BACHELOR THESIS

Automation of EB welded diaphragm

Lars Eriksson2013

Bachelor of ScienceMechanical Engineering

Luleå University of TechnologyDepartment of Engineering Sciences and Mathematics

Abstract The main object with this thesis was to find a valid concept to automate the creation and handling of EB welded diaphragms in CAD-system NX 6. In detail the purpose of the work was to achieve an understanding of the structure and variability of the diaphragm and to build an adaptable and flexible template that meet the demands. The template was based on a master sketch file that acted as a receiver for the calculated data and in turn connected the geometrical data to different solid components to represent the different stages of the diaphragm. The work showed that the concept is valid for automated creation of 3D models and 2D drawings of complete diaphragms to be used as production and visualization base in a virtual turbine, based on calculated data. Further development of the template is possible to fulfill the demands that may occur in the future.

Sammanfattning Det huvudsakliga målet med detta examensarbete var att hitta ett funktionellt koncept för att automatisera framtagandet och hanterandet av 3D-modeller och produktionsunderlag i CAD-programmet NX 6 för elektronsvetsade mellanväggar. Mer specifikt gick arbetet ut på att skapa en förståelse för mellanväggens uppbyggnad och variabilitet för att sedan omsätta denna information i en följsam och flexibel mall som leder till önskat resultat. Mallen centrerades kring en huvudsketchfil som agerade mottagare för den beräkningsgenererade indatan och som i sin tur länkade den geometriska informationen vidare till olika solida parter för att representera de olika stadierna av mellanväggen. Arbetet visade att det valda konceptet är funktionellt för att, baserat på beräkningsdata, automatiskt skapa 3D-modeller och 2D-ritningar på kompletta mellanväggar för användning som produktionsunderlag och för visualisering i en virtuell turbin. Vidareutveckling av mallen är möjlig för att även kunna generera ytterligare variationer av mellanväggens uppbyggnad för framtida varianter.

Preface Finally! I would like to thank Joachim and Andreas at Devex Mekatronik AB for making this possible. Without your determination and perseverance this would not have happened. I also would like to thank my supervisors Thomas and Stefan, and of course Martin and Katrin, for all your input and support. At last, but not at least, a big thank you to my always encouraging and positive examiner Peter Jeppsson at Luleå University of Technology. Thank you!

Table of contents 1.   Background ................................................................................................................ 1  2.   Purpose ...................................................................................................................... 3  3.   Objective .................................................................................................................... 5  4.   Delimitations .............................................................................................................. 7  5.   Task ........................................................................................................................... 9  6.   Analysis .................................................................................................................... 11  7.   Methodology and solution ........................................................................................ 13  

7.1.   The anatomy of a diaphragm ............................................................................ 13  7.1.1.   Components in a diaphragm ....................................................................... 13  7.1.2.   Inner ring ..................................................................................................... 14  7.1.3.   Inner guide vane strip ................................................................................. 14  7.1.4.   Guide vane ................................................................................................. 15  7.1.5.   Outer guide vane strip ................................................................................ 15  7.1.6.   Complement ring ........................................................................................ 16  7.1.7.   Outer ring .................................................................................................... 16  7.1.8.   Completion of the guide vane package ...................................................... 17  7.1.9.   Rough turning ............................................................................................. 17  7.1.10.   Parting ...................................................................................................... 17  7.1.11.   Drill and machining ................................................................................... 17  7.1.12.   Fine turning ............................................................................................... 17  

7.2.   The CAD-model ................................................................................................. 18  7.2.1.   Basic shapes that builds the geometry ....................................................... 19  7.2.2.   The combining of sketches ......................................................................... 27  

8.   Results ..................................................................................................................... 35  9.   Conclusion ............................................................................................................... 37  

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1. Background The design of steam turbines at Siemens Industrial Turbomachinery in Finspång has traditionally been a highly automated process. The level of automation has contributed to make the steam turbine department very efficient and profitable. In connection to the transition to NX 6 from CADDS5 Siemens Industrial Turbomachinery wanted to ensure a high level of automation of their steam turbine design. This study of the EB welded diaphragms has been made as a part of this automation process. Alongside the EBW diaphragms the automation project also intends to cover the automation of the rotor, diaphragm carriers, blades and other types of diaphragms.

