introduction to 3d surface machining

Licom Systems Ltd.,

Training Course Documentation

Introduction to 3D Surface Machining

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Licom Systems Ltd.Table of Contents

3D Surface Machining - Utilities --------------------------------------------------------------1Z Contour Roughing - -----------------------------------------------------------------------------2Abreviations for dialog boxes for Z Contour Roughing -----------------------------33D Surface Machining|Machine Surfaces| Main Menu ----------------------------43D Surface Machining Menu --------------------------------------------------------------------5Surface machining Parameter Lines ----------------------------------------------------------6Horizontal Z Contours -----------------------------------------------------------------------------7Z Contours - Steep Slopes ------------------------------------------------------------------------8Parallel -----------------------------------------------------------------------------------------------------9Parallel - Shallow Slopes ------------------------------------------------------------------------10Projected Contours --------------------------------------------------------------------------------11Radial -----------------------------------------------------------------------------------------------------12Spiral ------------------------------------------------------------------------------------------------------13Rest Machining --------------------------------------------------------------------------------------14Drive Curves ------------------------------------------------------------------------------------------15Flat Area Offset. -------------------------------------------------------------------------------------16Parallel Steep Slopes ------------------------------------------------------------------------------17Helical Z ------------------------------------------------------------------------------------------------18Z Contours + flat area offset ------------------------------------------------------------------19Cut Spline or Polyline ---------------------------------------------------------------------------20Glossary of surfacing and CAD terminology -------------------------------------------21Glossary of viewing terms and file formats ---------------------------------------------22

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Licom Systems Ltd.3D Surface Machining

3D Surface Machining - Utilities

Mouse Control - If your mouse has a wheel, it can be used to zoom the display in and out.The screen orientation can be altered by holding down the left mouse button and movingthe cursor. The view can be panned by holding down the Ctrl key and the left mouse buttonand moving the cursor to the desired position.

Menu Options - Can be selected from the pull down menu or the local pop up menu.

Quick Shading -This applies to 3D surfaces. This is a toggle to turn quick Shading on or off.3D surfaces are first covered with facets then shaded. Surfaces are displayed grey on the toolside, and red for the underside.

Reverse Tool side - If you set VIEW|Display Options|Ghost Tools to Yes, surfaces will havea 3D arrow pointing to the side that will be machined. AlphaCAM will automatically put thetool on the top side of each surface, including when surfaces are read in as CAD files. Butsometimes surfaces have the tool on the wrong side, the tool side can be switched to theother side by selecting this option and picking the surface with a click or with awindow.Surfaces are grey on the tool side, and red for the underside.

Advanced Shading - Right click in the graphics area menu to turn on and off the AdvancedShading in the ISO view. Advanced displays surfaces in their assigned layer colour.

3D Part Rotate This is a Command from the 3D Menu which allows rotation of 3D partsaround the X, Y or Z Axis. It also allows the user to select 3 points to define the plane whichwill then be rotated and twisted to make the part horizontal.

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Z Contour Roughing -

This is similar to contour pocketing in 2D. If you want to use a boundary to constrain themachining, draw the boundary before using this option and check Use Geometry BoundaryInstead of Material, Select when asked. The machining will be inside the boundary,regardless of whether the ghost tool is inside, on centre line or outside the boundary. If youdo not select a boundary, you must have defined a Material Size before selecting this optionand this will be used to constrain the machining, but unlike a geometry boundary, thematerial outline is treated as a Soft Boundary so the tool will cross the outline as far as thecentre line of the tool.

Contours are internally constructed at the Z levels specified by the values entered into theZ-Levels dialog box and the tool cuts at these Z levels. The contours at each Z level do notneed to be closed, so that there can be open sides (for example, a surface with inverted arcsfor one or more edges).

Also in the Z Levels dialog box there is another check Take Account of Previous Machining.The default is Yes, but there may be occasions when you do not want to do this for somereason. If you leave it checked, material removed by previous machining is ignored,eliminating tool paths that would simply cut air, thus reducing the machining time.

