Case Study
 

Feature-Based Machining


Focusing on the finished part by streamlining processes

By Tom McCollough
Vice President of Software Development, FeatureCAM / Engineering Geometry Systems

Producing machined parts as quickly, accurately and profitably as possible is the driving force at every machine shop. With the rapidly changing and evolving trends in manufacturing and computer technology, you have to ask yourself “Would I rather spend time honing my expertise in producing parts or in learning new technology?” When it comes to spending time in the shop or at the computer, the choice is obvious.

This is an age of ever faster and more powerful technology. Instead of making our jobs more complicated, computers should make our jobs easier by taking over the tedious, time-consuming tasks that are prone to error and leaving us free to apply our skills to more creative tasks. At Engineering Geometry Systems, developer of feature-based CAD/CAM products, increased shop productivity is the primary goal of all FeatureCAM products.

Traditional CAM systems are operations based and require you to program every operation, one at a time, to create your part. All the manufacturing details are left to the CNC programmer. That means you must specify the details for every rough and finish pass, spot drill, drill, and tap needed to create your part.

With feature-based machining, the part is created using features that describe that part, from simple holes to complex pockets to turned grooves, and the operations are automatically generated. Features give you the ability to think about and view the part at a higher level. Feature-based machining frees you from the time-consuming chore of creating and managing each machining operation. And since there are fewer objects to manage, part programming is accomplished more easily and with fewer errors.

Defining Features

Features are used as the building blocks to describe a complete part. First of all, they define shape. They define the faces of the part, the size and shape of pockets, slots, bosses, and grooves, the locations and types of holes, and so on and whether those shapes have chamfered or rounded edges. Features are easily revised by simply changing one or more individual parameters, such as depth or radius, and the entire part is updated.

But the beauty of features is that they not only describe shape, but they also describe how to produce those shapes at the NC machine. Features contain information and rules describing how and where material removal should occur, cutting depths, whether to use climb cutting, whether to spot drill or center drill, and preferred machining strategies for roughing and finishing. When a part is constructed of features, the CNC programming process becomes automatic.

Hole features are probably the most commonly used type of feature, so we’ll use them as an example. First you define the physical properties for the hole—from simple to complex—such as the hole diameter and depth, chamfer depth, counter bore diameter and depth, counter sink diameter and angle, thread information, and the coordinate location for each hole. Then you assign the drilling strategy and choose whether to spot drill or perform a chip break. Based upon your choices, FeatureCAM creates drilling operations automatically. These drilling operations are managed by FeatureCAM. The feature gives you a single point of control on how the hole is drilled. This is what sets FeatureCAM apart from other CAM products.

Drilling operations that come from the hole feature can be the result of a simple choice, such as the user clicking a checkbox to specify that a spot drill is desired. Other operations spring from rules preprogrammed into FeatureCAM. For example, there is a rule that determines when pecking is to occur based upon hole depth. There are many rules, all of which are user customizable by simple numeric parameters entered into easy-to-use dialog boxes. The rules work in concert with your choices so that once the feature is created it contains all the information needed to machine it. There is no faster way to get to G-code from a CAM system.

Knowledge-Based Technology

Once the operations are created, FeatureCAM automatically selects tools based upon customizable rules. For example, if you specify that the hole should be reamed, then FeatureCAM automatically creates a drilling operation followed by a reaming operation. The drill chosen will be based upon a percentage of the final hole size, with the percentage being customizable.

FeatureCAM’s ability to choose tools depends, as you might expect, on a database of tooling. FeatureCAM comes with a typical assortment, and you adjust the database to reflect actual tooling usage in your shop.

Finally, once operations and tooling have been determined, FeatureCAM recommends feeds and speeds. Here again FeatureCAM accesses a user-customizable database that ships with the software. If you are not satisfied with the recommendations for a specific application, then you can simply override feeds and speeds as you create the feature. Alternatively, you can edit the feed/speed database in order to adjust the feed/speed recommendations at the source, resulting in automatic recommendations that suit your particular shop.

Even with all of the automation, it is important to note that FeatureCAM also gives you complete control over even the finest details of your final part program. You can allow the rules to work as you have specified them, and then you can make final adjustments at the lowest level, should you choose to do so. Any property can be changed at any time and the toolpath is automatically updated to reflect your changes.

As you create features and define the parameters, all of the changes you make are made on a “live” feature. Changes are never made on an end-product that is lost when a change is made. Changes are instead made on the feature and the end product is automatically and constantly updated. The benefit here is that a change to the part never requires you to start over, as might be required by other CAM products.

