Zaxis sells lead screws and nuts with trapezoidal threads. The catalog contains parts of the most popular standard sizes. Lead screws are supplied in 1 meter long rods. At the customer's request, Zaxis employees will trim to size and machine a journal of the required diameter for coupling connection. Finished parts have chamfers, roundings, fillets, and no burrs. In your application, please indicate surface roughness and tolerance ranges for diametrical and linear dimensions.
Trapezoidal screws
The trapezoidal profile on screws is used more often than others due to the optimal combination of self-braking and driving performance. Conventional threads are not capable of transmitting as high forces as persistent threads, but their strength properties are sufficient to carry out working movements. We sell lead screws made from structural carbon and of stainless steel. The products are wear-resistant and have a high service life. The blank for the lead screws is a calibrated rod with heat treatment. The thread profile is formed by rolling, and its working surfaces are highly clean. The catalog contains lead screws with diameters of 8, 10, 12, 16, 20 and 28 mm with pitches of 2, 3, 4, 5. On the website you will find prices and technical descriptions for parts of all standard sizes.
Nuts
Zaxis sells nuts that are compatible with all types of acme screws. The catalog contains parts made from the following materials:
- become. The most cost-effective solution for non-critical nodes;
- bronze. In combination with steel lead screws they form pairs with a friction coefficient of 0.07-0.1;
- caprolon. The material is 6 times lighter than bronze and increases the working life of the lead screw by 2 times. When lubricated with water, the coefficient of friction in the pair is 0.005-0.02. The nuts are made with guaranteed tightness, which ensures high positioning accuracy.
Parts are manufactured with cylindrical outer surface and with flange. You can order lead screws on the Zaxis website or by phone.
The lead screw is important detail, which is used as a motion transducer. It changes rotational motion into linear motion. For this purpose it is equipped with a special nut. In addition, it provides movement with a given accuracy.
Screw quality indicators
The screw, as a very important part, must meet many requirements. So that it can be used, for example, in bench vise, it must be suitable for such parameters as: diametrical size, profile accuracy and thread pitch accuracy, the ratio of the screw thread to its support journals, wear resistance, thread thickness. It is also important to note that, depending on the degree of movement accuracy that the screws provide, they can be divided into several accuracy classes from 0 to 4. For example, lead screws of metal-cutting machines must correspond to an accuracy class from 0 to 3. Accuracy class 4 is not suitable for use in such equipment.
Lead screw blank material
As a blank for the production of a screw, an ordinary rod is used, which is cut from the grade metal. However, it is important to note here that there are some requirements for the material that serves as the workpiece. The metal must have good wear resistance, good machinability, and also have a state of stable equilibrium under the conditions of internal stress that occurs after processing. This is very important because this property will help to avoid deformation of the lead screw during its further use.
To produce this part with an average accuracy class (2nd or 3rd), which will not be subject to requirements for increased temperature resistance, A40G steel is used, which is medium carbon, with the addition of sulfur and steel 45 with the addition of lead. This alloy improves the machinability of the screw and also reduces the surface roughness of the material.
Profile of the screw
There are three screw profiles that are used in the production of a lathe or any other lead screw. The profile can be trapezoidal, rectangular or triangular. The most common type is trapezoidal thread. Its advantages include the fact that it is higher in accuracy than rectangular. In addition, using a split nut, you can adjust the axial clearances with a trapezoidal screw, which arise due to equipment wear.
It is also important to note here that cutting, as well as grinding, trapezoidal screw threads is much simpler than rectangular ones. But you need to understand that the accuracy characteristics of rectangular threads are higher than those of trapezoidal threads. This means that if the task is to create a screw with the best adjustment for accuracy, you will still have to cut a rectangular thread. Trapezoidal screws are not suitable for very precise operations.
Screw processing
The main parts on which the screw in the machine is based are the support journals and shoulders. The working surface of a screw is its thread. The greatest accuracy in a table vise and any other machines that have such a screw must be ensured between the working surface of the part, as well as the main basing surface. The technological basis for the production of the lead screw is considered to be it. For this reason, in order to avoid deformation, the processing of all these surfaces is carried out using the Application of this part determines the specifics of the processing of the lead screw.