Simulations can be output as STL Models for stock material.STLModels can then be used as the material in Z contour Roughingand Advanced Simulations.

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Abreviations for dialog boxes for Z Contour Roughing

Contour -Creates a contour around a surface, at each specified Z level until the full depth isis achieved.

Linear-.(straight line) Creates a toolpath in straight line paths.

Full- Pass around islands (default)

Inside - Start cutting from the inside out

Outside- Start cutting from the outside in

Safe Rapid Level- This is the safe level to retract to

Ramp - Ramp in two or three axis Z and X or Z and Y or XYZ.

Drill Points- This effectively drills out points at the start or end of a toolpaths to allow asmoother transition between moves. AlphaCAM asks you to select a drill when this optionis selected, it will automatically determine the correct depth for the drill from the machiningparameters.

Slope Angle for leadin/out- This is the approach angle in Z between toolpath levels.

Include Flat areas as additional Z levels- This will machine at the appropriate Z level flatareas which fall in between the depth of the specified cut .

Z Contour Roughing and Parallel machining are now available in Advanced Mill andRouter Modules Also available in 3D 3 Axis Mill/Router/Marble and 3D 5 AxisMill/Router/Marble.

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3D Surface Machining|Machine Surfaces| Main Menu

Selecting Machine Surfaces from the initial surface machining options will invoke a dialogbox where parameters for a number of different elements in the surface machining processare specified:

More than one surface can be machined in the same operation. You will be asked to selectwhich surfaces are to be machined only if there is more than one.

You do not have to use a boundary, but you can draw several boundaries (which can beany shape) to mark the areas to be machined. These will be treated as Hard or SoftBoundaries and the tool will be kept inside or outside or allowed to move until the toolcentre line is on the boundary. Note that if a boundary is more than a tool radius outsidea surface edge, a ball end tool will drop below the outside of the surface edge as it movesuntil the contact point is at the edge. The machining will be in the direction set for CutDirection in the last dialog box. The direction controls the direction of the tool tip, not thecontact point.The machining method is Along Line in XY Plane in the direction set for CutDirection in the last dialog box.

The first dialog box asks about the Type of machining, e.g., 3-, 4- or 5-axis, and themachining Action Machine Surfaces.

The next section shows Machine Surface with Tool Side, Z Contour Roughing and AlongIntersection. The next dialog box asks how the machining is to be done - Method, howmuch of the surface or surfaces is to be machined - Boundaries, and what Gouge Checkingis to be done.

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3D Surface Machining Menu

The next dialog box allows you to select the 3D surface machining Method.

Each of the machining methods displays dialog boxes which ask for Feeds, Speeds and Zvalues, similar to the 2D equivalent, as well as additional questions relating to the specificmethod selected. The options for gouge checking are dependant upon the methodselected.This option allows machining using boundaries, and is dependant upon the methodselected.

Lead-In/Out and LinksThe check box Specify Moves between Paths switches on the lead in and out options

Extension Length (1) the amount of overrun from the edge of the surface.

Ramp Length (2) the length of the extension ramp

Arc Radius (3) the arc radius between the Extension and the Ramp.

Ramp Angle (4) the angle between the Extension and the Ramp.

Join Paths with Arc (5) if not checked a straight line is used.

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Surface machining Parameter Lines

Parameter Lines These are drawn at intervals across the surface to let you see the shape ofthe surface. The density of the parameter lines indicates the accuracy with which the surfacehas been defined, determined by the Edge Tolerance or the Number of Lines in eachdirection set when the surface was defined. Very dense parameter lines indicate that manycontrol points have been used for the equations that define the surface, and calculations formachining will be slow. The results will not necessarily be better than for surfaces definedwith lower tolerances.

This method is best when used for machining one surface only, but two or more surfaces canbe machined if the parameter lines are in the same (or very similar) directions on all thesurfaces. You do not have to use a boundary, but you can draw several boundaries (whichcan be any shape) to mark the areas to be machined. These will be treated as Hard or SoftBoundaries and the tool will be kept inside or outside or allowed to move until the toolcentre line is on the boundary. The tool will move in one of the directions shown by theparameter lines on the screen. The set of lines used depends on the direction you set for themachining.

