Mechanical processing of any material primarily implies precision and productivity. Regardless of the type and purpose of the machine, there are basic elements whose parameters cannot be neglected. The basic component for a metal-cutting, woodworking or plastic processing device is guides that ensure error-free and cyclical processing.

What types of guides are there?

Any machine is based on the precision of processing, which is provided by guide rods. You have to make working units with your own hands, but there are some that you can’t make yourself; only factory-made parts are suitable.

For example, the working body milling machine It’s unlikely to be made, just like with a drill or. Therefore we have to use ready-made solutions- drills, drives, engravers or electric jigsaws. With guides, the situation is simpler, since their characteristics and appearance directly depend on the purpose of the unit.

Almost all of them used in factory and homemade structures There are only two types - sliding and rolling. According to the principle of bearings, their method of operation is clear - some are based on sliding, others use rolling bearings in their design.

For equipment low power and do not require precision and performance, use the sliding principle. Basically, such parts are used by desktop drilling and turning units, as well as woodworking units. There are also subspecies, but let’s look at those that are easiest to make with your own hands from what is on sale.

Guides for CNC machine

CNC machining centers for small batch and home use- an expensive thing and not everyone can afford to buy a format-boring or CNC machine, but you can easily make a device with your own hands that is decent in terms of processing quality and cleanliness of the cut. Let's look at several designs, but first we'll look at the factory-made parts to understand the basic principles of operation.

All guides for programmable machines are of circular motion or linear type, this depends on the trajectory along which the moving unit moves in coordinates. We will consider only linear ones, as they are the most popular among DIYers, and there is no particular need for the use of circular devices.

The simplest option for homemade programmable devices of any type is sliding parts. Their parameters vary depending on performance requirements. Basically, cylindrical rods are used, they are pre-polished, and bronze bushings move along them. The caliper is made without bushings, but this, naturally, will affect both the service life of the rods and the accuracy of processing the workpieces.

Galvanized pipe can be used as rods on a surface grinder, drilling or simple lathe different diameters. It is good because it is cheap, easy to process and shape, but there are also significant disadvantages:

However, in many low-power devices they are used and if the accuracy drops, the pipe is simply replaced with a new one. A more ingenious approach is to make a small router based on sliding devices from old dot matrix printers. This option has shown itself to be positive in practice and they will continue to work for more than one year. We presented several such structures in the photo. There is also another one good option, to get by with little expense when building programmable equipment.

CNC machines from furniture rods

An excellent option when you need to achieve thorough processing, especially in woodworking machines for the production of furniture in small batches, in belt sanding machines, milling machines based on a ready-made low-power milling machine. Furniture parts are inexpensive, although they have a shorter service life than similar sliding elements from printers or typewriters.

An example of using furniture rods on a format boring machine is shown in the photo. It is clear that the dimensions of the bed and movable table are adjusted depending on the purpose. However, if you use ball-type furniture on a drilling machine, there will be no demolition, since the load and frequency of work on a router or drilling machine are significantly different from the loads on a format-cutting machine.

There is always a way out, and based on the examples given, it is quite possible to select sliding guides for your CNC machine with the desired parameters. Good luck with your work!

Hello gentlemen 3D guys!
Please do not judge me strictly for my first post, since my last manuscripts are letters home from the army, so I am not much of a writer.
What prompted you to write? Yes, I just wanted to voice my thoughts out loud, consult and confer.
Maybe a similar solution has been discussed, to be honest I haven’t found it, please point me to it.
Like many of those present here, the journey of 3d_printing for me began with Rep-Strap.
I put together at least a printer and sculpt... for myself, for friends, I even bought some things.
Oh well... not about that.
In overall problem like many with linear bearings and guides.
Guides..... FULL. I work as an IT specialist, so I’ve had “quite a few” streamers go through me.
The only pity is that everyone’s diameter is different and non-standard: 9.5mm, 10.5mm, etc... There were 6-8 8mm axles.
I bought stainless steel guides with diameters of 8mm, 10mm, 12mm. and corresponding medicinal products.
It seems like everything is working, only some play or grooves are forming on the axles....
Previously, carriages rode on caprolon bushings, which sometimes jammed...
I agree that in some places my handiwork was to blame, and in general the first damn thing was lumpy).
Now I’m designing an H-Bot and my head is getting warm... what guides to take... so that there are no grooves, no backlashes, no wedges.
And also so that now, and free of charge, (those DADOM) (c) Owl), and so that it is printed quickly, efficiently, beautifully!)
Axis and LP.... - I drank too much...
Axles and caprolon bushings... - a familiar turner left town
Rails... - according to reviews, it depends on what kind of seller you run into.
The carriages are on rolling bearings... - it turned out to be cumbersome, it rattles, it rumbles, again, my handiwork.
I tried to print sleeves from trimer fishing line - the interlayer adhesion is weak, and I never learned how to print with fishing line.
I saw that good nylon is sold for printing, but I think it’s too early to take on “William, our Shakespeare” (c) with such a printer.
Opinions also differ about ABS bushings.
......................................................
Yesterday I couldn’t sleep, I found a video on Yuotube where one guy showed.... in short, here’s the video: I repeat: maybe a similar solution was discussed, to be honest, I didn’t find it, please point your finger.
But I liked it and decided to experiment with it.
In the video, the guy used Teflon tubes.
My idea was simpler - combine ABS and Nylon in a "linear bushing bearing".
Print a clip from ABS, and there will be pieces of trimmer line as roller balls.
I won’t explain it with my fingers, I’ll show you in FreeCade.
First thought:

