What is the best milling cutter for a cnc machine. How to choose a cnc router for a beginner

Types of CNC milling machines

In "nature" there are many types of milling machines that differ in design and scope: manual, floor, desktop, console milling: vertical and horizontal milling, longitudinal milling, rotary milling machines, etc.

In this article we will talk about milling machines made in China. What should a “newbie” look for when choosing a machine for various tasks: processing (cutting, engraving, manufacturing 3D parts) of wood, plywood, non-ferrous and ferrous metals, working with plastics, jewelry wax, stone, etc.

"Stuffing" of the milling machine:

Milling machines made in China are presented on the market in a wide range with various options, and machines can also be equipped with various types of electronics, guides, software. Let's talk in more detail about what we can meet in the configuration of the machine.

By type of machine - floor and desktop.
Spindle - water or air cooling.
Guides can be round or square profile.
The desktop can be movable or not, the portal itself moves.
The machine may have a centralized lubrication system.
The machines are equipped with stepper or servo motors.
By type of machine control: DSP controller RZNC, NCStudio - PCI board, Mach 3 - interface board (LPT).
The machine can be equipped with coolant.
Machine tools with automatic tool changer ATC.
The machine can be equipped with a vacuum table or only clamps, T-slots.
The movement can occur due to the ball screw, helical rack, straight rack.

What to look for when choosing a milling machine?

The main thing is the rigidity of the whole structure. The less in the design of the machine parts connected to each other by means of bolts, the less backlash will be. With insufficient rigidity of the structure, we get at the output a low processing speed, low productivity, and due to the vibrations that occur, we break the tool, in particular, engravers.

You can choose absolutely any spindle, based on the task - air or water cooling. Water-cooled spindles are less noisy, can “work” at minimum speed, and are not afraid of overheating, unlike air-cooled spindles. For example, processing (engraving) of magnesium occurs at 12000-15000 rpm. For a spindle up to 3 kW, a 220V ±10% 50Hz connection is required, over 3 kW - a 380 volt connection. Initially, in the design of the machine for certain tasks, the manufacturer lays down the spindle power that is needed. For example, small format machines for 3D engraving (making cliches for stamping, sealers, medals) will always be equipped with a spindle 800, 1.5, 2.2 kW. Such work does not require power processing. If this is a machine for cutting the same chipboard, MDF (furniture production), then it makes sense to set a spindle of 3 kW or more.

The choice of guides must be taken seriously, the accuracy of processing and, in general, the rigidity of the structure depend on it. The most budgetary machines have round guides, but this makes it easy to process wood, plastics, jewelry wax, etc. For more accurate processing, you need to choose square profile rail guides from well-known brands such as AMT-PMI, Hiwin, THK and others.

Working tables, as a rule, are movable only on small format machines - 200x300, 300x400 mm. On other machines of a larger format, the table is always stationary, the portal moves - the Y axis.

A very important feature in the design of the machine is the centralized lubrication system. It can be manual and automatic. Lubrication is important for lubricating the rubbing parts of the machine - guides. The automatic lubrication system is convenient, works on a timer. The lubrication system is installed on machines starting from the format 1200x1200 mm and more.

The choice of an engine does not always depend on the buyer, machines with a small working field up to 1200x1200 mm are almost always equipped with a stepper motor. On machines with a large working field of 2000x3000 mm, stepper and servo motors can be installed. The servo drive gives greater dynamics, more accurate positioning, but most importantly, it does not lose steps (a sensor (encoder) is built in, which detects violations, and then the system makes adjustments to the movement of mechanisms) at high speeds (the coordinate does not go astray). Of course, it is preferable to put a servo drive on the machine, but this leads to a significant increase in the cost of equipment. For example, for some tasks in the manufacture of facades in furniture production, you can work on a machine equipped with stepper motors. Here are some examples:

Travel speed: SM (stepping motor) - 20-25 m/min, the servo drive can move from 60 m/min or more.
Acceleration speed: stepper motor - up to 120 rpm in 1 second, servo - up to 1000 rpm in 0.2 seconds

