How does the disc tool magazine of the machining center work?

Machining center tool magazines are generally divided into three types: bucket-type tool magazines, disc-type tool magazines, and chain-type tool magazines. The most common forms of general machining centers are disc-type tool magazines and manipulator tool-change tool magazines.

Features of disc type tool magazine

The disc-type tool magazine should be called a fixed address tool change magazine, that is, each tool position has a number, generally 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 changed, it is always in the tool position.

1. Low manufacturing cost.

The main components are the tool magazine body and the indexing plate, as long as the machining accuracy of these two parts is guaranteed. The indexing of the tool magazine in the moving parts uses a very classic “Markovian mechanism”. Assembly and adjustment are more convenient and maintenance is simple. General machine tool manufacturers can make their own.

2. The counting principle of tool number.

Generally, a non-contact switch is installed in the tool change position, and a baffle is installed on the No. 1 tool position. Each time the machine tool is turned on, the tool magazine must “return to zero”. When the tool magazine is rotating, as long as the baffle is close (the distance is about 0.3mm) without a contact switch, the CNC system defaults to tool No. 1. And on this basis, the “Markovian mechanism” has been turned several times, the current number of knives. As long as the machine does not shut down, the current tool number will be memorized. When the tool is changed, generally according to the principle of the nearest distance rotation, the tool number number is in the counterclockwise direction. If the number of the tool magazine is 18, the current tool number is 8, the 6th tool should be changed. turn. If you want to change the 10th tool, the tool magazine rotates clockwise. The tool memory is cleared after the machine is turned off.

3. The tool change time of the fixed address tool change tool magazine is relatively long.

Domestic machine tools generally require more than 8 seconds (from one cutting to another cutting).

4. The total number of tools in the disc-type tool magazine is limited

and should not be excessive. Generally, the number of 40 # tool holders does not exceed 24, and the number 50 # does not exceed 20. Large-scale gantry machine tools also convert the disc into a chain structure. The number of tools is up to 60.

 Features of manipulator tool magazine

Manipulator tool changer is a random address tool changer. There is no number on each knife sleeve, its biggest advantage is that the knife is changed quickly and reliably.

  • 1. High manufacturing cost. The tool magazine has a chain of tool sleeves combined together, the movement of the manipulator tool is controlled by a cam mechanism, and the processing of parts is more complicated. Assembly and commissioning are also relatively complicated, generally produced by professional manufacturers, and machine tool manufacturers generally do not make their own.
  •  2. The counting principle of tool number. As with fixed address tool selection, it also has a basic tool number: tool number 1. But we can only understand it as the No. 1 tool set, not the No. 1 tool in the part program: T1. There is a tool table 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 machining program for three tools, the starting point of tool placement is tool set T1 (tool 1), tool set 2 (T2), tool set 3 (T3), we know that when T1 on the spindle is processing, The T2 tool is ready. After the tool is changed, T1 is replaced with the No. 2 tool sleeve. Similarly, when T3 is processed, T2 is installed in the No. 3 tool sleeve. After one cycle, the previous tool is installed in the tool holder of the latter tool. The memory of the tool set number and tool number of the CNC system is permanent, and the tool magazine can be restored after powering off without “returning to zero”. If “return to zero”, the corresponding tool number in the tool set number must be modified in the tool table.
  • 3. The tool change time of the manipulator tool magazine is generally 4 seconds (from one cutting to another cutting).
  • 4. The number of tools is generally more than the disc tool magazine, and the conventional ones are 18, 20, 30, 40, 60, etc.
  • 5. The cam box of the tool magazine should be regularly replaced with lubricating and cooling gear oil.

 How to choose both

These two types of tool magazines have their own advantages and disadvantages. When choosing, they need to be combined with reality. The main ones are the price and which type of parts are processed. Take 20 tools in 40 # tool magazine as an example. The price of disc-type tool magazine is about 35,000, and that of manipulator tool magazine is 65,000. Generally, it is better to use a disc type tool magazine for single-piece small batch production and a manipulator tool magazine for large-scale production. In addition, we all know that the reliability of the manipulator tool magazine is higher than that of the disc tool magazine, but the maintenance of the disk tool magazine is simple and convenient.

The failure of the tool magazine

The failure probability of the disc-type tool magazine is higher than that of the manipulator’s tool magazine, and the wearing parts are mainly the needle bearings on the forks in the “horse mechanism” damaged. The guide rail pair will wear out, and the bearings in the center of the disk will also wear out. But replacement is more convenient.

The manipulator tool magazine mainly relies on the cam mechanism to complete the tool change, which is simple and reliable. Normally, just replace the oil in the cam box on time. long lasting. If the cam groove is worn to a certain degree and is not replaced, the tool magazine cannot be used.