how the tension is maintained in a printing machine ? what's the working principle ?

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how the tension is maintained in a printing machine ? what's the working principle ?

which tension(s) should be same or should be close to each other ?

1) Unwind

2) Infeed

3) Outfeed

4) Rewind


Which motor's frequency(ies) should be same or close to be same ?

1) Unwind Motor

2) Infeed Motor

3) Outfeed Motor

4) Rewind Motor

Machine is Rotogravure Printing Machine (Press)
Made by : Sotech (China,Guangdong , Zhen Shen City)
Model No. : SAY1000A10
No. of Stations : 10 Stations (10 color job can be printed)
Simultaneously 2 jobs (or 2 orders) can be printed (2 unwinders & 2 rewinders)


thanks
 
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At first...
General principles in printing machine tension control:

Machine start:
All units of machine start slowly increase speed.
The unwind and infeed drives run a bit slower than the print units and the outfeed and rewind run a bit faster than the print units.
If the unwind rollstand is controlled only by brake, brake force for web tension is near zero.
Immediately after the machine has started , tension measuring in outfeed slowly decreases outfeed speed until tension setvalue for outfeed has been reached.
Rewind drive has own tension system between outfeed and rewind units to keep rewind roll tension stable.
Usually between outfeed and rewind has been placed so called dancer roller, which provides a small buffer storage of printed material to help keep tension in setvalue value.
Unwind and infeed has same principle for setting the desired tension, but opposite way , it is by decreasing speed.
Brake controlled unwind rollstand slowly increases brake force , until web tension is in setvalue between unwind and infeed.
Dancer roll system can be used here too.
If there is dancer arm, tension can be measured by setting pre-force for dancer arm and measuring arm position with potentiometer.

When the engine speed increased , there is three ways.
1. Speed up command increases speed of infeed roll and measured tension between infeed/outfeed increases outfeed roll speed,
until tension value = setvalue.
2. Speed up command increases speed of outfeed roll and measured tension between infeed/outfeed increases infeed roll speed,
until tension value = setvalue.
Usually unwind and rewind both have their own individual control systems.
3. Increase speed via unwind brake. ( not good system , all fluctuations in the brake affects the speed of machine.)
( Printing to paper can cause web-breaks very easy ).
Speed up decreases brake force of unwind roll and measured tension between infeed/outfeed increases infeed roll speed,
until tension value = setvalue and higher speed has been reached.

When the machine speed is decreased , same three ways used as opposite.


Made by : Sotech (China,Guangdong , Zhen Shen City)
Model No. : SAY1000A10
Click to expand...
Cant find Sotech machines tech. data or info in web.
 
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    munzir

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What should be the reference voltages (generated by the pots) to the PLC modules ? should they be remain same when machine is running smoothly ?

What should be the difference in frequencies for the unwind, infeed, outfeed & rewind motors ? if the machine is running (for e.g with 80m/min speed

thanks
 

What should be the reference voltages (generated by the pots) to the PLC modules ? should they be remain same when machine is running smoothly ?
Click to expand...

Reference voltage depends , how the basic adjustment and calibration is done.
Usually settings are done thisway....
- dancer arm or roller in midway = potentiometer in midway when machine run at "normal" speed and tension ,
thisway we have max. movement mechanically and in control signal.
Remember : pot. position and so pot. signal value is function of tension.
When machine is running smoothly, pot.meter signal should be relatively stable, small variations in control voltage is normal.
( Oscillations in fixed frequency and amplitude over +/-5% of control signal is abnormal.)

What should be the difference in frequencies for the unwind, infeed, outfeed & rewind motors ? if the machine is running (for e.g with 80m/min speed
Click to expand...

Impossible to say without knowing transmission ratios of the motors.
Generally infeed / outfeed speed variations should be very small and smooth.
Unwind & rewind speed variations are usually a bit higher .
 
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    munzir

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**broken link removed**

A printing press is a device for applying pressure to an inked surface resting upon a print medium (such as paper or cloth), thereby transferring the ink
 

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