In nature, there are many control systems machine, ranging from "amateur" Mach 3 and ending with the company's own developments of equipment manufacturers - Fanuc, HAAS, Moriseiki, Syntec, Seikos, Heidenhain. Simple controllers Mach 3, NC Studio, etc. can only work with 3-4 coordinates. Professional (industrial) equipment is equipped with its own "racks", which allow you to change the tool during operation. To control such equipment, the Fanuc Oi series control system is used, which is designed for 6-8-coordinate machines and allows you to simultaneously control 4 axes. For cutting, sampling and engraving, you can use inexpensive analogues: NC Studio, DSP controllers. They do an excellent job with the tasks, require a minimum of knowledge, are easy to use and are not expensive.

Machine tools that are designed for metal processing will always be equipped with coolant (from lubricant coolant).

It is advisable to use a machine with automatic tool change (ATC) for "short" processing cycles of 5-15 minutes, where more than 2 tools are used. Basically it will be 2D processing - cutting, sampling. For example, the manufacture of interior doors. Machines with autochange mainly come with a table format of 1500x3000 mm or more.

The workpiece on the milling machine can be fixed in a variety of ways. It can be a clamp, a vacuum table, self-tapping screws. The vacuum table allows you to fix the workpiece on the working table of the milling machine, using the power of a vacuum pump. The design of the vacuum table also includes a sealing cord, which allows you to “cut off” unnecessary sections, if, for example, the workpiece does not have a size for the entire working field of the machine.

The disadvantages of such a table include the following:

it is impossible to fix small workpieces;
incompatibility with some systems (in particular, with the tool cooling system, chip trapping system);
some materials, such as MDF, chipboard, wood, do not “attract” a vacuum cleaner, so a fairly powerful pump of the order of 5 kW is needed here, which leads to an increase in electricity consumption, and also relatively increases the cost. Therefore, the production worker must weigh all the pros and cons and make his own choice.

The second type of table that can be found in the design of small format machines is a table with T-slots. It is very convenient for working with MDF, chipboard and wood. Advantages of this table in reliable fastening of preparation. As a rule, pads made of PVC are installed on the table, which will need to be changed in the future due to their wear. Such a table is called "sacrificial".

For mechanical movement in the actuators of the CNC machine tool, the following can be used: Ball screw (ball screw), gear rack - helical and straight. In some homemade machines, you can find a screw-nut transmission. Each movement system has its pros and cons. A straight tooth gear can be used at low to medium speeds and should never be used on a machine equipped with a servo drive. The helical tooth gear provides high travel speed and high positioning accuracy. Such movement systems are equipped with machines with a field of 1200x2400 mm or more.

Ball Screws for CNC are used only for medium and small machines of the format 200x300 and up to 1200x1200 mm. This is due to the possibility of screw deflection when the housing is located in its middle part. Currently, the maximum allowable length of a ball screw is 1.5 m. There is an excellent example of buying similar machines, but at different prices: on one machine of the 900x600 mm format, a ball screw of 8 mm in diameter will be installed, and on the second 16 mm. A thinner ball screw at high working feeds will begin to vibrate (resonance) along its entire length, which will lead to tool breakage, and possibly breakage of machine components. A ball screw with a diameter of 16 mm on the same workers speed parameters will work without problems and move the nodes of the machine. And such a machine will be more productive.

From the foregoing, we can conclude: any machine that is selected correctly for the specific tasks for which it was designed will work properly, quickly and accurately without breakdowns. YUSTO experts will always help you make the right choice. Call the toll-free number 8-800-555-79-69, and we will select the machine exactly for your needs.

When choosing CNC Router(CNC Router) decide:

1. What material are you going to work with. The requirements for the rigidity of the design of the milling machine and its type depend on this.

For example, a plywood CNC machine will only process wood (including plywood) and plastics (including composite materials - plastic with foil).

On a milling machine made of aluminum, it is already possible to process non-ferrous metal blanks, while the processing speed of wood products will also increase.

Aluminum milling machines are not suitable for steel processing, massive machines with a cast iron bed are already needed here, while the processing of non-ferrous metals on such milling machines will be more efficient.

2. with the size of the workpieces and the size of the working field of the milling machine. This defines the requirements for the mechanics of a CNC machine.

