A wide variety of ball screws can be used to transmit force and movement. The most widely used ball screw. It provides a linear movement of the actuator, which converts rotation into translational motion. Among the features of this process, extremely low friction can be noted, since it leads to wear of the material and a significant decrease in efficiency, heating of rubbing elements. Let us consider the features of this process in more detail.
Functional purpose and device
As previously noted, a ball screw is used to transmit force and convert rotation into translational motion. The device is characterized by the presence of several elements:
- Stem with helical grooves.
- Nut with suitable thread and size.
The most widely used versions are characterized by a thread with a semicircular profile. Ball screws are quite simple in execution, which determines their reliability and long service life.
Principle of operation
The screw pair is characterized by a rather simple design, which works as follows
- At the moment of rotation of the nut, the balls roll along the created channels.
- The balls are able to translate the nut, pushing it out of the thread. At the same time, there is a bypass channel, due to which the balls return to their original position.
- The movement of the ball occurs along a closed contour, which is located inside the nut.
- The most widespread versions of ball screw gears, in which the return channel connects two adjacent turns.
There are a variety of different versions of the design under consideration. They are selected depending on the operating conditions and purpose. An example is that in the machine tool industry a ball screw with a three-loop nut is used. For this, a special insert is created, for which an oval-shaped window is created. To reduce friction and increase the efficiency index, three liners are used at once, placed at an angle of 120 degrees relative to each other.
High-speed or high-speed ball screws
Modern machines and other equipment are characterized by high productivity and versatility in use. As a rule, the force is generated by a motor that rotates. In order to convert rotation into reciprocating motion, a screw gear is used. Conventional screw and nut combinations are less efficient than new high speed designs.
The high-speed ball screw is characterized by the following features:
- In the manufacture of used material, which is characterized by high wear resistance. Excessive wear results in loss of accuracy.
- A special ball screw drive ensures fast movement of the nut.
Most often, high-speed ball screws are installed on CNC machines. Due to their use, the rapid movement of the executive bodies is ensured.
Classification
In the manufacture of a ball screw, most various technologies. Depending on their characteristics, they distinguish the following types designs:
- Rolled are obtained by applying the cold rolling method. As a rule, such technology is characterized by lower costs in its application. Due to this, the price-quality ratio is as high as possible, the accuracy of the resulting products is low.
- Ground - precision products that are ground after threading and hardening. This ensures a high degree of smoothness. Most products from this group are characterized by increased accuracy. However, the hardening and grinding process determines a significant increase in the cost of the product.
- You can also classify according to design features:
- Standard Ball Screws are manufactured according to DIN standards.
- Precision is obtained by applying grinding technology. The design may consist of one or two nuts that are pre-tensioned.
- There are versions obtained by grinding, with a cage. Such a design is characterized by the presence of a structure, due to which the return of the balls to the initial position is ensured.
- The rotating nut ball screw has a built-in bearing that ensures precise movement of the moving element.
- This category also includes a splined shaft with ball-type bushings. This ball screw design is compact and easy to install.
- Console type. Used when a compact transmission is required.
Such a classification is taken into account when choosing the required design.
When choosing a ball screw, its main characteristics are taken into account. As a rule, they are the following:
- The length of the rod. Characteristics Ball screws for CNC equipment are characterized by a maximum length of about 2 meters. This is due to the fact that a product that is too long can be deformed under a point impact.
- Linear high-speed movement is the main indicator that should be taken into account.
- The diameter and pitch of the screw can also be called important indicators. They determine what kind of load can be.
- The accuracy of the product, which varies from C1 to C10.
You can also find tabular information that is used to determine the main characteristics.
Transmission setting
The choice of ball screws can be carried out in the process of analysis of the structure and preliminary design. Before installing the screw-and-rack ball gear, the following calculation is carried out:
- Table strokes.
- The required force that must be on the screw.
- The most suitable screw length is selected.
- Accuracy determines whether it is necessary to carry out the installation of a ball screw obtained by grinding or cold rolling.