It is also important to note here that the screw with different class accuracy, processed to various values. Parts that will belong to 0,1 and 2 accuracy classes are processed up to the 5th quality. Screws belonging to the 3rd accuracy class are processed up to the 6th quality. Screws belonging to the 4th category are also processed up to the 6th quality, but at the same time they have a tolerance range for the outer diameter.
Centering and threading
In order to obtain an acceptable quality screw, it is necessary to carry out several more operations. One of them was the alignment of the part, which runs on lathe. The lead screw, or rather, the workpiece for this part, is centered on the specified equipment and its ends are cut here. In addition, the workpiece is polished. For this purpose, centerless or cylindrical grinding machines are used at centers. It is important to add here that grinding in the centers is carried out only for screws of 0.1 and 2 accuracy classes.
Next, before you start cutting the thread, the workpiece must be straightened. It should be noted here that only screws with 3rd and 4th accuracy classes are subjected to this operation. After this, their surface is additionally polished. A screw-cutting lathe is used as equipment for cutting threads on the lead screw.
Description of screw nut
The lead screw nut is designed to provide precise installation movements. In some rare cases, they may be made from a material such as anti-friction cast iron. This element must ensure constant engagement with the turns of the screw, and also act as a compensating part. You will have to compensate for the gap that will inevitably arise when the screw wears out. For example, nuts for lead screws used in lathes are made in double nuts. This is necessary in order to eliminate the gap that may arise either as a result of the production and assembly of the machine, or as a result of wear of its parts.
The peculiarity of a double-type screw with a nut is that it has a fixed and a movable part. The moving part, which is on the right, can move along the axis of the fixed part. It is this movement that will compensate for the gap. Nuts are produced only for screws of zero, 1st and 2nd accuracy classes. Tin bronze is used to make them.
What are nuts made of and how do they wear out?
The most common materials for the production of this type of parts are aluminum-iron bronze, according to machine tool building standards MT 31-2. In addition to this material, anti-friction cast iron can also be used as a substitute for non-responsible
It is important to add here that the nut wears out much faster than the lead screw itself. There are several reasons for this:
- the nut thread is poorly protected from any type of contamination, and it is also quite difficult to clean it of these unnecessary elements;
- it often happens that this element is initially poorly lubricated and this greatly affects its service life;
- when the nut engages with the screw, it turns out that all the turns of the second element work simultaneously, but the screw only has those that are engaged with the nut.
For these reasons, screws with nuts should be checked more often, since the nut wears out quite quickly.
When choosing milling machine(CNC Router) decide:
1. what material are you going to work with? The requirements for the rigidity of the milling machine structure and its type depend on this.
For example, a CNC machine made of plywood will allow you to process only wood (including plywood) and plastics (including composite materials - plastic with foil).
Using an aluminum milling machine, you can also process blanks of non-ferrous metals, and the processing speed of wood products will also increase.
Aluminum milling machines are not suitable for processing steel; massive machines with a cast iron frame are needed here, while processing 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 determines the mechanical requirements 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 significant alteration of the design!
Mechanics CNC milling machine made from plywood and aluminum is often the same. Read more below in the text.
But the larger the size of the working field of the machine, the more rigid and expensive linear movement guides will be required for its assembly.
When choosing machines for solving problems of manufacturing tall parts, with large differences in heights, there is a common misconception that it is enough to choose a machine with a large working stroke along the Z axis. But even with a large stroke along the Z axis, 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.
Let's look at the design of a milling machine and the selection options using the Modelist series CNC machines as an example.
A) Selection of CNC machine design
There are two options for constructing CNC machines:
1) designs with movable table, picture 1.
2) design with movable portal, Figure 2.
Picture 1Milling machine with movable table
Advantages The design of a machine with a movable table is ease of implementation, greater rigidity of the machine due to the fact that the portal is stationary and fixed to the frame (base) of the machine.
Flaw - big sizes, compared to a design with a moving portal, and the impossibility of processing heavy parts due to the fact that the movable table carries the part. This design It is quite suitable for processing wood and plastics, that is, lightweight 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 heavy workpiece weight,
Unlimited workpiece length,
Compactness,
Possibility of making the machine without a table (for example, to install a rotary axis).
