The Anatomy of a RhinoCAM Part

Advanced Robotic Technology (ART), located in Queensland (QLD) Australia is a family owned and operated company that prides itself in the design and manufacture of state-of-the-art CNC routers, plasma cutters, laser cutters and milling machines.

The following Rhino3D part, submitted for discussion by Greg White of the engineering staff at ART is a great example of the typical 2½ and 3 axis work-flow and anatomy of a 3D model programmed for CNC machining using RhinoCAM. The component is part of a robotic arm assembly of ART’s newest 10 axis CNC plasma cutter (a similar arm is shown here).

The 3D part geometry was originally designed in SOLIDWORKS and then loaded into Rhino. The associative CNC machining strategies (i.e., the toolpaths) are designed using the RhinoCAM plugin and are saved with the Rhino part file. Any revisions to the geometry in Rhino are automatically incorporated into the toolpath strategies!

Advanced Robotic Technology (ART) designs prototype & production components for their multi-axis routers and plasma cutters in the Rhinoceros CAD system. They then use the RhinoCAM plugin from MecSoft Corporation to design their machining strategy and post toolpaths to their CNC routers for manufacturing. This illustration identifies the anatomy of a typical RhinoCAM part from ART. Each item in the illustration is listed below with details.

1. Part Geometry

Part geometry for machining can be created in Rhino or imported using any of the file formats supported by Rhino. RhinoCAM machining strategies are associative to the Rhino part geometry. If geometry is revised, RhinoCAM flags all related toolpaths for regeneration, at which time, the revisions are reflected automatically in all toolpaths.

Any Rhino geometry type can be used for machining including points, curves, surfaces, meshes and solids. In this example, ART uses closed polysurfaces for 3 Axis part definition, closed poly-curves and surface edges for 3 Axis containment and a variety of open and closed poly curves for 2½ Axis containment.

In this example, ART is machining a set of prototype parts grouped together in one stock piece. ART has chosen to connect the parts with tabs, in this case, modeled directly in Rhino. RhinoCAM can also add tabs automatically during 2½ Axis Profiling operations.
ART uses polysurfaces for part definition and poly curves and surface edges for toolpath containment.

2. Machine Setup, Material & Stock Definition

The default Machine Coordinate System (MCS) is aligned with the World Origin in Rhino. This defines the XYZ orientation of the machine tool for the Setup. This part currently has one Setup defined that contains the toolpath strategies used to machine these series of parts from one side. RhinoCAM supports an unlimited number of Setups in any orientation in a single part file.

In this example, ART shows Setup 1 containing the toolpath strategies they need to cut the parts from one side. Depending on your RhinoCAM configuration, you can add additional setups to the Machining Job Tree (see Item #4 below) to machine the parts from the opposite side of the stock.
The Machine Coordinate System (MCS) is positioned on the top south-west corner of the stock definition with the stock material set to 6061 aluminum.

3. Tool Library & Knowledge Base

Once a tool is defined (ball mill, end mill, drill, tap, etc.), they can be saved to a Tool Library for later use. Once you create a toolpath operation, it can be saved to a machining Knowledge Base for later use.

The Knowledge Base contains all of the information for that specific type of toolpath, including feeds & speeds, tool, cutting parameters, clearances, etc. Feeds & speeds values can be assigned to a tool as well as an operation. You never have to define a tool or toolpath twice!

The machining Knowledge Base also supports Geometry Rules. This means that if you machine families-of-parts, your CAM programming can be automated from the Knowledge Base for true push-button machining!
The Tools available in ART’s active Tool Library are listed. Toolpath operations in the current part, assigned to each tool are listed under the Tools tree.

4. Machining Job Tree

When a toolpath operation is created, it is added to the Machining Job tree in the order you wish it to be processed. For example, you can group together all operations that use the same tool (minimizing tool changes) or by operation type (i.e., drilling, roughing, finishing, etc.). When operations are retrieved from your Knowledge Base, this organization is maintained. You can post one, multiple, or all operations from your Machining Job and their order will be maintained in the posted g-code file even if the MCS Setup changes.

