3D Advanced Roughing
CAD/CAMTechnology Solves the 3D Challenge
One of the challenges that CNC shops face when it comes to 3
Axis milling has been in the area of 3 Axis Z-Level milling.
This is also known as "waterline" and "Core milling" as well as
Z-Level Roughing in the world of CAD/CAM software part
programming. When leaving the world of 2D milling and
entering the world of complex 3D surface machining, a new
set of particular skills are required for generating an accurate
and efficient NC program.
Without CAD/CAM these types of cnc jobs can be nearly
impossible due to the math calculations involved. With this
being the case, modern cnc software products provide a
variety of 3D machining capabilities that continue to give
programmers faster, smarter and easier solutions to machining difficult 3D parts. The Z-Level Roughing
operations are generally used as a way to remove the majority of the material necessary to perform a
semi-finish roughing operation with a smaller tool that has a reduced step over and Z step-down during
cutting. These operations are very popular before using a finishing type toolpath operation that will
produce a clean surface finish for the part.
5Ways CAD/CAM Improves Advanced 3D Roughing
There are certain benefits in CAD/CAM software that you should look for in order to take full advantage of
the latest in 3 Axis cnc programming technology for your shop.
CAD/CAM software developed to support duel-core processors. Multi-threaded toolpaths are
important as calculation times are hugely reduced when the CAD/CAM software supports hardware with
duel-core processors. It could mean the difference of clicking the "calculate" button and going home for
the day versus clicking the calculate button and having your toolpath calculate within minutes.
CAD/CAM software that provides roughing "Step-Reduction" functionality. 3 Axis roughing
operations can leave a large stair-step type finish after machining that will require a second machining
operation to reduce the left over material before finishing. Using CAD/CAM that offers functionality for
"Intermediate Steps" or added forced steps in cutting is important. Equally important is the transition from
one tool and step over to another along with the characteristics of how such a machining operating
operation performs. Creating an efficient program is the main objective. It isn't always necessary to
perform a tool change from one set of cut-paths to another.
3D Advanced Roughing
Step reduction functionality allows you to machine the bulk of material from the top down and then
machine back up the walls of the part removing the remaining material in specified equal intervals. You
could call this, "Automatic Step reduction." The benefit is efficiency, whereas this type of functionality
makes the most out of the program and reduces the amount of finishing time while supporting tool life.
CAD/CAM that provides High Speed Advanced Roughing. Traditional Z-Level roughing toolpaths can
be hard on tools and even though advanced step-reduction functionality may exist, high speed machining
technology can consolidate the benefits of step reduction while greatly reducing machine cycle times. Not
to mention that high speed toolpath benefits also include extending tool life due to a constant cutting
engagement and increased cutter step-over advantages. Basically, using more of the tool at higher cutting
speeds. The nature of this toolpath is to use more circular machining movements rather than traditional
right and left turn movements. BobCAD-CAM software is currently the only CAD/CAM product in the world
that offers this level of advanced Adaptive High Speed roughing technology for 2, 3, 4 and full 5 Axis CNC
Advanced roughing toolpath operations for complex parts should also include toolpath "Linking" options.
This is the methods that a tool will take when moving from one toolpath to another. Your part may require
a retract from one cut to another, a direct move from one toolpath to another or a "S" type high speed link
from one cut to the next. The S-Link creates an S shape link between each path in the toolpath tangent to
both paths that lie on the surface of the model.
CAD/CAM that provides REST operations. Advanced roughing
operations will leave material behind where the larger tool could not
machine. CAD/CAM software should allow you to take the previous tool
data and generate toolpath for the next smaller cutter based off of the
previous operation and allow you to machine the rest. This operation will
save you time due to the pure automation value and recognizing leftover
material that needs machining.
CAD/CAM that optimizes the toolpath and uses ARC segments wherever possible rather than
line segments. Generally toolpath in CAM is created using tiny line segments that will result in individual
lines of g-code in the output program. When possible you may want to use arc segments through a feature
called, "ARC Fit" that will use arcs instead of lines for the toolpath. This has value in the cleanliness of the
machine path as well as the size of the g-code program that your machine will need. By using this option
you can greatly reduce the size of the program and produce improved toolpath results.
These are some of the attributes you should review when implementing CAD/CAM software into your
business for 3D machining. Each of them adds efficiency to offline program and gets you one step closer to
better parts finished faster.
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3D Advanced Roughing
How Advanced Roughing Step ReductionWorks
As discussed in earlier papers, CAM software should provide the operator with a JobTree Manager which is
the central command of creating toolpath and NC programs. The JobTree is where you will perform job
setup tasks, select tools, materials, create the stock and access all of the machine operations that the
program would offer.
BobCAD-CAM software offers this type of scenario where a JobTree is used for all of the above including
post processing configurations, cutting conditions, machine setup options, indexing operations and more.
By choosing "Mill 3 Axis", the 3 AxisWizard will open providing options for all 3 axis machining operations.
A machiningWizard is a series of dialog boxes
that step an operator through all actions/stages
associated with a machining operation. This is a
huge benefit to new users as they literally
remove the guesswork from programming.
Advanced users also appreciate the wizards as
they provide a large amount of flexibility in
creating a program as there are a lot of options
and override opportunities that make experi-
enced users feel totally in control. Use CAD/CAM
software that provides machining wizards.
The stages of the advanced roughing wizard include:
•Rapid Movement Settings. These input fields will include the Clearance Plane, Rapid plane, Feed Plane
and theTop of Part.
•Posting options. Most CAD/CAM software will allow the operator to add an index system to the job for
4th axis indexing. The index system will allow the operator to include machining operations. If this is the
case, the wizard allows the operator to input the output rotary angle for the selected machining operation.
This stage of the wizard should also offer the ability to use an ARC Fit option. This is where the operator can
input an arc tolerance value which will be used when the software uses arc segments wherever it can in the
toolpath. Once again, this will improve the quality of the toolpath and reduce the number of lines of
•Tool Data. The next phase of the wizard will give the
operator access to the tool library, tool crib library, tool
holders, feed and speed setting and override options as
well as height and diameter offset fields and coolant
options for the tool being used. The CAM software will
automatically supply tool speeds and feeds based off of
the material, operation and the size and type of tool
that is being used. The selected operation will dictate
the tools that are automatically inserted into the
program. However the operator always has full controll
over the tools that will be used in creating the program.
3D Advanced Roughing
•Machining Patterns and Cutting Direction. Depending on
the operation there will be styles of machining patterns that can
be used. In BobCAD-CAM Mill PRO software the Advanced
Roughing strategy offers three different patterns, one of which is
the new high speed adaptive roughing. Climb & conventional
milling options are available as well.
•Parameter Settings. BobCAD-CAM provides the operator
with Depth and Step Over options. This includes an "Intermedi-
ate Steps" option and the number of intermediate steps the user
wishes to use.
This is the phase of the wizard that gives you "step-reduction" benefits. The operator simply inputs the
number of intermediate steps which creates forced cuts at even depths. In addition to this, another unique
option is the ability to define what the top and bottom of the job will be. This allows the operator to
control machining within the Z axis of the part.
These options and others give the operator solutions to machining in a variety of scenarios while provid-
ing total control.
•Leads. There has to be options for the tool leads. Common options are Plunge, center cutting tool and
Ramping options. Along with Ramping will be settings that should provide further control for using a
linear ramp, spiral ramp, zig-zag style or a profile type ramp option. The lengths of ramp type and angle of
approach is also important depending on the style of ramping that is chosen.
•Special options for REST machining, Flatlands machining and how the operator would like to process the
part for depth and region machining (By area or By level) among other options. Depending on the
step-over and tool diameter there can sometimes be pegs left standing in corner areas where the toolpath
takes a left or right turn. Among special options is the setting to remove these potential pegs by extending
the toolpath slightly outward and back inward in these corners. It's these types of options that can be
useful when using advanced roughing toolpaths.
•Toolpath linking options. Toolpath that is for machining along
the part at the same Z level has links between cuts. Direct, s-links
or a retract type link can be used depending on the part and how
the operator wishes to output the toolpath and program.
Once the operator has completed the process of setting up the
operation with the wizard they would simply click a "Compute"
button and the software would automatically create the toolpath
and load everything into the CAM JobTree.
The advanced roughing toolpath would first machine everything from the top down based off of the input
parameters and then start back upward from the bottom performing the intermediate cuts along the outer
walls of the surface or cavety, reducing the large stair type effect that normal roughing can cause and
leaving behind a much smoother and easier surface for the finishing toolpath to machine.
Advanced Roughing Simulation & Deviation Analysis
A CAM system should have simulation capabilities so that the operator can visually inspect the operations.
Complex part programs will most likely have several machining strategies that makes the job. Each of
these can be analyzed through simulation including a part deviation analysis, machine cycle time
calculation and much more.
Advanced Roughing down in Z Intermediate Steps FinishingToolpath
Deviation Analysis Simulated Program
CNC Software advanced roughing with intermediate steps is an important machining operation to use
when programming complex 3D parts. It can be a huge time saver with a lot of different programming
NOTE: All of the information in this paper is available as functionality in BobCAD-CAM CNC Software. The
advanced roughing, REST, High Speed Adaptive Roughing and advanced Machine Simulation are available
in the Mill 3 Axis PRO version of the software.
For more information on CAD/CAM software call BobCAD-CAM, Inc. at 877-262-2231 or 727-442-3554.
Visit www.bobcad.com for a free demo.
3D Advanced Roughing
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