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2. Purpose The purpose of this work is to design, and validate, a model of a diaphragm that is functional for the creation of a virtual turbine that can be used in the design and development process of the steam turbines at Siemens Industrial Turbomachinery. Another aim of this project is, in long-term, to gather all the rules and regulations of the company’s diaphragm design in one place to allow easier maintenance of the models and rules. The time needed to design a turbine is, by a more automated workflow, expected to decrease at the same time as the possibilities to refine the information passed on to the production line increases. As the models reach a higher level of automation the downstream workflow also gains the advantage of predictability. This means, for instance, that certain geometric properties, like bodies, faces and edges, among others, are constant and reoccurring for a specific section of the model and thereby allow for an easier setup in for example CAE (calculation) or CAM (manufacturing). The benefit of this is that the CAE and CAM departments are, in an easier way, able to create templates that are set up to receive the automated models and thereby reuse previously created load sets and boundary conditions as well as tool paths. This work is however not covered in this thesis.

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3. Objective The main objective of this work is to develop a valid concept for creating a template for the electronic beam welded, EBW, diaphragm that works as a receiver for calculated data and as a generator of a complete diaphragm. The objective includes the work to design a part structure that will allow for the template to adapt to different shapes and features of the diaphragm as well as creating assembly structures that will allow for different assembly instances to be used for different purposes. This could mean that a certain component will act as a target model for wave linked data in one (build up -) assembly whereas it acts as the representation of the finished results in another assembly. This way a component can be described by a set of source components like standard parts and other details shared by other turbines.

The template should also be made in such a way that it ensures the model to work in a virtual turbine (large assembly) and as a base for comparative FEM analysis.

Figure 1. Simplified structure of build up and result assemblies.

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4. Delimitations As the time is limited to 10 weeks of work, the focus has been set on creating a template that, in general, handles the types of geometrical variations that a typical diaphragm has. This work does not aim to deliver a complete diaphragm with all of its variations, but to validate that the concept is valid for this purpose. A complete set of drawings has not been made for the same reasons.

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5. Task The task is to investigate and capture the design intent of the diaphragm and find an approach that allow for the diaphragm template to be automated. This will be done by reviewing existing models and drawings and therefrom create an understanding of why things are done in a certain way. The task is also to investigate the need for manufacturing information, like 2D drawings, and see to that the template is designed in a way that ensures that all the needed information can be generated. This information along with the need for components that will be functional in the virtual turbine will be essential for creating the assembly structure. Based on the design intent and the need for manufacturing information the template will be built with a structure that describes the different manufacturing steps, as well as with components that has different features describing different areas of the diaphragm and the logic needed to control these features.

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6. Analysis To ensure that the design intent was captured a complete set of drawings for different EB welded diaphragms were studied. Focus was set on finding different, reoccurring, features of the diaphragm that could be used as main features to build the diaphragm around. The drawings also indicated the need for different levels of the model since several pre-machining and welding levels of the diaphragm are put onto the drawings. Existing parameters were studied to make sure that the intent of these parameters were kept and that the existing data was reused wherever possible. The suggested workflow in the model was selected to ensure a stable model with good performance. A model is considered to be stable when it consistently delivers the expected results regardless of the process of reaching the results. This means that a result, C, can be reached from the start, A, with, or without, passing trough B as long as C sufficiently consists of the relevant data. This decision led to that as basic features as possible were used to describe the diaphragm. I.e. datums, sketches, extrudes, revolves, Boolean operations, dress up features and hole features together with interpart expressions and wave linking.