Flaws:
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 a design with a movable table).
B) Selection of CNC Router Mechanics
The mechanics are presented (see numbers in Fig. 1, Fig. 2 and Fig. 3):
3 - guide holders
4 - linear bearings or sliding bushings
5 - support bearings (for fastening the lead screws)
6 - lead screws
10 - coupling connecting the lead screw shaft to the shaft stepper motors(SD)
12 - running nut
figure 3
Selecting a linear movement system for a milling machine (guides - linear bearings, lead screw - lead nut).
The following can be used as guides:
1) roller guides, Figure 4.5
Figure 4 
Figure 5
This type of guides found its way into the designs of amateur lasers and machines from the furniture industry, Figure 6
Disadvantage - 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, low strength aluminum profile guides leads to collapse, Figure 5 and, as a consequence, irremovable play, which makes it unusable further use 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 hardening and hard chrome plating, shown under number 2 in Figure 2.
This is the optimal solution for amateur designs, because... cylindrical guides have sufficient rigidity for processing soft materials with a small size CNC machine at a relatively low cost. Below is a table for choosing the diameter of cylindrical guides depending on the maximum length and minimum deflection.
Some Chinese Manufacturers of cheap machines I install guides of insufficient diameter, which leads to a decrease in accuracy, for example, when using 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).
At making the right choice diameter of the shaft, the design of machines using them is quite strong, the large weight of the shafts gives the structure good stability and overall rigidity of the structure. On machines larger than a meter, the use of round guides requires a significant increase in diameter to maintain minimal deflection, which makes the use of round guides an unreasonably expensive and heavy solution.
| Axial length | Plywood machine | Aluminum machine for woodworking | 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 support along the entire length of the guide allows the use of guides of significantly smaller diameters. But the use of this type of guides imposes high demands on the rigidity of the supporting frame of the machine, since beds made of sheet duralumin or sheet steel themselves are not rigid. The small diameter of the rail guides requires the use of a thick-walled steel professional pipe or a large-section structural aluminum profile 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 guides.
Figure 8
4) Cylindrical guides on a support
Cylindrical guides on a support are a cheaper analogue of profile guides.
Just like profile ones, they do not require use in the machine frame sheet materials, and professional pipes of large cross-section.
Advantages - no deflection and no spring effect. The price is twice as high as cylindrical guides. Their use is justified for travel lengths above 500mm.
figure 9 Cylindrical guides on a support
The movement can be done as follows: bushings(sliding friction) - Fig. 10 on the left, and using linear bearings(rolling friction)- rice. 10 on the 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 increased effort to overcome sliding friction, requiring the use of more powerful and expensive stepper motors (SM). Their advantage is low price.
IN Lately The price of linear bearings has dropped so much that their choice is economically feasible even in inexpensive hobby designs. The advantage of linear bearings is a lower friction coefficient compared to sliding bushings, and, accordingly, most of The power of stepper motors is used for useful movements, and not for combating 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 drive ( lead screw ). Due to the rotation of the screw, the nut moves forward. Can be used in milling and engraving machines helical sliding gears And helical rolling gears .
The disadvantage of the sliding screw transmission is the rather high friction, which limits its use when high speed and leading to wear of the nut.
Sliding helical gears:
1) metric screw. The advantage of a metric screw is its low price. Disadvantages - low accuracy, small pitch and low speed of movement. Maximum speed of propeller movement (velocity mm`s per min) based on the maximum motor speed (600 rpm). The best drivers will maintain torque up to 900 rpm. At this rotation speed, linear movement can be obtained:
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 initially specified torque, and this mode is used exclusively for idle movements.
When working at such a low feed rate, the consumption of cutters increases; after just a few hours of work, carbon deposits form on the cutters.
2) trapezoidal screw. In the twentieth century, it occupied a leading position in metalworking machines, before the advent of ball screws. The advantage is high accuracy, large thread pitch, and therefore high speed of movement. You should pay attention to the type of processing, the smoother and Smooth surface the longer the service life of the screw-nut transmission. Rolled screws have an advantage over threaded screws. Disadvantages of the trapezoidal screw-nut transmission - quite high price compared to a metric screw, sliding friction requires the use of stepper motors high power. The most widely used screws are TR10x2 (diameter 10mm, thread pitch 2mm), TR12x3 (diameter 12mm, thread pitch 3mm) and TR16x4 (diameter 16mm, thread pitch 4mm). In machines, the marking of such gear is TR10x2,TR12x3,TR12x4,TR16x4
Helical rolling gears:
Ball screw drive (ballscrew). 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 thread. Recirculation of the balls is ensured using return channels that run parallel to the screw axis.