Automation occurs not only within a feature, but also between features in the process plan. As you create features, a process plan is constructed and ordered based upon analysis that reduces tool changes, rapid distance, and tools used. This gives you the power to not only increase efficiency by spending less time programming parts, but it also helps you utilize more efficient methods at the production level. At any point in time you can make minor adjustments to the ordering to suit your particular needs.

In effect, you simply describe the physical attributes of the part you want to machine and your machining preferences based on your particular shop conditions, then FeatureCAM uses cutting-edge technology to analyze that information and automate the process of creating the parts for you. We’ve been using holes as an example, but the concept of feature-based machining exists throughout FeatureCAM’s milling, turning and wire products. With feature-based machining, the focus is on the end result because, after all, that is where your focus is and that is what your customers are paying you to produce.

Ease of Use

Ease of use is a guiding principle of FeatureCAM products. With an easy-to-use graphical interface, FeatureCAM is perfect for the new or infrequent user. It’s easy to jump in, create or import a part, and produce programs quickly. In addition, web-based training is available so that customers can receive training on a variety of topics without leaving the shop. Since FeatureCAM does not require extensive training you can hire a CNC programmer who is an expert in machining, but doesn’t need to be an expert on a particular CAM product.

Automatic Feature Recognition

With the rapid advances in solid modeling CAD technology we see today, it seems wasteful to expect the CNC programmer to recreate a part in his CAM system. With FeatureCAM’s Automatic Feature Recognition, a part program can be generated directly from a CAD solid model!

FeatureCAM provides Automatic Feature Recognition with a one-button solution that automates CNC programming and increases speed-to-market. With the push of a button, Automatic Feature Recognition automatically recognizes the features on an imported solid, from holes to bosses to pockets, and creates associative features that are used to automatically generate toolpaths using the customer’s own CNC programming preferences.

With Automatic Feature Recognition, a 2.5D part can be made immediately. There is no longer a need to draw geometry and create features. It’s all automatic. With the majority of the programming work already done, the CNC programmer can then fine-tune the program to get it exactly the way he wants. Today’s solid modelers are producing great solid models, so there is no time wasted recreating that information in the CAM system. Parts get to the finish line as fast as possible.

Also, features are associative with the imported solid. If there is a design change, the revised model can be imported and Automatic Feature Recognition will associate the new model with the original features. After it makes this association, FeatureCAM then displays a list of all features and whether they are new, unchanged, modified, or deleted. There is no need to reprogram the part when changes are made to the design. FeatureCAM is smart enough to leave the unchanged features alone. When features are revised, changes are made only to the specific machining parameters that are different from the original solid, such as the depth of a hole or pocket. Design changes are inevitable, so FeatureCAM makes it as easy as possible to accommodate those changes.

User-Defined Features

Customization makes a huge difference in the efficiency of any company. Having the ability to tailor a software package to specific business requirements is essential in today’s competitive market. Companies should be able to define their own sets of features along with specialized machining processes that improve the productivity of their shop.

In addition to the robust selection of standard features already available in FeatureCAM, a company can create a whole library of features along with associated toolpath parameters to suit their own design and programming needs and then access them from the standard feature dialog within FeatureCAM. Once again using holes as an example, many companies have one or more elaborate or unusual holes that they frequently drill. By encompassing their custom holes into user-defined features, the company reaps the following benefits:

  • Shorter part programming times due to the ease-of-use of features.
  • Consistently high part quality because all NC programmers are using the same machining parameters encoded into the user-defined feature.
  • Fewer errors during CNC programming because the user is only managing one feature, not a collection of individual operations.
 

The user-defined feature gives you the single-point of control that makes creating part programs so easy in FeatureCAM.

Conclusion

Feature-based machining lets the CNC programmer focus on the finished part by streamlining every step in the process to achieve that part. With much of the programming performed automatically in FeatureCAM, the CNC programmer can concentrate on fine-tuning the program for his own specific shop floor conditions.

With improved automation and customization of part production, companies can respond much more quickly to changes in the global market. Investing the time to evaluate and harness the power of the latest in technology leads to enhanced revenues through an increase in productivity and a reduction of programming and training costs.

Contact Information:

For more information on FeatureCAM, please call 888-393-6455 or visit www.featurecam.com

For technical information, please contact Tom McCollough at 801-575-6021 or wtm@featurecam.com