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7. Methodology and solution As the diaphragms come in different variations depending on which stage in the turbine and which kind of turbine they belong to, a classification of the diaphragm was made. The reason for this was to limit the number of variations needed to describe the different shapes that the diaphragm takes.

7.1. The anatomy of a diaphragm To create an understanding of the design of the diaphragm the manufacturing flow of the participating parts was studied. The first step in this process was to identify the parts that constitute the diaphragm. Thereafter the variations of the participating parts, prior to machining and joining to other parts, were studied.

7.1.1. Components in a diaphragm • Outer ring • Complement ring (in some cases) • Outer guide vane strip • Guide vane • Inner guide vane strip • Inner ring

Figure 2. The components in a diaphragm.

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7.1.2. Inner ring The inner ring is the part of the diaphragm closest to the rotor axis. The inner ring covers the distance between the inner guide vane strip and the rotor axis where it holds the seals that prevent the steam from leaking to the next stage in the turbine.

7.1.2.1. Blank The blank is defined as the starting material for a manufacturing operation. The blank for the inner ring consists of a ring with a rectangular cross section. The rectangular cross section covers the final cross section of the inner ring with a few millimeters of material added both axially and radially.

7.1.2.2. Turning prior to welding The turning prior to welding is a fine turning operation of the blank with the intention to produce the surfaces needed to weld the inner ring to the inner guide vane strip. Depending on the width of the inner ring a cutout is turned to grant access for the welding unit.

7.1.3. Inner guide vane strip The inner guide vane strip is the inner part, or the hub, of the steam channel. It holds, together with the outer guide vane strip, the guide vane in place and is welded to the inner ring.

7.1.3.1. Blank The blank for the inner guide vane strip consists of a ring with a rectangular cross section. The rectangular cross section covers the final cross section of the inner guide vane strip with a few millimeters of material added both axially and radially.

7.1.3.2. Turning prior to guide vane mounting The turning prior to guide vane mounting is a turning operation of the guide vane strip to create the steam channel and the general shape of the guide vane strip. The steam channel is finalized at this point. This operation prepares the guide vane strip to be mounted to the guide vane.

7.1.3.3. Cutting of the guide vane holes The hole profile for the guide vanes in the guide vane strip is cut by water jet.

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7.1.4. Guide vane The guide vane in an EB welded diaphragm consists of a profile with constant cross section that is cut to the correct length. It has the role of guiding, or rather directing, the steam in the turbine to the rotor blades. The dimensions and number of guide vanes is depending on the properties of the diaphragm. A cutout is in some cases made to the guide vane to ensure that the guide vane does not intersect with the fine turning of the diaphragm. This cutout is in that case made to the outlet edge on the side of the guide vane closest to the rotor.

7.1.5. Outer guide vane strip The outer guide vane strip is the outer part, or the roof, of the steam channel. It holds, together with the inner guide vane strip, the guide vane in place and is welded to the outer ring.

7.1.5.1. Blank The blank for the outer guide vane strip consists of a ring with a rectangular cross section. The rectangular cross section covers the final cross section of the outer guide vane strip with a few millimeters of material added both axially and radially.

7.1.5.2. Turning prior to guide vane mounting The turning prior to guide vane mounting is a turning operation of the guide vane strip to create the steam channel and the general shape of the strip. The steam channel is finalized at this point. This operation prepares the guide vane strip to be mounted to the guide vane.

7.1.5.3. Cutting of the guide vane holes The hole profile for the guide vanes in the guide vane strip is cut by water jet.

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7.1.6. Complement ring Since the EB welding unit is limited to a certain weld depth, a cutout sometimes is needed to decrease the depth of the weld. The complement ring is an insert that is used to fill that cutout in the diaphragm where needed.

7.1.6.1. Blank The blank of the complement ring consists of a ring with a rectangular cross section. The rectangular cross section covers the final cross section of the complement ring with a few millimeters of material added both axially and radially.

