NX helps guarantee the accuracy of critical nuclear reactor components
SEC Nuclear Power Equipment Co., Ltd. (SEC Nuclear Power) is China's first Class-I manufacturer of nuclear power plant components. Examples of the company's products include the pressure vessels, evaporators, and pressure stabilizers at the Qinshan Phase-I nuclear facility; evaporators and stabilizers for Pakistan's Chashma plant; a high-temperature pressure vessel and air-cooled reactors at Tsinghua University; and pressure vessels, pressure stabilizers, and evaporators at Qinshan Phase-II.
Nuclear reactor components must be perfect
Pressure vessels are enclosed containers that house reactor cores and limit the fission of nuclear fuels within an enclosed metal shell. If a fuel enclosure is considered the first barrier preventing the escape of radioactive material, pressure vessels are the second barrier. Pressure vessels must be able to operate reliably for 40 to 60 years under conditions of high temperature, high pressure, strong radiation and corrosion.
The inlet and outlet pipes of pressure vessels are critical components that transfer the energy generated by nuclear fission. Welded to cylindrical surfaces, these pipes must withstand very high temperatures and pressures. It is a challenge to design these components, particularly their connections to the pressure vessel itself, where a special curved surface called a "saddle curve" is used. A saddle curve is challenging to design and manufacture correctly.
In the past, SEC Nuclear Power relied on third parties to design the pipes and connections. Not only was the cost of outsourcing high, manufacturing a single component costs hundreds of thousands of yuan. "The cycle time was long and it was difficult to fully control quality," says Li Zhiguo, chief technician at SEC Nuclear Power. "When something had to be scrapped due to errors by a third party, the result could be a serious delay in the development of the pressure vessel – a delay that had the potential to result in financial penalties for us and lost confidence on the part of our customers."
Digital factory based on NX
When SEC Nuclear Power decided to bring this work in house, the company installed a piece of the world's most advanced numerically controlled (NC) manufacturing equipment, as well as one of the world's most advanced computer-aided design (CAD)/computer-aided manufacturing (CAM) solutions, NXTM software from Siemens PLM Software. SEC Nuclear Power selected United Digital Systems (UDS), Siemens PLM Software platinum partner in China, to help implement the new solution. UDS developed training courses and a service plan tailored to the unique needs of SEC Nuclear Power. UDS also helped by cultivating more NC professionals and specialists.
A project team composed of technical engineers from SEC Nuclear Power and UDS developed a highly efficient and completely integrated process for producing pressure vessel components using NX. Zhiguo established the new design and manufacturing practices, while UDS handled the implementation. In the new process, parts are modeled in NX. NX CAM is used to program toolpaths directly from the NX part model. Then the machining sequence is simulated. Errors that show up during the simulation are fixed and then the part is machined. "Throughout the entire process, a single platform, NX, is used," says Zhiguo. "NC data is output from NX CAM to drive a machine tool controlled by a Siemens SINUMERIK 840D, thus realizing the concept of a fully integrated CAD-CAM-CNC (computer numerical control) process chain."
Because the inlet and outlet pipes of different pressure vessels have similar structures but different dimensions, full parametric modeling has been implemented within NX. Key parameters have been assigned values derived from expressions. As a result, for other pipes of the same type, a new 3D model can be built rapidly simply by changing the value of a few expressions. "This has eliminated a lot of rote modeling work," says Zhiguo.
Luo Wei, chief technology officer for CAM, UDS, adds, "For a safety-critical application such as this, which requires the highest level of accuracy in design, simulation and manufacturing, NX is no doubt the best choice."
Saddle curve problem solved
Using NX CAM to simulate machining operations is an indispensable part of the new process, and one that the company believes has been the key to its success. Digital models of a part, along with the associated tooling and fixtures, are assembled on-screen using the assembly modeling functionality of NX.
3D models of the part and associated tools and fixtures are designed in NX using a full range of CAD functions. NC programs and G-codes that match the machine tool and controller are defined in NX CAM. The NC programs are checked and validated in NX CAM, using a 3D simulation of the actual motion of the machine tool. All interferences and collisions are shown, as well as are out-of-range operations, undercuts and gouges. With NX CAM, problems can be eliminated before the actual machining takes place.
One of the most important capabilities of NX for SEC Nuclear is its support for design automation (knowledge re-use). Templates, which the company refers to as processing forms, have been created to capture the various design and manufacturing parameters of each pipe. Once the detailed design characteristics of a new pipe – such as size, shape, etc. – have been specified, the NC programs are updated, and a complete and validated NC code is generated within minutes. NC programs and G-code output are optimized for the job at hand, because the integrated postprocessor in NX CAM has been configured to match the specified machine and controller. With proven design and manufacturing parameters defined in the template, the entire design-through-manufacturing process is safe and reliable.
The new, integrated design-manufacturing process based on NX has solved the tricky saddle-curve issue that posed problems for SEC Nuclear Power in the past. In fact, it has enabled the company to handle the manufacturing of these parts in a unique way. Rather than using multiple machines to perform a sequence of different operations on the part, there is now just a single machine – a vertical mill. "This method is unprecedented abroad, as far as we know, and SEC Nuclear Power is the first to adopt it," says Zhiguo. The ability of NX to support the functions of the vertical mill, which is 10 feet (3.15 meters) in diameter, has reduced the effort needed to produce these parts by eliminating many of the fixtures and changing operations needed previously.
Since implementing NX, the development cycle for parts with saddle curves has dropped from one month to 4 days (approximately 40 working hours). Another part with rounded corners that took 18 days to make in the past now takes less than 8 days. "This is a significant success," says Zhiguo.
Zhiguo adds, "One reason this project went so successfully was because NX provides a very good implementation platform. Any requirement we have is perfectly supported by this software, which is crucial for us."