When choosing a machine, pay attention to studying the mechanics of the machine, the capabilities of the machine depend on its choice, and it is impossible to replace it without a significant alteration of the design!

The mechanics of a CNC milling machine made of plywood and aluminum are often the same. More details below in the text.

But the larger the size of the working field of the machine, the more rigid and expensive linear motion guides will be required for its assembly.

When choosing machines to solve problems in the manufacture of high parts, with large height differences, there is a common misconception that it is enough to choose a machine with a large Z-axis travel. But even with a large Z-axis travel, it is impossible to produce a part with steep slopes if the height of the part is greater than the working length of the cutter, that is, more than 50mm.

Consider the device of a milling machine and options for choosing on the example of CNC machines of the Modelist series.

A) Choice of CNC machine design

There are two options for building CNC machines:

1) designs with movable table, picture 1.
2) design with movable portal, figure 2.

Picture 1Sliding Table Milling Machine

Advantages design of the machine with a movable table - this is ease of implementation, greater rigidity of the machine due to the fact that the portal is fixed and fixed to the frame (base) of the machine.

Flaw- large dimensions compared to the design with a movable portal, and the impossibility of processing heavy parts due to the fact that the movable table carries the part. This design is quite suitable for processing wood and plastics, that is, light materials.

figure 2 Milling machine with a movable portal (gantry machine)

Advantages designs of a milling machine with a movable portal:

Rigid table that can withstand the heavy weight of the workpiece,

Unlimited workpiece length,

compactness,

Possibility of execution of the machine without a table (for example, to install a rotary axis).

Disadvantages:

Less structural rigidity.

The need to use more rigid (and expensive) guides (due to the fact that the portal "hangs" on the guides, and is not fixed to the rigid frame of the machine, as in the design with a moving table).

B) Choice of mechanics of CNC milling machine

The mechanics are presented (see the numbers in Fig. 1, Fig. 2 and Fig. 3):

3 - guide holders

4 - linear bearings or sleeves

5 - support bearings (for fastening lead screws)

6 - lead screws

10 - coupling for connecting the shaft of the lead screw with the shaft of stepper motors (SM)

12 - running nut

figure 3

Selection of the linear movement system of the milling machine (guides - linear bearings, lead screw - lead nut).

As guides can be used:

1) roller guides, Figure 4.5

Figure 4

Figure 5

This type of guide has found its way into the designs of amateur lasers and machine tools from the furniture industry, Figure 6

The disadvantage is low load capacity and low resource, since they were not originally intended for use in machines with a large number of movements and high loads, the low strength of the aluminum profile of the guides leads to collapse, Figure 5 and, as a result, unrecoverable backlash, which makes it unsuitable for further use of the machine.

Another version of roller guides, Figure 7, is also not suitable for high loads and therefore is used only in laser machines.

Figure 7

2) round guides, are a steel shaft made of high quality wear-resistant bearing steel with a ground surface, surface hardened and hard chromium plating, shown under the number 2 in figure 2.

This is the optimal solution for amateur designs, because. Cylindrical guides have sufficient rigidity to handle soft materials in small CNC machine sizes at a relatively low cost. Below is a table for selecting the diameter of cylindrical guides, depending on the maximum length and minimum deflection.

Some Chinese manufacturers of cheap machine tools guides of insufficient diameter, which leads to a decrease in accuracy, for example, when used on an aluminum machine at a working length of 400 mm, guides with a diameter of 16 mm will lead to deflection in the center under its own weight by 0.3..0.5 mm (depending on the weight of the portal).

With the right choice of shaft diameter, the design of machines using them is quite strong, the large weight of the shafts gives the structure good stability, overall structural rigidity. On machines larger than a meter, the use of round guides requires a significant increase in diameter to maintain minimum deflection, which makes the use of round guides an unreasonably expensive and heavy solution.