The Machining Job tree organizes your machining strategy. Here, ART uses a machining operation set called MOp Set 1 as a container for a variety of 2½ and 3 Axis operations while using MOp 5mm End Mill to contain all operations that use a 5mm end mill. Another MOp Set called 4mm End Mill appears lower in the tree (not shown) and contains all operations that use a 4mm end mill.

5. Hole Machining Strategies

These parts have a series of 41 holes of different sizes and depths that need to be drilled. The depths allow for the Standard Drill type to be used.  Other types include Deep DrillBreakchip DrillCountersink Drill and User Defined DrillART has utilized the Drill Sorting feature in RhinoCAM that allows for various sorting rules. In this case, Minimum Distance Sorting has reduced drilling time by 25%!
2½ Axis Hole Machining is utilized to drill a series of 41 holes of various sizes and depths. Using Minimum Distance Sorting, ART has reduced machining time for drilling by 25%!

6. 2½ Axis Blind & Thru Pocketing Strategies

Being a 2½ Axis operation, Pocketing only needs surface edges or simply 2D curves to control them in X and Y. A Pocket’s Z depth can be entered directly or extracted from 3D geometry by simply picking a point on the model. Pocketing also combines both Roughing and Finishing in one operation with separate Depth per Cut controls for both. In this example, ART defines both blind and thru pockets.
2½ Axis Pocketing operation: Control Geometry: Closed poly curve, Tolerance: 0.5, Stock: 0, Tool: 4mm End Mill, Cut Pattern: Offset, Cut Direction: Climb, Step Over: 40% of Tool Diameter, Location of Cut Geometry: At Top, Total Cut Depth: 23.5, Rough Depth: 21.5, Finish Depth: 2, Rough Depth per Cut: 2.5, Finish Depth per Cut: 1

Top view of 2½ Axis Pocketing operation

2½ Axis Pocketing operation: Control Geometry: Closed poly curve, Tolerance: 0.5, Stock: 0, Tool: 12mm End Mill, Stock: 0, Cut Pattern: Offset, Cut Direction: Mixed, Step Over: 40% of Tool Diameter, Location of Cut Geometry: At Top, Total Cut Depth: 40.5, Rough Depth: 30.5, Finish Depth: 10, Rough Depth per Cut: 5.5, Finish Depth per Cut: 3

Top view of 2½ Axis Pocketing operation

7. 2½ Axis Engraving Strategies

Engraving is an extremely versatile strategy because (a) the center tip of the tool will always follow the open or closed curve selected to control it and (b) it supports a full variety of tool types (14 actually). In this case, ART uses the 2½ Axis Engraving operation to cut two open-ended blind slots using lines as control geometry.

2½ Axis Engraving operation: Control Geometry: Lines, Tool: 5mm End Mill, Tolerance: 0.03, Location of Cut Geometry: At Top, Total Cut Depth: 10, Rough Depth: 8, Finish Depth: 2, Rough Depth per Cut: 2, Finish Depth per Cut: 2, Cut Traversal between Cut Levels: ZigZag.

Top view of 2½ Axis Engraving operation

8. 3 Axis Horizontal Roughing Strategies

3 Axis Horizontal Roughing is used as an area clear operation. The control geometry selected serves to contain the toolpath in X and Y. The part surface and the Stock value entered for the operation limits the tool depth in Z. A Step down value also determines the number of cut levels in Z. This operation is often referred to Z-Level Roughing or Roughing in Levels.

If no control geometry is selected, the entire stock is cut in relation to the part, wherever the selected tool can reach. If control geometry is selected (such as closed curves), it will limit the toolpath in X and Y. In the first operation shown below, ART uses a closed loop of surface edges as control geometry and limits the Top and Bottom of the cut in the Z axis. In the second operation, a closed planar curve is used to contain the operation to a limited area of the stock and part.

