2023年课程精品讲义Teaching Plan.pdf

学习好资料 欢迎下载 Teaching Plan-3:Form feature Learning Outcomes On the completion of this unit you will be able to correctly use the following skills as follows:Create solid models form features and Position features correctly.Edit the parameters and position of features.operations.Assessment Competency will be assessed by operation tasks throughout this section.Please forward the Practical Applications Manual to your supervisor for assessment on completion of operation tasks.Resources Practical Applications(Period:2 classes in classroom)Practical Applications of UG NX4.0（Student Guide）Lesson3:Positional Form Features Operation(Period:2 classes in computer training room)Practical Applications Manual Operation 3:Form Features Key Point Position the Form Features,Edit the position of the form features.Creating Form Features Form features are used to add detail to a model.These features include holes,学习好资料 欢迎下载 slots,bosses,pads,pockets and grooves.Form features are fully associativeto the geometry and parameter values used to create them.Placement Face All form features require a placement face.For a groove,the placement facemust be cylindrical or conical.For all other form features,the placement face must be planar.A datum plane may be used as the planar placement face.Horizontal and Vertical Reference The Horizontal Reference defines the X axis of the feature coordinate system.Any linear edge,planar face,datum axis,or datum plane that canbe projected onto the planar placement face may be selected to define the horizontal direction.A Horizontal Reference is required to define the length direction of form features having a Length parameter(slot,rectangular pocket,and pad).Itis also required to define horizontal or vertical positioning dimensions for features that do not initially require a Horizontal Reference(holes,bosses,and cylindrical pockets).1 Planar Placement Face 2 Horizontal Reference 3 X Length of Feature If there are no selectable objects to define a horizontal direction,you canspecify a Vertical Reference instead.The horizontal direction will be inferred as being 学习好资料 欢迎下载 perpendicular to it.Positioning Form Features 1 Horizontal 2 Vertical 3 Parallel 4 Perpendicular 5 Parallel at a Distance 6 Angular 7 Point onto Point 8 Point onto Line 9 Line onto Line Positioning dimensions are distance values measured along the placement face.They may be used to place the form feature at the proper location onthe placement face.These dimensions should be considered as constraints,or rules,that the geometry must obey.Positioning Terminology Fully Specified The feature is uniquely located by the positioning dimensions specified.Underspecified The feature position is not completely constrained.Overspecified The feature has had more positioning constraints applied to it than are necessary.Target Solid The solid body that a Boolean operation acts upon.Target Edge An edge on the Target Solid that is selected for positioning purposes.Tool Solid The solid representation of the feature being definedby the current operation.Tool Edge An edge on the Tool Solid that is selected for positioning purposes.Parameter Entry Options Parameter Entry Options let you easily define your model parametrically as you specify values during feature creation.They are accessed by choosingthe“down-arrow”icon located next to many of the parameter entry fields throughout the 学习好资料 欢迎下载 Modeling application.Options are provided to let you specify a value based on a formula,a referenceto an existing value,or a derived value from a measurement without havingto copy and paste or reenter the values.You can use these options to easily lookup functions and define relationships between features.You can use values that already exist in your model,making downstream changes easier and in agreement with your designintent.Hole Simple 1 Diameter 2 Depth 3 Tip Angle Counterbore 1 C-Bore Diameter 2 C-Bore Depth 3 Hole Depth Countersink 1 C-Sink Diameter 2 C-Sink Angle 3 Hole Depth Hole Creation Procedure Choose the Hole icon(InsertDesign FeatureHole).学习好资料 欢迎下载 Choose the Type(Simple,Counterbore,or Countersink).Select the placement face.Select the thru face if applicable.Key in the required parameter values.Choose OK or Apply.Create positional dimensions as required.Boss The Boss feature is used to add a cylindrical shape with a specified height toa model,having either straight or tapered sides.1 Diameter 2 Height 3 Taper Angle Slot This option allows you to create a slot in a solid body as if cut by a milling machine tool.In each case,the shape of the cutting tool corresponds to the slot type and dimensions.The slot feature will be created so that the axis of the cutting tool is normal to the face or datum plane selected.Initially,the path of the slot will be parallelto the selected Horizontal Reference.1 Length 2 Width 3 Depth The Width of the rectangular slot represents the diameter of the 学习好资料 欢迎下载 cylindricalcutting tool.The Depth of the slot is measured in a direction parallel to the tool axis from the placement face to the bottom of the slot.Depth values must be positive.The Length is measured parallel to the horizontal reference(X in the feature coordinate