1 Introduction
Traditional cable cutting machines have relatively large tracking errors. To solve this problem, the built-in flying shear function of the Delta 20PM motion controller has been used to successfully meet various requirements, achieving synchronization between the conveying and cutting line speeds. By adjusting the width of the speed synchronization zone, different lengths of cables can be cut, ensuring the accuracy of the cutting.
2. Structure and Working Principle
2.1 Cable Cutting Machine
The structure of the cable cutting machine is shown in Figures 1 and 2. This is a typical application of the flying shear function in cable cutting equipment. The Delta 20PM has a built-in flying shear function, and the overall Delta electromechanical product solution with the DVP-20PM as the control core can be used to complete the control of the cutting blade and meet the equipment control requirements.
Figure 1 Cable cutter head
Figure 2 Cable cutting machine
2.2 DVP20PM Motion Controller
The Delta DVP-20PM00D is a programmable controller with dedicated motion control functions. The most significant feature of the DVP-20PM00D is that the PLC host directly provides electronic cam (CAM) functionality; in other words, the DVP-20PM00D is a PLC with built-in CAM capabilities. Therefore, in some applications, the DVP-20PM00D is simply referred to as the Delta 20PM motion controller.
The 20PM features two 500kHz inputs and outputs. In the CAM function, the X-axis is defined as the slave axis, and the encoder input axis as the master axis. After the CAM table is defined, the slave axis follows the master axis according to the defined curve. It adopts a high-speed dual-CPU structure, utilizing an independent CPU to process motion control algorithms, effectively implementing various motion trajectory control, logic action control, linear/circular interpolation control, etc. The cable cutting machine utilizes the electronic cam function of the 20PM motion controller to effectively solve the problem of unequal lengths that occurs during high-speed cutting. Key features of the 20PM:
(1) 20PM is suitable for high-speed, high-precision, and highly complex motion control applications;
(2) Multi-speed execution and interrupt location;
(3) 64K large capacity, built-in Flash storage;
(5) Two sets of differential pulse outputs, with the highest pulse output reaching 500KHz;
(6) Two sets of hand cranks for control;
(7) Built-in electronic cam (CAM) function, easily realizes applications such as winding, flying shear, and tracking shear;
(8) Supports PLC sequential logic control and NC control (G code and M code).
3. Cutting machine software design
3.1 I/O definition
X0 Counting Photoelectric
X1 Cutter Start
X2 cutting blade stopped
X3 Protection
X4 DC motor caused a malfunction.
X5 servo malfunction
X6 main control box emergency stop
OITPUT
Y0servoon
Y1 fault reset
Y2 Cutting Start
Y3 Push Line
Y4 buzzer
Y5 Cutting Indicator Light
3.2 Flying Shear Program Design Process
When writing a program to utilize the 20Pm flying shear function, the following steps should be followed:
Use DTO commands to set the flying shear data.
The program needs to calculate the fill data D100-D112, and its parameters are defined as follows:
D101..D100 Spindle Length
D103..D102 From the shaft length
D105..D104 Synchronization Length of Axis
D107..D106 Slave shaft synchronization ratio (F2/F1)
D109..D108 Maximum magnification limit of the slave axis
D110 acceleration curve:
0 const speed,
1 const Acc,
2 SingleHypot,
3 Cycloid)
D111CAM curve = 0
0 leftCAM,
1 midCAMall,
2 midCAMbegin,
3 midCAMend)
The calculation process for the parameters used to fill in data D100-D112 in the program is as follows:
(1) Calculation of D100:
D210 Cutting Length
D222 Meter wheel circumference
D212 Meter Wheel Count
D224 Actual Meter Wheel Total Pulse Count
D226 Cutting Length Pulse Count
D100=D226=D224=D210/D222*D212
(2) Calculation of D102:
D416 cutter wheel pulse x D426 speed ratio = D200 cutter wheel pulse = (D102)
(3) Calculation of D104:
D200 cutter wheel pulse x D172 synchronization range = D204 synchronization pulse = (D104)
(4) Derivation of D106 ratio calculation:
a. Spindle diameter D1 (mm)
Pulse count per spindle revolution R1 (Pulses/Rev)
Spindle speed F1 (Hz)
Spindle speed V1 (mm/sec)
b. From the shaft diameter D2 (mm)
From the axis, the pulse count R2 (Pulses/Rev)
From the shaft speed F2 (Hz)
From the shaft speed V2 (mm/sec)
c: Based on the fact that the linear velocity is the same during synchronization, i.e.