- The design features of the nut are determined: the return of the balls to their original position, whether a bearing is needed, what the nut should be. An example is that the single nut design is much cheaper, but the double nut design is more wear resistant.
- It is specified whether the free end should be securely fixed.
- Determines how the ball screw connects to the housing.
Once a suitable version of the ball screw has been selected, it is installed. Fastening can be carried out using screws and rivets or by welding.
Application area
The main characteristics determine the wide distribution of ball screws. An example is the various components of cars and machine tools. A more illustrative application of ball screws can be called the following cases:
- Production of a CNC machine tool drive. Modern versions have several linear drives. An example is the case when the Tornos machine has 14 controlled axes.
- KAMAZ and some other automakers use a similar rack in the manufacture of the steering gear. This simplifies the process of changing the position of heavy wheels that are burdened with dirt.
- In the production of printers and other printing equipment, a similar rail is installed.
As previously noted, the engine is installed as the main source of effort. Rotation is converted by the rack into reciprocating motion, which is very common.
Advantages of ball screws over other types of gears
There are quite a few advantages to the CVD. Such a design is characterized by the following advantages:
- Low coefficient of friction, which is achieved through the use of balls.
- Higher efficiency value. If we compare other analogues that can transmit translational motion, then they are significantly inferior. For many versions of the ball screw, the efficiency index is at the level of 90%.
- There is no sliding due to the use of grooves with balls. This also significantly increases the service life.
- Ease of maintenance and repair. If necessary, you can quickly add oil to the area of the screw stroke. The lubricant is evenly distributed over the surface, thereby increasing the service life.
- High travel speed, which can be achieved through the use of special versions of the ball screw.
- Reduced drive requirement in terms of power. This is due to the low resistance of the screw.
However, there are several significant drawbacks that must be considered when choosing a drive. An example is the high probability of backswing when the screw is installed at a large angle or vertically. This disadvantage is due to the fact that friction is minimal.
The ball screw in question is not recommended for use when creating manual feeds. In addition, the high cost of the product can be called a negative factor, since it consists of several precise elements. To ensure a low degree of wear, the surface is hardened, which also increases the cost of the product.
A ball screw drive (BSC) consists of a screw and a nut and is used to convert rotational motion into translational motion. In ball screws on screw 1 and nut 2, helical grooves (thread) of a curved profile are made, which serve as raceways for balls placed between the turns of the screw and nut. The most widely used thread with a semicircular profile. In this case, the rotation of the nut fixed from axial movements causes the translational movement of the screw, or the rotation of the screw fixed from axial movements leads to the translational movement of the nut.
The main geometric parameters of the transmission: nominal diameter d 0, i.e. the diameter of the location of the centers of the rolling elements, the thread pitch P and the diameter D w of the rolling elements (usually D w \u003d 0.6P).
Advantages of a ball screw: the ability to create large axial forces; low friction losses (transmission efficiency 0.9 and higher); the possibility of obtaining translational movement with high accuracy; small dimensions with high bearing capacity; significant resource.
The disadvantages include the complexity of the design of the nut, the need for high manufacturing accuracy and good protection of the transmission from contamination. Ball screw transmissions are used in precise movement mechanisms, in servo systems and in critical power transmissions (machine tool building, robotics, aviation and space technology, nuclear energy, forging and pressing equipment, etc.).
DEVICE AND PRINCIPLES OF WORK
When the screw rotates, the balls are entrained in movement along the helical grooves, progressively move the nut and. rolling out of the thread, through the bypass channel (return channel) they return to their original position. Thus, the movement of the balls occurs along a contour closed inside the nut. The most common design of the ball screw. in which the return channel connects two adjacent turns.
In the machine tool industry, three-circuit nuts are used. The bypass channel is made in a special insert, which is inserted into the oval window of the nut. In a three-loop nut, three inserts are provided, located at an angle of 120° to one another and offset along the length of the nut by one thread pitch relative to each other. Thus, the balls in the nut are divided into three (according to the number of working turns) independent groups.
During operation of the transmission, the balls, having passed along the helical groove on the screw, a path equal to the length of one or more turns, roll out of the thread into the bypass channel of the liner and return back to their original position on the original turn of the nut.