And then Ostap suffered. And if like this:
Thought two:

or like this:

In general, you can fantasize a lot.
Today is Friday and the printer is at work. Here's what I managed to implement today:

Profile linear guides, made or purchased with your own hands, are roller or ball high-precision rolling bearings that serve in linear movements. They have the ability to perceive forces acting in any direction, excluding the direction of movement.

Types of linear guides

Linear guides come in two types:

• with ball circulation;
• with circulation of rollers.

Roller guides are made in the form of cylindrical guides and guides with a flat cage.

All guides must have the following main properties:

• low friction;
• high efficiency;
• smooth linear movement;
• ability to maintain operating parameters.

Linear Motion Modules

IN lately in connection with the development of automation great value has acquired the use of linear motion modules, which consist of:

• durable supporting profile;
• precise guiding system;
• durable drive mechanism;
• Servomotor with easy control.

In such a modular component, guides with both ball bearings and roller bearings are used. The working drive is carried out using a linear motor, toothed belt or ball screw mechanism.

Linear tables have also found their application, used when it is necessary to move large masses along axes. Due to their dimensions, they absorb large moment loads. Linear tables use:

• linear motion bushings;
• guides with ball circulation.

Accuracy measurement technique

If you make your own linear guides, you need to control the accuracy. This is done quite simply. The rail is placed on the installed base surface. In this case, accuracy is the expression of the average value of the indicator readings in the central part of the measured surface. Also, the accuracy of linear guides is determined by measuring the width and length. In this case, the dimensional tolerance is measured for each block that is installed on the rail.

Stiffness and preload

During operation, profile rail guides are subjected to elastic information due to the applied load. Indications of the amount of deformation depend on the types of rolling elements. But one way or another it becomes smaller when the load increases.

To increase the rigidity of the system, preload is applied. It reduces the life of linear guides by causing internal stress in them, but is capable of absorbing deformation loads when the linear guide is operated under severe vibration or shock loads. Due to the fact that preload causes elastic deformation of bearings, they become dependent on negative influence installation errors. This suggests that more attention should be paid to the precision of the mounting surface.

Types of preload:

• normal - used in the presence of minor vibrations;
• light - used in the presence of light vibrations and light torque;
• medium - used for shock loads and strong vibrations, as well as for overturning loads.

Installation of rail guides

It is important to know that linear rail guides are subject to force and torque. For them, the following values ​​must be determined: permissible static moment and load capacity, which are calculated using formulas. When calculating the nominal life of ball and roller guides, it is necessary to use different formulas.

With a constant stroke length and frequency of movements, the service life is expressed in terms of time. With compact installation dimensions, profile rail guides have a high load capacity. Installed in various types machines or other equipment, they are mounted by two in various ways: in the form of a horizontal rail and side installation method.

Since the assembly consists of two parallel rails, the first rail is located on the base side, and the other on the adjustable side.

When working with large shock loads and vibrations, installing additional side parts - a side pressure plate, set tension screws, a conical wedge - helps eliminate them.

Installation of additional clamping parts when working with low loads and low speeds of movement is not necessary.

Linear guides for CNC machines

What makes up the system linear movements? This is a combination of gear and linear guides.

Linear guides for CNC are linear bearings, guide bushings, shafts. The guides themselves must solve three main tasks:

• be a support for completing the machine;
• with minimal friction, with the required accuracy along a given trajectory, ensure the movement of machine parts;
• accept the loads arising during the work process.

