Licom Systems Ltd., Training Course Notes. 3D Surface Creation

Transcription

1 , Training Course Notes

2 Work Volume and Work Planes Overview Work Volume Work Plane Work Plane Commands Slice through Work Volume lines for X and Y-axes Existing Geometry Parallel to the current plane Reverse Current Plane As Current Plane, Different Origin By Name Set Work Plane Origin Work Plane Properties Cancel Work Plane Best Fit Plane through Points Make local axis Horizontal D Project D Part Rotation What is a Surface Licom Systems Ltd. Table of Contents Surface Creation Methods Flat Surface Extruded Surface Ruled Surface Ruled Surface Example Swept Surface (2 Curves) Swept Surface (2 Curves) Example Swept Surface (3 Curves) Swept Surface (3 Curves) Example Revolved Surface Revolved Surface Example Rotation Direction Coons Patch Coons Patch 3 and 4 Curves Example Fillet 2 Surfaces Surface from Sections Surface From Sections Example D Surface Editing Commands Break Intersecting Surfaces Edit Surface Control Points Un-Trim Surfaces Extend Surface Surface Finder Extract Edges from Surfaces Convert to STL Facets

3 1 Work Volume and Work Planes Overview The work volume and work planes are controlled from the 3D menu. The 3D and Work Planes Button Bars contain shortcuts to the work volume and work plane commands. The Work Plane tab on the Project Manager allows easier manipulation and naming of the work planes. Work Volume A work volume is a rectangular volume, which encloses the machining envelope of the part, or features that are to be machined. The work volume defines the position of X,Y,Z Zero and the display limits of the work planes. Work Plane A work plane is a 2 dimensional section through the work volume on which 2D geometry is drawn and machined. The orientation of the plane is used by the post processor to output the correct indexing data. Work planes may be defined in several ways dependent upon the information available. 3D work volumes and work planes are utilised for 3D applications for surface edge creation. NOTE: - The format of the NC code is controlled by the post processor configuration. It determines whether the co-ordinates are Local or Global and what indexing is allowed. In some cases several posts are used for the same machine to create the NC code for specific requirements When creating work planes to control machining you MUST ensure that: 1 The Z axis points out of the plane. This is the side from which the cutting tool will approach the job. 2 The X and Y axis are in the correct orientation. Remember in the way your machine orientates the plane perpendicular to the tool.

4 2 Work Plane Commands. Slice through Work Volume. This is achieved by selecting a line, The view in which the line is picked is used to control the direction of cut. Lines selected in the ISO view will always produce a vertical slice. 2 lines for X and Y-axes Any two lines that represent the X and Y-axis can be selected. The first line selected will define the X-axis. The second line selected, which must lie in the required X, Y plane, will define the orientation of the X, Y and Z-axes. The lines selected MUST be connected at one end. Existing Geometry This command is used to activate the work plane to which the selected geometry is associated. When geometry is created it is linked to the current work plane. Parallel to the current plane This allows a new work plane to be activated which is parallel to the current plane by specifying an offset in the local Z-axis. Reverse Current Plane This allows the four axis orientations to be cycled through As Current Plane, Different Origin This will create a duplicate of the active work plane upon which a different local origin can be set.

5 3 By Name Allows work planes to be selected or their properties to be edited from a list of all current work planes. Empty redundant Work Planes used can be deleted from the list. Set Work Plane Origin This allows the local origin on the current plane to be repositioned. Work Plane Properties Work plane properties allow work planes to be named and work plane offset number to be specified. Cancel Work Plane This deactivates the current work plane and returns the status to Flat Land (normal 2D) Best Fit Plane through Points This will create a work plane that fits best between various points. The points will be extracted from the items selected (Geometries, Polylines, Splines, and Surfaces). Make local axis Horizontal This will alter the current plane or cycle through all work planes, and re-orientate each work plane so that the specified axis, X or Y, is horizontal. This is usually used when models have been imported. 3D Project This allows geometry/toolpaths to be projected from one plane to another. 3D Part Rotation This displays a dialog that allows the job to rotated about an axis or so that a plane defined by 3 points is horizontal.

6 4 What is a Surface. A surface is an mathematical description of the outer skin of a part. Therefore surfaces have no thickness and cannot be seen when looking perpendicular to the edge. The diagram opposite shows a flat surface. It can be seen in the YZ view (bottom left) that the surface is displayed as a line though mathematically its value is ZERO. If the shaded view is rotated to look on the edge it would disappear. Surface Creation Methods 3D surfaces can be created in a number of ways defending upon the number and form of the geometrical edge definition. Within AlphaCAM there are currently 11 methods for creating 3D surfaces. When creating a surface you have to specify an Edge Tolerance. The smaller the edge tolerance the finer the the surface detail, this however increases the storage size of the surface. The edge tolerance should be set with regard to the size and detail in the surface. E.G. Setting the edged tolerance for the Surface of a car roof to.1 would be ok but it would be to course for an electrode 20mm Diameter this would be set around.005. The edge tolerance will be used in determining the number of steps along the first edge. If the number of steps along first edge is altered this will affect the density of the surface detail. The greater the number of steps the finer and more complex the surface. Surfaces edges cannot contain sharp corners. as any geometries or polylines are converted to splines for the surface edge. If a surface needs a sharp corner it has to be made from two surfaces.

