Technology

Understanding CNC Machining Services

Understanding CNC Machining Services

CNC machining is used to produce accurate, high-quality parts with an exceptional finish. CNC machining services includes parts production by physical removal of material using computer-controlled milling, turning, EDM machines and 5-axis CNC for high precision.

CNC machining services provide:

  • Parts with high accuracy and precision.
  • Bulk quantities of parts are being produced by a single CAD file.
  • Fastest and cost effective way to produce parts.

Choosing the Right Machine shop:

The right machine shop’s aim is to build a long-term relationship with the customers by their services, ethics and capabilities. While choosing the machine shop for CNC services following things must be taken into consideration;

  • They should have on-site machining specialists.
  • Capability to produce drawings.
  • They should have advance machinery for parts production.
  • Must be dedicated towards customer satisfaction.

Advantages of CNC Machining:

The advantages of CNC machining are;

  1. Continuous quality control production:CNC machines can work 24 hours a day for parts production, and only occasional maintenance is required. As these machines are completely computer operate So, quality control for bulk production is much easier to maintain.
  2. Easy to Control: CNC machines are easy to operate than manual lathe/milling machines that even a person with basic knowledge of CNC can operate it easily.
  • Bulk production: Bulk quantity of parts can be produced by a single CAD files and each manufactured product will be exactly the same. It yield more output with minimum exercise.
  1. Complicated product design: CNC machines are programmed to produce complicated parts that cannot be manufactured by manual machines.You can produce multiple parts in a much shorter amount of time than using other manufacturing processes.
  2. Cost Effective: A well maintained machine should work perfectly over a long period of time which minimizes the maintenance cost. CNC machinery also cuts down your labor costsas there are fewer workers involved than manual machinery.

CNC Machining Processes:

There are the following main types of CNC machining processes;

  • Milling process.
  • Turning process.
  • EDM

Milling Process:

In CNC milling operation, the part is mounted onto the bed and material is removed by the rotation of cutting toolwhich generally moves perpendicularly on an axis.As shown in Fig (a).

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Fig(a). CNC milling process

Milling is used to machine flat surfaces but, also used for irregular surfaces to produce, holes, slots, and even three-dimensional surface contours. Milling is also used to machine the manufactured product to add some additional features in it.

Cutting parameters:

In milling, the speed and motion of the cutting tool are based on working material, tool material, and tool size.

  • Cutting feed: Cutting feed is defined as the distance that the tool travels during one revolution of the part. Feed rate is adjusted according to the choice of material.
  • Cutting speed: Cutting speed is related to the surface quality (such as hardness) of workpiece and measured in surface feet per minute (SFM).
  • Spindle speed: It is the rotational speed of the spindle and tool in revolutions per minute (RPM). It is equal to the cutting speed divided by the circumference of the tool.
  • Axial depth of cut: In the axial depth of cut the cutting is done by the machine tool along its axis (x y z) to the workpiece. Low feed is used for a large axial depth of cut to avoid tool failure.
  • Radial depth of cut: In the radial depth of cut the cutting is done by the machine tool along its radial axis to the workpiece and it is equal to the diameter of the tool. It is also done on low feed to avoid tool failure.

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Schematic of CNC milling machine

Basic CNC milling Operation:

The basic overview of CNC milling operation is;

  • Convert the CAD model to G-code.
  • The material block is mounted onto the bed of CNC machine.
  • Then the material is removed from the block using the cutting tools that rotate at very high speeds.
  • After machining the part is being deburred to remove small defects.
  • After quality control inspection now a part is ready to use.

Turning Process:

In CNC turning, the part is mounted on a rotating chuck and material is removed using stationary cutting tools moving parallel to the workpiece.

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CNC turning operation

Basic CNC Turning Operation:

The basic overview of CNC turning operation is:

  • Convert the CAD model to G-code.
  • The part material is mounted in the chuck and the part starts rotating at high speed and a stationary cutting tool removes material until the designed geometry is created.
  • If the part is needed to be flipped or moved, then the process is repeated. Otherwise, the part is ready to use.

Electric discharge machining EDM:

Metal removal by a series of discrete electrical discharges (sparks) causing localized temperatures high enough to melt or vaporize the metal. It can only be used on electrically conducting work materials.

It has two main processes:

  1. Electric discharge machining
  2. Wire electric discharge machining

Electric Discharge Machining:

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  • EDM overall setup, and (b) close-up view of gap, showing discharge and metal removal

It is one of the most widely used nontraditional processes; in it sparks occur across a small gap between tool and work which results in material removal. It requires dielectric fluid to complete the process.

Limitations:

  • Only work with electrically conducting materials.
  • Hardness and strength of the work material are not factors in EDM.
  • Material removal rate is related to melting point of work material

EDM Wire cut:

Special form of EDM that uses small diameter wire as electrode to cut a narrow kerf in workpiece.

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EDM wire cut process

In it CNC is used for motion control and while cutting, wire is continuously advanced between supply spool and take-up spool to maintain a constant diameter.Dielectric required, using nozzles directed at tool-work interface or submerging workpiece.

Precision CNC machining (5-axis CNC machining):

5-axis CNC machining involves using a CNC to move a part or cutting tool along five different axes simultaneously.5-axis CNC is a common manufacturing and prototyping solution in the aerospace industry because this enables the machining of very complex parts.

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5-axis CNC machine

Why 5-axis CNC machining:

There are several factors which contribute in the adoption of 5-axis CNC machining.

  • It provides single-step machining to reduce lead time.
  • The ability to avoid collision with the tool holder by tilting the cutting tool or the table, by which you can easily machine complex designs.
  • It improves the tool life and cycle time

What are the axis in 5-axis?

As there are only 3 axis: X, Y, and Z but 5-axis CNC add one additional “axis” of rotation around each of the X and Y axes.Which allows it to work in 5 different directions?

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Axis defined of 5-axis CNC

Low Volume CNC Machining:

Producing precision components and assemblies in low volume from any machine-able material is termed as low volume machining. It generally refers to the production of 50 to 100,000 parts.

It has the following advantages;

  • It allows flexibility in design changing; you may change your design after its modification.
  • To launch your own product in market as early as possible.
  • No need to invest in huge amount of money for bulk production.

A low volume approach to CNC machining is very different from the regular volume production strategies.

Applications:

  • Custom CNC machined parts
  • Quality customized products
  • Plastic injection molded parts
  • Bridge production
  • Functional prototypes
  • Pre-production components for verification tests

Conclusion:

Outlined above are the basics of the CNC machining services dealing with the different processes of CNC machining and prototyping which includes; CNC milling, turning, and EDM. It is the fastest and precise way to produce a product. Various CNC operations and their processes machine are discussed in detailed. We also discuss the fastest way of producing a product by using different types of EDM, and the working of 5-axis CNC machine that how it will produce part having complicated geometry and at last, we discussed about the low volume CNC machining, which play an important role for a new brand to introduce it in market by investing very considerable amount of money.

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