2D Sketching Techniques PDF

Unit – II SKETCHING 2.1 Introduction When you open a new part document, first you create a sketch. The sketch is the basis for a 3D model. You can create a sketch on any of the default planes (Front Plane, Top Plane, and Rig...

Unit – II SKETCHING 2.1 Introduction When you open a new part document, first you create a sketch. The sketch is the basis for a 3D model. You can create a sketch on any of the default planes (Front Plane, Top Plane, and Right Plane), a created plane or face of a part. General procedure : 1) Click Sketch on the Sketch toolbar, or click Insert > Sketch. 2) Click a sketch entity tool (line, rectangle, and so on) on the Sketch toolbar. 3) Select one of the three planes (Front, Top, and Right) displayed or face of a part. Default Sketch Planes 4) Create a sketch with the sketch entity tool. 5) Dimension the sketch entities. 6) Click Exit Sketch on the Sketch toolbar. Also Click Exit Sketch or Cancel in the Confirmation Corner. 2.2 Sketch Modes è There are two modes for sketching in 2D: click-drag or click-click. è If you click the first point and drag, you are in click-drag mode. è If you click the first point and release the pointer, you are in click-click mode. è Double-click or press Esc to terminate the chain of entities. 15 2.3 Sketch Toolbar The Sketch toolbar controls all aspects of sketch creation. It includes the following tools : Tool Description Tool Description Tool Description Select 3 Point Arc Extend Entities Grid/Snap Ellipse Split Entities Sketch or Exit Sketch Partial Ellipse Mirror Entities 3D Sketch Parabola Dynamic Mirror Entities 3D Sketch On Plane Conic Move Entities Slicing Spline Rotate Entities Rapid Sketch Style Spline Scale Entities Instant2D Spline on Surface Copy Entities Shaded Sketch Contours Equation Driven Curve Replace Entity Line Point Stretch Entities Corner Rectangle Centerline Linear Sketch Pattern Center Rectangle Midpoint Line Circular Sketch Pattern 3 Point Corner Rectangle Construction Geometry Make Path 3 Point Center Rectangle Text Modify Sketch Parallelogram Plane No Solve Move Straight Slot Sketch Fillet Sketch Picture Center point Straight Slot Sketch Chamfer Sketch Numeric Input 3 Point Arc Slot Offset Entities Sketch Dimension Driven Center point Arc Slot Offset On Surface Add Dimension Polygon Convert Entities Insert Pen Sketch Circle Intersection Curve Detach Segment On Drag Perimeter Circle Face Curves Reverse Endpoint Tangent Center point Arc Segment Dissolve Entities Tangent Arc Trim Entities 16 2.4 Sketch entities 2.4.1 Sketching lines 1) Click Line on the Sketch toolbar, or click Tools > Sketch Entities > Line. The pointer changes to. 2) Click in the graphics area and sketch the line. 3) Complete the line in one of the following ways: è Drag the pointer to the end of the line and release. è Release the pointer, move the pointer to the end of the line, and click again. 4) Sketch the line with approximate length and angle. 5) After sketching the line, the orientation , length and angle can be modified by one of the following methods : è Click on the line. The Line Properties PropertyManager is displayed. Under Parameters, Set a value for Length. Set a value for Angle. è The line parameters can be modified using Smart Dimension on the Sketch tool bar. 6) Click or double-click to accept the line with modified parameters. Options : Option Description For construction To sketch a construction line Infinite length To sketch a line of infinite length Midpoint line To sketch a line that is symmetrical from the midpoint of the line Centre line To sketch centerlines to create symmetrical sketch elements and revolved features 2.4.2 Sketching rectangles You can sketch the following rectangle types : Rectangle type Tool Rectangle properties Corner Rectangle Sketches standard rectangles. Center Rectangle Sketches rectangles at a center point. 3 Point Corner Rectangle Sketches rectangles at a selected angle. 3 Point Center Rectangle Sketches rectangles with a center point at a selected angle. Parallelogram Sketches a standard parallelogram. 17 To sketch corner rectangles : 1) Click Rectangle. 2) Click to place the first corner of the rectangle, drag, and release when the rectangle is approximately correct size and shape. Rectangle with Modified rectangle approximate size after smart dimension 3) Modify the dimensions of the rectangle using Smart Dimension on the Sketch tool bar. 4) Click. 2.4.3 Sketching circle You can sketch the following circle types: Circle type Tool Circle properties Circle Sketches center-based circles. Perimeter Circle Sketches perimeter-based circles. To sketch circles : 1) Click Circle. 2) Click to place the center of the circle. 3) Drag and click to set the approximate radius. 4) Modify the dimensions using PropertyManager or Smart Dimension 5) Click. 2.4.4 Sketching arcs You can sketch the following arc types : Arc types Tool Arc properties Center point Arc Sketches arcs from a center point, a start point, and an end point. Tangent Arc Sketches arcs that are tangent to sketch entities. 3 Point Arc Sketches arcs by specifying three points (start, end, and midpoint). 