Figure 12
The ball screw provides the ability to operate under heavy loads, good smooth running, significantly increased service life (durability) due to reduced friction and lubrication, increased efficiency (up to 90%) due to less friction. She is able to work on high speeds, provides high positioning accuracy, high rigidity and no backlash. That is, machines using ball screws have a significantly longer service life, 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 numbers are the screw diameter, the second two are the thread pitch.
Lead screw The milling machine can be mounted as follows:
1) Single support bearing design. Fastening is carried out on one side of the screw with a nut to the support 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 bearing of the stepper motor.
2) Design with two thrust bearings. The design uses two support bearings in internal sides portal. The disadvantage of the design is that the implementation is more complex compared to option 1). The advantage is less vibration if the screw is not perfectly straight.
3) Design with two support bearings in tension. The design uses two support bearings on the outer sides of the portal. Advantages - the screw does not deform, unlike the second option. The disadvantage is that the implementation of the design is more complex compared to the first and second options.
Running nuts there are:
Bronze backlash-free. The advantage of such nuts is durability. Disadvantages - they are difficult to manufacture (as a result - high price) and have a high coefficient of friction compared to caprolon nuts.
Caprolon backlash-free. Currently, caprolon has become widespread and is increasingly replacing metal in professional structures. A running nut made of graphite-filled caprolon has a significantly lower coefficient of friction compared to the same bronze.
figure 14 Running nut made of graphite-filled caprolon
In a ball screw nut, sliding friction is replaced by rolling friction. Advantages: low friction, ability to operate at high rotation 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, there is no backlash under heavy loads. Disadvantages: require precise installation, since this coupling does not compensate for misalignment and distortion 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 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 service life of the stepper motor. It also allows you to dampen the resulting vibrations.
3) connection using a jaw coupling. Advantages: allows you to dampen vibrations, transmit more torque from shaft to shaft, compared to a split type. Disadvantages: less misalignment compensation, misalignment of the drive shaft and the stepper motor axis up to 0.1 mm and misalignment up to 1.0 degrees.
C) Electronics selection
The electronics are presented (see Fig. 1 and 2):
7 - stepper motor controller
8 - power supply unit for the SD 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 made using a four-wire circuit. The remaining 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 skipping. The larger the screw thread pitch, the more powerful motors will be required. Typically, the greater the motor current, the greater its torque (power).
Many motors have 8 terminals for each half-winding separately - this allows you to connect a motor with windings connected in series or in parallel. With parallel-connected windings, you will need a driver with twice the current than with series-connected windings, but half the voltage will be enough.
In case of 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 usually 1.8 degrees.
For 1.8 it turns out 200 steps per full revolution. Accordingly, to calculate the value, 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 steps/mm.
Controller selection
1) DSP controllers. Advantages - the ability to select ports (LPT, USB, Ethernet) and the independence of the frequencies of the STEP and DIR signals from the operation of the operating system. Disadvantages - high price (from 10,000 rubles).
2) Controllers from Chinese manufacturers for amateur machines. Advantages - low price (from 2500 rubles). Disadvantage - increased requirements for the stability of the operating system, requires compliance with certain configuration rules, it is preferable to use a dedicated computer, only LPT versions are available.
3) Amateur designs of controllers based on discrete elements. The low price of Chinese controllers is displacing amateur designs.
Chinese controllers are the most widely used in amateur machine designs.
Selecting a power supply
Nema17 motors require a power supply of at least 150W
Nema23 motors require a power supply of at least 200W
The peculiarity of its design is that the lead screw along the X axis is fixed motionless (does not rotate). A static screw requires a special threaded nut. In CNC machines small size Usually the running nut is rigidly fixed, and the screw rotates to move the carriage. I have the opposite - the running nut rotates around the screw, driven by a stepper motor. Well, it’s obvious that a large-sized running nut for CNC must be made by hand, because one like this is simply not sold anywhere!
