable may be having some error. By double check the manual of the touch panel, we found that we have confused with the Male Port and Female Port of the Cable. Thus, the wiring method of the cable for the connection is incompatible.
The Setting of the HMI
The setting of the HMI is also a barrier of connect the PLC. We needed many time for using the software since we never use the EasyBuilder Pro software before. Thus. In the beginning of the testing process we just set the HMI into START and STOP. However the setting at the beginning can also work for the robot, we decided to separate the HMI into different parts. We think that the setting of the touch panel should be separate into two main parts, one of the functions is the Auto Mold and the other is the Manual Mold. For example, we need to show the Auto selection menu and display the START, STOP and BACK button so the robot can reset the all the cylinders to Home position for the START button. Also, the STOP button can reset all the cylinders and the memories. In the manual function, the user can select different cylinders which they want to control.
The setting of the HMI is also a barrier of connect the PLC. We needed many time for using the software since we never use the EasyBuilder Pro software before. Thus. In the beginning of the testing process we just set the HMI into START and STOP. However the setting at the beginning can also work for the robot, we decided to separate the HMI into different parts. We think that the setting of the touch panel should be separate into two main parts, one of the functions is the Auto Mold and the other is the Manual Mold. For example, we need to show the Auto selection menu and display the START, STOP and BACK button so the robot can reset the all the cylinders to Home position for the START button. Also, the STOP button can reset all the cylinders and the memories. In the manual function, the user can select different cylinders which they want to control.
Problems in Mechanical Aspect
Limitation on Both Tools and Machines
Due to the limited tools in Industrial Centre, we encountered fastening problem. A part of the system, rotatory actuator, was demanding some shorter screws for the installation. We needed M3x6 and M4x6 for fastening but we only have M3x12 and M4x12 of screws. Therefore, we decided to saw the screw to the appropriate length and use file for surface finishing. It is a simple but effective method to solve our problem by using the least cost in the project. Other than the lack of shorter screws, some longer screws were also needed, Which is M3x35 for the connection of cylinder and aluminium profile. In this case, saw is not available to use. To avoid the usage of long screws, we have to design a new mounting for it.
Our T-shaped nuts were not enough for the fastening as we just ordered the nuts with a few buffer. To figure out this shortage, we have found other types of nuts in the store room of Industrial Centre. It can be the substitutes although it’s not perfect fit, so we added some rings with nuts. As a result, the structure was strengthened.
The long queuing time of the CNC machines were a unexpected situation in our manufacturing stage. Our parts are not possible to do by it. As the parts include hypotenuse or large hole, we planned to use CNC machining to do that which are not suitable for the milling machine. To overcome this incident, we changed our planning to use CNC punching machine and wire cut machine. The benefit of CNC punching machine is having a quick processing to punch the parts, but we got restriction in punching a 2.5mm diameter of hole as the minimum size of tools are 3mm. The further machining is required. Besides, wire cut is a high accurate machine for the very low tolerance. Although we do not need that advantage for the parts, it was just a possible solution other than CNC machining. The cost and time-consumption of wire cut would be the disbursement of this situation.
Due to the limited tools in Industrial Centre, we encountered fastening problem. A part of the system, rotatory actuator, was demanding some shorter screws for the installation. We needed M3x6 and M4x6 for fastening but we only have M3x12 and M4x12 of screws. Therefore, we decided to saw the screw to the appropriate length and use file for surface finishing. It is a simple but effective method to solve our problem by using the least cost in the project. Other than the lack of shorter screws, some longer screws were also needed, Which is M3x35 for the connection of cylinder and aluminium profile. In this case, saw is not available to use. To avoid the usage of long screws, we have to design a new mounting for it.
Our T-shaped nuts were not enough for the fastening as we just ordered the nuts with a few buffer. To figure out this shortage, we have found other types of nuts in the store room of Industrial Centre. It can be the substitutes although it’s not perfect fit, so we added some rings with nuts. As a result, the structure was strengthened.