V1=V2
(F1*3.14*D1/R1) = (F２*3.14*D２/R２)
F2/F1 = (D1*R2*K reduction ratio)/(D2*R1)
= (D250*D256*D258 reduction ratio)/( D252*D254)
=D274
=D106 Pulse Ratio Synchronization Rate
(5) D108 multiplier cap
(6) Selection of D110 acceleration curve:
0-3 curve selection with stepwise smoothing
(7) D111CAM curve selection:
Choosing option 0 ensures that the cutter returns to the upper zero point after cutting and waits.
8: D112 result is OK
The above section completes the calculation and data filling process for D100-D112, which means it completes the design of the flying shear program.
3.3 Flying Shear Program Operation Monitoring
D1799 sets the X-axis input terminal polarity (PG0).
D1800 input point status b5DOG origin signal to count point D50LDPm125 invalid.
D1816=530 Origin Regression DOG Falling Edge Detection Origin Regression Direction A/B Phase Pulse
D1828 X-axis origin regression velocity
D1830 X-axis origin return deceleration speed
D1832 X-axis zero-point signal count N
After D1833 returns to the origin, the X-axis distance P k0 is supplemented.
D1838 X-axis target position (I) P(I) (Low word)
The current position of the D1848 X-axis is CP (PLS) (Low word).
D1864=H305 X-axis handwheel input response speed setting A/B phase pulse wave 4x frequency
D1846=100 X Single-speed positioning motion mode activated
D1846=40 Origin Regression Mode Activation
D1846=2000 Insert single-speed positioning motion mode start
The main program design is completed by writing the analysis process into a program based on the above analysis. Other security protections and additional functions are the same as those in WPL programming, so they will not be described in detail.
3.4 Electronic Camshaft CAM Curve
In CAM planning, the 20PM programming software—PMsoft—first generates the relative displacement relationships and then the velocity and acceleration relationships. However, here we are planning based on velocity relationships, so we need to generate the velocity relationships first and then the displacement and acceleration. PMsoft provides a convenient function that allows the exported displacement data to be imported as velocity data to complete the CAM drawing. The steps are as follows:
(1) Set the required resolution. Here we set it to 200 dots:
(2) Establish the velocity relationship on the displacement relationship diagram. Here we assume that position 1 is at principal axis position 100, position 3 is at principal axis position 200, and position 4 is at principal axis position 300:
(3) Export the displacement relationship graph and then import it as velocity data to obtain the velocity relationship graph we need:
In the generated displacement graph, the horizontal axis represents the pulse quantity fed back by the main shaft (feeding shaft), and the vertical axis represents the pulse quantity of the driven shaft (cutting shaft). The displacement (number of pulses) of the main shaft is the cutting length. During the movement of the main shaft, the driven shaft (cutting shaft) follows for one revolution, making one cut. In the speed graph, we can see that there is a synchronous cutting zone between the driven shaft and the main shaft, ensuring that their speeds are synchronized.
The above is an introduction to the flying shear function and how to establish a CAM relationship diagram. In the cable cutting machine, the main shaft (feeding) is not controlled by the 20PM, but its movement is fed back to the 20PM by the meter counter encoder. Therefore, the motion relationship between the feeding main shaft and the cutting driven shaft can also be established. The dynamic adjustment of the cutting curve is introduced. The CAM curve can be modified in real time within the program. Dynamic adjustment of the cutting curve is accomplished through the FROM/TO command. As long as it is written before the completion of the cutting cycle, it will automatically change in the next cycle. Various smooth curves are provided in the CAM curve parameters to meet the needs of smooth acceleration and deceleration.
4. Conclusion
The cable cutting machine based on the Delta 20PM motion controller has been debugged and is operating normally, with a cutting repeatability accuracy within ±1mm as required by the customer's process. The 20PM flying shear function has been successfully applied to the cable cutting machine. This is another successful application case of the 20PM flying shear function, which can be widely used in material cutting and other applications in various industries.
The DVP20PM is a motion controller in Delta's PLC family. It has powerful computing capabilities and can easily complete various two-axis and three-axis motion control. It is especially suitable for high-speed positioning applications with high requirements for position control and real-time response. It also has built-in advanced application functions such as high-speed winding, flying shear, and tracking shear. It is widely used in food processing, packaging, woodworking, machine tools, cable cutting and other industries.
