This article mainly introduces the CNC transformation process of the mcfhd80a horizontal machining center.
Mcfhd80a horizontal machining center is a numerically-controlled machine tool for producing reducer housings in Dongfeng Bridge. The machine tool was imported from the Czech Republic in the early 1990s. The original control system was the Siemens 820m CNC system. Because of the aging of the system, unstable operation, and frequent failures, the CNC was proposed.
First, the numerical control system hardware configuration
The NC transformation of the machine tool adopts the fanuc-0i-mc control system + αi series AC digital servo control scheme. The hardware configuration is shown in Figure 1.
Figure 1 hardware configuration
Mcfhd80a machining center in addition to the three basic geometric axes, there is a rotary table is also used servo drive. Therefore, the servo axis has four axes, which are x, y, z, and b. Among them, three basic axes of x, y and z all use grating scales to directly detect the displacement of the worktable to form a full-closed-loop control.
Its magazine is a hydraulically driven chain magazine, which can accommodate up to 60 knives, and the tool exchange uses a mechanical tool changer.
The main components of the control system hardware
Basic Control Unit (2 slots): Specifications a02b-0309-b502;
Motherboard: The specification is a02b-0309-h102. It contains a programmable machine controller pmc-sb7;
Cpu board (32m dram/486): specification is a02b-0309-h006;
8.4 inch color lcd/mdi device (horizontal): Specifications a02b-0309-h124#m;
i/o unit: The specification is a02b-0309-c001. Input/output points are 96/64 points;
I/O module for operation panel: Specification a02b-2002-0520. 48/32 points for input/output points, hand pulse generator interface;
Portable hand pulse generator: specification is a860-0203-t012;
Position encoder: Specification a860-0309-t302. 10000 rpm, 1024 pulses/rev.
Feed servo motor
The new servo motor is selected according to the original machine feed feed servo motor rated torque. The x-axis, y-axis and z-axis are all motor a40/3000i with fan rated torque 53n.m. Among them, the y-axis motor has a brake to prevent the spindle box from falling vertically when the machine is powered down;
Due to the limitation of the installation location, the b-axis motor cannot be selected according to the original motor specifications. The specific description is as follows:
In the original control system, the model of the b-axis servo motor is 1ft5076-0ac71 and the locked-rotor torque is 22nm. The corresponding fanuc servo motor model is α22/3000i. However, the α22/3000i flange size is larger than the 1ft5076-0ac71 motor flange size. The existing structure of the machine tool determines that the flange size of the new motor cannot be larger than 142×142. Therefore, the b-axis motor cannot select α22/3000i. Not only α22/3000i cannot be selected, but α12/3000i cannot be selected. The flange size of the α12/3000i is also 174×174. In the end, it had to use α8/3000i motor to drive the table rotation;
Spindle servo motor: Select the new motor according to the spindle motor power of the original machine tool. Select the motor a22/7000i;
Servo amplifier: b-axis servo amplifier selection svm1-40i. The servo amplifiers of x-axis, y-axis and z-axis all use svm1-160i;
Spindle amplifier: specification spm-26i;
Power module: According to the selected spindle motor and servo motor, calculate the rated output capacity of the power module, the maximum output capacity of the power module, the peak output capacity of the power module, the power module should be selected psm-55i;
Raster Interface Board: Specifications a02b-0236-c205;
Scale: The x, y, and z axes are equipped with a grating to form a full closed loop control. The scale model is HEIDENHAIN lS106. The scale output 11μa sine wave signal;
The scale signal conversion circuit converts the 11μa sine wave signal output by ls106 into a ttl square wave signal.
Second, the bus settings
1. I/O bus settings
The installation location of each module is represented by the group number, base number, slot number, and module name, so the address of each module can be identified by these data and input/output addresses. The number of di/do points (bytes) occupied by each module is stored in the programmer, so only the first byte address of each module needs to be specified, and the addresses of the remaining bytes are automatically specified by the programmer.
Since 0i-c itself does not have a built-in i/o board, connecting peripheral devices must be extended through the i/o module. Two sets of slave units are attached to the i/o link connector: the operator panel i/o module and i/o unit, and the handwheel is connected to the i/o unit. Two sets of slave units are used, as shown in FIG.
Figure 2 i/o link connection diagram
The i/o address of two groups of slave units can be set as follows:
The i/o address input of the operation panel i/o module starts from x0, 0.0.1./6, and the output starts from y0, 0.0.1./4. The i/o address of the i/o unit starts from x006, 1.0.1.oc02i; the output starts from y004 and is 1.0.1./8. Figure 3 shows the i/o setting screen.