Why would we rotate a lead nut instead of a lead screw on a large size CNC machine?
- An industrial ball screw with a length of 2 meters or more costs just crazy money (compared to a construction pin). He must be pretty large diameter- from 20 mm and thicker, which costs even more money. Plus, not every stepper can pull off such a colossus, and you need to install a servo, which costs even more money (compared to a stepper). And, generally speaking, a large CNC machine usually has 2 lead screws (one on each side). It turns out to be double madness on a budget.
- An extremely budget-friendly and good option is a construction pin (see), but if we try to rotate it with a length of 2 meters, it will start jumping like a jump rope and eventually fall off.
- On a long bed of 2-3 meters with a fixed screw along the X axis, you can install not one, but two or even three independent Y axes, each of which will individually work on its own order. Those. on one bed there will be installed, as it were, 2 independent CNC machines with one mechanically common X axis. Obviously, with a rotating screw, independent carriages will not be obtained, but only axis cloning will be obtained.
Making a running nut for CNC with your own hands is quite simple: we take a piece of caprolon required length and just cut it internal thread under the construction stud. Caprolon is quite soft and threads can be cut even with the most construction pins, having previously made a tap from it by cutting grooves with a grinder. I made the internal threads on my home lathe, and then made a pass with a homemade tap from a hairpin for a more accurate and tight fit of the thread. To do this, on a lathe you need to specifically not cut the thread, so as to leave it for the passage of the pin itself. Then the running nut will move tightly and without play. Backlash is also removed by increasing the length of the running nut. Already at a length of 35-40 mm, the backlash completely disappears. On the Internet you can find many designs with a double adjustable running nut, which can also remove backlash, but its disadvantage is that it significantly complicates the design. If you use your CNC machine for a hobby, then a regular caprolon running nut will serve you for a very, very long time - several years for sure! I still have them, although I even saw aluminum off of them. 
Running nut for my large machine with CNC will rotate itself around a fixed screw, so we support it on both sides with bearings and clamp it quite tightly between the two aluminum plates. These plates are milled seats under the bearings. It doesn’t matter if the seats turn out to be a little crooked. Aluminum is very soft, so the bearing can then be pressed tightly in a vice through plywood spacers. And this is even better, because we need to completely eliminate the longitudinal movement of the nut in the gap between these two plates. For rigid fixation of plates to each other, as well as for transmitting the translational movement of the nut to the machine carriage, we use sheet metal 4-5 mm thick (there it is - the scraggly rusty piece of iron in the photo). The photo is missing a similar bunch of plates in the horizontal plane (right under the nut) - I’ll finish that later.
All that remains is to transfer the rotation from the stepper motor to the nut. I plan to do this using a timing belt. But the catch is that I'll have to make my own custom gear, something I've never done before.
To make my own gear, I had to puff a little. And I had to puff away at the computer. I wrote my own program for calculating pulleys with given parameters, because I couldn’t find anything useful or free. The basis was an open file on Thingiverse in OpenSCAD, which I rewrote in Python and exported to DXF. I made the gear from caprolon - this is a durable structural and easily processed plastic. In addition to the gear itself, the toothed belt also needs a tensioner roller (also known as a tensioner) for the belt. I also made it from caprolon, but inserted a bearing inside.
After installing the rotating nut on the machine, I had a little trouble with the pulleys for the motors, which kept slipping due to the very high rotation speed and high tension. I even had to drill small grooves into the stepper motor shafts and secure the pulleys to the shafts with Allen set screws. But in the end, the result was pleasing: along the entire length of the lead screw, the nut moved smoothly and did not flutter the screw one bit.
The reduction of the running nut turned out to be 30:12 (30 teeth on the nut, 12 teeth on the engine pulley), i.e. The gearbox increases the engine torque by 2.5 times. The resolution of the machine on a hairpin with a step of 2 mm/revolution turned out to be 0.004 mm (2mm/revolution ÷ (200 steps/revolution * 2.5)).
Review of a specific product: a set of ball screws type SFU1605-1000 as elements of CNC machine gears.
