Computer-aided manufacturing

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CAD model and CNC machined part

Computer-aided manufacturing (CAM) is the use of software to control machine tools and related ones in the manufacturing of workpieces.[1][2][3][4][5] This is not the only definition for CAM, but it is the most common;[1] CAM may also refer to the use of a computer to assist in all operations of a manufacturing plant, including planning, management, transportation and storage.[6][7] Its primary purpose is to create a faster production process and components and tooling with more precise dimensions and material consistency, which in some cases, uses only the required amount of raw material (thus minimizing waste), while simultaneously reducing energy consumption.[citation needed] CAM is now a system used in schools and lower educational purposes. CAM is a subsequent computer-aided process after computer-aided design (CAD) and sometimes computer-aided engineering (CAE), as the model generated in CAD and verified in CAE can be input into CAM software, which then controls the machine tool. CAM is used in many schools alongside Computer-Aided Design (CAD) to create objects.

Overview[edit]

Chrome-cobalt disc with crowns for dental implants, manufactured using WorkNC CAM

Traditionally, CAM has been considered as a numerical control (NC) programming tool, where in two-dimensional (2-D) or three-dimensional (3-D) models of components generated in CAD. As with other “Computer-Aided” technologies, CAM does not eliminate the need for skilled professionals such as manufacturing engineers, NC programmers, or machinists. CAM, in fact, leverages both 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.

History[edit]

Early commercial applications of CAM was in large companies in the automotive and aerospace industries, for example Pierre Béziers work developing the CAD/CAM application UNISURF in the 1960s for car body design and tooling at Renault.[8]

Historically, CAM software was seen to have several shortcomings that necessitated an overly high level of involvement by skilled CNC machinists. Fallows created the first CAD software but this had severe shortcomings and was promptly taken back into the developing stage.[citation needed] CAM software would output code for the least capable machine, as each machine tool control 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 or skilled machine operator 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 Product lifecycle management (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 or Parasolid formats that are supported by a wide variety of software. The output from the CAM software is usually a simple text file of G-code/M-codes, sometimes many thousands of commands long, that is then transferred to a machine tool using a direct numerical control (DNC) program or in modern Controllers using a common USB Storage Device.

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.[9][10] As CAM software and machines become more complicated, the skills required of a machinist or machine operator 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
  • Feature recognition and machining
  • Automation of Machining processes
  • Ease of Use

Overcoming historical shortcomings[edit]

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:

  1. Ease of usage
  2. Manufacturing complexity
  3. Integration with PLM and the extended enterprise[11]
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, waterjet, laser / plasma cutting, and wire EDM. Today’s CAM user can easily generate streamlined tool paths, optimized tool axis tilt for higher feed rates, better tool life and surface finish, and ideal cutting depth. In addition to programming cutting operations, modern CAM softwares can additionally drive non-cutting operations such as machine tool probing.
Integration with PLM and the extended enterpriseLM 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. To prevent these solutions from detailed tool specific information a dedicated tool management

Machining process[edit]

Most machining progresses through many stages,[12] each of which is implemented by a variety of basic and sophisticated strategies, depending on the part design, material, and software available.

Roughing
This process usually begins with raw stock, known as billet, or a rough casting which a CNC machine cuts roughly to shape of the final model, ignoring the fine details. In milling, the result often gives the appearance of terraces or steps, because the strategy has taken multiple "steps" down the part as it removes material. This takes the best advantage of the machine's ability by cutting material horizontally. Common strategies are zig-zag clearing, offset clearing, plunge roughing, rest-roughing, and trochoidal milling (adaptive clearing). The goal at this stage is to remove the most amount of material in the least amount of time, without much concern for overall dimensional accuracy. When roughing a part, a small amount of extra material is purposely left behind to be removed in subsequent finishing operation(s).
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 (called the scallop) so the tool can cut accurately, but not so little that the tool and material deflect away from the cutting surfaces.[13] Common strategies are raster passes, waterline passes, constant step-over passes, pencil milling.
Finishing
Finishing involves many light passes across the material in fine steps to produce the finished part. When finishing a part, the steps between passes is minimal to prevent tool deflection and material spring back. In order to reduce the lateral tool load, tool engagement is reduced, while feed rates and spindle speeds are generally increased in order to maintain a target surface speed (SFM). A light chip load at high feed and RPM is often referred to as High Speed Machining (HSM), and can provide quick machining times with high quality results.[14] The result of these lighter passes is a highly accurate part, with a uniformly high surface finish. In addition to modifying speeds and feeds, machinists will often have finishing specific endmills, which never used as roughing endmills. This is done to protect the endmill from developing chips and flaws in the cutting surface, which would leave streaks and blemishes on the final part.
Contour milling
In milling applications on hardware with four 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 work piece 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. This process is commonly used to machine complex organic shapes such as turbine and impeller blades, which due to their complex curves and overlapping geometry, are impossible to machine with only three axis machines.[15]