18 To sketch center point arcs: 1) Click Center point Arc. 2) Click to place the center of the arc. 3) Release and drag to set the radius and the angle. 4) Click to place a start point. 5) Release, drag, and click to set an end point. 6) Modify the dimensions using PropertyManager or Smart Dimension 7) Click. To sketch tangent arcs: 1) Click Tangent Arc. 2) Click on the end point of a line, arc, ellipse, or spline. 3) Drag the arc to the desired shape and release. 4) Click. To sketch 3 point arcs: 1) Click 3 Point Arc. 2) Click to set a start point. 3) Drag the pointer , then click to set an end point. 4) Drag to set the radius. 5) Click to set the arc. 6) Click. 2.4.5 Sketching ellipse è Use the Ellipse tool to create a complete ellipse. è Use the Partial Ellipse tool to create an elliptical arc. To create an ellipse: 1) Click Ellipse on the Sketch toolbar. 2) Click in the graphics area to place the center of the ellipse. 3) Drag and click to set the major axis of the ellipse. 4) Drag and click again to set the minor axis of the ellipse. 5) Modify the dimensions using PropertyManager. 19 2.4.6 Sketching polygons Equilateral polygons with any number of sides between 3 and 40 can be created. To create a polygon: 1) Click Polygon on the Sketch toolbar. 2) Set the properties in the Polygon PropertyManager as necessary. 3) Click in the graphics area to place the center of the polygon, and drag out the polygon. 4) Modify the dimensions using PropertyManager. 5) Click. 2.4.7 Sketching text To sketch text on a part: 1) Click Text on the Sketch toolbar. 2) To create a profile for placing the text, sketch a circle or a continuous profile from lines, arcs, or splines in a sketch, close the sketch, then open another sketch for the text. 3) In the graphics area, select an edge, curve, sketch, or sketch segment. The selected item appears under Curves. 4) In the PropertyManager, under Text, type the text to display. 5) The text appears in the graphics area as you type. 6) Set the properties in the Sketch Text PropertyManager as necessary. 7) Click. 2.5 Dimensions You can specify dimensions between entities such as lengths, angles and radii. When you change dimensions, the size and shape of the part changes. To fully define the sketch, you add relations and apply dimensions using the Smart Dimension tool (Dimensions/Relations toolbar). The software uses the following two types of dimensions : è Driving Dimensions : Driving dimensions change the size of the model when you change their values. Ordinate and baseline dimensions in sketches are driving dimensions. è Driven Dimensions : Some dimensions associated with the model are driven. You can create driven, or reference dimensions, for informational purposes. The value of driven dimensions changes when you modify driving dimensions or relations in the model. You cannot modify the values of driven dimensions directly unless you convert them to driving dimensions. 20 2.5.1 Dimensions/Relations Toolbar and Menus The Dimensions/Relations toolbar provide tools to dimension and to add and delete geometric relations. It includes the following : Tool Description Tool Description Smart Dimension Path Length Dimension Auto Insert Dimension Chamfer Dimension Horizontal Dimension Fully Define Sketch Vertical Dimension Add Relation Baseline Dimension Automatic Relations Ordinate Dimension Display/Delete Relations Horizontal Ordinate Dimension Scan Equal Vertical Ordinate Dimension Isolate Changed Dimensions Angular Running Dimension 2.5.2 Dimensioning a Sketch You dimension 2D or 3D sketch entities with the Smart Dimension tool. You can drag or delete a dimension while the Smart Dimension tool is active. Dimension types are determined by the sketch entities you select. For some types of dimensions (point-to-point, angular, circular), the location where you place the dimension also affects the type of dimension that is added. To add a dimension to a sketch or drawing : 1) Click Smart Dimension on the Dimensions/Relations toolbar, or click Tools > Dimensions > Smart. 2) The default dimension type is Parallel. Optionally, you can choose a different dimension type from the shortcut menu. Right- click the sketch, and select More Dimensions. Choose from Horizontal, Vertical, Ordinate, Horizontal Ordinate, or Vertical Ordinate. 3) Select the items to dimension. As you move the pointer, the dimension snaps to the closest orientation. 4) Click to place the dimension. 