THREAD PROFILE
The main parameters of a semicircular thread profile (Fig. 1. a):
R = (0.515...0.525) Dw- groove radius;
α = 45°- ball contact angle;
ψ = arctan- thread lead angle (here z is the number of thread starts).
On fig. 1. b shows in normal section the thread profile of a screw with a relief groove, and in table. 1 shows the dimensions of the relief grooves according to OST 2 RZ1-5-89.
1. Dimensions of relief grooves, mm
| Nominal diameter d 0 | Pitch P | b | r | Nominal diameter d 0 | Pitch P | b | r |
| 16 25 25 32 32 40 40 40 50 |
2,5 5,0 10,0 5,0 10,0 5,0 6,0 10,0 5,0 |
- 1,0 1,5 1,0 1,5 1,0 1,0 1,5 1,0 |
- 0,55 0,85 0,55 0,85 0,55 0,55 0,85 0,55 |
50 50 63 80 80 100 100 125 |
10,0 12,0 10,0 10,0 20,0 10,0 20,0 20,0 |
1,5 1,8 1,5 1,5 3,0 1,5 3,0 3,0 |
0,85 0,95 0,85 0,85 1,60 0,85 1,6 1,6 |
Ball screw with preload
In order to eliminate the axial clearance in the screw-nut interface and thereby increase the axial rigidity and accuracy of movement of the driven element, the ball screws are assembled with a preload.
For a gear with a semicircular thread profile, the interference is created by installing two nuts, followed by their relative axial displacement. The relative displacement of the nuts is carried out by installing gaskets between them or by their relative angular rotation.
The thread profile and nut design (ball return channel, preload control, etc.) are determined by the manufacturer.
Ball screws are used in a wide range of sizes.
BALL SCREW DIMENSIONS
according to GOST 25329-82
| nominal diameter, d o , mm |
Nominal step Р, mm | |||||||||
| 2,5* | 3 | 4 | 5* | 6 | 8 | 10* | 12 | 16 | 20* | |
| 6 | + | |||||||||
| 8 | + | |||||||||
| 10 | + | |||||||||
| 12 | + | + | + | + | ||||||
| 16 | + | + | + | + | + | |||||
| 20 | + | + | + | + | + | |||||
| 25 | + | + | + | + | + | |||||
| 32 | + | + | + | + | + | + | ||||
| 40 | + | + | + | + | + | |||||
| 50 | + | + | + | + | + | + | ||||
| 63 | + | + | + | + | + | + | + | |||
| 80 | + | + | + | + | + | + | ||||
| 100 | + | + | + | + | + | |||||
| 125 | + | + | + | + | ||||||
| 160 | + | + | + | + | ||||||
| 200 | + | + | + | + | ||||||
| * Preferred Steps | ||||||||||
TECHNICAL CONDITIONS
Specifications for ball screws used in the machine tool industry have been established GOST 2 RZ1-5-89. This standard applies to ball screws used to complete metal and woodworking machines, industrial robots, forging and pressing equipment.
The standard establishes the main dimensions, basic parameters, completeness, marking, procedure and composition of acceptance tests, packaging, conditions of transportation and storage, operating instructions and manufacturer's warranties for centrally manufactured ball screws.
The standard takes into account the requirements ISO/DP 8931, ISO/DP 8932, ISO/DP 3408, ISO/DP 9783, ISO/DP 9784.
Body gears produced in 4 versions:
I - ball screw with one or two nuts without body;
II - ball screw with two nuts in a cylindrical body with a flange;
III - ball screw with two nuts in a prismatic housing with through mounting holes;
IV - Ball screw with two nuts in a prismatic housing with blind threaded mounting holes.
The use of ball screws version III is not preferred.
According to the accuracy parameters, ball screws are divided into positional and transport ( OST 2 RZ1-7-88). Positional ball screws allow indirect measurement of axial movement depending on the angle of rotation and the lead of the screw thread. In transport ball screws, displacements are measured by a direct method using a separate measuring system that does not depend on the angle of rotation of the screw.