Linear guides are divided depending on the method of attachment to the machine. These are guides that provide full support - the method of attachment to the frame along the entire length of the guides, and partial support - the method of end attachment.

Fully supported rails have a higher load capacity than partially supported rails. Sometimes there are options when linear guides are installed along the axes - both with full and partial fixation.

Representatives of this group are linear cylindrical guides. They make it possible to use several types of cylindrical guides:

• polished guide shafts - the most common (high availability, ease of installation);
• splined shafts - high wear resistance and rigidity, the ability to accept torsional forces from the bushing. Used for end mounting of guides;
• the shafts on the support are cylindrical rails. They are used as direct attachment to the machine.

Mounting surface accuracy

Profile rail guides are installed using fastening on a machined base surface. The fastening method consists of creating a shoulder on the seating surface and placing the base surface or carriage on it. It is possible to avoid distortions if there is a groove in the corner of the bead itself.

There is a direct relationship between rail surface accuracy and moving accuracy. The accuracy of all equipment will depend on this. In this case, the accuracy of the processed mounting surface necessarily corresponds to the specified movement accuracy. It is important to remember that it is necessary to take into account the flatness of the block, while eliminating the deformation of the carriage.

Base surfaces

To ensure accurate and more easy installation, it is necessary to create base surfaces that should be located on the carriage and on the rail on one side.

In this case, the label should be located with opposite side. If sufficient accuracy is not ensured due to the peculiarities of the installation scheme, then the base surfaces are processed on the second side as well.

Corrosion protection and lubrication

To protect the guides from corrosion, they are made from a special material. There is an option with the application of a special protective coating. Its use is carried out when necessary in high degree protection against corrosion.

The finished factory guides are lubricated with lithium soap-based grease. After this, they can be used for their intended purpose. Different operating conditions will require the desired frequency of adding the same type of lubricant.

Cylindrical guides are used in CNC machines, for which processing accuracy is not so important, and the cost of the equipment comes first. The technology of induction hardening of the surface (hardness reaches 60 HRC) increases wear resistance, subsequent grinding to Ra 0.8 max reduces the coefficient of friction. They are used in combination with bronze or fluoroplastic sliding bushings, and with rolling bearings.

Polished shafts

They are characterized by affordability and ease of installation, which reduces repair costs. They are not recommended for use as guides for moving tables whose flow exceeds 1 m, since fastening to the frame at two points leads to sagging under loads. At the same time, they are suitable for moving the spindle along the Z axis, provided that the spindle is not loaded (engraving, cutting thin sheet metal, wood carving, etc.) and is balanced by a counterweight.

Flaws:

• when using rolling bearings, pressure from the ball is applied at one point, and over time a groove is pressed at this point;
• increased sensitivity to chips and dust;
• impossibility of fitting the bearing to the shaft and creating preload.

However, these disadvantages are offset by the low cost and ease of replacing the shaft, and the problem of dust and shavings in wood and stone processing workshops is solved by installing a hood with a socket directly in the work area.

Cylindrical rails on supports

The main disadvantage of a polished shaft is the lack of support along the length; in this design it is compensated by the fact that the shaft is laid on aluminum profile, attached directly to the frame. The resistance to bending load is the same at all points along the shaft length, so the cylindrical rail does not bend.

Used in the construction of budget machines with work area more than 1 m. But there is one nuance determined by the design of the bearings. The open loop of the bearing absorbs the forces applied in different directions, in different ways, which requires monitoring the coincidence of the center of mass of the workpiece installed on the table and the geometric center of the table. For the same reason they are not used in kinematic schemes Z axes in machines with heavy spindles.

Cylindrical guides – budget option, ideal for use in small or light-duty machines with light spindles.

This article will discuss the types of guides for a CNC machine, their main features and advantages.

GUIDE POLISHED SHAFT

The most common and budget look guides. It is characterized by low cost, ease of processing and installation.

They are made from high-alloy steels, usually structural bearing steels, and undergo induction hardening of the surface followed by grinding.

This ensures long operating time and is associated with less shaft wear.

The ground shafts have a perfect surface and provide movement with very little friction.

The shafts are attached only at 2 points at the ends, and therefore their installation is not particularly difficult.

However, many unscrupulous manufacturers often make shafts from cheap and soft grades of high-carbon steel, taking advantage of the fact that the buyer does not always have the means to check the type of material and its hardness.