Axis length	Plywood machine	Aluminum woodworking machine	Aluminum machine for aluminum work
200mm	12	12	16	12
300mm	16	16	20	16
400mm	16	20	20	16
600mm	20	25	30	16
900mm	25	30	35	16

3) profile rail guides
Polished shafts on large machines are being replaced by profile guides. The use of a support along the entire length of the guide allows the use of guides of much smaller diameters. But the use of this type of guides imposes high requirements on the rigidity of the machine's supporting frame, since the beds made of sheet duralumin or sheet steel are not rigid in themselves. The small diameter of rail guides requires the use of a thick-walled steel profiled pipe or a structural aluminum profile of a large section in the design of the machine to obtain the necessary rigidity and load-bearing capacity of the machine frame.
The use of a special shape of the profile rail allows for better wear resistance compared to other types of rails.

Figure 8

4) Cylindrical guides on a support
Cylindrical guides on a support are a cheaper analogue of profile guides.
As well as profile ones, they require the use of not sheet materials in the frame of the machine, but professional pipes of large cross section.

Advantages - no deflection and no spring effect. The price is twice as high as that of cylindrical guides. Their use is justified when the travel length is above 500mm.

figure 9 Cylindrical guides on a support

The move can be done as bushings(sliding friction) - fig.10 on the left, and using linear bearings(rolling friction)- rice. 10 right.

figure 10 Bushings and linear bearings

The disadvantage of sliding bushings is the wear of the bushings, leading to the appearance of backlash, and the increased effort to overcome sliding friction, requiring the use of more powerful and expensive stepper motors (SM). Their advantage is low price.

Recently, the price of linear bearings has dropped so much that it is economically viable to choose even in inexpensive hobby designs. The advantage of linear bearings is a lower coefficient of friction compared to sleeves, and, accordingly, most of the power of stepper motors goes to useful movements, and not to combat friction, which makes it possible to use motors of lower power.

To convert rotational motion into translational motion on a CNC machine, it is necessary to use a screw gear ( lead screw ). Due to the rotation of the screw, the nut moves forward. In milling and engraving machines can be used sliding screw gears And helical rolling gears .

The disadvantage of a sliding screw gear is a rather large friction, which limits its use at high speeds and leads to wear on the nut.

Sliding screw gears:

1) metric screw. The advantage of a metric screw is its low price. Disadvantages - low accuracy, small step and low speed. The maximum propeller speed (velocity mm`s per min) based on the maximum speed of the stepper motor (600rpm). The best drivers will keep torque up to 900rpm. With this rotation speed, you can get a linear displacement:

For M8 screw (thread pitch 1.25mm) - no more than 750mm/min,

For M10 screw (thread pitch 1.5mm) - 900mm/min,

For M12 screw (thread pitch 1.75mm) - 1050mm/min,

For M14 screw (thread pitch 2.00mm) - 1200mm/min.

At maximum speed, the motor will have about 30-40% of its originally specified torque, and this mode is used exclusively for idle movements.

When working at such a low feed, increased consumption for cutters, after a few hours of work, carbon deposits form on the cutters.

2) keystone screw. In the twentieth century, occupied a leading position in machine tools for metalworking, before the advent of ball screws. Advantage - high accuracy, large thread pitch, and consequently, high speed of movement. It is necessary to pay attention to the type of processing, the smoother and even the surface of the screw, the longer the service life of the screw-nut transmission. Rolled screws have an advantage over threaded screws. The disadvantages of the trapezoidal screw-nut transmission are a rather high price compared to a metric screw; sliding friction requires the use of stepper motors of sufficiently high power. The most common screws are TR10x2 (diameter 10mm, thread pitch 2mm), TR12x3 (diameter 12mm, thread pitch 3mm) and TR16x4 (diameter 16mm, thread pitch 4mm). In machine tools, the marking of such a gear TR10x2, TR12x3, TR12x4, TR16x4

Rolling screw drives:

Ball screw transmission (SVP). In the Ball Screw, sliding friction is replaced by rolling friction. To achieve this, in a ball screw, the screw and nut are separated by balls that roll in the recesses of the screw threads. Recirculation of the balls is ensured by means of return channels that run parallel to the axis of the screw.