Classes of kinematic and geometric accuracy of ball screws must comply with OST 2 RZ 1-4-88. According to this standard, accuracy classes are established for positional (P) and transport (T) ball screws, respectively: P1, P3, P5, P7 and T1, T3, T5, T7, T9, T10.
Intrafactory acceptance standards for kinematic accuracy must comply with GOST 2 R31-5-89.
According to OST 2 RZ1-5-89 the quality of materials, processing and assembly of ball screws must comply with GOST 7599-82, and for export deliveries - OST 2 N06-1-86.
LOAD CAPACITY
When designing, in accordance with the main criteria for the performance of ball screws, the calculation is carried out according to the dynamic load capacity to prevent fatigue failure (chipping of working surfaces) and according to the static load capacity to prevent plastic deformation of rolling bodies and surfaces.
When choosing the values of dynamic C a and static C oa load capacities, as well as the minimum and maximum values of the moment T xx of the idle speed of the ball screw, you can focus on the data in Table 2.
Basic static axial load capacity C oa - static axial force (N), which causes a total permanent plastic deformation of the ball, screw grooves and nut, equal to 0.0001 of the ball diameter.
2. Basic lifting characteristics of ball screws
| Size d 0 x Р, mm | load capacity, H | idle moment T xx , N m |
||
| static C oa | dynamic SA | min | max | |
| 16x2.5 25x5 25x10 32x5 32x10 40x5 40x6 40x10 50x5 50x10 50x12 63x10 80x10 80x20 100x10 100x20 125x20 |
9600 28100 48800 37500 65000 49400 56400 85900 62800 112500 119900 149700 197700 297600 251100 386400 729000 | 5000 16580 46400 17710 49800 19170 23700 54700 20640 57750 65400 62030 66880 143400 71840 151800 278000 |
0,05 0,08 0,11 0,18 0,22 0,30 0,32 0,45 0,50 0,48 0,49 0,75 1,23 2,30 2,04 2,75 2,80 |
0,20 0,32 0,35 0,56 0,60 0,84 0,83 0,95 1,35 1,23 1,09 2,03 3,25 3,88 5,20 5,23 5,50 |
Note. The given values for housing ball screws correspond to executions II, III and IV.
Basic dynamic axial load rating C a is the axial force that the Ball Screw can take with a basic life of 1,000,000 screw revolutions.
Basic load capacities correspond to a gear made of commonly used steels (see Table 3). If the properties of the material differ from the usual ones, and also depending on the accuracy class, the hardness of the working surfaces, etc., the value of the corrected static and corrected dynamic load capacity is calculated.
TECHNICAL REQUIREMENTS
Technical requirements on the main parts of ball screws used in machine tool industry, installed OST 2 RZ1-5-89(Table 3). Screw accuracy standards - according to OST 2 RZ1-4-88.
3. Technical requirements for the main parts of the ball screw
Notes:
1. Heat treatment according to RTM2 MT11-1-31.
2. For balls, the degree of accuracy is 20 according to GOST 3722-81.
3. The difference in size of balls in one gear is not more than 0.001 mm.
4. Deviation of the average diameter of the balls at D u
Screws are also made from steel grades CVH and 7G2VM with bulk hardening, steel grade 8XV hardened with induction heating, steel grade 20Х3IMF with nitriding.
For nuts, steel grades are used CVH volume-hardened and case-hardened steel grades 18HGT, 12HN3A, 12H2H4A.
Balls are made from chromium steel SHH20SG.
The materials of the screw, nut and rolling elements must ensure the hardness of the working surfaces is not lower than 61 HRC e.
During assembly, the cavity of the nut is filled with grease grade CIATIM-201 or CIATIM-203.
Gears require good protection against contamination. The most commonly used are harmonic-shaped bellows, telescopic casings and dirt removers - plastic sealing nuts with two or three convex turns along the groove profile. Dirt removers are attached to each end of the main nut.