The disadvantages of polished shafts include:

1. Lack of attachment to the frame.

The shaft is attached at two points at the ends - this facilitates the installation of the guides, but leads to the fact that the guides are installed independently of the working surface of the table. At the same time in portal machines It is highly advisable to install the guides in a rigid connection with the table. This connection reduces processing errors, if the work table has been subjected to curvature, “driven by a screw” - the guides, repeating the bends of the table, level out part of the error.

Shaft mounting

2. Sagging over a long length.

In practice, due to sagging, shafts are used with a length of no more than 1 meter. In addition, the ratio of the shaft diameter to its length is important - to obtain acceptable results, its value should be at least 0.05, preferably within 0.06-0.1. More accurate data can be obtained by modeling the shaft load in CAD packages.

Types of linear bearings on the shaft:

1. Ball bushings

Linear rolling bearings have larger backlashes compared to rail guide carriages and lower load characteristics.

In addition, to protect the carriage from rotation, it is necessary to use at least two guide shafts per axis. Disadvantages of linear rolling bearings:

• Low load capacity.
• A consequence of the previous point, as well as the structural structure of linear bearings.
• Fragility.
• Each linear bearing ball touches the shaft at one point, creating a very high blood pressure. Over time, the balls can roll a groove into the shaft, after which the shaft must be replaced.

Ball bushings

• Backlash
• Low-cost linear bearings by many manufacturers are often manufactured with very significant backlash.
• Quite sensitive to dust and chips on the shaft

2. Linear plain bearings

Sliding bushings use sliding friction and are made of bronze, brass, caprolon and other materials.

When the tolerances are properly maintained, a bronze plain bearing is as good as a rolling bearing in terms of precision and load-carrying capacity, and at the same time tolerates dust and chips more easily. However, you need to be sure that you can always get the bearing material and process it as needed.

In addition, periodically, as the sliding bearing wears out, it must be adjusted to eliminate gaps. In most cases, ball bushings are preferred for beginners due to their high availability and interchangeability.

BALL SPLINE

Spline shafts have special raceways for the bushing balls. They are more wear-resistant and rigid than conventional shafts and can also absorb torsional forces from the bushing.

Combining the advantages of shaft mounting, the wear resistance of profile rails with the ability to create tension, splined shafts are used where it is necessary to install guides exclusively at the ends.

However, due to their significantly higher cost (compared to polished shafts), they are rarely used in the construction of conventional machine tools.

SHAFT ON SUPPORT

Profile rails are complex and expensive to produce, so there are fewer rail manufacturers than shaft manufacturers. As a rule, they value their reputation, which is why the quality of profile rails is much more stable.

ROLLER PROFILE RAIL GUIDES

Roller rails are a subtype of profile guides in which the raceways are flat, and rollers are used in the support modules instead of balls.

This made it possible to increase guide rigidity, load capacity and durability.

Roller guides are used in highly loaded CNC metalworking machines designed for milling ferrous metals, steel, and stone.

It is unlikely that you are looking for just such guides, otherwise you would not be reading this article.

DOVE-TAIL GUIDES
AND PRISMATIC GUIDES

This type of guide is used where very high rigidity is needed, for example, in industrial metalworking machines. - low rigidity and load capacity, limited accuracy, the need for periodic adjustment, low price, low availability finished products on the market. The shaft sags when it is long.

shaft and plastic bushing- low rigidity and load-bearing capacity, low accuracy, the need for periodic adjustment, low price, high wear, low availability of finished products on the market. The shaft sags when it is long.

Roller profile guide

• Shaft and ball bushing- low rigidity and load capacity, limited accuracy, average cost. The shaft sags when it is long. Used in hobby machines and middle class machines.
• Support shaft and linear bushing- average rigidity and load capacity, limited accuracy, average cost. The rail repeats the deformations of the frame, leveling out the error. Used in hobby machines and middle class machines.
• Profile guides- high rigidity, precision, wear resistance, high load capacity, no adjustment required, high cost. An important factor is the complexity of installing profile guides and the need for appropriate preparation mounting surfaces. Used in medium and industrial class machines.

If you have read everything, but the situation has not become clearer, in conclusion there are some specific recommendations:

• If you plan to mill metals or stone on the machine, there is no alternative to profile rails.
• If your machine has a working area greater than 0.7 sq. m, it is best to also use profile guides.
• If your machine has a working area smaller than A4 format, you plan to process soft materials- shafts with a diameter of 16–25 mm are suitable.
• If you still find it difficult to choose, contact our specialists for advice.