The Dot rotor is driven by a hydraulic motor that is controlled by a PVG valve. The PVG valve adjusts the hydraulic flow to the motor (The speed of the motor). The PVG is controlled by an electric signal. The electric signal is between ½ supply voltage (no speed) and ¼ supply voltage (max speed).
Plug to PVG valve:
1 = + supply
2 = Signal
Ground = Ground
If the supply is 12 Vdc , then the signal will be 6 Vdc when no speed and 3 Vdc when maximum speed.
Manuel: When you set the rotor speed in manual (In the LineMaster), you set the signal to the PVG valve manual. If you set the speed to 50 % the electric signal will be 4.5 Vdc (If the supply voltage is 12 Vdc).
Auto: If you set the speed in Auto (In the LineMaster) you set the speed by entering dot pro meter. The standard rotor drum will make 4 dots for each round it rotates. The hydraulic motor have a sensor, the sensor at our standard motor will send 22 signals (+ supply) for each round it rotates. The pulse transmitter (the sensor for the speed of the machine) is “telling “ the LineMaster the speed of the machine. Now the LineMaster will calculate how fast the rotor must turn to obtain the Dot pro meter that is set in the Dot pro meter. It will then adjust the signal to the PVG valve by a PID Regulator. (It will always try to regulate so the speed of the rotor will make the Dot pro meter that have been set in the display.
The Controller PID function consists of three main input variables: proportional control, integral control and derivative control.
P: The proportional controller has the effect of reducing the rise time and will reduce, but never eliminate, the steady-state error. (Standard setting 20)
I: The integral controller has the effect o eliminating the steady-state error, but it may make the transient response worse. (Standard setting 25)
D: The derivative control has the effect of increasing the stability of the system, reducing the overshoot, and improving the transient response. (Standard setting 0)
Ms: This is how often the LineMaster should make the calculation: (Standard setting 300)
The sensor mounted at the front wheel, sends signals (+ supply) when the machine moves. The LineMaster receives these signals. To be sure that the LineMaster know how many signals it should receive pro meter it is important that the pulse transmitter have been calibrated. (See the manual for the LineMaster page 8)
Blockage of the rotor
It is very important that the rotor can rotate stabile. Therefore every day you use the Dot´n Line you should open all the shutters (one at the time), both the one for the normal flat lines and them for the Dot´n Line, and let some material run through. (Even if you are only using one of them)You must do this to prevent that the thermoplastic will settle inside the head. Settled material inside the head can block the rotor and also block the opening.
The thermoplastic must have the correct temperature, if the material is too cool, it will block the rotor.
It is important that the thermoplastic is melted and well mixed in the preheaters, and then filled in the machine through the strainer, and then there are no big parts (max 3 mm) of the material inside the machine boiler.
It is important that the material is not heated and mixed directly in the machine boiler, because it is very likely that there then can be “bigger parts” of the material that can flow in the Dot´n Line. This can block “disturb” the rotor and the outlet to the lines.
- The thermoplastic must generally be used within 6 hours after heated up (see manual for Dot´n Line page 25)
- If the rotor is lowered too much this can block “disturb” the rotor. (See the manual for the Dot´n Line page 22)
- Other mechanic errors can also block “disturb” the rotor. (Damage hydraulic motor, bearing or hoses)
When you are only making Dots (no flat lines) it is recommended that the recirculation plate is open maximum.