The nomenclature of quality indicators used in assessing the quality level of ball screws used in metal and woodworking machines, sections, lines, complexes, industrial robots and forging and pressing equipment, installed OST 2 RZ1-6-87.
Related Documents:
GOST 3722-81: Rolling bearings. Balloons. Specifications;
calculation of lead screws;
calculation of cargo propellers;
lead screw drawing example
Since there were many questions after the first publication, I will post information step by step for self-assembly of the CNC router
To start basic elements- bearing supports for ball screws type BK12 and BF12
They are required to install the lead screw of the ball screw for each axis of the machine.
Appearance, characteristics, drawings under the cut
So, I gradually receive ordered components for self-assembly of a CNC milling machine.
Just recently received a package with mechanics and chassis.
The running gear for the planned design of the router is. For its fastening, special bearing assemblies are required - these are BK12 and BF12 supports
As a matter of fact, the screw is installed with both ends in the supports, at one end the support rigidly fixes the screw (longitudinally and radially) and provides connection to the engine through the coupling, and on the other hand, the support is “floating”, which fixes the screw only radially and allows it to be “pulled” .
The photo shows a pair of such supports required to install one ball screw 
I’ll say right away: block support with fixed end and engine side installation is BK12
Second block support with " floating"the end is BF12
Usually sold in sets.
Additional information - types of running gear and types of supports
As for the SFU1605 ball screw, there are different kinds supports: in the form of a support block, flange, etc. 
That is, for flange installation, FF12 (floating end) and FK12 (fixed end) supports are used.
So, support type BK12 is designed for rigid fixation of the ball screw 1605 (and 1610). The support has two 6001ZZ radial bearings. The kit comes with a special lock nut for preloading the screw with M12x1.0 thread.
Support type BF 12 is designed to support the second end of the ball screw, fixation is provided only by a retaining ring.
That is, the BF12 bearing block is a "floating" support block. The floating bearing has a 6000ZZ radial bearing.
External view of a pair of supports 
Got everything in one big package 
Inside there were several different sets of BF12 / BK12 / FK12 / FF12 - I took a lot of things, for several axles 
Here is the appearance of the packaging of one of the support kits 
Inside a pair of supports, in bags, in oil. Plus fittings - locking ring, nut. In my kit there was also an elastic coupling for connecting the motor shaft. Coupling size 6.35x10mm 
The kit includes:
1 x support type VK12
1 x support type BF12
1 x mufra 6x10
1 x nut
1 x circlip
So, I got everything, unpacked 
Weighing and checking dimensions
The mass of the parts of the kit, for an approximate estimate 
Coupling for connecting the engine. On the motor side, the diameter is 6 mm (for NEMA23), on the ball screw side, the diameter is 10 mm. Naturally, after installation, the coupling is tightened with hexagon screws 
The length of the coupling is 3 cm, keep this in mind when designing the working stroke of the axle. 
Support BK12 (fixing). Screw diameter 12mm, nut thread M12x1.0mm. The distance between the mounting holes is 46mm, that is, I need to drill holes in the profile of the 30th series 
Support BF12 (floating). The diameter is already 10 mm. The screw is fixed with a retaining ring from the kit. 
Now some photos of supports.
Support BK12 (fixing). Two bushings (of different sizes) can be removed, they are freely inserted into the bearings on both sides, plus a separate fixing nut M12. 
With reverse side there is an oil seal with a mounting plate 
Inside is a pair of 6001 radial bearings (28mm x 12mm x 8mm) 
The photo shows the marking 6001RS 
Here is a photo of the support with the oil seal and plate removed 
Support BF12 (floating).
Inside there is one radial 6000zz bearing (26mm x 10mm x 8mm) 
Mounting hole spacing similar to 46 mm 
The end of the screw is fixed with a retaining ring. 
Now a little about the assembly.
For starters, the "floating" BF12. Initially, the presence of oil seals was assumed, but the Chinese are more cunning than any GOSTs 
Support BF12 is installed on the frame of the machine, fastened. then the end of the screw is threaded into it (where the diameter is 10 mm). 
The screw is secured with a retaining ring 
Further assembly BK12 
Assembly with seals is also assumed. In fact, we have only one omentum. 