7 5 Flat Surface The Flat Surface Command will create a flat surface which is bounded by a close profile. The boundary profile must lie in one plane and be Geometry or Polylines not a Spline.

8 6 Extruded Surface The Extrude Surface Command will create a of flat surface for each element in the profile selected. Each surface is extruded with respect to the Z axis of the plane of the geometry.the profile must be Geometry or Polylines but not a Spline.

9 7 Ruled Surface The Ruled Surface Command will create one surface, (different to the extruded surface), which is suspended between two edge curves. The edge curves can, be open or closed, lie in different planes, and be either, geometry, polylines, splines or surface edge. The start point of each edge curve will be connected with a straight line, this straight edges is moved along each edge curve to generate the surface, hence its type name. When creating a ruled surface with open edges, If the edges are in different directions, i.e.drawn opposite, a warning dialog will be displayed, with an option to automatically reverse one of the edges. When creating a ruled surface with closed edges it is important to ensure the start points are perpendicular otherwise the surface will be twisted. Ruled Surface Example Using the training example produce the surface opposite.

10 8 Swept Surface (2 Curves) The Swept Surface (2 Curves) Command will create one surface, by sweeping the first edge curve along and in the direction of the second curve. When the two curves are selected you are asked whether to rotate the sections along the sweep of curve. The tighter the arcs in the curve of sweep the bigger the effect of rotating the curve being swept. Example Geometries Non Rotated Edge Rotated Edge Both Curve of Sweep Starting Section If the Curve of sweep is a straight line then the resultant surface is the same. The major error that occurs with swept surfaces is when the starting section is longer than the internal radius on the curve of sweep. this causes the edge to fold over its self. Swept Surface (2 Curves) Example Using the training example produce the surface opposite.

11 9 Swept Surface (3 Curves) The Swept Surface (3 Curves) Command will create one surface, by sweeping the first edge curve along and in the direction of a second curve whilst changing into the third edge curve. When the curves are selected you are asked whether to rotate the sections along the sweep of curve. The tighter the arcs in the curve of sweep the bigger the effect of rotating the curve being swept. The same rules that applied to Swept Surface (2 Curves) also apply to Swept Surface (3 Curves) Swept Surface (3 Curves) Example Using the training example produce the surface opposite.

12 10 Revolved Surface A Revolved Surface is generated by rotating a profile around an axial line. The geometry profile MUST NOT cross the axial line. Revolved Surface Example Using the training example produce the surface opposite. Rotation Direction The rotation direction will depends upon which axis X Y of Z the axial line lies in. If the axial line has some X axis movement on it, you view down the line in the X - ve direction and + ve rotation is CCW. If the axial line has no X axis movement then you view down the line in the Y + ve direction and + ve rotation is CCW. If the axial line has no X or Y axis movement then you view down the line in the Z - ve direction and + ve rotation is CCW. Y X

13 11 Coons Patch A Coons Patch is a surface which is subtended between 3 or 4 edges. The edges can be in different planes but their ends MUST be coincident. Coons patch 3 Curves is created differently to the other surface creation methods, in that all other cases create parameter lines parallel to the edges. However it is not possible to make the 2 parameter lines parallel to 3 edges. A coons patch 3 curves creates its parameter lines radiating between edges 1 and 3 and parallel to edge 2. Edge 2 Edge 3 Edge 1 Coons Patch 3 and 4 Curves Example Using the training example produce the surfaces opposite.

14 12 Fillet 2 Surfaces The Fillet 2 Surfaces command will generate a fillet rad between two surface. The fillet is always positioned between the GREY (Top) sides of the surfaces. If the Surfaces to which the fillet is to be applied are closed then the Start and End fillet radius MUST be the same. If the Surfaces to which the fillet is to be applied are open then the Start and End fillet radius can be different creating a tapered fillet. The surface extending past the fillet surface is deleted.

15 13 Surface from Sections This command will create a surface from a minimum of 6 sectional geometry profiles. The Sections must have their direction all to be the same. If the sections are close the start points should be perpendicular to each other. Surface From Sections Example. Using the training example produce the surface opposite.

16 14 3D Surface Editing Commands The 3D Edit Surface sub menu provides the following surface editing commands. Break Intersecting Surfaces This works in a similar manor to the Fillet between 2 Surfaces command where the 2 intersecting surfaces are broken and made into 4 separate surfaces. This command will not work if the 2 surfaces do not make 4 independent surfaces. Edit Surface Control Points This command will display the control points on the surface and allow one to be selected and distorted along its vertex constrained by the surrounding control points. This command allows you to push and pull the surface skin about. Un-Trim Surfaces This will return a trimmed surface to its original form prior to being trimmed. Extend Surface This command will produce extra surfaces extending a set distance from either a picked surface edge or all 4 edges of a surface. Extend will only extend non trimmed surfaces. Surface Finder. This command is used to separate inner and outer skinned surface models. The user is asked to pick a point in 3D space and the command will separate all the surfaces that can be seen from that point onto a separate layer. The command may be executed from different points in order to separate the required surfaces. Extract Edges from Surfaces This command will work its way around the outer edges of adjoining surfaces producing a continuous polyline.. Used with surface Finder to produce a 5 Axis Trim Edge.

17 15 Convert to STL Facets This converts surfaces to stl facets. Within AlphaCAM we cannot modify imported stl models. Additional surfaces can be used to create the additional features. These surfaces then can be converted to stl facets so the model and be machined fully using Solid Machining..

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