The cooperation between Siemens, UDS and SEC Nuclear Power has paved the way for a new direction in how challenging parts are produced. "NX brought an end to our history of outsourcing these parts," says Zhiguo. "Now that we can do the work in-house, we can be more innovative with how these complex parts are manufactured."
Pressure vessels are enclosed containers that house reactor cores and limit the fission of nuclear fuels within an enclosed metal shell. If a fuel enclosure is considered the first barrier preventing the escape of radioactive material, pressure vessels are the second barrier. Pressure vessels must be able to operate reliably for 40 to 60 years under conditions of high temperature, high pressure, strong radiation and corrosion.
The inlet and outlet pipes of pressure vessels are critical components that transfer the energy generated by nuclear fission. Welded to cylindrical surfaces, these pipes must withstand very high temperatures and pressures. It is a challenge to design these components, particularly their connections to the pressure vessel itself, where a special curved surface called a "saddle curve" is used. A saddle curve is challenging to design and manufacture correctly.
In the past, SEC Nuclear Power relied on third parties to design the pipes and connections. Not only was the cost of outsourcing high, manufacturing a single component costs hundreds of thousands of yuan. "The cycle time was long and it was difficult to fully control quality," says Li Zhiguo, chief technician at SEC Nuclear Power. "When something had to be scrapped due to errors by a third party, the result could be a serious delay in the development of the pressure vessel – a delay that had the potential to result in financial penalties for us and lost confidence on the part of our customers."
Digital factory based on NX
When SEC Nuclear Power decided to bring this work in house, the company installed a piece of the world's most advanced numerically controlled (NC) manufacturing equipment, as well as one of the world's most advanced computer-aided design (CAD)/computer-aided manufacturing (CAM) solutions, NXTM software from Siemens PLM Software. SEC Nuclear Power selected United Digital Systems (UDS), Siemens PLM Software platinum partner in China, to help implement the new solution. UDS developed training courses and a service plan tailored to the unique needs of SEC Nuclear Power. UDS also helped by cultivating more NC professionals and specialists.
A project team composed of technical engineers from SEC Nuclear Power and UDS developed a highly efficient and completely integrated process for producing pressure vessel components using NX. Zhiguo established the new design and manufacturing practices, while UDS handled the implementation. In the new process, parts are modeled in NX. NX CAM is used to program toolpaths directly from the NX part model. Then the machining sequence is simulated. Errors that show up during the simulation are fixed and then the part is machined. "Throughout the entire process, a single platform, NX, is used," says Zhiguo. "NC data is output from NX CAM to drive a machine tool controlled by a Siemens SINUMERIK 840D, thus realizing the concept of a fully integrated CAD-CAM-CNC (computer numerical control) process chain."
Because the inlet and outlet pipes of different pressure vessels have similar structures but different dimensions, full parametric modeling has been implemented within NX. Key parameters have been assigned values derived from expressions. As a result, for other pipes of the same type, a new 3D model can be built rapidly simply by changing the value of a few expressions. "This has eliminated a lot of rote modeling work," says Zhiguo.
Luo Wei, chief technology officer for CAM, UDS, adds, "For a safety-critical application such as this, which requires the highest level of accuracy in design, simulation and manufacturing, NX is no doubt the best choice."
Saddle curve problem solved
Using NX CAM to simulate machining operations is an indispensable part of the new process, and one that the company believes has been the key to its success. Digital models of a part, along with the associated tooling and fixtures, are assembled on-screen using the assembly modeling functionality of NX.
3D models of the part and associated tools and fixtures are designed in NX using a full range of CAD functions. NC programs and G-codes that match the machine tool and controller are defined in NX CAM. The NC programs are checked and validated in NX CAM, using a 3D simulation of the actual motion of the machine tool. All interferences and collisions are shown, as well as are out-of-range operations, undercuts and gouges. With NX CAM, problems can be eliminated before the actual machining takes place.
One of the most important capabilities of NX for SEC Nuclear is its support for design automation (knowledge re-use). Templates, which the company refers to as processing forms, have been created to capture the various design and manufacturing parameters of each pipe. Once the detailed design characteristics of a new pipe – such as size, shape, etc. – have been specified, the NC programs are updated, and a complete and validated NC code is generated within minutes. NC programs and G-code output are optimized for the job at hand, because the integrated postprocessor in NX CAM has been configured to match the specified machine and controller. With proven design and manufacturing parameters defined in the template, the entire design-through-manufacturing process is safe and reliable.
The new, integrated design-manufacturing process based on NX has solved the tricky saddle-curve issue that posed problems for SEC Nuclear Power in the past. In fact, it has enabled the company to handle the manufacturing of these parts in a unique way. Rather than using multiple machines to perform a sequence of different operations on the part, there is now just a single machine – a vertical mill. "This method is unprecedented abroad, as far as we know, and SEC Nuclear Power is the first to adopt it," says Zhiguo. The ability of NX to support the functions of the vertical mill, which is 10 feet (3.15 meters) in diameter, has reduced the effort needed to produce these parts by eliminating many of the fixtures and changing operations needed previously.
Since implementing NX, the development cycle for parts with saddle curves has dropped from one month to 4 days (approximately 40 working hours). Another part with rounded corners that took 18 days to make in the past now takes less than 8 days. "This is a significant success," says Zhiguo.
Zhiguo adds, "One reason this project went so successfully was because NX provides a very good implementation platform. Any requirement we have is perfectly supported by this software, which is crucial for us."
The cooperation between Siemens, UDS and SEC Nuclear Power has paved the way for a new direction in how challenging parts are produced. "NX brought an end to our history of outsourcing these parts," says Zhiguo. "Now that we can do the work in-house, we can be more innovative with how these complex parts are manufactured."