Gouge Checking requires prodigious calculations, and you should not ask for gougechecking if it obviously is not necessary.

Check for Gouging on Current Surface: Check this box only if the surface being machinedhas undulations or folds which create valleys into which the tool will not fit. This check isonly applicable for the Parameter Line method.

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Horizontal Z Contours

This method creates paths that are at constant Z Levels. The distance between the levels iscontrolled by either Width of Cut or Cusp Height. The Upper Z Level and Lower Z Levelcan also be set to limit the machining to within the reach of the tool. You can machine anyamount of surfaces. There are options to machine all of the selected surfaces or contain themachining within boundaries which can be any shape. These will be treated as Hard or SoftBoundaries and the tool will be kept inside or outside or allowed to move until the toolcentre line is on the boundary.

The cutting direction can be controlled to give Climb or Conventional Milling, givingclockwise or anti-clockwise tracking around the profiles. The links between the subsequentZ Levels can be controlled to obtain a smooth transition and even helically ramp from onelevel to the next by checking the Join Paths with Arcs option. The cutting order can becontrolled when several Islands or pockets are identified at different levels, ensuring that thetool will cut all areas at each level or cut all levels at each area first to reduce lift off andexcess rapiding. There is also an option to reverse the order of the Z levels and cut from thelower Z level to the upper. This can be achieved by checking Bottom to Top.

3D Surface Machining|Accuracy Width of Cut is normally used for roughing with a flat endor bull nose tool and Cusp Height is normal for finish machining with a ball end tool, buteither one can be used with any tool.

If you select Cusp Height, AlphaCAM will calculate the position of each cut to produce thecusp height set. If you ask for a very small cusp height, in an attempt to produce a mirrorfinish, the NC program will be very a big, calculation which will be slow, and machiningwill take a long time. A sensible practical value for metric work is 0.1.

Chord Tolerance Along Cut: All 3D machining is output as straight line moves in X Y and Z,and this figure determines how many lines are output for a curved cutting move. A verysmall chord tolerance will produce very large NC programs, without much effect on thesurface accuracy. A sensible practical value for metric work is 0.1

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Z Contours - Steep Slopes

This method is an enhanced version of Horizontal Z Contours, all the functionality of whichapplies.

The added benefit of this method is that it will automatically identify the areas on the modelthat are considered to be steep. The steep areas are controlled by setting the angle to Cutsurfaces with a slope greater than the given angle. The complete surface model will beanalysed and only the areas matching the criteria will be cut.

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Parallel

An excellent general purpose method for semi roughing or finishing. The toolpaths will begenerated in straight lines in any direction over any amount of surfaces. The step overbetween cuts is controlled either by Width of Cut or Cusp Height. The cuts can be single orBi-Directional. The lead and links between cuts can be configured controlling the pathextension length, the ramping angle and length and the radius size between the pathextension and ramp. Bi-directional paths can also be joined with arc type moves to givepaths for high speed machining. The upper and lower Z Levels can be configured to containthe machining within the reach of the tool. Any amount of boundaries can be used to limitthe machined areas. These will be treated as Hard or Soft Boundaries and the tool will bekept inside or outside or allowed to move until the tool centre line is on the boundary.

It is always wise to allow stock to be left as the cutter has some work to do on the finalcut.You can allow stock in X & Y or just in Z.

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Parallel - Shallow Slopes

This method is an enhanced version of Parallel, all the functionality of which applies.

The added benefit of this method is that it will automatically identify the areas on the modelthat are considered to be flat or shallow. The shallow areas are controlled by setting theangle to Cut surfaces with a slope less than the given angle. The complete surface model willbe analysed and only the areas matching the criteria will be cut.

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Projected Contours

This method requires one or more boundaries to control how the toolpaths are calculated.The ghost tool sets whether it is used as Hard or Soft Boundaries. The method constantlyoffsets the closed boundaries to create projected paths onto any amount of surfaces. Thestep over is controlled by Width of Cut or Cusp Height. Cut in a clockwise or anti-clockwise direction. Cut from inside to outside, or outside to inside. Two variations of pathcan be achieved. One method is to offset the outer boundary inwards and trim it to theinner boundary. The other is to offset the inner boundary outwards and trim it to the outerboundary. This is set by checking the Offset Islands option.