Do not forget to screw the nut onto the screw, with the body immediately. Next, we put the support, wind the lock nut. We install the support on the frame of the machine. Fasten, fix the nut. This nut can pre-tighten the screw. 
Do not forget to fasten the clutch, which will then drive the screw from the engine 
So, here is my ball screw assembly with supports 
Now about the application.
From sets of supports BK12 / BF12, axes are assembled to move the desktop, the portal and the tool of the CNC milling machine.
As a matter of fact, here is a drawing of the placement of axes for a small router 
X axis close-up. Removed excess from the drawing. You can clearly see the screw SFU1605, and two supports BK12 and BF12 
Appearance of the future milling cutter. Three ball screws are used, profile type 6060. 
I'll finalize the drawings and post them to the public.
Overview of a specific product: a set of ball screws type SFU1605-1000 as elements of CNC machine gears.
The review will provide brief information about what a ball screw is and how to use it.
As a matter of fact, when trying to calculate and build an amateur CNC machine (milling cutter), I ran into the fact that we either have expensive components for machine tools, or not quite what we need. Specifically, there was a problem with the acquisition of a lead screw or ball screw as transmission elements along the axes of the machine. 
The following types of CNC gears are available:
- belt are used together with gears mainly for lasers, since the laser has a light “head”
- jagged. These are spur or helical gear racks and gears for moving along them.
- lead screws there are type T8 (mainly used in 3D printers and other small-sized machines), type TRR, for example TRR12-3 with a POM nut (plastic).
- ball screws- this is a screw and a nut to it. The nut has special bearings that move through a channel inside the nut.
As a rule, they are chosen taking into account the load (mass of the portal / axis being moved) and the effect of backlash. In ball screws, the backlash is less due to bearings, they are considered more accurate and preferable, but at the same time quite expensive for homemade products.
Quote from
Screw gear - a mechanical transmission that converts rotational motion into translational, or vice versa. In general, it consists of a screw and a nut....one of the main types: ball screw rolling (ball screw).
Ball screw(hereinafter referred to as the ball screw) is a more reliable analogue of the lead screw, but instead of a brass nut (or a plastic nut like for screws like TRR-12-3, like I have on an old project), a special nut with balls is used that engages with the ball screw, take out all the play and at the same time reduce friction. For self-assembly of a CNC machine or a 3D printer on a ball screw, you will need a ball screw screw, a nut to it, a coupling to the engine and outboard bearings.
Here is a small render from the internet. You can clearly see how the balls are distributed over the screw. Similar to T8, the ball screw has a thread in several passes. 
For the CNC machine, two sets of 1000 mm ball screws were needed for the Y axis, and 600 mm for the X axis.
ShVP received by courier mail. This is not an expensive option, given the weight of the package (about 8 kg). 
The packaging is a long narrow box, inside carton packaging there is a synthetic bag type packaging, a very durable material. Unpack carefully. Inside is the familiar bubble-wrap, that is, a pimply film that protects the product from mechanical stress. 
We remove the film. There were three sets of ball screws in the package: screw + nut, of different sizes. Two sets are for moving the machine gantry along the Y axis, the third short set is for the X axis. 
All kits are wrapped in an inhibitory green film that prevents moisture from entering. Plus there is a fair amount of lubricant on the surface of the product. 
In this set, I paid extra for the end of one set by 600 mm (it turned out cheaper). I ordered the ending (machined) separately from the same seller (he has such a service in the catalog), it cost 1 bucks for each end of the screw. A good option for those who take screws in a specific size. 
That's what "ending" is. This is turning a 16.05 mm screw to a diameter of 12 mm for installation in an outboard bearing, then a threaded part to fix the screw, then turning to 10 mm to clamp the end into an elastic coupling of the engine 
The parcel arrived safe and sound Express delivery This is not Russian Post. I applied a ruler in different places to find the curvature. I didn’t find it, the ball screws are even. The rest will show the installation and use. 
