Coordinate transformation in CNC lathe machining programming

Different, through the coordinate system transformation, using two major algorithms, developed an operating mode for the user rather than the numerical control system.

In order to realize NC programming, the CNC machine tool specifies the origin of the machine coordinate system, the machine point and the programming origin. The machine coordinate system is established by the return point operation, so that the machine coordinate value of the machine tool is X=0, Z=0. After the power is turned back on, the machine is stopped, and the machine overtravel alarm is released, the return point must be executed in three cases.

CNC machining mainly relies on numerical control programming, while numerical control programming should first solve the problem of establishing the programming coordinate system. Although the CNC system can provide the corresponding code to set up the machine coordinate system, most of the current NC programming is specific to the numerical control system, and the methods are different, sometimes even cumbersome. If the workpiece coordinate system is set at a certain point of the workpiece, it is necessary to consider the clamping and tool setting of the workpiece. When programming, first set the workpiece coordinate system, program on this coordinate, and then convert the nominal value on the pattern. If the coordinate system is set differently, the programming size will change greatly and cannot match the nominal value of the pattern. The program is different. Finally, when machining on the machine, different programs are implemented using different tool setting methods. All of these bring inconvenience to the operation. According to the two algorithms of the lathe coordinate system transformation and the tool-making method, this paper explores a surface-making resource and improves the economic efficiency and flexibility of the system. The system management layer can dynamically reconstruct the supply chain model and achieve overall information integration. With the help of the intermediary agent layer, the agile manufacturing unit can dynamically change the resource structure of the unit or accomplish tasks by working with other agile units. The agile manufacturing units in the system are fully autonomous. They can decide the production plan of the unit independently. There is no strict control and control relationship between the system and the superior. The controller of the system management only serves as the recommendation, supervision and macro organization. effect.

The MAS-based agile supply chain framework has the following characteristics: 1) The system is reusable, reconfigurable and scalable (Reusable, Reconfigurable Scalable-RRS). 2) The system mediation agent layer can effectively achieve loose coupling between nodes and reduce the communication load of the network. 3) The system has strong robustness. Most functional nodes in the system have the ability to make local decisions independently and independently.

This paper studies the internal supply chain system of agile manufacturing mode, systematically analyzes the connotation and essence of agile supply chain management, and points out a way to build an internal supply chain system through MAS.

Further research is needed in the future of MAS-based integration mechanisms, such as the packaging and reorganization of Legacy systems, as well as system security (such as mutual authentication and authorization of agents, message encryption, signature and verification).

In the NC machining process, the most common error factors for the operator are the error in the programming and the tool setting error. Under normal circumstances, the user must establish the workpiece coordinate system for programming convenience, which can be established by using G92 or G54 command settings. G92 is the workpiece coordinate system setting command. By setting the tool starting point (pairing point) relative to the coordinate origin to the starting point The relative position of the workpiece is established, and the coordinate system of G92 is independent of the machine coordinate system. G54 is the predetermined workpiece coordinate system, which is related to the machine coordinate system. At present, most of the machine tool numerical control systems provide these two operating modes for the numerical control system.

Use the G92 method to establish the workpiece coordinate system. There is a tool setting process, that is, using G92 before or after each work, or changing different parts. It is necessary to set the G92 value again, and the tool can only be used in G92. The tool is taken at the point and must be returned to the starting point after machining to repeat the machining. Using the G54 coordinate system, you can start at any point, you can also return to any point (the point allowed by the process), but there is a pair of good G54 (including G55G59) point values, input into the computer, each knife (Each process) corresponds to a value. The default value of the G54 value after power-on of the CNC system is extremely error-prone and must be paid attention to during programming.

When machining CNC lathes, there are often many tools, and a reference knife needs to be established. The other tools are used as the reference, and the tool compensation values ​​of each knife are generated in turn. If the reference tool is damaged, the tool compensation values ​​of all the tools will change, and all the tools must be re-paired to increase the workload.

CNC machining programming is based on the established workpiece coordinate system. The part pattern size should be converted into the workpiece coordinate system. Other methods can be selected, but there is a conversion relationship. It is difficult to directly press the nominal value on the part pattern. Programming.

In order to achieve the matching value of the part programming program and the nominal value on the part pattern, reduce the tool setting process and avoid the inconvenience caused by the reference tool failure, an operation mode for the user rather than the numerical control system is needed. The user-oriented operation mode sought by the system transformation is the two algorithms of the lathe coordinate system transformation and the tool setting. On this basis, substantial processing can be realized for the language format and operation mode.

Since the actual programming origin and the absolute zero point (ie, the coordinate origin of the machining plane or the machine point) are not coincident, in order to implement the machining value of the part machining program and the nominal value on the part pattern, the coordinate system transformation is adopted, which is linear. , to meet the principle of superposition.

