2.1 CNC High Precision Engineering Technology

Today, Computer Numerical Control (CNC) machines are found almost everywhere from SMEs to Fortune 500 companies. The CNC technology has supported and in many ways contributed to the development of industries where high precision components are used such as the ICT, electronic and electrical, semiconductor, aeronautical, healthcare, heavy industries, etc. Many of these industries are the driving force behind the advancement of today’s living standards.

The utilization of CNC technology to produce high-quality and high-precision components and tools rests largely on the ability of design engineers and skilled technicians to value-add to the technology through in-house R&D activities. Having the CNC machines and software is not a guarantee for success as the key and vital component is the competency and expertise of the R&D and production team to improve and refine the core technology.

The design engineer must possess a thorough and in-depth knowledge of CNC technology to ensure perfect dimensioning and tolerancing techniques for workpieces to be machined on CNC machines. The tool engineer must be well-versed in CNC technology and mechanical design knowledge in order to design fixtures and cutting tools for use with CNC machines. The technical staff in-charge of QA and QC must understand the intricacies of the various CNC machine tools to incorporate proper quality control and statistical process control procedures. Production planning and control personnel must keep abreast of their company's CNC technology and schedule production to meet customers’ needs and ensure optimum uses of the resources.

CNC Technology offers three main benefits in the manufacturing of parts and components:

• Improves automation, which produces side benefits such as reducing operator fatigue and
human errors and increasing the consistency of production and predictable time for each
workpiece.
• FAbility to produce mass copies of workpieces with consistent accuracy, repeatability and
quality.
• Flexibility to produce different workpieces using same tools with just a mere change of program. This is particularly important in the age of Just-In-Time manufacturing.
• The heart of the CNC technology is the Motion Control that allows the CNC system to perform its task automatically, precisely and consistently. It is important to know how to choose and control the motion type, the axes to move, amount of motion and the motion rate (feedrate).
There are three basic motion types, namely rapid motion, straight line motion and circular motion. Most of the modern CNC machines today have 5 axes of movements enabling them to create complex parts. However, in the case of the SPM, the Company owns a number of 3-axes systems.

Almost all CNC controls use a word address format for programming, where the program is made up of sentence-like commands. The word address format is normally called the conversation controller where the CNC machine will issue a ‘question’ to the CNC operator of the steps to take. The CNC operator will then ‘answer’ the machine by instructing it to take specific actions through information such as reference point, degree of chamfer, etc. The CNC program will then execute its command one step at a time in a sequential order. The program will continue to execute the steps until completion unless stopped by the CNC operator or via other external interruptions. A program in CNC machines also controls other functions such as probing systems, tool length, pallet changers, spindle control and coolant control.

CNC accessories are primarily external jigs and fixtures, tools, electronic and mechanical assemblies, probing system, gauging system, feeders and other automation systems that can be use together with the CNC machine as part of the production assembly to manufacture components or parts.

The following are brief descriptions of the major process methodologies used in producing high precision engineering components using CNC technology:

• Milling
Milling is a multi-point cutting process in which material is removed from a work piece by a rotating tool. Both the end and the periphery of the tool usually remove the material. Generally, the cutter rotates about an axis perpendicular to the surface. On occasion a single-point tool, such as a fly cutter, may be used.
• Turning and Facing
Turning is a material-removal process in which the major motion of the single-point-cutting tool is parallel to the axis of rotation of the rotating work piece. Facing is a special case of turning in which the major motion of the cutting tool is at right angles to the axis of rotation of the rotating work piece.
• Reaming
Reaming is a cutting process in which an existing hole is enlarged and accurately sized by means of a multi-fluted cutting tool. As the reamer and work piece are advanced toward each other, chips are produced by shaving thin sections from the existing hole. A reamer is an accurate tool and is designed for removing only a small amount of material.
• EDM Wire Cut
Electrical discharge machining wire cutting is a thermal mass-reducing process that uses a continuously moving wire to remove material by means of rapid controlled repetitive spark discharges. A dielectric fluid is used to flush the removed particles, regulate the discharge, and keep the wire and work piece cool. The wire and work piece must be electrically conductive.
• Lapping
Lapping is an abrasive process in which a rotation lap, charged with loose abrasive slurry, removes very small amounts of material from flat metallic or non metallic surfaces. Low speed and low pressure result in finely finished surfaces of extreme flatness.
SPM’s technical resources comprise of experienced and competent engineers, machinists, programmers and supervisors who possess the required technical know-how with regards to the CNC machine operations and maintenance.