The review will 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 machine) on my own, I was faced with the fact that we either have expensive components for the machines, or are not quite what we need. Specifically, there was a problem with purchasing a lead screw or ball screw as transmission elements along the axes of the machine.
There are the following types of gears for CNC:
- belt used together with gears mainly for lasers, since the laser has a light “head”
- gear. These are spur or helical racks and gears for moving along them
- lead screws There are T8 type (mainly used in 3D printers and other small-sized machines), TRR type, for example TRR12-3 with a POM nut (plastic).
- ball screws- this is a screw and a nut for it. The nut has special bearings that move along a channel inside the nut.
As a rule, they are chosen taking into account the load (weight of the moving portal/axle) and the influence of backlash. In ball screws, there is less play due to bearings; they are considered more accurate and preferable, but at the same time they are quite expensive for homemade products.
Quote from Wiki:
A helical gear is a mechanical transmission that converts rotational motion into linear motion, or vice versa. IN general case it consists of a screw and a nut…. one of the main types: ball screw (ballscrew).
Ball screw(hereinafter referred to as a ball screw) is a more reliable analogue of a lead screw, but instead of a brass nut (or a plastic one as for TRR-12-3 type screws, as I had on my old project) there is a special nut with balls that engage with the ball screw, select all the play and at the same time reduce friction. For self-assembly A CNC machine or 3D printer for a ball screw will require a ball screw, a nut for it, a coupling for attaching to the motor and hanging bearings.
Here is a small render from the Internet. You can clearly see how the balls are distributed along the screw. Similar to T8, the ball screw has multi-start threads.
For the CNC machine, two sets of 1000 mm ball screws were needed for the Y axis, and 600 mm for the X axis.
I received the ball screw by courier mail. This is not an expensive option, considering the weight of the package (about 8 kg).
The packaging is a long narrow box, inside the cardboard package there is a synthetic bag type packaging, a very durable material. Carefully unpack. Inside is the familiar bubble-wrap, that is, a bubble film that protects the product from mechanical influences.
We remove the film. The parcel contained three sets of ball screws: screw + nut, different sizes. Two sets are designed to move the machine portal along the Y axis, the third short set is for the X axis.
All kits are wrapped in inhibitory green film, which prevents moisture from entering. Plus there is a fair amount of lubricant on the surface of the product.
In this kit, I paid extra for ending one kit at 600 mm (it turned out cheaper this way). I ordered the ending (machined) separately from the same seller (he has such a service in the catalogue), it cost 1 buck for each end of the screw. A good option for those who take screws in a specific size.
That's what the "ending" is. This is grinding a 16.05mm screw to 12mm diameter to fit into the outboard bearing, then the threaded part to secure the screw, then grinding down to 10mm to clamp the end into the elastic coupling of the engine
The parcel arrived safe and sound, courier delivery is not Russian Post. I put a ruler in different places to find the curvature. I couldn’t find it, the ball screws are straight. Installation and use will show the rest.
Photo of the threaded part of the screws
Appearance of the kits
And further. The nuts arrived already screwed onto the screw... The balls are filled inside, there is lubricant. When ordering, ask for spare balls, at least a few.
Next, we begin to check the sizes of the screws. Short by 600 mm. That is, these 600 include a threaded part on both sides. The actual travel along the machine axes will be less.
note, that in the lot the size is indicated for a ball screw along with threads and turned ends, that is, the working stroke of the ball screw will be less than its length! Specifically, 65 mm less.
Second and third ball screws 1000 mm
The diameters of the threaded part are respectively 1605
seats for bearings BK12 and BF12 10 and 12 mm, respectively.
And on the other side 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 check that everything is in stock))))
In fact, you can remove the nut, wipe it, re-lubricate it, and put the balls back in. Plastic cover It is secured with a countersunk 2.5 hexagon screw (it can be seen at the top).
To install the ball screw in the machine, you will need suspension bearings of type BK12+BF12 (straight) or FK12+FF12 (flange), an elastic coupling 6.35*10mm for connection to a NEMA23 type motor on one side (6.35mm) and to the end of the ball screw on the other (10mm ).
External view of the assembled axle kit: 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 planning to purchase or are designing machine mechanics
And separately for SFU1605
Appearance of nut SFU1605