Photo of the threaded part of the screws 
Appearance of the kits 
And further. The nuts came already screwed onto the screw ... The balls are covered inside, there is grease. Ask for spare balls when ordering, at least a few. 
Next, we begin to check the size of the screws. Short at 600 mm. That is, these 600 include a threaded part on both sides. The actual travel along the axes of the machine will be less.
note that in the lot the size is indicated for the ball screw screw together with the thread and turned ends, that is, the working stroke along the ball screw will be less than its length! Specifically, 65 mm less. 
Second and third ball screws 1000 mm 
Thread diameters respectively 1605 
seats for bearings 10 and 12 mm, respectively. 
And on the other hand under the bearing. The diameter of the SFU1605 nut itself is 28 mm. 
If you remove the plastic plug from the nut, you can service the ball screw, lubricate or change the balls. I make sure everything is in stock. 
In fact, you can remove the nut, wipe it, re-lubricate it, load the balls back. The plastic cover is fastened with a countersunk screw for a hexagon 2.5 (it can be seen at the top). 
To install the ball screw in the machine, you will need outboard bearings of the BK12 + BF12 (straight) or FK12 + FF12 (flange) type, an elastic coupling 6.35 * 10mm for connecting to a NEMA23 type motor on one side (6.35mm) and to the end of the ball screw on the other (10 mm) ).
Appearance of the complete axle set: bearings BK12, BF12, retaining ring, nut for fixing the screw, nut holder SFU1605, coupling for the motor and the screw itself with the nut. 
Ball screw dimensions for those who are going to purchase or design machine mechanics 
And separately for SFU1605 
Nut SFU1605 appearance 
Appearance of bearings (left) and flanged bearings (right). They differ in the way they are mounted on the frame. 
The ball screw nut is fastened through a special adapter housing. , aluminum 
To mount on one axis (I have two per axis for Y) you will need:
- 1 x screw SFU1605-1000mm;
- 1 x BK12 bearing;
- 1 x BF12 bearing;
- 1 x motor coupling 6.35x10mm
- 1 x circlip
- 1 x nut.
Through the holes on the bearing we attach to the profile / frame of the machine. For FK12/FF12 bearings, everything is the same, only they must be fastened with a flange to the hole for the ball screw. The meaning does not change.
Now a little video explaining the principle of operation of the ball screw. Pay attention to the movement of the balls (along the built-in channel inside the nut).
And this is how the thread rolling on the ball screw screws takes place
Machining the ends of the ball screw (what I called "machined"). We are asked for 600 .... 1000 rubles for such an operation, in China $ 1.
The following photographs give an overview of the use of ball screws in the design of a CNC machine. 
Here is a photo of a home-made machine in which the ball screw is fixed motionless, and the nut rotates using a belt drive and gear 
As a result, the ball screw is a more expensive and reliable gear option for machine tools, suitable for moving heavy portals with high accuracy. Depending on the weight and design of the machine, the SFU1205, SFU1605/1610, SFU2005/2010 or the even more massive SFU2505/2510 can be used.
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To create machine tools with program numerical control, it is necessary to use ball screws. They differ not only appearance but also by design. To select a specific model, you should familiarize yourself with the structure and components of the ball screw in advance.
Purpose of ball screws
All types of ball screws for CNC machines are designed to convert rotational motion into translational. Structurally, they consist of a body and a lead screw. They differ from each other in size and technical characteristics.
The main requirement is to minimize friction during operation. To do this, the surface of the components undergoes a thorough grinding process. As a result, during the movement of the lead screw, there are no sharp jumps in its position relative to the housing with bearings.
Additionally, to achieve a smooth ride, not sliding friction relative to the pin and body is used, but rolling. To obtain this effect, the principle of ball bearings is applied. Such a scheme increases the overload characteristics of ball screws for CNC machines, and significantly increases efficiency.
Main Components of a Ball Screw:
- lead screw. Designed to convert rotational motion into translational. A thread is formed on its surface, the main characteristic is its pitch;
- frame. During the movement of the lead screw, displacement occurs. Various components of the machine can be installed on the body: cutters, drills, etc.;
- balls and inserts. Necessary for smooth running of the body relative to the axis of the lead screw.
