Computer-aided manufacturing

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Computer-aided manufacturing (CAM) is the use of computer-based software tools that assist engineers and machinists in manufacturing or prototyping product components. CAM is a programming tool that makes it possible to manufacture physical models using computer-aided design (CAD) programs. CAM creates real life versions of components designed within a software package. CAM was first used in 1971 for car body design and tooling.

[edit] Overview

Traditionally, CAM has been considered as a numerical control (NC) programming tool wherein three-dimensional (3D) models of components generated in CAD software are used to generate CNC code to drive numerically controlled machine tools.

Although this remains the most common CAM function, CAM functions have expanded to integrate CAM more fully with CAD/CAM/CAE PLM solutions.

As with other “Computer-Aided” technologies, CAM does not eliminate the need for skilled professionals such as Manufacturing Engineers and NC Programmers. CAM, in fact, both leverages the value of the most skilled manufacturing professionals through advanced productivity tools, while building the skills of new professionals through visualization, simulation and optimization tools.

[edit] Early Use of CAM

The first commercial applications of CAM were in large companies in the automotive and aerospace industries for example UNISURF in 1971 at Renault for car body design and tooling.

[edit] Historical shortcomings

Historically, CAM software was seen to have several shortcomings that necessitated an overly high level of involvement by skilled CNC machinists. CAM software would output code for the least capable machine, as each machine tool interpreter added on to the standard g-code set for increased flexibility. In some cases, such as improperly set up CAM software or specific tools, the CNC machine required manual editing before the program will run properly. None of these issues were so insurmountable that a thoughtful engineer could not overcome for prototyping or small production runs; G-Code is a simple language. In high production or high precision shops, a different set of problems were encountered where an experienced CNC machinist must both hand-code programs and run CAM software.

Integration of CAD with other components of CAD/CAM/CAE PLM environment requires an effective CAD data exchange. Usually it had been necessary to force the CAD operator to export the data in one of the common data formats, such as IGES or STL, that are supported by a wide variety of software. The output from the CAM software is usually a simple text file of G-code, sometimes many thousands of commands long, that is then transferred to a machine tool using a direct numerical control (DNC) program.

CAM packages could not, and still cannot, reason as a machinist can. They could not optimize toolpaths to the extent required of mass production. Users would select the type of tool, machining process and paths to be used. While an engineer may have a working knowledge of g-code programming, small optimization and wear issues compound over time. Mass-produced items that require machining are often initially created through casting or some other non-machine method. This enables hand-written, short, and highly optimized g-code that could not be produced in a CAM package.

At least in the United States, there is a shortage of young, skilled machinists entering the workforce able to perform at the extremes of manufacturing; high precision and mass production. As CAM software and machines become more complicated, the skills required of a machinist advance to approach that of a computer programmer and engineer rather than eliminating the CNC machinist from the workforce.

Typical areas of concern:

High Speed Machining, including streamlining of tool paths
Multi-function Machining
5 Axis Machining
Ease of Use

[edit] Overcoming historical shortcomings

Over time, the historical shortcomings of CAM are being attenuated, both by providers of niche solutions and by providers of high-end solutions. This is occurring primarily in three arenas:

Ease of use
Manufacturing complexity
Integration with PLM and the extended enterprise

Ease in use

For the user who is just getting started as a CAM user, out-of-the-box capabilities providing Process Wizards, templates, libraries, machine tool kits, automated feature based machining and job function specific tailorable user interfaces build user confidence and speed the learning curve. User confidence is further built on 3D visualization through a closer integration with the 3D CAD environment, including error-avoiding simulations and optimizations.

Manufacturing complexity

The manufacturing environment is increasingly complex. The need for CAM and PLM tools by the manufacturing engineer, NC programmer or machinist is similar to the need for computer assistance by the pilot of modern aircraft systems. The modern machinery cannot be properly used without this assistance. Today's CAM systems support the full range of machine tools including: turning, 5 axis machining and wire EDM. Today’s CAM user can easily generate streamlined tool paths, optimized tool axis tilt for higher feed rates and optimized Z axis depth cuts as well as driving non-cutting operations such as the specification of probing motions.

Integration with PLM and the extended enterprise

Today’s competitive and successful companies have used PLM to integrate manufacturing with enterprise operations from concept through field support of the finished product. To ensure ease of use appropriate to user objectives, modern CAM solutions are scalable from a stand-alone CAM system to a fully integrated multi-CAD 3D solution-set. These solutions are created to meet the full needs of manufacturing personnel including part planning, shop documentation, resource management and data management and exchange.

[edit] Machining process

Most machining progresses through four stages, each of which is implemented by a variety of basic and sophisticated strategies, depending on the material and the software available. The stages are:

Roughing: This process begins with raw stock, known as billet, and cuts it very roughly to shape of the final model. In milling, the result often gives the appearance of terraces, because the strategy has taken advantage of the ability to cut the model horizontally. Common strategies are zig-zag clearing, offset clearing, plunge roughing, rest-roughing.

Semi-finishing: This process begins with a roughed part that unevenly approximates the model and cuts to within a fixed offset distance from the model. The semi-finishing pass must leave a small amount of material so the tool can cut accurately while finishing, but not so little that the tool and material deflect instead of shearing. Common strategies are raster passes, waterline passes, constant step-over passes, pencil milling.

Finishing: Finishing involves a slow pass across the material in very fine steps to produce the finished part. In finishing, the step between one pass and another is minimal. Feed rates are low and spindle speeds are raised to produce an accurate surface.

Contour milling: In milling applications on hardware with five or more axes, a separate finishing process called contouring can be performed. Instead of stepping down in fine-grained increments to approximate a surface, the workpiece is rotated to make the cutting surfaces of the tool tangent to the ideal part features. This produces an excellent surface finish with high dimensional accuracy.

[edit] Software providers today

The largest CAM software companies (by revenue 2005) are UGS Corp (now owned by Siemens and called Siemens PLM Software, Inc) and Dassault Systèmes, both with over 10% of the market; CAMWorks (From Geometric Ltd) is the first CAM package with Automatic Feature Recognition Technology,PTC, Hitachi Zosen and Delcam have over 5% each; while Planit-Edgecam, Tebis, TopSolid, CATIA, CNC (Mastercam), SolidCAM, DP Technology's ESPRIT, OneCNC, and Sescoi between 2.5% and 5% each. The remaining 35% is accounted for by other niche suppliers like T-FLEX,Dolphin CAD/CAM, MecSoft Corporation, SurfCAM, BobCAD, Metamation, GibbsCAM,and SUM3D .