5) You can change Smart Dimension values by clicking over the value and using the Modify box. 21 2.5.3 Sketch Geometry Status Sketches include a status, and sketch entities within the sketch include a state. Sketch entity states are displayed in different colors to facilitate identification. Sketch states include the following : è Dangling : Appears as brown in the graphics area. Indicates sketch geometry that cannot be resolved. For example, deleting an entity that was used to define another sketch entity. è Driven : Appears as gray in the graphics area. Indicates a dimension that is unnecessary and cannot be modified. è Item Conflicts : Appears as yellow in the graphics. Indicates a redundant dimension or an unnecessary relation. è Under Defined : Appears as blue in the graphics area. Indicates a sketch entity which requires a dimension or relation to another sketch entity. è Fully Defined : Appears as black in the graphics area. Indicates all required dimensions and relations to sketch entities are present. è Over Defined : Appears as yellow in the graphics area. Indicates sketch entities that are invalid, creating a sketch without resolution in its current state. Requires deleting some relations or dimensions, or returning the sketch entity to its prior state. è Item is Unsolvable : Appears in red in the graphics area. Indicates the geometry cannot determine the position of one or more sketch entities. Sketch solved with 50 dimension Sketch is unsolvable with 80 dimension 2.5.4 Fully Defined Sketches The Fully Define Sketch tool calculates which dimensions and relations are required to fully define under defined sketches or selected sketch entities. You can access Fully Define Sketch at any point and with any combination of dimensions and relations already added. To fully define a sketch : 1) Create a sketch. 2) Click Fully Define Sketch (Dimensions/Relations toolbar) or Tools > Dimensions > Fully Define Sketch. 22  3) Set the options for relations and dimensions in PropertyManager. Click Calculate. 4) Modify each dimension by clicking on it. 5) Click. Before modification After modification Fully defined sketch 2.6 Relations Relations establish geometric relationships between sketch entities. Automatic Relations is a setting that is turned on by default. When you are sketching, it displays relations that are suggested by the sketch as small yellow icons attached to the cursor and adds those relations to the current sketch entity. Depending on the sketch entities and the position of your pointer, more than one sketch relation can display simultaneously. Inferencing refers to the blue dotted lines that display in Sketch mode when the cursor aligns with endpoints, center points, or the origin. Inferencing creates sketch relations only when the symbol shown on the sketch cursor has a yellow background. 2.6.1 Adding relations You can add relations in the following ways : 1) As you sketch, allow the SOLIDWORKS application to automatically add relations. Automatic relations rely on: è Inferencing è Pointer display è Sketch Snaps and Quick Snaps 2) After you sketch, manually add relations using the Add Relation tool, or edit existing relations using the Display/Delete Relations tool. If you right-click with one or more sketch entities selected, the toolbar that displays stays visible to allow you to add multiple relations. For example, you have two lines selected. You can add vertical and parallel relations to the lines and make them equal without making changes in the PropertyManager or displaying the toolbar. 23 2.6.2 Description of Sketch Relations The following table describes the entities that you can select for a relation and the characteristics of the resulting relation. Relation Entities to select Resulting relations Horizontal One or more lines The lines become horizontal. Vertical One or more lines The lines become vertical. Collinear Two or more lines. The items lie on the same infinite line. Coradial Two or more arcs. The items share the same center point and radius. Perpendicular Two lines. The two items are perpendicular to each other. Parallel Two or more lines. The items are parallel to each other. AlongZ A line and a plane. The line is normal to the face of the selected plane. Tangent An arc, ellipse, or spline, The two items remain tangent. and a line or arc. Concentric Two or more arcs, or a The arcs share the same center point. point and an arc. Midpoint Two lines or a point The point remains at the midpoint of the line. and a line. Intersection Two lines and one The point remains at the intersection of the lines. point. Coincident A point and a line, arc, The point lies on the line, arc, or ellipse. or ellipse. Equal Two or more lines or The line lengths or radii remain equal. two or more arcs. Equal Two splines. The radius of curvature and the vector (direction) Curvature matches between the two splines. Symmetric A centerline and two The items remain equidistant from the centerline, on a points, lines, arcs, or line perpendicular to the centerline. ellipses. Fix Any entity. The entity’s size and location are fixed. Pierce A sketch point and an The sketch point is coincident to where the axis, edge, axis, edge, line, or or curve pierces the sketch plane. The pierce relation is spline. used in sweeps with guide curves. On Edge Edges of a solid. The edges of the solid are projected to the sketch plane using the Convert Entities tool. On Surface Sketch entities on a The sketch entities reside on the surface. surface. 24 2.7 Sketch Tools 2.7.1 Sketch Fillets The Sketch Fillet tool trims away the corner at the intersection of two sketch entities to create a tangent arc. This tool is available for both 2D and 3D sketches. The Fillet tool on the Features toolbar fillets entities such as edges in parts. To create a fillet in a sketch : 1) In an open sketch, click Sketch Fillet on the Sketch toolbar, or Tools > Sketch Tools > Fillet. 