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Everything You Need to Know About CNC Milling

What is CNC Milling

Various types of processing can be performed on a CNC machine. They can be cut (milled), drilled, planed, sharpened, and so on. The machines for their intended purpose have different designs and tools, but the programs used in the control system are of the same type.

Milling programming allows you to easily master other machining programs. For those who understand the milling program, it will not be difficult to master other types of processing.

cnc milling

In the process of milling, a layer of material is cut off in order for the workpiece to acquire the desired parameters, as well as to give it smoothness. In some models, the cutter (main tool) moves along a predetermined path, in others, the work platform moves with the workpiece.

In this process, 2 main movements are considered: rotation of the cutter (main) and movement of the part (translational). During milling, artificial deformation and detachment of the surface layer of the material occur. The process is accompanied by the release of chips. There are two types of milling: counter and passing.

Why Does CNC Milling Important

The machining of various materials by mechanical milling has some excellent characteristics:

  • * There is no thermal effect on the base;
  • * The ability to manufacture both small and large parts;
  • * Engraving or cutting of the surface to the required depth;
  • * Obtaining an accurate and high-quality end face, including with the desired angle to the surface;
  • * Finishing of complex elements;
  • * High productivity of equipment;
  • * Speed ​​of parts manufacturing;
  • * Does not require a large number of specialists to work on the machine.

These characteristics significantly reduce production and service costs, speed up the process while allowing the production of parts of complex geometric shapes in any quantity.

Milling cutting is widely used in a wide variety of industries:

Different types of CNC Milling Machine

By design features, there are two types of machines under consideration – vertical milling and horizontal milling. In the first case, the machining tool (spindle) is located perpendicular to the table, which allows the machining of one side of the workpiece.

In the second, the spindle is mounted parallel to the working surface of the table, which allows multi-sided machining of the workpiece without the need to re-fix it.

Distinctive features of modern CNC milling machines are:

  • * powerful and massive body, which is additionally reinforced with stiffening ribs;
  • * high requirements for the strength and reliability of the spindle fastening;
  • * the possibility of high-quality surface treatment, regardless of the direction of milling – oncoming or passing;
  • * comfortable and durable rail guides, which are designed to move the processing tool horizontally.

An example of a high-quality CNC milling machine are two models of similar equipment from Wattsan: M4S 1325 and M9 1325. They combine a reasonable level of cost with excellent technical and operational characteristics. Do not forget about such an important advantage of the products of this manufacturer as long service life.

CNC Milling Methods

Face milling

Whenever possible, milling of planes with the intersection of grooves and holes should be avoided, since this will cause the cutting edges to work in unsatisfactory interrupted cutting conditions. A hole-making operation should be carried out after milling. If this option is not possible, then when the cutter crosses the hole, you need to reduce the feed rate by 50% of the recommended.

When machining large planes, you should try not to interrupt the contact of the cutter with the workpiece, bypassing the surface around the perimeter, and not in several parallel passes. Corner processing must be carried out along a radius exceeding the cutter radius to exclude the possibility of vibrations associated with a sharp increase in the cutter wrap angle.

Milling narrow grooves

A long and narrow groove cannot be machined using circular interpolation but must be done in a single pass over the full groove width. If the power of the equipment allows, it is advisable to choose the cutter diameter as close as possible to the final size of the groove.

After such processing, there will be a minimum finishing allowance. For pre-drilling the groove, it is recommended to choose a drill with a diameter of 5 – 10 mm larger than the cutter diameter. The maximum drilling depth should be no more than the cutter diameter. It is necessary to reduce the feed at the start of cutting to ensure reliable chip evacuation.

Drilling and plunge milling

It is necessary to choose a drill with a diameter Dc 1 mm larger than the cutter diameter. Maximum radial cutting depth 12 mm (at Dc = 50 mm). The number of teeth simultaneously participating in cutting must be equal to two.

Plunging in two axes

The maximum infeed angle depends on the cutter diameter (for a Dc = 50 mm cutter, the infeed angle is 5). For maximum machining performance, select 12mm or 16mm inserts and a small pitch cutter.

