Kangwon National University Department of MEMS

Prof. B. H. Kim

Adv. Solid ModelingBasic of CAM systems

Department of Mechatronics

Kangwon National University Department of MEMS

Prof. B. H. Kim

• Review of basic concepts

What is CAD/CAM?

Kangwon National University Department of MEMS

Prof. B. H. Kim

What is CAM ? • Computer-aided manufacturing (CAM) is the use of computer-based

software tools that assist engineers and machinists in manufacturingor prototyping product components.

• CAM system is a programming tool that allows you to manufacturephysical models using computer-aided design (CAD) programs.

• CAM was first used in 1971 for car body design and tooling.

• Traditionally, CAM has been considered as an NC programming toolwherein 3D models of components generated in CAD software are used togenerate CNC code to drive numerical controlled machine tools.

• As with other “Computer-Aided” technologies, “CAM does not eliminatethe need for skilled professionals” such as Manufacturing Engineersand NC Programmers.

• CAM, in fact, both leverages the value of the most skilled manufacturingprofessionals through advanced productivity tools, while building theskills of new professionals through visualization, simulation andoptimization tools.

Kangwon National University Department of MEMS

Prof. B. H. Kim

Machining process

• 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.

Kangwon National University Department of MEMS

Prof. B. H. Kim

Overview of GibbsCAM• GibbsCAM is a CAM program developed by Gibbs and Associates.

– Early versions of GibbsCAM were called Virtual Gibbs.

• GibbsCAM specializes in providing a powerful range of CNCprogramming functionality that is easy to learn and use.

• GibbsCAM can read a wide variety of CAD formats.– Plug-ins for Autodesk Inventor, Solid Edge and SolidWorks allow parts to be

transferred directly from within the CAD system to GibbsCAM for machining.

• GibbsCAM's modules support 2- through 5-axis milling, turning,mill/turning, and wire-EDM.

• Major features1. Wireframe, Surface and Solid Based Machining

2. Native Graphical User Interface (GUI)

3. Associativity between Geometry, Processes and Toolpath

4. Import native CAD files

5. Import industry standard CAD formats: IGES, STEP AP203 & AP214, VDA-FS

6. Template-based, Do-It Yourself Post Processors

Kangwon National University Department of MEMS

Prof. B. H. Kim

Thank you very much!Be a cool & innovative designer!

Kangwon National University Department of MEMS

Prof. B. H. Kim

• UNISURF developed by Pierre Bézier at Renault in 1971, it was a pioneering surface CAD CAM system for car body design and tooling

Unisurf

Bezier Curve

Kangwon National University Department of MEMS

Prof. B. H. Kim

First NC mchine

Kangwon National University Department of MEMS

Prof. B. H. Kim

• John T. Parsons pioneered numerical control for machine tools in the 1940s.

• APT is a high-level computer programming language used to generate instructions for numerically controlled machine tools.

NC programming

Kangwon National University Department of MEMS

Prof. B. H. Kim

• G-Code, or preparatory code are functions in the Numerical control programming language.

– G-codes that begins with the letter 'G‘ are “the codes that position the tooland do the actual work”.

– Rapid move, Controlled feed move in a straight line or arc, series ofcontrolled feed moves that would result in a hole being bored, a workpiececut (routed) to a specific dimension, or a decorative profile shape added tothe edge of a workpiece., change a pallet , set tool information such as offset.

• M-Codes control the overall machine.

– M means “miscellaneous”. – Stop, start, turn on coolant, etc..

• T-Code is used for tool selection.

• S-Codes is used for spindle speed selection.

• F-Codes is used for feedrate selection.

• Other codes: “X, Y, Z”, “A, B, C”, “u, v, w”, “I, J, K”, “N”, “R”, “P”,

“D”, “H”

CNC codes

Kangwon National University Department of MEMS

Prof. B. H. Kim

CNC codes

Kangwon National University Department of MEMS

Prof. B. H. Kim

• Basic format

• G codes

CNC codes

Kangwon National University Department of MEMS

Prof. B. H. Kim

• G codes

CNC codes

Kangwon National University Department of MEMS

Prof. B. H. Kim

• G codes

CNC codes

Kangwon National University Department of MEMS

Prof. B. H. Kim

• M codes

CNC codes

Kangwon National University Department of MEMS

Prof. B. H. Kim

• Programming example

NC programming

z

x

Kangwon National University Department of MEMS

Prof. B. H. Kim

Beginning of NC • NC was developed in the late 1940s and early 1950s by John T. Parsons

(President of the Parsons Works) in collaboration with the MITServomechanisms Laboratory.

– Parson & F. Stulen were the first to use computer methods to solve machiningproblems, more in particular, the accurate interpolation of the curves describinghelicopter blades in 1946.

– In 1948, Parsons' company was awarded a contract to make the innovative andchallenging tapered wings for military aircraft; they won the contract because theydeveloped the computer support to do the difficult three-dimensional interpolation forthe complex shapes, as well as the 800 steps long production cycle for the wingmanufacturing.

– The initial developments of Parsons and Stulen were only about the calculations,and not the control:

– MIT lab boosted the developments of CNC machining in the following decades, bydeveloping reliable servo control in 1952 and the APT (Automatic Programmed Tool)programming language for CNC machines. Real "numerical control"

– Parsons saw the potential of connecting computers to the machine motors. OnJanuary 14th, 1958, he received a patent for a Motor Controlled Apparatus forPositioning Machine Tool.

• The need of the U.S. Air Force for templates more precise than could be obtainedby state-of-the-art methods.• An entire manufacturing technology known as CAD/CAM has developed around

the NC concept.