The long queuing time of the CNC machines were a unexpected situation in our manufacturing stage. Our parts are not possible to do by it. As the parts include hypotenuse or large hole, we planned to use CNC machining to do that which are not suitable for the milling machine. To overcome this incident, we changed our planning to use CNC punching machine and wire cut machine. The benefit of CNC punching machine is having a quick processing to punch the parts, but we got restriction in punching a 2.5mm diameter of hole as the minimum size of tools are 3mm. The further machining is required. Besides, wire cut is a high accurate machine for the very low tolerance. Although we do not need that advantage for the parts, it was just a possible solution other than CNC machining. The cost and time-consumption of wire cut would be the disbursement of this situation.
The Accuracy of Mechanism
The factory had requested that the tolerance of the machine should be within 0.05mm. Thus, the pin on gripper and platforms should have high reliable to fit the cable holder. The pin is machining by screws as the screw thread can tap into the parts. A screw is like a cylinder-shaped, the cable holder can not enter smoothly if the shape is keeping like that. So, our solution is to cut screw to become a cone-shaped holder by lathe. It would be a tailor-made pin for our holder. The cone shape is allowing the larger tolerance of the starting position of gripper. And the end point of cone-shaped holder is to pull the cable holder to precise position. For the easy installation, screw thread is helpful for fastening. Therefore, we encountered the special requirement of the pin and solve it by screws.
The factory had requested that the tolerance of the machine should be within 0.05mm. Thus, the pin on gripper and platforms should have high reliable to fit the cable holder. The pin is machining by screws as the screw thread can tap into the parts. A screw is like a cylinder-shaped, the cable holder can not enter smoothly if the shape is keeping like that. So, our solution is to cut screw to become a cone-shaped holder by lathe. It would be a tailor-made pin for our holder. The cone shape is allowing the larger tolerance of the starting position of gripper. And the end point of cone-shaped holder is to pull the cable holder to precise position. For the easy installation, screw thread is helpful for fastening. Therefore, we encountered the special requirement of the pin and solve it by screws.
The Adjustability of Each Parts
According to the mobility of customer’s options and varieties of the installation of designer, adjustability is necessary to exist. It is for fine tuning the system and avoiding the manufacturing errors.
For customer, we have chosen to install a polyurethane rubber in Z-axis cylinder. The stroke of cylinder can be tuned with the customer decisions. The reason of using rubber is the high enough toughness to insert between the stroke of cylinder.
For designer, we have drilled several sets of holes and used aluminium profile for adjusting the parts position. As aluminium profile has slot for the fastening, we can tune the connection to the most accurate position without any drilled holes or machining. Plus, the function of several sets of holes is to minimize the machining time. We can fasten the assembly through different sets of holes for tuning the desired position. If we take the method of trial and error, time is wasted in unnecessary approach. Therefore, we preset the holes for our adjustment.
According to the mobility of customer’s options and varieties of the installation of designer, adjustability is necessary to exist. It is for fine tuning the system and avoiding the manufacturing errors.
For customer, we have chosen to install a polyurethane rubber in Z-axis cylinder. The stroke of cylinder can be tuned with the customer decisions. The reason of using rubber is the high enough toughness to insert between the stroke of cylinder.
For designer, we have drilled several sets of holes and used aluminium profile for adjusting the parts position. As aluminium profile has slot for the fastening, we can tune the connection to the most accurate position without any drilled holes or machining. Plus, the function of several sets of holes is to minimize the machining time. We can fasten the assembly through different sets of holes for tuning the desired position. If we take the method of trial and error, time is wasted in unnecessary approach. Therefore, we preset the holes for our adjustment.
The Cost
Cost is not just meaning the price, but also the time cost for our manufacturing stage. It is important to decide for selecting the effective way among the method. Two challenges are going to illustrate in the following.
During the machining process, a tap is broken inside parts. We have three options to tackle it, which is doing again with a new material, changing dimension or eliminating the broken tap by EDM Machining. The first option is not chosen by time saving and second option is not chosen by not suitable in this case. The last one is selected due to the cost saving. The material did not need to make it again and remove the broken tap accurately.