Milling technology for parts with conjugate planes and polyhedrons. Mating surfaces of one part, that is, surfaces located in different planes, can be parallel, perpendicular, or located at any angle. Such planes include adjacent faces of a rectangular and square prism, cube, hexagon, pyramid, etc.

Processing of workpieces with conjugate planes is carried out on vertical and horizontal milling machines with end and cylindrical mills, as well as sets of milling cutters. On the machine table, workpieces are fixed in universal or special devices.

Processing of polyhedra

When milling a square from a bar, the workpiece, depending on its length, can be fixed in one of the following ways:

  • * in a three-jaw chuck;
  • * in the three-jaw chuck and the center of the tailstock;
  • * in the centers of the universal dividing head and tailstock. Milling the edges of the squares is done with end, end, disc cutters.

When machining hexagons, high productivity can be achieved using a set of disc cutters. Machining of planes conjugated at acute and obtuse angles is carried out in the same way as for inclined planes. The relative position of the conjugate planes (parallel and perpendicular), machined with the resetting of the workpieces in the vice of a universal horizontal milling machine, is controlled by vernier calipers, squares, curved rulers, and planers.

The planes located at obtuse and acute angles are controlled by templates and planers, regardless of which cutters are used for this processing: cylindrical or end cutters.

Overview of CNC Milling Process

Modern CNC machines can perform 3D milling – this is the processing of a part by several working bodies at the same time while being in different planes. Before starting work, the operator first builds a 3D model of the part on a computer, the machine then reproduces it with maximum accuracy.

Two objects are involved in the milling process – a cutter and a workpiece. The workpiece is a future part. The control of such CNC machines occurs through a computer or other computing device. The signal about the movement of the equipment is sent to the controllers, which generate a signal of the desired frequency and voltage, after which this electrical signal is sent to the motors of the machine and they move its elements to the desired distance or position.

The milling cutter itself on a CNC machine is rotated by a spindle at a given number of revolutions per minute. The main task of the machine is to move the spindle with a rotating cutter in space and describe a given trajectory of movement at a certain speed (feed).

The system for converting the signal to the movement (Numerical Control, CNC) is different for each machine. This system accepts a text file with control codes (G-codes). The type of this file is individual in relation to the equipment, it is he who is formed in special CAM programs.

Considering the Materials for CNC Milling

All programmable milling machines are equipped with the ability to adjust the power, the feed rate of the warp, the choice of cutting mode. A wide range of settings allows you to use a wide variety of materials for cutting:

  • * wood, plywood, chipboard, fiberboard, MDF;
  • * PVC plastic;
  • * composite;
  • * polystyrene, PET;
  • * acrylic and organic glass;
  • * metal

Plywood milling

Plywood is a fairly popular material, inexpensive, and environmentally friendly. There is no area of ​​life where it was impossible to use a plywood product. These can be interior items, advertising structures, packaging, and parts for industry. In recent years, plywood blanks for the hobby are in great demand.

Milling cutting of composite panels

Aluminum composite panels are increasingly used for facades, interiors, and more recently in the production of outdoor advertising. This scope of application is due to their characteristics – high strength with low weight, as well as good wear resistance.

PVC milling

Polyvinyl chloride is a type of plastic that is resistant to aggressive environments, to the effects of unfavorable environmental factors. Ease of processing, plasticity, and excellent characteristics in terms of wear resistance allowed this material to become in demand both in the industrial field and in the household.

Aluminum milling

Aluminum is in great demand in almost all areas of industry and high technology. Parts made of this metal are lightweight, resistant to corrosion and aggressive chemical compounds, and have a low melting point.

Conclusion

CNC devices have changed the look of the production hall. They control turning, drilling, milling, grinding machines, greatly speed up and simplify human work. Almost every enterprise that deals with the mechanical processing of parts have a computerized system. CNC milling provides manufacturing facilities with new opportunities to improve product quality and increase profitability.

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