Advantages and disadvantages of hard rail and linear rail in machining center

Generally, if the machining center is used to make products, buy line rails. If it is to process molds, buy hard rails. The precision of the line rails is higher than that of the hard rails, but the hard rails are more durable. Today’s article explains the advantages and disadvantages of line rails and hard rails, and collect them and read them slowly.

 

 

Hard track features

 

The advantages of hard rail:

 

1. It can withstand larger loads, and is suitable for roughing machine tools with large tool volume and large feed.

2. Because the contact area of ​​the guide rail is large, the machine tool runs more smoothly, which is suitable for machine tools with high requirements on machine tool vibration, such as grinding machines.

 

Disadvantages of hard rail:

 

1. The material is uneven. Because it is generally cast, it is easy to produce casting defects such as sand inclusion, air holes, and looseness in the material. If these defects exist on the guide rail surface, it will have a negative impact on the service life of the guide rail and the accuracy of the machine tool.

2. It is difficult to process, because this type of guide rail is generally connected with the main parts of the machine tool such as base, column, worktable, saddle, etc., so in the process of processing, its shape and position tolerance, roughness requirements, aging Processing, quenching and other processes are difficult to control, so that the processing quality of parts cannot meet the requirements of assembly.

3. Assembly is difficult. The word “assembly” means both assembly and assembly. The assembly process is a process of combining technology and physical strength, which cannot be completed by ordinary workers. It requires a relative quantity of skills. The overall accuracy of the machine tool can only be completed by assembly workers who are quite sure. At the same time, it also needs to be equipped with corresponding tools such as a blade, a ruler, a square ruler, a square ruler, a dial indicator, and a dial indicator.

4. The service life is not long. This can only be relatively speaking. Under the same maintenance and use conditions, the service life of the general hard rail is less than the service life of the linear rail, which has a great effect on the way they move. The relationship between the hard rail is sliding friction operation, and the line rail is rolling friction operation. In terms of friction, the friction force of the hard rail is far greater than that of the line rail, especially in lubrication In the case of insufficient, the friction of the hard rail is even worse.

5. The maintenance cost is too high. The maintenance of the hard rail is far greater than the maintenance of the linear rail in terms of difficulty and maintenance cost. If the scraping allowance is insufficient, it may involve dismantling all the large parts of the machine tool. The quenching treatment and machining are re-made, and even more, the large piece may have to be recast, and the wire gauge only needs to replace the corresponding wire rail, which basically will not greatly affect the use of the relevant large piece.

6. The running speed of the machine tool is low, and the hard rail usually cannot bear the excessively fast running speed because of its movement mode and the friction force it bears, which is contrary to the current processing concept. In particular, many factory workers do not have the corresponding maintenance knowledge of machine tools. Many times they only know how to use machine tools, but largely ignore the maintenance of machine tools, and the maintenance of machine tool rails is the top priority. Once the rails are not sufficiently lubricated, It will cause the track to burn or wear transition, which are fatal to the accuracy of the machine tool.

 
Line rail features

 

The advantages of line rails

1. The assembly is convenient and simple, and high-quality assembly can be completed with a little training. Because the accuracy of the machine tool is very large, the degree of accuracy determines the accuracy of the transmission mechanism. The transmission mechanism is generally composed of a wire rail and a screw rod, that is to say, the accuracy of the wire rail and the screw rod itself determines the accuracy of the machine tool, while the wire rail and the screw rod are generally They all exist in the form of standard parts. As long as you choose the corresponding precision provided by the manufacturer, there will generally not be a big problem.

2. There is a lot of room for choice, whether it is from the structure of the rail or the accuracy level, the lubrication method or the load-bearing capacity, the processing method to the running speed and other parameters can be selected. You can configure it arbitrarily according to the specific conditions of the machine tool you design. The type of rail you need.

3. The running speed is fast. Now many machine tools run extremely fast, especially the idle speed. This is largely due to the credit of the line rail. Because of the rolling friction operation mode and high-precision machining, the machine tool is effectively guaranteed. The accuracy and stability of high-speed operation greatly improve the processing efficiency and processing accuracy.

4. High machining accuracy, because the line rail is a standard commodity, both the material and the processing method have entered a benign controllable range, so most of the machine tools in many finishing fields use high-precision line rails As a machine tool guide rail, this also greatly ensures the machining accuracy of the machine tool. There are Nanjing craftsmanship, Hanjiang line rails, Taiwan’s Shangyin line rails, Germany Rexroth company, Japan’s THK line rails, etc. These brands have greatly enriched and met the market’s demand for various wire rails. Personally, I like to use Japan’s THK, which has stable performance and fine workmanship, but the price is on the high side.

5. Long service life, because the running mode of the line rail is rolling friction, the steel ball in the slider drives the movement of the feeding part by rolling on the rail, and the friction force of this rolling friction is smaller than that of the hard rail Therefore, whether it is transmission efficiency or service life, the line rail is much more ideal than the hard rail.

6. The maintenance cost is low. Whether it is in terms of maintenance cost or convenience of maintenance, the line rail has its natural advantages and convenience, because as a standard part, the replacement form of the line rail is the same as the replacement of a screw. , of course there are some revert adjustments in accuracy, but compared to hard rails, that’s really convenient.

7. The delivery cycle is short, and the general delivery cycle of wire rails can be completed within half a month, unless you choose foreign brands, such as Rexroth and THK. In fact, these two brands also have corresponding processing plants in China. , as long as the line rail model you choose is not very biased, basically the delivery period of about half a month can still be guaranteed, and the line rail of Taiwan Shangyin can even achieve a one-week delivery period, but the same Hard rails do not have such a good time control ability. If the action is relatively large, such as re-casting, the cycle may be more than a few months.

 

Disadvantages of line rails

1. The carrying capacity is relatively small. This relatively small size is only for hard rails. In fact, the line rails of many large factories have greatly improved their carrying capacity through some structural designs. Of course, they are relatively hard rails. In terms of carrying capacity, it is still relatively small.

2. The stability is somewhat weaker than the hard rail, such as the ability to resist vibration, etc., but I still want to emphasize that this weakness is relative to the hard rail. In fact, the stability of many line rails is also done now. It is very good, as long as the equipment you design is not too special, it is generally able to meet the needs.

3. Special attention should be paid to the protection of the line rail during transportation and assembly, because as a standard part, its unique structural characteristics make it in an embarrassing situation that is more easily damaged, such as the slender shape which leads to the line rail. The rigidity is insufficient, and it is easy to bend and deform when it is squeezed, which leads to the loss of accuracy; for example, because it is a steel part, if the anti-rust treatment is not done, it is easy to be exposed to water or other solvents during transportation and assembly. Phenomena such as rust and corrosion are produced, resulting in loss of accuracy.


Post time: Aug-13-2022