Figure 12

The ball screw provides the ability to work under heavy loads, good running smoothness, significantly increased resource (durability) due to reduced friction and lubrication, increased efficiency (up to 90%) due to less friction. It is capable of operating at high speeds, provides high positioning accuracy, high rigidity and no backlash. That is, machines using ball screws have a much longer resource, but have a higher price. The machines are marked SFU1605, SFU1610, SFU2005, SFU2010, where SFU is a single nut, DFU is a double nut, the first two digits are the screw diameter, the second two are the thread pitch.

lead screw milling machine can be attached as follows:

1) Design with one support bearing. Fastening is carried out on one side of the screw with a nut to the thrust bearing. The second side of the screw is attached to the stepper motor shaft through a rigid coupling. Advantages - simplicity of design, disadvantage - increased load on the stepper motor bearing.

2) Design with two thrust bearings. The design uses two support bearings in the inner sides of the portal. The disadvantage of the design is a more complicated implementation compared to option 1). The advantage is less vibration if the screw is not perfectly even.

3) Design with two support bearings in tension. The design uses two support bearings on the outer sides of the portal. Advantages - the screw is not deformed, unlike the second option. The disadvantage is a more complex implementation of the design, compared with the first and second options.

Lead nuts there are:

Bronze backlash-free. The advantage of such nuts is durability. Disadvantages - difficult to manufacture (as a result - high price) and have a high coefficient of friction in comparison with caprolon nuts.

Caprolon backlash-free. Currently, caprolon has become widespread and is increasingly replacing metal in professional designs. A running nut made of graphite-filled caprolon has a significantly lower coefficient of friction compared to the same bronze.

figure 14 Lead nut made of graphite-filled caprolon

In the ball screw nut (ball screw), sliding friction is replaced by rolling friction. Advantages - low friction, the ability to work at high speeds. The disadvantage is the high price.

Coupling selection

1) connection using a rigid coupling. Advantages: rigid couplings transmit more torque from shaft to shaft, no backlash under heavy loads. Disadvantages: requires precise installation, as this coupling does not compensate for misalignment and misalignment of the shafts.

2) connection using a bellows (split) coupling. The advantage of using a bellows coupling is that its use allows you to compensate for misalignment of the installation of the drive shaft and the axis of the stepper motor up to 0.2 mm and misalignment up to 2.5 degrees, resulting in less load on the stepper motor bearing and a longer stepper motor resource. It also allows you to dampen the resulting vibrations.

3) connection using a cam clutch. Advantages: allows you to dampen the resulting vibrations, transmit more torque from shaft to shaft, in comparison with a split one. Disadvantages: less misalignment compensation, misalignment of the installation of the drive shaft and the axis of the stepper motor up to 0.1 mm and misalignment up to 1.0 degrees.

C) Choice of electronics

Electronics is presented (see fig. 1 and 2):

7 - stepper motor controller

8 - power supply of the stepper motor controller

11 - stepper motors

There are 4-wire, 6-wire and 8-wire stepper motors . All of them can be used. In most modern controllers, the connection is carried out using a four-wire circuit. The rest of the conductors are not used.

When choosing a machine, it is important that the stepper motor has sufficient power to move the working tool without losing steps, that is, without gaps. The larger the screw thread pitch, the more powerful motors will be required. Usually, the greater the current of the motor, the greater its torque (power).

Many motors have 8 outputs for each half winding separately - this allows you to connect a motor with windings connected in series or in parallel. With windings connected in parallel, you will need a driver with twice the current as with series-connected windings, but half the voltage will be enough.

With series, on the contrary - to achieve the rated torque, half the current will be required, but to achieve maximum speed, twice the voltage will be required.

The amount of movement per step is typically 1.8 degrees.

For 1.8, you get 200 steps per full turn. Accordingly, to calculate the number of steps per mm ( "Steps per mm" (Step per mm)) we use the formula: number of steps per revolution / screw pitch. For a screw with a pitch of 2mm, we get: 200/2=100 pitches/mm.

Controller selection

1) DSP controllers. Advantages - the ability to select ports (LPT, USB, Ethernet) and the independence of the STEP and DIR signal frequencies from the operation of the operating system. Disadvantages - high price (from 10,000 rubles).