Another case is to solve the problem in time-consuming machining. Three options were popped up, which is spending long time to finish it, using CNC machining instead of traditional machining or redesigning to other simple design. The last option was selected by the cost saving too. We spread it to two parts connected with screws to simplify the design of parts.
Cost is not just meaning the price, but also the time cost for our manufacturing stage. It is important to decide for selecting the effective way among the method. Two challenges are going to illustrate in the following.
During the machining process, a tap is broken inside parts. We have three options to tackle it, which is doing again with a new material, changing dimension or eliminating the broken tap by EDM Machining. The first option is not chosen by time saving and second option is not chosen by not suitable in this case. The last one is selected due to the cost saving. The material did not need to make it again and remove the broken tap accurately.
Another case is to solve the problem in time-consuming machining. Three options were popped up, which is spending long time to finish it, using CNC machining instead of traditional machining or redesigning to other simple design. The last option was selected by the cost saving too. We spread it to two parts connected with screws to simplify the design of parts.
Problems in Pneumatic Aspect
The Mounting of the Cable Carrier
In this project, we would use the cable carrier to carry out all the tubing in the machine. If we are not considered the position of the installation, the problem will happen because of the interference. So the position of the cable carrier should be flexible and cannot interrupt them. To solving these problem, we should make sure cable carriers are moving along with the moving parts of the machine, and double check they are no interference before the testing.
In this project, we would use the cable carrier to carry out all the tubing in the machine. If we are not considered the position of the installation, the problem will happen because of the interference. So the position of the cable carrier should be flexible and cannot interrupt them. To solving these problem, we should make sure cable carriers are moving along with the moving parts of the machine, and double check they are no interference before the testing.
The Installation of the Solenoid Valves
The second problem we met was about the installation of the solenoid valves. In our machine, there are 8 cylinders and the tubing may be a litter much. We should make sure the cylinders are connecting in the right position with solenoid valve. That can bring the benefit of the controlling. The procedure of the installation should be step by step. That can reduce the human errors.
Besides, the of position of solenoid valves should be feasible, that is easy for maintenance. We finally decide the position of the solenoid valve is on the bottom of the machine.
The second problem we met was about the installation of the solenoid valves. In our machine, there are 8 cylinders and the tubing may be a litter much. We should make sure the cylinders are connecting in the right position with solenoid valve. That can bring the benefit of the controlling. The procedure of the installation should be step by step. That can reduce the human errors.
Besides, the of position of solenoid valves should be feasible, that is easy for maintenance. We finally decide the position of the solenoid valve is on the bottom of the machine.
The Safety of using high pressure tubing
Safety issue is very important on this project. During the operating, the piping are maintaining high pressure gas. If the accidents happen, this is very dangerous for the operator. To reduce the damage of that situation, emergency stop is necessary on this machine. Emergency stop can control the electric valve and give it a signal to stop the high pressure gas. It is difference with the on off switches.
Also, the emergency lighting is important for avoiding the accident. When the accidents happen, the light would turn on and tell the people around the machine these are something wrong.
Safety issue is very important on this project. During the operating, the piping are maintaining high pressure gas. If the accidents happen, this is very dangerous for the operator. To reduce the damage of that situation, emergency stop is necessary on this machine. Emergency stop can control the electric valve and give it a signal to stop the high pressure gas. It is difference with the on off switches.
Also, the emergency lighting is important for avoiding the accident. When the accidents happen, the light would turn on and tell the people around the machine these are something wrong.
The Precision of the X-axis Cylinder
On our project, one of the cylinder should be stopped in three different positions. The midpoint position should be precised. To solving this problem, the additional valve is added to control the retract speed of the x axis cylinder and make sure the position of the stopping is on the high precise position
On our project, one of the cylinder should be stopped in three different positions. The midpoint position should be precised. To solving this problem, the additional valve is added to control the retract speed of the x axis cylinder and make sure the position of the stopping is on the high precise position