7.1.6.2. Turning prior to welding The turning prior to welding is a fine turning operation of the blank to produce the surfaces needed to weld the fill ring to the outer ring.

7.1.7. Outer ring The outer ring is the part of the diaphragm closest to the rotor casing. The outer ring covers the distance between the outer guide vane strip and the rotor casing where it is inserted to carry the axial load due to the steam pressure in the turbine.

7.1.7.1. Blank The blank of the outer ring consists of a ring with a rectangular cross section. The rectangular cross section covers the final cross section of the outer ring with a few millimeters of material added both axially and radially.

7.1.7.2. Turning prior to welding The turning prior to welding is a fine turning operation of the blank with the intention to produce the surfaces needed to weld the outer ring to the outer guide vane strip. Depending on width of the outer ring a cutout is turned to grant access for the welding unit.

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7.1.8. Completion of the guide vane package The next step in the process is to mount and turn the guide vane package. The guide vane package consists of inner and outer guide vane strips and the guide vanes. In this step the weld surfaces of the guide vane package are turned, which at the same time gives the guide vanes their final length. The inner and outer rings are welded to the guide vane package, and occasional complement ring, whereon further machining is taking place.

7.1.9. Rough turning A rough turning operation of the diaphragms completes the cross section apart from the steam channel. In this operation a radius is fine turned at the inlet of the steam channel and in some cases the whole inlet side is completely fine turned. Whether the diaphragm is carrying another diaphragm decides to what extent the fine turning occurs.

7.1.10. Parting The diaphragm is divided in the xy-plane into two halves by sawing or by electric discharge machining, EDM. The size of the diaphragm determines which parting method that shall be used. Due to the material removal of this process the parting operation gives the diaphragm a slight “lemon” looking shape.

7.1.11. Drill and machining A number of holes, key grooves and sockets are made in the dividing plane on the diaphragm to position and mount it into the turbine casing and diaphragm carrier.

7.1.12. Fine turning The inner and outer radius, the outlet and the shroud of the diaphragm is fine turned to resolve the issue with the lemon shape that the diaphragm got after the parting. Depending on whether the inlet was fine turned in the rough turning operation of the inlet it is also fine turned in this operation. The steam channel is not affected by this operation.

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7.2. The CAD-model The geometrical shape of the diaphragm is decided by factors depending on which stage in the turbine it belongs to. The shape of the turbine casing in the actual position of the diaphragm, the distance to previous stage, if the diaphragm is mounted to another diaphragm, the number of seals on the blade and the shape of the rotor control the shape of the diaphragm. The diaphragm is divided into a number of areas to reduce the number of separate sketches needed to describe the different variations of the diaphragm.

One way of creating the geometry is by the use of ”chunky solid” modeling. That is by subtracting the (tool) bodies of respective area from the blank (target) body. Hence the surface IDs, which are assigned to the surfaces in the tool body while creating the tool body, are inherited to the target body when subtracted. This way the identity of surfaces and edges are constant for a certain feature and will allow for the creation of automated associative drawings despite changes to the shape.

Figure 3. Classification of areas.

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7.2.1. Basic shapes that builds the geometry A number of basic sketches are the base of this model. These sketches are used for generating the tool features for the different areas of the diaphragm. This approach is meant to reduce the number of variations needed to describe the complete diaphragm.

7.2.1.1. Inner radius [Inrad] The part of the diaphragm that is located closest to the rotor axis. This part is defined by which kind of seal that are used between stator and rotor and includes a T-groove that contains the seal.

Figure 4. Inner radius sketches. Inrad_fine_turning and Inrad_machining.

Figure 4 shows the rough turning operation in orange and the fine turning in blue. The T-groove is positioned by the center of the stem of the T (reference curves in the sketch).

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7.2.1.2. Steam channel [Stmchn] The steam channel describes the geometrical shape of the area where the steam passes through the diaphragm. The steam channel is defined by calculated data and varies in shape by angle and the shape of the meridian profile.