Software: large vendors[edit]

The top 20 largest CAM software companies, by direct revenues in year 2015, are sorted by global revenues:

See also[edit]

References[edit]

  1. ^ a b U.S. Congress, Office of Technology Assessment (1984). Computerized manufacturing automation. DIANE Publishing. p. 48. ISBN 978-1-4289-2364-5.
  2. ^ Hosking, Dian Marie; Anderson, Neil (1992), Organizational change and innovation, Taylor & Francis, p. 240, ISBN 978-0-415-06314-2
  3. ^ Daintith, John (2004). A dictionary of computing (5 ed.). Oxford University Press. p. 102. ISBN 978-0-19-860877-6.
  4. ^ Kreith, Frank (1998). The CRC handbook of mechanical engineering. CRC Press. p. 15-1. ISBN 978-0-8493-9418-8.
  5. ^ Matthews, Clifford (2005). Aeronautical engineer's data book (2nd ed.). Butterworth-Heinemann. p. 229. ISBN 978-0-7506-5125-7.
  6. ^ Pichler, Franz; Moreno-Díaz, Roberto (1992). Computer aided systems theory. Springer. p. 602. ISBN 978-3-540-55354-0.
  7. ^ Boothroyd, Geoffrey; Knight, Winston Anthony (2006). Fundamentals of machining and machine tools (3rd ed.). CRC Press. p. 401. ISBN 978-1-57444-659-3.
  8. ^ Dokken, Tor. "The History of CAD". The SAGA-project. Retrieved 17 May 2012.
  9. ^ Joshua Wright. Forbes. March 7, 2013. https://www.forbes.com/sites/emsi/2013/03/07/americas-skilled-trades-dilemma-shortages-loom-as-most-in-demand-group-of-workers-ages/
  10. ^ Hagerty, James R. (2013-06-10). "Help Wanted. A Lot of It". Wall Street Journal. ISSN 0099-9660. Retrieved 2018-06-02.
  11. ^ Gopi (2010-01-01). Basic Civil Engineering. Pearson Education India. ISBN 9788131729885.
  12. ^ CAM Toolpath Strategies. CNC Cookbook. Retrieved on 2012-01-17.
  13. ^ "Optimization of CNC isoscallop free form surface machining using a genetic algorithm". International Journal of Machine Tools and Manufacture. 46 (7–8): 811–819. 2006-06-01. doi:10.1016/j.ijmachtools.2005.07.028. ISSN 0890-6955.
  14. ^ Pasko, Rafal (1999). "HIGH SPEED MACHINING (HSM) – THE EFFECTIVE WAY OF MODERN CUTTING" (PDF). International Workshop CA Systems And Technologies.
  15. ^ Gomes, Jefferson de Oliveira; Jr, Almeida; De, Adelson Ribeiro; Silva, Alex Sandro de Araújo; Souza, Guilherme Oliveira de; Nunes, Acson Machado (September 2010). "Evaluation of 5-axis HSC dynamic behavior when milling TiAl6V4 blades". Journal of the Brazilian Society of Mechanical Sciences and Engineering. 32 (3): 208–217. doi:10.1590/S1678-58782010000300003. ISSN 1678-5878.
  16. ^ http://www.3ds.com/investors/earnings/earnings-details/fiscal-year-2015-quarter-4-and-full-year-2015/
  17. ^ http://www.engineering.com/PLMERP/ArticleID/12946/PLM-This-Week-CIMdata-Report-Shows-Dassault-Systemes-is-a-PLM-Revenue-Leader-in-2015.aspx
  18. ^ http://geometricglobal.com/media-section/2016-media-release/geometrics-revenues-grow-11-6-in-fy16/

External links[edit]