Basic Knowledge

CAD/CAM: Creating Machines and Products with Computer-Aided Techniques

| Editor: Steffen Donath

How do computer-aided modelling and computer-aided manufacturing work? Read know everything you need to know about the basics of CAD/ CAM.

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CAD/CAM is a central part of the industry. One stage flows into the next.
CAD/CAM is a central part of the industry. One stage flows into the next.
( Source: Pixabay / CC0 )

In the world of industrial fabrication, computers play vital roles in taking ideas from concepts to realities. Digitised production workflows are practically everywhere, but they can still be somewhat confusing. If you're struggling to make heads or tails of computer-aided design, or CAD, and computer-aided manufacturing, or CAM, you're probably not alone. Foundrymen have to meet a wide variety of requirements. Modern CAD systems help to prepare components for die casting with little effort. But how do these techniques work, and what's the big deal about mastering them? Here's why understanding them is essential for everyone from factory workers and product concept designers to start-up CEOs.

In the past, tools for the die casting technology were manufactured on the basis of drawings, today designers work with 3D CAD data and use state-of-the-art IT technologies. In the design of casting molds, both the casting process – and thus the melt flow and the cooling – and the geometry and the dimensions of the die cast parts to be manufactured must be considered.

Exploring the Functional Definitions

What are CAD and CAM? Much confusion arises over the fact that the two techniques are commonly used in the same industrial settings. In reality, however, they're quite distinct disciplines:

Computer-aided design, also known as computer-aided drafting, is the process of using software and hardware to create, improve or otherwise tweak product plans. By allowing designers to modify the specifications that will later be used to fabricate products, these application-based workflows make it easier to achieve common tasks.

Computer-aided manufacturing involves using computers to control the actual industrial processes that result in the production of prototypes and finished goods. For instance, one common technique, known as computer numerical control, or CNC, involves the use of machinery that automatically guides a tool head, such as a rotating router or lathe bit, across a raw workpiece.

Key Distinctions

Still confused about how computer-aided drafting and manufacturing differ? Here are a couple of good clues on how to distinguish between the two:

  • Location and context

Computer-aided drafting usually occurs entirely on a computer, tablet or similar device. Although some machining shops and engineers might use specialised peripherals, such as multi-button mice, graphics tablets, trackballs or even augmented-reality enclosures, these physical interfaces aren't necessarily critical to the process.

Computer-aided manufacturing, on the other hand, primarily occurs in 3D space. Since it involves the fabrication of an actual physical object, it only needs computers for controlling the machinery.

  • Output

This one is pretty easy to understand. At the end of a successful computer-aided drafting session, the user is left with a digital file in some format, such as an AutoCAD DXF, a DWG or an STL. With computer-aided manufacturing, the end result is something tangible, such as a flange, an electronics enclosure or a bespoke tool.

What Are These Tools Used For?

Another good way to tell the difference between the two computer-aided processes is to look at their purposes. Even though both play a part in streamlining mission-critical technical tasks, they each focus on distinct aspects of the production line.

Effective Conceptualisation

Computer-aided drafting makes it far faster to fiddle with the concepts underlying part models. For instance, a designer can instantly see how different product modifications might look without having to redraw numerous variations manually.

Drafting with computers also heightens the shareability of models. As engineering workforces become increasingly distributed, it behoves companies to use models that they can quickly disseminate via email, version control and other conventional methods. This workflow tweak also makes it a lot simpler to suggest changes and improvements without going back to the proverbial drawing board.

Digital models can also undergo advanced testing processes before they reach the field as tangible items. By importing these files into computer-aided engineering applications, it's possible to simulate forces like fluid flow, wear and other real-life factors that a product might eventually face. Such steps help creators provide consumers with more satisfying products that have lower mean time between failure rates.

Finally, it's worth nothing that digital drawings and models are far less open to interpretation. Instead of worrying about whether a third-party fabrication firm's lead engineer paid attention in their drafting classes, you can spend more time checking your work. As long as they've calibrated their machinery to the proper specifications, your model will be faithfully reproduced.

Enhanced Fabrication Success

Computer-controlled manufacturing processes have dramatically changed the way companies create products. Instead of needing to ship technical drawings off and wait for them to be prototyped, any start-up firm with enough money for a small CNC platform or 3D printer can create its prototypes in-house. This seemingly small process improvement results in more efficient testing, and it can cut down on mistakes by giving designers a chance to interact with the results of their efforts while the ideas are still fresh.

In most cases, computer-controlled machinery consistently outperforms its skilled organic counterparts. Although there are still some jobs that necessitate the manoeuvrability of human fingers and the creativity of human brains, robot arms and mechanical routers don't succumb to forces like fatigue or distraction.

When it's important to do things a certain way every time, using a machine to complete the work is the obvious choice. This is especially relevant considering the fact that you don't have to teach computer manufacturing systems like you would need to train humans.

Examples from the Software World

Now that you understand the basics, you can build a physical part from a model, right? Not so fast. Before leveraging computer-aided anything, you'll need to know how the different aspects come together.

Bridging the Gap: Formats and Processes

One important yet commonly overlooked part of using computer-aided drafting and manufacturing involves translating a model into something that a fabrication device can work with. For instance, even if you've created a 3D DXF file that represents an object's dimensions, the router or other machinery needs specific guidance that tells it how to make that shape from a block of plastic, metal or wood.