Figure 5 Steam channel sketches. Meridian_points, Stmchn and Steam_inlet_radius.

Figure 5 shows the shape of the steam channel in orange, the inlet radius to the left in blue and the meridian profile as points in blue. The rear edge of the guide vane is shown as the orange reference (phantom) curve that divides the meridian profile in the definition of the steam channel.

7.2.1.3. Shroud [Shroud] The shroud is a stepped part of the outlet of the diaphragm. The shroud is adjusted depending on the number of seals between the diaphragm and rotor, which defines the number of steps needed. The number of steps in the shroud equals the number of seals in the blades plus 2 (the number of seals in the diaphragm).

Figure 6. Shroud sketches. Shroud_fine_turning and Shroud_machining.

Figure 6 shows the rough turning operation of the shroud in orange and the fine turning operation in blue. The shroud is completed with grooves for mounting seals and, in some cases a chamfer to avoid collisions with the rotor blades.

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7.2.1.4. Outer radius [Outrad] This area is made to fit the mounting of the diaphragm in the turbine casing. There are three different ways to incorporate the diaphragm into the turbine casing:

• Diaphragm mounted in a diaphragm carrier (HP turbines only) • Diaphragm carried by another diaphragm • Diaphragm mounted directly into the turbine casing

These ways to incorporate the diaphragm decides the shape of the outer radius and the production workflow. The variation of the outer radius includes significantly different shapes and angles.

Figure 7. Outer radius sketches. Outrad_fine_turning_1 and 2.

Figure 7 shows the fine turning sketches of the outer radius. The features that are not applicable for a certain diaphragm are axially displaced until they don't alter the shape of the diaphragm.

Figure 8. Outer radius sketches. Outrad_machining and Outrad_mach_fine_2.

Figure 8 shows the rough turn operations for the outer radius. The blue sketch defines the fine turn of the forward part of the outer radius closest to the inlet. This operation is used for all types of diaphragms that are not mounted into a diaphragm carrier.

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7.2.1.5. Inlet [Inlet] The inlet defines the inlet side of the diaphragm. The inlet varies depending on if the diaphragm carries another diaphragm or not.

Figure 9. Inlet sketches. Inlet_fine_turning and Inlet_machining.

Figure 9 shows the fine turning operation in orange and the scrub turning operation in blue. The curves that divide the fine turning sketch at steam channel are there to allow different axial widths on inner and outer rings.

Figure 10. Inlet sketches for diaphragm carrying another diaphragm. Inlet_carrier_width_fine_turn and

Inlet carrier_width_machining with detail view.

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Figure 10 shows the fine turning operation of the diaphragm-carrying inlet in orange and the rough turning operation in blue. This feature generates the tool body that is subtracted from the inlet feature in Figure 9. Inlet sketches. Inlet_fine_turning and Inlet_machining. and creates the extra inlet level that allows for the carrying of another diaphragm.

7.2.1.6. Outlet [Outlet] The outlet defines the outlet side of the diaphragm, except from the shroud.

Figure 11. Outlet sketches. Outlet_fine_turning and Outlet_machining, with detail view.

Figure 11 shows the fine turning operation in orange and the rough turning in blue. Additionally there are a number of features that controls other features of the diaphragm:

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7.2.1.7. Weld access [Weld_access] The weld access is a socket that allows the EB welder to reach the welding area. It also determines the weld depth for welding the guide vane package to the inner and outer rings. The weld access socket is defined by a set of rules.

Figure 12. Weld access sketch for the outer ring. Weld_access_outer.

The weld access channel in Figure 12 shows the shape of the channel after turning prior to welding in blue and the fine turning operation of the channel in orange. The fine turning operation is performed together with the fine turning operation of the inlet side.

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7.2.1.8. Sealing groove [Sealing_groove] One or two sealing grooves are turned in the shroud to contain the seals. The shroud determines the number of seals. The sealing groove has a standardized shape.

