The tool magazine of machining center is generally divided into three types, hat type, disc type and chain type. The most commonly used forms of general machining center are disc type tool magazine and manipulator tool changer magazine.
1、 Features of disc magazine
Disk type tool magazine should be called fixed address tool changer magazine, that is, each tool position has a number, which is usually from 1 to 12, 18, 20, 24, etc., which is the tool number address. After the operator installs a tool into a certain tool position, no matter how many times the tool is replaced, it is always in the tool position
- Low manufacturing cost. The main components are the tool magazine body and index plate. As long as the machining accuracy of these two parts is guaranteed, the indexing of the tool magazine in the moving parts uses the very classic “Markov mechanism”, and the cylinder is mainly used for the forward and backward, up and down movement. It is convenient to assemble and adjust, and easy to maintain. General machine tool manufacturers can make their own.
- Counting principle of tool number. Generally, a contactless switch is installed at tool change position, and baffle plate is installed on tool position 1. The tool magazine must “return to zero” after the machine tool is started. When the tool magazine rotates, as long as the baffle plate is close to the contactless switch (the distance is about 0.3 mm), the CNC system will default to No.1 tool. With this as the counting benchmark, the “Markovian mechanism” has been turned several times, and the current number of knives. As long as the machine tool is not turned off, the current tool number will be memorized. When changing the tool, generally according to the principle of the nearest distance rotation, the tool number is counter clockwise. If the number of tool magazine is 18 and the current tool number is 8, tool No. 6 needs to be changed. According to the principle of tool change according to the nearest distance, the tool magazine rotates anticlockwise. If you want to change tool No.10, the tool magazine will rotate clockwise. The tool memory is cleared after the machine is shut down.
- The tool change time of fixed address tool changer is relatively long, and domestic machine tools generally take more than 8 seconds (from one cutting to another cutting).
- The total number of tools in the disc type magazine is limited and should not be too much. Generally, there are no more than 24 pieces of 40 pieces of tool holder, and no more than 20 pieces of 50 pieces of tool. Large gantry machine tools also change the disc into chain structure, and the number of tools is up to 60.
2、 Characteristics of manipulator magazine
Manipulator tool magazine tool change is a random address tool change. There is no serial number on each tool sleeve. Its greatest advantage is that the tool can be changed quickly and reliably.
- High manufacturing cost. The tool magazine has a chain combination of tool sets, and the tool changing action of manipulator is controlled by cam mechanism, so the machining of parts is more complicated. Assembly and debugging is also more complex, generally produced by professional manufacturers, machine tool manufacturers generally do not self-made.
- Counting principle of tool number. Like the fixed address tool selection, it also has a reference tool number: No. 1 tool. But we can only understand it as tool sleeve No.1, not tool No.1 in part program: T1. There is a tool list in the system. It has two columns. One column is the tool set number, and the other column is the current program tool number corresponding to the tool set number. If we compile a three tool processing program, the tool placement starts with No.1 tool set T1 (No.1 tool set), No.2 tool set T2, No.3 tool set T3. We know that when T1 on the spindle is being processed, tool T2 is ready. After tool change, T1 is replaced by No.2 tool sleeve. Similarly, if working time is added at T3, T2 is installed in No.3 tool sleeve. After a cycle, the former tool is installed in the latter tool sleeve. The memory of tool set number and tool number in CNC system is permanent. After the machine is shut down, the tool magazine can be restored to the state before shutdown without “returning to zero”. If “return to zero”, the corresponding tool number in the tool set number must be modified in the tool table.
- The tool change time of manipulator tool magazine is generally 4 seconds (from one cutting to another cutting).
- The number of tools is generally more than that of disc magazine, and the conventional ones are 18, 20, 30, 40, 60, etc.
- The gear oil for lubrication and cooling shall be replaced regularly for cam box of tool magazine.
3、 How to choose the two
These two types of tool magazine have their own advantages and disadvantages. When selecting them, we need to combine them with practice. The most important one is the price and which type of parts to process. Take 20 knives in 40 pieces of knife magazine as an example. The price of disc magazine is about 35000, and that of manipulator is 65000. In general, it is better to use disc type tool magazine for single piece small batch production, and manipulator magazine for mass production. In addition, we also know that the reliability of manipulator magazine is higher than that of disc magazine, but the maintenance of disc magazine is simple and convenient.
4、 Fault condition of tool magazine
The failure probability of disc type magazine is higher than that of manipulator magazine. The main vulnerable parts are the needle roller bearing on the fork in “horse mechanism”. If the magazine is loaded or overloaded for a long time. The guide pair will wear and the bearing in the center of the disc will also wear. But the replacement is more convenient.
The tool magazine of manipulator is simple and reliable, which is mainly accomplished by cam mechanism. Usually as long as the oil in the cam box can be replaced on time. Long service life. If the cam groove is not replaced after wear to a certain extent, the tool magazine can not be used.
About the author