system).Length values must be positive.The other available slot profiles are shown below.Ball-End U-Slot T-Slot Dove-Tail Pocket The pocket feature is used to create a cavity in a solid body.There are three types of pockets:Cylindrical(not covered in this lesson),Rectangular,General(not covered in this lesson).The Rectangular Pocket option allows a rectangular pocket to be defined to a specified depth,withor without a floor and/or corner radius,having either straight or tapered walls.Pad This option allows a raised pad on a solid body.There are two types of pads:Rectangular,General(not covered in this lesson).The Rectangular Padoption allows a rectangular pad to be defined to a specified height,withor without a corner radius and/or taper.Groove The groove feature requires a cylindrical or conical placement face.A groove can be thought of as a feature that would result from a part being cut in a lathe.After specifying the groove parameters,you will be shown a previewof the tool solid.学习好资料 欢迎下载 The tool solid can be thought of as the path that the lathe would make as it cuts the solid.You only have to position a groove along the axis of the cylindrical or conical placement face.The Positioning dialog will not appear.Instead,you are only required to specify a horizontal dimension along the axis by selecting a target edge followed by a tool edge or centerline.Two grooves are shown in the following example.1 Target Edge 2 Tool Edge(or centerline)Editing the Size and Location of Form Features As features are created the parametric data is captured in expressions.The parametric data consists of the actual feature size definition(i.e.diameter,height,length)as well as the positional data that is captured in the positioning dimensions.Edit Parameters The Edit Parameters and Edit with Rollback options allow you to redefine the parameter values of any parametric feature and update the model to reflectthe new values.Edit with Rollback This option allows you to edit the parameters of a feature but it also temporarily returns the model to its state when the feature was created.The features that occur after the edited feature in the model history are hidden from the display.This simplifies the display and makes it easier to select features to reference when using the Parameter Entry options.Edit Positioning This option allows a feature to be moved by editing its positioning dimensions.In addition,positioning dimensions may be added to features that are 学习好资料 欢迎下载 either underspecified or were not given any positioning dimensions at the timeof creation.Once the feature has been selected,the following options are offered based upon the positioning status of the selected feature.If the selected feature has no positioning dimension associated withit,the Add Dimension option is automatically selected.Add Dimension This option may be used to add a positioning dimension to a feature.When adding positioning dimensions,any edge(1)resulting from theintersection of the feature being positioned(2)and a face on the target solid(3)may not be selected as the tool edge.The intersection edge is a child object of the tool and target solids face andis defined by the boolean operation associated with the feature type being created.The boolean operation does not occur until after the position of the feature has been defined.Therefore,the intersection edge is not a valid selection to specify location.When adding positioning dimensions to a Thru Hole,no edges will be selectable as the target edge because both edges are intersection edges.The 学习好资料 欢迎下载 Identify Solid Face option is used to select the center of the cylindrical face(1).Valid target edges for positioning purposes must belong to features existingin the feature creation list of the model before the feature being positioned.Edit Dimension Value Features may be moved by changing the values of the features positioning dimensions.To use this option:Select the dimension to edit(if there is only one positioning dimension,itis selected automatically).Key in the new value.Continue editing as many dimension values as desired.Once all the desired dimension values have been edited,choose OK.Delete Dimension Use this option to delete a positioning dimension from a feature.The feature will then remain in its current location as its position is no longer associatedto the model.If you are replacing a dimension,add the new dimension before deleting the old one.The Edit Positioning dialog is maintained whenyou add a dimension but is automatically dismissed when you deletea dimension.Error Messages If the model cannot be updated based on the new parameters or location of the feature,the Edit During Update dialog will be presented.This dialog provides several options for dealing with the failed update.学习好资料 欢迎下载 Editing Features with the Part Navigator The Part Navigator is a powerful tool that may be used to identify and edit features.Holding down MB3 on a feature node in the Part Navigator displaysa feature specific pop-up menu.This menu provides an alternative method to edit the parameters and the position of a form feature.To access the Part Navigator,choose the icon on the resource bar on the right side of the NX window.学习好资料 欢迎下载