Figure 13. Radial seal sketch alongside the shroud. Radial_seal

Figure 13 shows the sealing groove feature in blue alongside the shroud in orange.

The sealing groove feature is created in such way that it allows for the use of only one groove without modifying the subtract operation.

7.2.1.9. Shroud chamfer [Shroud_chamfer] A chamfer is in some cases created to make sure that the diaphragm and the rotor blade does not collide. The position of the chamfer is determined by the shroud and controlled by an expression.

Figure 14. Shroud chamfer sketch alongside the shroud. Shroud_chamfer.

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7.2.1.10. Inner radius chamfers [Inrad_chamfer] Depending on the shape of the rotor chamfers are needed on the inlet and/or outlet side of the diaphragm. Chamfers are respectively controlled by expressions.

Figure 15. Inlet and outlet chamfer sketches. Inrad_fine_turn_inlet_chamfer and

Inrad_fine_turn_outlet_chamfer.

Figure 15 shows the inlet and outlet chamfers in orange together with the fine turning operation of the inner radius in blue.

7.2.1.11. Moist barrier [Moist_barrier] The moist barrier is a cutout that is turned into the inlet side of the diaphragm. This cutout is needed in some stages of the turbine to drain off the moist that occurs in the turbine.

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7.2.2. The combining of sketches The sketches for describing the geometry of the diaphragm are collected in a master sketch file [master_sketch] to ensure that the interpart expressions are kept as simple as possible. I.e. a majority of the expressions goes from bnr_params to the master_sketch and as few expressions as possible goes to other components in the assembly. Troubleshooting and updates will be easier this way since all geometry is derived from this file thus only representing the shape generated herein. Sketches, and datums, are linked to respective component from the master sketch file where needed. The presence of different features is determined by expressions in the bnr_params file in a way that they fulfill the geometrical demands of the diaphragm.

Figure 16. Master_sketch.

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7.2.2.1. Blanks The most fundamental solids are the blanks. The blanks are defined as the starting material for a (manufacturing) process. Material suppliers provide the blanks, in this case, as rings with a rectangular cross section in the desired material. These are the components that represent the foundation of the diaphragm.

Figure 17. Blanks of the diaphragm.

Figure 17 shows the components 1_BLANK_Inner_ring, 1_BLANK_Inner_GVS, 1_BLANK_Outer_GVS, 1_BLANK_Fill_ring and 1_BLANK_Outer_ring. The red areas represent the areas where the blanks intersect prior to turning. The blanks are bodies of the blank sketches revolved around the turbine axis.

Outer ring

Inner ring

Inner guide vane strip

Outer guide vane strip Fill ring

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7.2.2.2. Guide vane package The guide vane strips undergo a series of turning operations to prepare for mounting of the guide vanes. The steam channel and the general shape are fine turned while the welding surfaces are rough turned before the guide vanes are mounted. Holes are then made in the guide vane strips, to accommodate the guide vanes, with a water jet cutting operation. The guide vanes are mounted to the guide vane strips and the whole package is then fine turned to the final dimensions in the welding areas.

Figure 18. The guide vane package prior to the fine turning of the weld areas.

Figure 18 shows the components 2_Inner_GVS, 2_GV and 2_Outer_GVS.

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7.2.2.3. Welding of the diaphragm The guide vane package is welded to the inner and outer rings.

Figure 19. Diaphragm assembly ready to be welded (w/o complement ring).

Figure 19 shows the components 2_Inner_ring, 2_Inner_GVS, 2_GV, 2_Outer_GVS and 2_Outer_ring.

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7.2.2.4. Rough turning After the welding operation the diaphragm is ready for rough turning. The rough turning operation is an operation to reduce the amount of material needed to be removed by the fine turn operation. The inlet is fine turned in this operation except from in the cases where the diaphragm should carry another diaphragm. In all cases the inlet of the steam channel is fine turned with a radius.

Figure 20. Rough turned diaphragm.

Figure 20 shows the component 3_Diaph_machining.

7.2.2.5. Dividing the diaphragm The diaphragm is divided in the xy-plane into two halves after the diaphragm is rough turned. This operation is needed to allow for the diaphragm to be mounted into the turbine casing. The diaphragm is divided by sawing or by electric discharge machining, EDM. With EDM the amount of removed material from the dividing plane is less than with sawing. The component that is divided is 4_Diaph_parting.

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7.2.2.6. Fine turning and machining The holes and sockets needed for the mounting of the diaphragm into the turbine casing are milled alongside the holes and key grooves in the dividing plane. The inner and outer radius, the outlet and the shroud of the diaphragm is fine turned to resolve the issue with the lemon shape that the diaphragm got after the parting. Depending on whether the inlet was fine turned in the rough turning operation of the inlet it is also fine turned in this operation. The steam channel is not affected by this operation. The sealing grooves and chamfers in the shroud are also turned in this operation. At this point the diaphragm is ready for mounting into the turbine casing.

Figure 21. Completed diaphragm.

Figure 21 shows the component 5_Diaph_final.

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7.2.2.7. Relations The relations in the model are made to be as simple as possible. That is to avoid unnecessary and performance lowering cross linking between different parts. Figure 22 shows the relations in the model starting with the bnr_params file. Most of the parameters in the bnr_params file are linked directly to the master_sketch file with only a few exceptions for some design parameters that are linked to other parts in the assembly. Top to bottom Figure 22 shows

• bnr_params; The parameter file • master_sketch; The origin of the shape of the diaphragm • First and second manufacturing steps; The blanks and the first

milling/turning operations. • Assembly of diaphragm; This is where all the parts are welded together. • Parting of diaphragm; Parting of diaphragm depending on size. • Final manufacturing operations; The last milling and turning operations to

complete the diaphragm.

Figure 22. Relations in model.

7.2.2.8. Drawings At this point the drawings are only tested to verify that they are updating and behaving as planned. However a set of complete drawings are to be made as soon as the diaphragm template is completed with all of its variations and features.

bnr_params

master_sketch

Assembly of diaphragm

Parting of diaphragm

Final manufacturing operations

First and second manufacturing steps

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8. Results By this work it is shown that it is possible to create a template for automated generation of a diaphragm. This template meets the demands of model stability and performance to act as a generator of diaphragms in a design environment. The modeling approach, to adjust sketches to fulfill different needs, used in this work limits the need of parameters to control different features. This template is made by using as basic features as possible, wherever possible. With few exceptions the template is built solely with sketches, extrude and revolve features and Boolean operations which suggest that the template will be easy to migrate to later versions of NX.

Figure 23. Diaphragm.

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9. Conclusion It is by all means possible to automatically generate a complete diaphragm by defining the parameters needed to control the diaphragm. The modeling approach used in this work can be argued to limit the number of needed parameters due to the use of multi purpose sketches. This will however render the defining sketches to be quite complex, and thereby difficult to understand for an arbitrary user. Another approach could be to address the template creation as a simple print function that only reflects the input parameter data as geometrical models. By doing so the need for logical expressions is kept to a minimum thus reducing the number of levels where the describing data could be altered or affected by logic. This method will grant that the model represents the data as it is presented in parameters and any deviating shape will derive from the given data instead of from within the template. The use of multi purpose sketches is another area where there is room for improvement. The multi purpose sketches could be replaced with a larger amount of simple sketches that together represent more complex features that easily could be added to, to further describe and develop the diaphragms. The drawbacks of this method is that the number of parameters needed increases as well as the size of the models, but at the same time it delivers a more intuitive, maintainable and easy to understand model structure. The chances of efficiently accomplish an automation project can be maximized by thoroughly define the way of work from start to finish. I.e. to decide how the template should be used and how the data flows throughout the process. This reduces the risk of getting sidetracked and ending up spending much time aiming for the wrong target.