The background coordinate system is set to the programmed coordinate system zero point, and its position relative to the absolute zero point O has only a scene coordinate system with r. There is a point (on the part processing plane) M is r in XOZ, and / in X'Of, there is: /=r (vector) Z' coordinate system is selected appropriately, and all the processing planes required for the parts are satisfied. Within the bounded plane n. The purpose of constructing r is to match the nominal value of the part pattern after the part program is programmed. In this way, the program only outlines the shape of the part, and regardless of the actual size of the part, it is realized by the movement of the tool (tool tip), and the background coordinate system is established by the return point.

X, 'completed in completion> see) = +zrk, the nominal value of the part in the spoon vector is /=x, +z, k, where the x, z' value is the current coordinate value displayed on the CNC system during the tool setting process .

The tool (tool nose) coordinate system and these two values ​​are the required tool offset values ​​and stored in the computer, ie the display value is subtracted from the nominal value of the point at which the tool hits the part.

Combine rp=r'-rj and r'=r-ro two types rp=r?r?rj This is the transformation formula of the lathe coordinate system.

There is a part, and the nominal value of point A on the pattern is x=200, which is the rp value.

The relationship between the nominal value of the pattern and the background coordinate system is X. The tool tip of a certain knife (J01) is paired to point A. At this time, the computer screen 232.399, this value is r, then the formula rj=/一rp is converted according to the lathe coordinate system. A 432.399, and this value is stored in the computer as the offset value of the knife (J0101).

Determine a tool change point M. The coordinate value of this point in the background coordinate system X, ' is x=80z =?109 (the tool change point M should ensure that there is no tool interference).

T0101 (changing the No. 1 knife and adjusting the No. 1 tool) The tool (tip) moves to the M point, and the workpiece coordinate system is displayed as (r/= thus the coordinate transformation of the tool (tip) in XjOrYr is established, and the nominal value can be performed. The programmed program allows the tool to start at any point (avoiding tool interference) and can be changed at any point.

When using the above formula, both r and r are easy to implement. The former redefines the coordinate system at the point position, and the latter is obtained at the back point. The implementation of rr is one of the second largest algorithms for users, namely the tool-to-tool implementation. It is entered by the person based on the calculated value into the offset table of the computer.

Soft implementation: that is, the servo axis is not moved, but you must cancel the rr of the previous tool and then transfer the current rr. The biggest advantage of this is to save time. It can establish a matching tool (point) coordinate system in the background coordinate system X'O'Z' every time the rr transformation is performed.

Hard implementation: by moving the servo axis, using the current position to adapt to the position of the background coordinate system XZZ', it can also perform rr transformation, but rr is not independent (with reference), by moving to find its position in the background coordinate system , is a single coordinate system, extending the processing time, there are problems with the infeed and the retraction.

In the above example, if the tip of the second knife (702) is used to point A, the computer screen displays: x=?129.096z=?202399, which is the new rZ according to the lathe coordinate system. The transformation formula rr calculates m 096,z=?402399, and stores this value in the computer as the offset M of the knife. The coordinate value of this point in the background coordinate system X' O'Z' should be guaranteed to not exist. Tool interference is appropriate).

The tool coordinate transformation relationship T0202 (changing the No. 1 knife and adjusting the No. 1 tool compensation) moves the tool to the M point, and the workpiece coordinate system shows that (rn=rm is obviously new in the same tool change point.) The tool (point) coordinate system (N point), and the same background is converted in the same background coordinate system XrOrYr. It is a soft implementation that does not move the servo axis, saving time.

If you want to implement hard, you must ensure that the N point coincides with the M point. The servo axis will move m?rri. It can be seen that the rr transformation can be performed, but rr is not independent (with reference), and it is moved to find it in the background coordinate system. s position.

Finally, on the basis of understanding the transformation of the lathe coordinate system and the realization of the tool setting, the specific numerical control language is combined with the process and programming.

The realization of the machining dimensions of the part is made up of a series of coordinate transformations, and has the same zero point, ie the machine point.

Each tool is independently tooled to obtain the tool offset value (the same method). If a knife is damaged, you only need to change the tool (request) to continue machining without affecting other tools.

If someone changes the coordinate value of the CNC system for some reason, only need to perform the return point operation, re-establish the background coordinate system X'OZZ to restore all the tool (point) coordinate transformation rr, no need to re-tool.

The final realization of the part size can be done by modifying the tool nose coordinate transformation rr. The modified value is: nominal value - measured value = difference.

Use this difference as the tool (tip) compensation value (wear). If the measured value is large, the tool offset value will be changed and the computer can automatically compensate.

When performing a tool change operation, perform a 000 undo tool offset.

In this paper, using the two real-time algorithms of lathe coordinate system transformation and relative coordinate tool setting, a simple user-oriented operation mode is sought, which realizes the dynamic correspondence between the programmed value of the part processing program and the nominal value on the part pattern, and reduces the tool setting. The process avoids the inconvenience caused by the failure of the reference tool. With this method, multiple tools on the lathe need only be independently matched to each other. There is no need to establish a reference tool. All the tools have their own tool compensation values, which provides a good operation mode for the user to carry out numerical control machining.

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