2) Controllers from Chinese manufacturers for amateur machine tools. Advantages - low price (from 2500 rubles). The disadvantage is the increased requirements for the stability of the operating system, it requires compliance with certain configuration rules, it is preferable to use a dedicated computer, only LPT versions are available.

3) Amateur designs of controllers on discrete elements. The low price of Chinese controllers is crowding out amateur designs.

The most widespread in amateur machine designs are Chinese controllers.

Selecting a power supply

Nema17 motors require at least 150W power supply

Nema23 motors require at least 200W power supply

In a CNC axis drive, a gear is used to convert the rotary motion of a motor shaft into translational motion along an axis. To make it easier for you to choose a CNC gear, the most commonly used gears in CNC machines are listed below. Gears that are exotic to the DIY sector, such as the linear servo motor and the linear stepper motor, will be left out of this article for practical reasons, and the most common ones will be considered.

Transmission screw-nut

A screw-nut transmission means a pair of steel screw with a trapezoidal or metric thread and a nut. This type of transmission is a transmission with sliding friction and in practice, in turn, has several varieties.

Construction stud and nut. The most budget option. The construction stud is not intended for use in machine tool building at all, its manufacturing process is aimed at use in the construction industry, as a result of which this type of transmission has the most complete set of disadvantages - high error, low straightness, low load characteristics, low wear resistance, high friction, etc. . However, it is still used in DIY machines made for educational purposes due to low cost. If you decide at all costs to save on gear and install a construction stud, be sure to consider replacing it with a trapezoidal screw or ball screw! Most likely, the machine on a construction hairpin will not meet your expectations.
Drive screw with trapezoidal or rectangular thread. The trapezoidal threaded screw is the most common type of gear in metalworking machines in the last century and to the present. Trapezoidal screws are produced from various types of structural carbon steels by threading or knurling a steel bar. Rolled screws have significantly better characteristics than threaded ones. The widespread use of trapezoidal screws is due to their wide range, availability on the market of screws of different accuracy classes, from C10 to C3. The screw nut is made of wear-resistant materials such as polyamides (caprolon, nylon), teflon, bronze. Correctly calculated and manufactured trapezoidal gears are characterized by high wear resistance, because friction occurs with low pressure (due to the relatively large friction surface). On many still working Soviet-made machines, pairs have been in place since the machine was released, and have not changed for 30-40 years. It is also possible to use split nuts on such lead screws, which makes it possible to adjust the tightness by compressing the nut and to choose the backlash that appears over time. Of the minuses, it is worth noting, oddly enough, the ease of manufacture of the screw, which automatically means the presence of many manufacturers, with a very wide range of quality indicators. Low cost propellers are made of #45 steel without surface hardening, which can lead to misalignment of the propeller (in other words, small diameter propellers are soft and often bend during shipping). The minuses and pluses at the same time include high friction in the transmission. On the one hand, this reduces the efficiency, a more powerful engine is required to rotate the propeller. On the other hand, friction somewhat dampens the rotational vibrations of the screw, which can be useful when using stepper motors (see resonance of stepper motors). This effect, however, is rather weakly manifested, and other methods are needed to combat the resonance. Summing up, we can say that the trapezoidal screw has not yet lost its significance as a transmission of a CNC machine and is successfully used in machines of all classes.
Ball screw () Ball screw, or ball screw (also called "ball screw"), is currently the de facto standard in the construction of CNC machines. Steel screw with ball races, induction hardened and then ground, and specially fitted nut with internally circulating balls. When the screw rotates, the nuts roll along the treadmills, transferring force to the nut body. Such a transmission is distinguished by high accuracy, high efficiency (80, 90% or more) and resource. The ball screw is more often used in CNC machines, since its use allows the use of lower power motors (there is no need for such significant breakout forces as in the case of a screw-nut transmission). The ball screw is supplied as a complete pair, does not require any adjustment of the nut, and often does not require end processing for installation in supports - this is done by the manufacturer, i.e. Ball screws are often plug and play, whereas in the case of trapezoidal screws, nuts and screws are often made in different places and may require careful fitting, without which gaps, backlash, increased friction, wear, etc. can occur. The ball screw tolerates sawdust, dust and lack of lubrication worse than the screw-nut transmission; if a foreign body even of a very small size enters, the transmission can wedge, because neighboring balls in the channel rotate in the opposite direction. Often additional protection of the propeller with the help of corrugated materials is required. Ball screws, as well as a trapezoidal screw, have length limitations - a too long screw sags under its own weight and when the screw is rotated (the rotation speed of the screw with a pitch of 5 mm in portal machines reaches 10-15 rpm and higher) behaves like a skipping rope, from which the machine vibrates, and the nodes fixing the screw experience shock loads, their resource is rapidly reduced, gaps appear in the seats, which in turn increases the vibration of the machine and reduces the quality of manufactured products. Experience shows that the ratio of the ball screw diameter to its length should not be less than 0.022, and it is also not recommended to exceed the screw length of 2000 mm. To eliminate the "jump rope" effect, designs with a fixed screw and a rotating nut are used, but such units, as a rule, are much more expensive and more difficult to manufacture, and also require space, which is not always possible to implement on compact portals. If you plan to sometimes turn off the drive motors and work on the machine in manual mode, then it is better not to use a ball screw - a transmission without self-braking can give you a lot of trouble. For the types of ball screws and their features, see the main article.

