dog ear

[bspillai78]

hi all,

i am facing dog ear problem after perfecting unit, need help and suggestion from you all.

thanks & regards,

balaji.s

 

[couriergraphics]

a little more info would help. Type of press paper weight and such.

 

[bspillai78]

sorry for delayed reply,

press - sm102 4p

paper weight 70gsm,

problem occurs after perfecting unit, above 10000iph

 

[rapid3]

If the paper has an excessive curl (either up or down) when laying on
the storage drum, it will cause this. If the stock has a down curl and you
are not using suckers on the storage drum, then put suckers on & this will help
to straighten the stock out. If the stock has an up curl and you are using suckers
then take them off or flip the stock in the feeder.

 

[Mike Herndon]

If the paper has an excessive curl (either up or down) when laying on
the storage drum, it will cause this. If the stock has a down curl and you
are not using suckers on the storage drum, then put suckers on & this will help
to straighten the stock out. If the stock has an up curl and you are using suckers
then take them off or flip the stock in the feeder.

These are excellent suggestions. You can also check to make sure the sucker bar on the storage drum is not clogged and all are swiveling properly. The individual holes are small and can clog easily. The stock you start with is what makes the biggest difference. Small discrepancies in sheets size will limit how much speed you can get out of a perfector. We have two 640 perfectors running 12-13iph all day long. We've found the air bar settings for the storage drum to be critical. To much air the sheet will wrinkle and sometimes dog ear, too little air the sheet registration front to back will bounce. You should have a dial on the DS catwalks for these air settings; make sure it is working correctly. We set the air bar to 35-70 mbar depending on the thickness of the stock. The older presses have one dial the newer presses have 3-4. Make sure you are not losing air here. Check the small compressor underneath the OS side catwalks and follow the hoses, make sure none are kinked, dry rotted or broken. This will make a huge difference in how well your perfector works. Also, check the compressor itself and make sure it's working properly.

Head stop settings also make a difference and sometimes cause a dog ear ; make sure they are not maxed out one way or the other.

One last thing- Lock off the storage drum suckerbar when straight printing and turn the air bars down or off. Leaving the air bars on can cause the sheet to wrinkle in straight mode. Locking the sucker bar off can help eliminate fit problems and saves a lot of wear and tear. