3D Advanced Roughing

CAD/CAM Software3D Advanced Roughing

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CAD/CAM Technology Solves the 3D ChallengeOne 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.

5 Ways CAD/CAM Improves Advanced 3D RoughingThere 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.

They are:

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.

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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

Milling.

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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How Advanced Roughing Step Reduction WorksAs discussed in earlier papers, CAM software should provide the operator with a Job Tree Manager which is

the central command of creating toolpath and NC programs. The Job Tree 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 Job Tree 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 Axis Wizard will open providing options for all 3 axis machining operations.

A machining Wizard 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 the Top 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

g-code.

•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.

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•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 Job Tree.

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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 AnalysisA 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 Finishing Toolpath

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

benefits.

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.

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