Gear

gears used in CNC machines, there are 2 types

How to choose a gear for a CNC machine

In order to select gear for CNC machine, the choice should be based on those characteristics that are most critical for your machine. Screw-nut gears are used where there are no high requirements for accuracy and speed of movement, if self-braking is required from the gear, as well as in case of severe budget restrictions. The ball screw has the widest range of applications, you can buy a ball screw with the required accuracy class, pitch, the ability to create a preload and without it. The only case when a ball screw cannot be used is if self-braking is required from the transmission, however, if it is a question of braking the transmission for safety purposes (holding the headstock), then the issue is solved by using an electromagnetic brake on the engine, a counterweight, etc. The rack and belt are used in machines with a large working area - from 1.5 square meters and more - primarily to achieve high cutting speed and idle movements. On machines of this size, the goal is not to achieve an accuracy of tens of microns, 0.2-0.3 mm in most cases is more than enough, so the extensibility of the belt and the accuracy of the rack and pinion are not an obstacle to their use.

In total, if you have a large sawing machine, you should choose a rack or belt drive. If you have a desktop router/engraver for study or hobby purposes, a screw-nut gear is the way to go. If you are building a medium format machine for business, production, ball screws are the best choice. After choosing the type, you should decide on the specific transmission parameters.

Copying is allowed with a direct link to the source

On this complex equipment, all kinds of parts are made of metal, plexiglass, acrylic or plastic, wood. Their versatility lies in the fact that they are well suited for cross planing, the formation of the most complex surfaces, in particular, curved ones; carry out selections of the crest, tongue, folds, groove, slots and moldings.

Description of the machine

The standard equipment of the machine includes:

heavy and powerful base;
Desktop;
, with the simultaneous presence of the spindle shaft;
a set of several tools for cutting materials;
front disc brake.

The design of machine tools today includes many important devices that ensure the accuracy of processing and ease of use. It is important to know about them so that the choice of a CNC milling machine is meaningful and correct.

Don't forget the spindle!

One of the important qualities in the operation of the spindle shaft electric motor is the ability to rotate it smoothly and evenly. When assembling, bearings of the highest (accuracy class) are selected, and the collet must have increased tolerances for runout and size.

There are main types of spindle cooling systems:

Liquid (it is based on the circulation of water or antifreeze in a closed circuit). One of the advantages is reliable heat dissipation. Among the disadvantages is a complex design, because the coolant must be placed in the tank.
Air (such cooling consists in forcing air through slots-air intakes in the spindle cavity). Among the advantages of the system - compactness and simplicity. There is also a minus - filters, especially for equipment processing solid wood, must be changed often, they become contaminated with dust.

When choosing a spindle for a CNC machine, you should pay attention to its indicators indicated in the technical data sheet (power and speed during milling), which depend on how hard the materials are processed. For example, for sheet plywood, the required processing power is 800 W; over an array of hardwood, light metals - copper, brass and aluminum, plastic works more powerful machine - 1500 W; and the stone is processed at a power of 3000 - 4000 watts.