Despite all the advantages of this design, ball screws for CNC are used only for medium and small machines. This is due to the possibility of screw deflection when the housing is located in its middle part. In on standing tense the maximum allowed length is 1.5 m.
The screw-nut transmission has similar properties. However, this scheme is characterized by rapid wear of components due to their constant friction with each other.
Ball screw applications
The relative simplicity of design and the possibility of manufacturing a ball screw with different characteristics expands its scope. Nowadays, ball screws are an integral part of homemade CNC milling machines. Well, the scope is not limited to this.
Due to their versatility, ball screws can be installed not only in CNC machines. Smooth running and practically zero friction make them indispensable components in precision measuring instruments, medical devices, and mechanical engineering. Often for picking homemade equipment take spare parts from these devices.
This is made possible by the following properties:
- minimization of friction losses;
- high coefficient of load capacity with small dimensions of the structure;
- low inertia. The movement of the body occurs simultaneously with the rotation of the screw;
- No noise and smooth running.
However, the disadvantages of ball screws for CNC equipment should also be taken into account. First of all, they include a complex hull design. Even if one of the components is slightly damaged, the ball screw will not be able to perform its functions. There are also restrictions on the speed of rotation of the screw. Exceeding this setting may cause vibration.
To reduce the axial clearance, the assembly is carried out with an interference fit. To do this, balls of increased diameter or two nuts with axial displacement can be installed.
Characteristics of ball screws for CNC equipment
To select the optimal model of ball screw for machine tools with numerical control, you should familiarize yourself with the technical specifications. In the future, they will affect the performance of the equipment and the time of its non-repair operation.
The main parameter of a ball screw for CNC machines is the accuracy class. It determines the degree of error in the position of the mobile system according to the calculated characteristics. The accuracy class can be from C0 to C10. The displacement error must be given by the manufacturer, indicated in the technical data sheet of the product.
| Accuracy class | C0 | C1 | C2 | C3 | C5 | C7 | C10 |
| Accuracy at 300 µm | 3,5 | 5 | 7 | 8 | 18 | 50 | 120 |
| Error per screw turn | 2,5 | 4 | 5 | 6 | 8 |
In addition, when choosing, you need to consider the following parameters:
- the ratio of the maximum and required motor speed;
- total length of lead screw thread;
- average load indicators for the entire structure;
- value of axial load - preload;
- geometric dimensions - the diameter of the screw and nut;
- motor parameters - torque, power and other characteristics.
These data must be pre-calculated. It should be remembered that the actual characteristics of ball screws for CNC equipment cannot differ from the calculated ones. Otherwise, it will cause the machine to work incorrectly.
The number of revolutions of the balls in one circle will determine the degree of torque transfer from the shaft to the body. This parameter depends on the diameter of the balls, their number and the cross section of the shaft.
Installing a ball screw on a CNC machine
After choosing the optimal model, it is necessary to think over the installation scheme of the ball screw on the CNC machine. To do this, a design drawing is preliminarily drawn up, other components are purchased or manufactured.
During the execution of the work, it is necessary to take into account not only specifications ball screw. Its main purpose is the movement of machine elements along a certain axis. Therefore, you should think in advance about the fastening of the processing unit to the body of the ball screw for CNC machines. It is necessary to check the dimensions of the mounting holes, their location on the body. It should be remembered that any mechanical processing of the ball screw may lead to negative changes in its characteristics.
The order of installation in the body of the CNC machine.
- Determination of optimal technical characteristics.
- Shaft length measurement.
- Creation of a scheme for pairing the mounting part of the shaft with the motor rotor.
- Installing the gear on the machine body.
- Checking node health.
- Connection of all main components.
After that, you can perform the first test run of the equipment. In the course of work there should be no oscillations and vibrations. If they appear, perform an additional calibration of the components.
If the ball screw breaks down during the operation of the CNC machine, the gear repair can be done independently. To do this, you can order a special kit. You can get acquainted with the features of the restoration work in the video:
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