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What are the advantages and disadvantages of the hard rails and linear rails used in CNC machine?

If a general CNC machine is used to make products, it is recommended to purchase linear rails. If it is a machining mold, it is recommended to purchase hard rails. linear rails have higher accuracy than hard rails, but hard rails are more durable and sturdy. So, what are their respective advantages and disadvantages?

The guide rail of the hard rail and the bed body are integrated castings, and then the guide rail is machined on this basis, and then processed into a guide rail through quenching and grinding. Nowadays, there are also bed frames and guide rails that are not integrated, such as embedded steel guide rails, which are nailed to the bed frame after processing. Hard rail guide is sliding friction, with good rigidity and strong load-bearing capacity.

Advantages of hard rails

1. Able to withstand larger loads, suitable for rough machining machines with large cutting and feed rates.

2. Due to the large contact area of the guide rail, the machine tool runs more smoothly and is suitable for machines with high vibration requirements, such as grinders.

Disadvantages of hard rails

1. Uneven material. 

Because it is usually cast, casting defects such as sand inclusion, porosity, and looseness are prone to occur in the material. If these defects exist on the guide surface, they have a very adverse effect on the service life of the guide and the accuracy of the machine tool.

2. The processing difficulty is relatively high. 

Because this type of guide rail is generally connected to the main components of the machine tool such as the base, column, worktable, and slide saddle, it is difficult to control the dimensional tolerances, roughness requirements, aging treatment, and quenching treatment during the machining process, resulting in the machining quality of the parts not meeting the assembly requirements.

3. The assembly is difficult. 

The meaning of the word "assembly" is to both assemble and assemble, and the process of assembly is a combination of technology and physical strength, which cannot be completed by ordinary workers. It requires assembly workers who are relatively skilled in technology and have a certain degree of confidence in the overall accuracy of the machine tool to complete. At the same time, they also need to be equipped with corresponding tools such as shovels, rulers, angle rulers, square rulers, dial indicators, and micrometers to complete it.

4. The service life is not long, 

this can only be relative. Under the same maintenance and usage conditions, the service life of common hard rails is generally shorter than that of track rails, which is closely related to their movement mode. Hard rails operate by sliding friction, while track rails operate by rolling friction. In terms of friction force, the friction force experienced by hard rails is much greater than that experienced by linear rails, especially in the case of insufficient lubrication, where the friction of hard rails is even greater.

5. The maintenance cost is too high. 

The maintenance of hard rails is much more difficult and costly than the maintenance of linear rails. If there is insufficient scraping allowance, it may involve dismantling all the large parts of the machine tool, re quenching and mechanical processing, or even re casting the large part. The wire gauge only needs to replace the corresponding wire rail, and it will not greatly affect the use of related large parts.

6. The running speed of the machine tool is low. 

Hard rails, due to their movement mode and excessive friction, usually cannot withstand excessively fast operating speeds, which is somewhat contrary to current machining concepts. Especially many factory workers do not have the corresponding maintenance knowledge of machine tools. Often, they only know how to use machine tools, but largely ignore the maintenance of machine tools. The maintenance of machine tool tracks is of utmost importance. Once the track lubrication is insufficient, it will cause the track to burn or wear excessively, which is fatal to the accuracy of the machine tool.

Line rails usually refer to rolling guides, which are commonly referred to as "linear guides". The linear guide rail itself is divided into two parts: the slide rail and the slider. The slider has internally circulating balls or rollers, and the length of the slide rail can be customized. It is a modular component that is a standardized and serialized individual product produced by specialized manufacturers. It can be installed on machine tools and can be disassembled and replaced after wear and tear. The track is subject to rolling friction, with fast speed, low resistance, and easy lubrication.

Advantages of Linear rails

1. Easy and simple assembly. 

With a little training, high-quality assembly can be completed. Because the accuracy of machine tools largely depends on the precision of the transmission mechanism. The transmission mechanism is generally composed of linear rails and screw rods, which means that the accuracy of the linear rails and screw rods themselves determines the accuracy of the machine tool. linear rails and screw rods generally exist in the form of standard parts, and as long as you choose the corresponding accuracy provided by the manufacturer, there are generally no major problems.

2. There is ample room for choice. 

Whether it is the structural form or precision level of the track, lubrication method or load-bearing capacity, processing method or operating speed, all parameters can be selected, and the required track model can be configured according to the specific situation of the designed machine tool.

3. Fast running speed. 

Nowadays, many machine tools operate at extremely fast speeds, especially in terms of idle speed, which is largely due to the contribution of the track. The rolling friction operation mode and high-precision machining effectively ensure the accuracy and stability of the machine tool's high-speed operation, greatly improving machining efficiency and precision.

4. High processing accuracy. 

As a standard commodity, linear rails have entered a benign and controllable range in terms of material and processing methods. Therefore, in many precision machining fields, most machine tools use high-precision linear rails as machine guide rails, which greatly ensures the machining accuracy of the machine tools.

5. Long service life.

Because the operation mode of the track is rolling friction, the steel balls in the slider drive the movement of the feed component by rolling on the track, and the frictional force borne by this rolling friction is much smaller than that of the hard rails. So whether it is transmission efficiency or service life, the wire rail is much more ideal than the hard rail.

6. Low maintenance costs. 

Whether in terms of maintenance cost or convenience, track has its natural advantages and convenience, because as a standard component, the replacement form of track is the same as replacing a screw.

7. Short delivery cycle. 

The general delivery cycle for Linear rails can be completed within half a month, as long as the selected rail model is not too biased, the delivery time of about half a month can still be guaranteed.

Disadvantages of Linear rails

1. The carrying capacity is relatively small. 

This relatively small size is only applicable to hard rails. In fact, many large manufacturers' linear rails have greatly improved their load-bearing capacity through structural design. Of course, compared to the load-bearing capacity of hard rails, it is still relatively small.

2. The stability is relatively weak compared to the hard rails. 

For example, the ability to resist vibration, but this weakness is relative to hard rails. In fact, the stability of many linear rails is also very good nowadays. As long as the equipment you design does not have too special requirements, it can generally meet the needs.

3. Special attention should be paid to the protection of the track during transportation and assembly. 

Due to its unique structural characteristics as a standard component, it is in a relatively vulnerable position to damage, such as a slender shape that leads to insufficient rigidity of the track, and is prone to bending and deformation when compressed, resulting in loss of accuracy; For example, because it is a steel component, if it is not treated with rust prevention, it may come into contact with water or other solvents during transportation and assembly, which can easily lead to rust and corrosion, resulting in loss of accuracy.