Conversion: From Model to Manufacturing Instructions

Special applications usually fulfil this role by turning completed model files into instruction files. For instance, with many consumer- and professional-grade 3D printers, the model takes the form of an STL file. This format specifies the geometry of a part by numerically describing the positions of the points that represent its triangular faces in three-dimensional Cartesian space. Other formats, such as AMF, also include instructions for different material colours and constellations, or object-grouping arrangements.

Upon opening an STL or AMF file, the software that runs the printer might translate it into something like a G-code file. These files contain the actual movements that the printer will have to make to create something. For instance, instead of saying "This object includes a point at such-and-such XYZ coordinates," the G-code might say "Send the tool head to such-and-such XYZ coordinates and squeeze out some melted plastic."

In the case of 3D printing, this conversion process is referred to as slicing a model, since it results in a set of instructions that tell the printer where to move for each thin layer of the print. With routers and other numerically controlled devices, the files may be converted into similar command sets known as M-code files. This goes to show how easy it is to employ completely different fabrication processes with the same original model.

Choosing the Right Tools for the Job at Hand

Different kinds of fabrication demand distinct flavours of computer-aided manufacturing formats. For instance, printed circuit boards, or PCBs, are commonly arranged in layers containing traces, or the paths of copper connecting different chips and components. Common tools like Fritzing and Eagle let you place different parts where you want them and draw the links between them or even have the program calculate optimal routes automatically. Depending on your chosen circuit board fabrication method, such as screen printing and chemical etching, you may be able to convert the result into a vector-graphics-format Gerber file and send it straight to the printer.

Getting Started on the Cheap

One of the coolest things about computer-aided manufacturing and modelling is that there are a ton of open-source programs out there. Anyone with an inexpensive laptop capable of running a basic version of a *nix operating system can easily download tools that let them set up their own garage-based manufacturing plant. Some common options with varying capabilities include:

  • PCB Creation Tools: TinyCAD, PCBWeb Designer, Kicad, Fritzing and ExpressPCB.
  • General 3D Modeling Tools: OpenSCAD, OpenJSCAD, Blender, QCad, Sculptris and FreeCAD.
  • 3D Printer Control Tools: Repetier-Host, Slic3r, 3DPrinterOS, MatterControl and Cura.

It's important to stress that these tools offer widely varied feature sets. For instance, one common open-source workflow bottleneck involves the fact that there aren't too many free CNC device controllers that have the full set of capabilities needed for professional work. While options like LinuxCNC are highly popular and relatively well supported, the computer-aided manufacturing industry has historically been dominated by companies that create their own proprietary hardware and custom applications to go with it.

Common Proprietary Tools

Fortunately for companies that demand reliable processes, there's no shortage of paid programs on the market. Many, such as Mastercam, Vectric and Autodesk, help unify workflows by making it possible to create models and control manufacturing hardware within the same application. Corporate requisitioning officers might also be interested in learning that several of these tools include free trials, so it's usually pretty easy to test them out.

CAD and CAM as critical players in tool and mould making

One of the biggest advantages of the computer-aided workflow is that it empowers companies to make better use of classic techniques. For instance, enterprises that create parts using injection moulding and similar methods have to invest significant amounts of capital into the creation of moulds. While such expenses are by no means prohibitive, the costs start climbing rapidly with imperfect processes. For instance, imagine that your firm fails to catch a mistake made during the modelling phase before sending the plans to the production line. You might suddenly find yourself sitting on thousands of expensive, unusable parts.

Computer-aided models are also vital for creating high-quality tooling. As more advanced techniques become available, it grows increasingly necessary to implement testing and quality control processes for consistency's sake. Since applications can include alerts and safety notifications, it may be a bit easier to avoid silly mistakes, such as creating a tool with an overly thin shaft or the wrong fitting for the device that uses it.

The Technology and Brief History Behind CAD/CAM

Computer-aided production processes aren't anything new, but they've certainly come quite a long way from their origins.

Engineering professionals have jumped at the chance to integrate computers into their workflows since their industrial introduction in the 1940s and 1950s. While those early tools weren't much more than glorified calculators by today's lofty standards, they set the tone for what was to come.

Towards the Modern Era

As computer technology and interfaces became more advanced, it was only natural for humans to begin using these tools to reshape the world. Much of the early groundwork was decidedly theoretical.

In the late 1950s, mathematician Paul de Casteljau published an eponymous algorithm used to describe polynomial curves in a numerically consistent manner. These ideas were subsequently popularised by Pierre Bézier, a Renault engineer who created a new notation and used it to describe the shapes of vehicle bodies. These Bézier curves would go on to become the standard for early typesetting languages like Postscript, the 1984 vector graphics brainchild of Adobe engineers.

Things Coming Together

Coincidentally, the proliferation of vector graphics modelling occurred at around the same time that computer technology was becoming democratised. With more people and companies able to access monitors, trackballs and other then-novel tools, businesses and academics naturally began hooking them up to production lines to see what they could create. Since digitised industrial systems, such as programmable logic controllers, had already been used in the automotive industry for decades by this point, it wasn't a huge leap to connect fabrication devices to computers.

The State of the Future

Many of today's manufacturing machines continue to operate on the same underlying principles that early industrial processes leveraged. CAD and CAM, however, have undeniably made life more comfortable. As technologies like virtual- and augmented-reality interfaces become increasingly widespread, computer-aided production methods will almost certainly take on exciting new dimensions.

This article was first published by ETMM.

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