3 Axis horizontal roughing: Control geometry: closed edge surface loop, Tool: 12mm End Mill, Tolerance: 0.25, Stock: 0.6, Cut Pattern: Offset, Cut Direction: Mixed, Step over: 25% of Tool Diameter, Stepdown: 3.0, Top containment: 1.0, Bottom Containment: -35.0, Engage/Retract: Ramp, Ramp, Always engage in previously cut area: YES

3 Axis horizontal roughing: Control geometry: Closed Polycurve, Tool: 12mm End Mill, Tolerance: 0.25, Stock: 0.6, Cut Pattern: Offset, Cut Direction: Mixed, Step over: 25% of Tool Diameter, Stepdown: 3.5, Top containment: 1.0, Bottom Containment: -37.0, Engage/Retract: Ramp, Always engage in previously cut area: YES

3 Axis horizontal roughing: Control geometry: closed edge surface loop, Tool: 12mm End Mill, Tolerance: 0.25, Stock: 0.6, Cut Pattern: Offset, Cut Direction: Mixed, Step over: 25% of Tool Diameter, Stepdown: 3.0, Top containment: 1.0, Bottom Containment: -35.0, Engage/Retract: Ramp, Ramp, Always engage in previously cut area: YES

Top view of 3 Axis Horizontal Roughing operation

9. 3 Axis Parallel Finishing Strategies

3 Axis Parallel Finishing is a toolpath strategy used either as a pre-finishing operation or as a finishing operation. In this method, the cutter is restricted to follow the contours of the part in Z while being locked to a series of parallel vertical planes. ART uses this strategy as a finishing operation cutting areas previously roughed out. The cutter is controlled in X and Y by the same closed poly curve used for Horizontal Roughing shown in Item 8 above) and is controlled in Z by the contour of the part’s surfaces.

3 Axis Parallel Finishing: Control geometry: Closed Polycurve, Tool: 12mm Ball Mill, Tolerance: 0.03, Stock: 0, Cut Direction: Mixed, Angle of Cuts: 90, Cutting Area Control: Tops Only, Stepover: 0.5, Z Containment Highest Z: 1.0, Lowest Z: -37.5, Entry/Exit: Linear, Cut Connections: Straight

Closeup of 3 Axis Parallel Finishing operation showing Stepover, Angle of Cut, and Cut Connections

Top view of 3 Axis Parallel Finishing operation. Notice that the cut is limited to the part’s surfaces even though the control geometry selected is a larger closed poly curve. The red toolpaths represent retracts in areas where the there is no part geometry to cut.

10. Cut Material Simulation & G-Code Posting

Advanced Cut Material Simulation is now available in all RhinoCAM configurations. One or all operations can be simulated at the same time. The cut material simulated from the previous operation automatically serves as the stock model for the next operation simulated. You can control the simulation speed, accuracy, as well as the display states for the tool and holder. You can also Compare the cut material from an operation to the actual part with graphic feedback with color-coded tolerance bands.

Hole machining and the first 3 Axis Horizontal Roughing operation is simulated.

Hole machining and the second 3 Axis Horizontal Roughing operation simulated.

The 3 Axis Parallel Finishing operation is simulated.

Cut material simulation comparison with the actual part showing tolerance bands in various colors. Tighter toolpath operation tolerances will affect the tolerance bands displayed.

More about Advanced Robotic Technology (ART)

Advanced Robotic Technology (ART) came from humble beginnings to become an international supplier of quality and state of the art CNC Router and Plasma profile machines. Now employing over 40 personnel, ART is developing machines with up-to-the-minute cutting technology locally and internationally. Today, ART is a world leader in CNC technology. Their CNC machines have enabled manufacturers to make drastic increases in productivity. Manufacturers ranging from ship and boat builders, cabinet makers, sheet metal workers, steel fabrication, plastic engineering as well as others, have been able to benefit from ART’s CNC routers and plasma cutters.

Greg White, Advanced Robotics

More about RhinoCAM

RhinoCAM is a Computer Aided Machining (CAM) plug-in for CNC that runs completely inside of Rhinoceros 5.0. This plug-in is a general purpose machining program targeted at the general machinist. RhinoCAM marries the power of Rhino’s freeform modeling with the legendary machining capabilities of VisualCAM to bring you a product of unrivaled capability for free form surface machining.

RhinoCAM
Don LaCourse

Don LaCourse

Don LaCourse is an Application Engineer with MecSoft Corporation. Don brings over 20 years of experience in CAD/CAM operations in both automotive and mold design applications. Don also has extensive experience in documenting CAD/CAM products and is actively involved with writing the on-line help as well as creating training tutorials for MecSoft's products.
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