2) Set the properties in the Sketch Fillet PropertyManager. 3) Select the sketch entities to fillet. You can select two sketch entities or select a corner. 4) Drag the preview to adjust the fillet size if necessary. 5) Click to accept the fillet. 2.7.2 Sketch Chamfers The Sketch Chamfer tool applies a chamfer to adjacent sketch entities in 2D and 3D sketches. This tool is available for both 2D and 3D sketches. The Chamfer tool on the Features toolbar chamfers entities such as edges in parts. To create a sketch chamfer : 1) In an open sketch, click Sketch Chamfer on the Sketch toolbar, or click Tools > Sketch Tools > Chamfer. 2) In the PropertyManager, set the Chamfer Parameters as necessary. 3) In the graphics area, select the two sketch entities to chamfer. To select the sketch entities, you can: è Hold Ctrl and select two sketch entities. è Select a vertex. 4) The chamfer is applied immediately. Angle- Distance- Equal distance distance distance 5) Click to accept the chamfer. Chamfer Parameters Angle-distance Distance 1 : Applied to the first sketch entity selected. Direction 1 Angle : Applied from the first sketch entity towards the second. Distance - distance Equal distance selected : è Distance 1 is applied to both sketch entities. Equal distance cleared : è Distance 1 is applied to the first sketch entity selected. è Distance 2 is applied to the second sketch entity selected. 25 2.7.3 Offset Entities Offset one or more sketch entities, selected model edges, or model faces by a specified distance. For example, you can offset sketch entities such as splines or arcs, sets of model edges, loops, and so on. If the original entity changes, then the offset entity also changes when you rebuild the model. To create a sketch offset : 1) In an open sketch, select one or more sketch entities, a model face, or a model edge. 2) Click Offset Entities (Sketch toolbar) or Tools > Sketch Tools > Offset Entities. 3) Set the properties in the Offset Entities PropertyManager. When you click in the graphics area, the offset entity is complete. Set the properties before you click in the graphics area. Before offset After offset 4) Click or click in the graphics area. 2.7.4 Trim Entities Select the trim type based on the entities you want to trim or extend. You can use any of the following trim options : Option Description Power Trim You can use Power trim to trim multiple, adjacent sketch entities by dragging the pointer across each sketch entity. Corner Extends or trims two sketch entities until they intersect at a virtual corner. Trim Away Inside Trims open sketch entities that lie inside two bounding entities. Trim Away Outside Trims open sketch entities outside of two bounding entities. Trim to Closest Trim or extend the selected sketch entities. You can also use : è Keep trimmed entities as construction geometry è Ignore trimming of construction geometry Trimming with Power Trim You can use Power trim to trim multiple, adjacent sketch entities by dragging the pointer across each sketch entity. To trim with the Power trim option : 1) Click Trim Entities (Sketch toolbar) or Tools > Sketch Tools > Trim. 2) In the PropertyManager, under Options, select Power trim. 3) Click in the graphics area next to the first entity, and drag across the sketch entity to trim. 26  4) The pointer changes to as it crosses and trims the sketch entity. A trail is created along the trim path. 5) Continue to hold down the pointer and drag across each sketch entity you want to trim. 6) Release the pointer when finished Before Trim After Trim trimming the sketch, then click. 2.7.5 Extend Entities You can add to the length of a sketch entity (line, centerline, or arc). Use Extend Entities to extend a sketch entity to meet another sketch entity. To extend a sketch entity : 1) In an open sketch, click Extend Entities on the Sketch toolbar, or click Tools > Sketch Tools > Extend. The pointer changes to. 2) Move the pointer over the sketch entity to extend. 3) A preview appears in the direction to extend the entity. Before Extend After Extend & Trim 4) If the preview extends in the wrong direction, move the pointer to the other half of the line or arc. 5) Click the sketch entity to accept the preview. 2.7.6 Split Entities You can split a sketch entity to create two sketch entities. Conversely, you can delete a split point to combine two sketch entities into a single sketch entity. Use two split points to split a circle, full ellipse, or a closed spline. To split a sketch entity : 1) In an open sketch, click Split Entities (Sketch toolbar) or Tools > Sketch Tools > Split Entities. 2) The pointer changes to. 3) Click the sketch entity at the location where you want the split to occur. 4) The sketch entity splits into two entities, and a split point is added between the two sketch entities. 2.7.7 Mirror Entities Select Mirror Entities to mirror pre-existing 2D sketch entities on a plane, and then select the entity about which to mirror. If you want to first select the entity about which to mirror, and then sketch the entities to mirror, select Dynamic Mirror Entities. 27