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Radial

This method requires one single closed boundary. The ghost tool sets whether it is used asa Hard or Soft Boundary. The user selects the centre of the radius from which all the radialcuts omit towards the boundary. The width of cut is controlled by degree of angle betweenradial lines. The start and end angles are configurable to further control the area to be cut.Cut from the inside out or outside to inside. Remember that the cut width gets wider as thetool gets further from the centre of the radius thus limiting the areas for which this strategymight be suitable.

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Spiral

You can machine several surfaces. You do not use a boundary but are asked to specify aninner radius and an outer radius for the spiral, whether the machining is to be from the insideto the outside or vice versa, and whether the spiral is to be clockwise or counter-clockwise.The spiral toolpaths are projected onto the surfaces and trimmed to keep the tool contactpoint to be at the edge of the outer surfaces. Note that this means that a ball end or bull nosetool will drop off the edge of a surface if the outer radius is outside the surface edge.

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Rest Machining

This method is used to remove material that has been left between surfaces because theprevious tool has had a cutting radius bigger than the fillet between the surfaces. You canselect many surface intersections by picking adjacent surfaces or with a window. You do nothave to use a boundary, but you can draw several boundaries (which can be any shape) tomark the areas to be machined. There are four options

Along Corners The tool is moved in the same direction as the corner or fillet between theadjacent surfaces for the full length of the fillet or corner as many times as needed to removeas much material as possible.

Across Corners The tool is moved at right angles to the direction of the fillet or cornerbetween two adjacent surfaces. As many moves as needed are made to drive the tool the fulldistance of the corner or fillet.

Automatic Along or Across This is normally used when there are several intersectingsurfaces, which you will select with a window. AlphaCAM determines which strategy isbetter for each corner or fillet between adjacent pairs of surfaces.

Pencil Tracing This is used to make a single pass along the intersections between surfaces.This is similar to the Along Intersection option (for which you select the two surfaces thatintersect) but is more powerful because it allows you to select many surfaces with a window,and will drive the tool along all the relevant intersections.

The example Empty Box with Rest Machining in the LICOMDIR\3DTutor folder shows theresult of using Rest Machining to clean up all the corners between the internal vertical andhorizontal surfaces.

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Drive Curves

This method is a superior version of 3D Project. The type of drive curve isset in the surface machining dialog box. The geometry/polyline or toolpath can be in anyworkplane and any orientation to generate a drive curve over any number of surfaces. Thetool will track along the drive curve being projected onto the surfaces. For example, acomplex 2D pocketing operation could be made to form several boundaries giving anefficient no lift off path. This could then be used as the drive curve to create a veryefficient 3D toolpath over the surface model.

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Flat Area Offset.

This method is ideal for the machining of flat surfaces with flat or bull nose tools.Set theangle and tolerance and AlphaCAM will automatically identify the flat areas. Boundaries areautomatically created and the area pocketed by the tool. You can set the tool width of cutand opt to start cutting from the inside or outside with clockwise or counter-clockwisedirections. When isolated areas are less than a given distance apart, then the tool can becontrolled from retracting by adjusting the Connect Aircut Length.

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Parallel Steep Slopes

This machining strategy allows you to analyze surfaces of a certain angle and apply Parallelmachining to slopes greater than the angle specified. You can specify a width of cut toproduce either a rough or fine finish toolpath. The smaller the setting the more toolpaths willbe produced and longer NC Code.

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Helical Z

This cuts a helical toolpath around a surface either from top to bottom or bottom to top. Youcan specify a width of cut which will equal a helical pitch and this can be limited betweenan upper Z level and lower Z level.It can also be either Climb milling or conventionalmilling. Ideal for use with side and face cutters.