Now in equipment for milling, imported spindles are mainly used:

Italian - high quality, running at high speed, with smooth rotation and low runout, mainly air-cooled and high price.
Chinese has a solid cylindrical body, which is closed at the ends with covers, and bearing assemblies are used to hold the shafts. Among the advantages - the design has a sufficient level of rigidity and minimal vibration, insensitivity to the presence of chips and dust, affordability. Unfortunately, Chinese-made spindle models have a high probability of marriage, it can be difficult to replace bearings. And for models that have water cooling, there is a weak anti-corrosion resistance of internal parts.

Types of milling machines

Choosing such equipment, one must proceed from how it fits the purpose. The Russians have a choice:

high-speed CNC automatic machines that cut and cut metals, process parts made of cardboard and wood, cope with two-layer plastic and acrylic, PVC, plexiglass and gypsum, natural stone - granite and marble;
models (milling and engraving) working with sheets (maximum dimension 2000 x 4000 x 200 mm);
engravers (from 2D modeling to 4D);
narrow-profile machines that work with one kind of material - varieties of stone, plywood, wood, stainless steel or aluminum;
small portable CNC models. For example, a milling machine model with "Desktop 3D" is used for milling printed circuit boards, MDF and processes products with extreme precision.

In the line of equipment series for professionals, you can give preference to vertical and horizontal machining centers with program control; large three-, four- and five-axis CNC milling engravers that are made in Taiwan.

They are considered quite reliable and buyable (after Germany and Japan - in third position). In addition, it is profitable to purchase them both for individuals and enterprises, due to the presence in Moscow and Tula of service centers that supply equipment, cutting tools, adjust equipment and train personnel.

ATTENTION: It is not difficult to distinguish a machine from Taiwan: it has a one-piece cast bed (the material of manufacture is Brazilian fine-grained cast iron). In addition, the machine is equipped with American or Japanese bearings, imported spindles.

And if the customer is looking for a high-precision jewelry machine, the best model for this is P 0403 from the manufacturer Vector.

furniture equipment

Woodworking and furniture production, workshops that manufacture windows, doors and facades will not be able to function without equipment of wide functionality - CNC woodworking machines.

In recent years, retro-style furniture has become fashionable - with elegant carved armrests, legs and other details. In this case, the technology of automated cutting of a pattern is used on a milling machine, on which numerical control is installed. It provides high precision and quality when complex wood milling is performed and a carved element is created.

With the help of such equipment, it is possible to establish the production of:

wooden furniture facades and decorative consoles;
balusters, curly legs and slotted elements;
embedded carved details;
symbols, figurines, figurines and frames of various shapes for paintings and mirrors.

Those who are on a budget may buy an inexpensive Chinese standard CNC router - CC-M1, especially for. In the manufacture of facades, engraving decor and bas-relief - usually a lot of dust. Therefore, choose the complete set, where there is a vacuum aspiration for dust absorption. This model has it.

What are the best milling machines? No one will give a definite answer. But there is still more trust in software working equipment. Each master has his own approach to choosing the right technique.

And the CNC router is good, which has higher accuracy, lower power consumption, more convenient to use, reliable in any working situation.

We can formulate three tips for the right choice:

Specify in advance with company managers all the data about the model; materials with which the machine works. If there is a video, watch it. This will help you decide.
Consult prior to purchase regarding the functionality of the equipment and the range of tasks performed. And the best option is to sign up for a demonstration of the CNC machine and do not be shy to ask questions during operation.
When the desired model is selected, be careful at the time of purchase: check the purchased equipment for a complete set of nodes. There must be a program control unit for the machine; cords with connectors of the appropriate configuration, and disks with software. Usually the software is installed by the specialists of the firm selling the machine during its adjustment.

Conclusion

Basically, we tried to help a person facing a choice. We figured out how to choose a milling machine (the thing is expensive, and will work with the owner for more than one year - with metal or wood). At least now there is plenty to choose from. I hope that readers will use this information to purchase a working tool.