Figure 3 i/o address allocation
2. Setting of fssb servo bus
Systems using fssb, cnc, servo amplifiers, and split detector interface units are connected to each other by fiber optic cables. These amplifiers and pulse modules are referred to as the driving part. The drive numbers (1, 2, 3, ..., 10) are sorted in ascending order according to the drive allocation; the smaller the number, the closer the drive specified to the cnc. Closed-loop servo system connection diagram shown in Figure 4. M1 in FIG. 3 denotes a first separate detector interface unit.
Figure 4 Closed-loop servo system connection diagram
When the automatic setting is performed using the fssb setting screen, the axis numbers of the x, y, z, and b axes are set to 1, 2, 3, and 4 on the amplifier setting screen. The separation detectors m1 for the x, y, and z axes on the axis setting screen are 1, 2, and 3. The b-axis has no separate detector and is not set. Figure 5 shows the fssb setup screen.
Figure 5 fssb setting screen
Third, the work table indexing function design
1. Indexing table mechanical transmission scheme
The rotary table is an indispensable part of CNC machine tools such as CNC milling and machining centers. Its role is to perform rotary indexing or continuous rotary feed in accordance with the cnc system's instructions. The commonly used rotary table has indexing tables and CNC rotary tables.
The function of the indexing table is to rotate the table and its workpieces at a certain angle when indexing is required. Its role is to automatically complete the workpiece in the processing of the indexing surface, to achieve a complete installation of a few surfaces to complete the processing. According to the different positioning elements used, there are positioning pin type indexing table and rat tooth disc type indexing table. Generally, the indexing motion of the indexing table is limited to certain specified angles, and it is not possible to achieve indexing at any angle within the range of 0 to 360°. Mcfhd80a is a horizontal machining center produced in the Czech Republic in the 1990s. Its worktable is a rat tooth disc indexing table. The indexing plate consists of the same upper and lower toothed plates. The tooth number of the toothed plate is 360 teeth, so the minimum graduation is 1°. The advantage of this indexing table is its high positioning accuracy, good rigidity, and ability to withstand external loads.
The b-axis of the machining center, ie, the rotary axis of the table, adopts a semi-closed-loop control method. In this design, the indexing function is designed using indexing CNC axes.
2. Gradient NC axis pmc programming
Indexing NC axis positioning timing shown in Figure 6.
Figure 6 Indexing table positioning work sequence diagram
The sequence of actions is as follows:
The program specifies b instructions;
Cnc sets the b-axis release signal buclp(f61.0);
The worktable is lifted and the b-axis clamping is released. After the worktable is lifted, the b-axis release completion signal *beucl(g38.6) is 0;
Then cnc sets the b-axis release signal buclp(f61.0) to 0, indicating that it has received the *beucl signal;
When pmc knows buclp is already 0, pmc sets the *beucl signal to 1;
b axis rotation;
When the deviation of the b-axis from the command position is less than the in-position width of the axis (parameter 1826), cnc sets the b-axis clamp signal bclp(f61.1) to 1; at the same time, the b-axis servo is turned off;
When pmc knows that bclp(f61.1) is 1, the worktable falls and the b-axis clamps. After the clamping is completed, the b-axis clamping completion signal *beclp(g38.7) is set to 0;
When *beclp is 0, cnc sets bclp to 0, indicating that cnc has received the clamping completion signal *beclp;
On the pmc side, *beclp becomes 1 when bclp becomes 0.
Using the indexing axis function, using the b command to specify the indexing angle in automatic or mdi mode, you can program incrementally or in absolute values; in manual mode, you can only perform manual referencing. When manually reset to zero, the indexing operation timing is basically the same as the b command.
According to the timing chart in Figure 6, the corresponding PMC (programmable machine controller) program can be programmed, as shown in Figure 7. In this program, the m code is also designed for the lifting and falling of the workbench, which is required for maintenance and adjustment. Therefore, there are two startup signals for the table to lift: buclp (f61.0) and m54 (r10.6); there are also two signals for drop start: bclp (f61.1) and m55 (r10.7).
Figure 7 Indexing table pmc program
Also for maintenance and adjustment purposes, the b-axis hand crank and jog feed functions are also designed in the pmc program. When these manual operations are performed, first set the 8132#3 parameter to 0 to cancel the b-axis indexing function. In addition, before the manual operation, the table must be raised with the m code to release the interlocking of the shaft; after the manual operation is over, the table is dropped with the m code. If manual operation is no longer performed, set parameter 8132#3 to 1 to restore the indexing function. It is worth mentioning here that the modification of parameter No. 8132#3 requires the restart of the power-off cnc, which brings some inconvenience to the operation. However, the manual operation is only used when the maintenance is adjusted and is not required during normal operation.
IV. Conclusion
This paper proposes a fanuc-0i-mc numerical control system + αi AC digital servo control scheme, which has been successfully applied to CNC transformation of mcfhd80a horizontal machining center. After the transformation, the machine tool fully met the anticipated requirements for processing and invested more than 9 tons of heavy-duty vehicle reducer housings. The past two years of operation show that the system is stable and reliable.
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