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Z Contours + flat area offset

This is a combined machining strategy that will rough out first using Z contour roughing thenit will analyse the surfaces to see if there are any flat surfaces that can be machined using theinformation from the menu.AlphaCAM automatically sets the Z-heights to match flat areas,with due allowance for stock and tolerances.

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Cut Spline or Polyline

This command will drive any tool along any spline or polyline. If a spline is being machined,the chord Tolerance is asked for, which determines the accuracy with which the straight lineXYZ tool moves match curves in the spline. For a polyline, the tool is simply moved alongthe straight line segments.

In Standard, Advanced 3D 3-axis MILL,ROUTER,LASER or MARBLE modules, the tool isassumed to be vertical, with the tool tip centrally on the spline or polyline, and you are notgiven any options about tool angle.

If the module is 3D 5-axis MILL, ROUTER,LASER or MARBLE and you have selected a 4 or5 axis post processor, you are able to set the tool to be left, centre or right of the spline orpolyline. The check box Show Ghost Tools will immediately show the direction of the splineor polyline so that you can determine which side is left and which is right.

You can set the Tool Angle to be Normal to nearest Surface, Parallel to nearest Surface or atangles relative to the line or as absolute angles. For angles relative to the line, the angle ismeasured from the vertical, and the sign is set by looking along the direction of the splineor polyline.That is, looking at the back of the tool as it moves away from you along the line.If the tool is leaning to the left, the angle is counter-clockwise and is therefore positive. Ifthe tool is leaning to the right, the angle is clockwise and the sign is negative.

If the selected post processor has been configured to take account of the ability of thecontroller to apply Tool Radius Compensation (G41/42) (this is indicated in the post bysetting $148 to 1 and the tool has been set to be right or left of the spline or polyline, thena check box - Machine Compensation - is enabled. Select this to produce the necessary codePlease note that the post has to have the correct code in $40. post variable TCF = 1 ifG41/42 is selected when AlphaCAM is used, TCX, TCY, TCZ gives the tool displacementunit vector, that is the direction from the contact point to the tool tip. CPX, CPY, CPZ givesthe contact point on the polyline.

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Glossary of surfacing and CAD terminology

IGES - An acronym for Initial Graphics Exchange Specification. It is a file format for theexchange of CAD information (both 2D and 3D). A 3D iges file contains surfaceinformation and details of a part.

B-Spline - A sequence of parametric polynomial curves (typically quadratic or cubicpolynomials) forming a smooth fit between a sequence of points in 3D space. The definedcurve maintains a level of mathematical continuity dependent upon the polynomial degreechosen. It it used extensively in mechanical design applications in the automotive andaerospace industries.

PARASOLID - A geometric modelling kernel provided by Unigraphics Solutions Inc. Itsupports 3D surfaces and solids and is based upon NURBS and B-Rep solid modellingtechnology.

PART - A particular type of CAD model describing a single object. It will usually be builtfrom features and represented as a unique solid.

STEP - An acronym for STandard for the Exchange of Product model data. It is a fileformat for the exchange of CAD information (3D). A 3D step file contains information onthe volume and physical properties of a part. It is used heavily by the automobile industry

Coons Patch - A method for finding a surface from the curves which form its boundary.

Fillet Surface - The transition surface which blends together two surfaces, for example, acar wing and the car body.

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Glossary of viewing terms and file formats

2D Two-Dimensional.Refers to an object or drawing having no depth. A common shortterm for CAD software supporting planar representation like the drafting table, usually Xand Y coordinates.

ISOMETRIC VIEW - A three-dimensional view of an object without foreshortening

3D - Three-Dimensional. A common short term for a CAD software supporting spatialrepresentation like the actual world, usually X, Y and Z coordinates.

DWG - AutoCAD's native file format for CAD models.

DXF - An acronym for Drawing Exchange Format. It is a file format for the exchangeofCAD information (usually 2D).

ENGINEERING DRAWING - a drawing of an object usually consisting of three views(front, top, and right side). Dimensions are normally provided.

CAM - Software dedicated to Computer Aided Manufacturing.

CAD - Computer Aided Design

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introduction to 3d surface machining

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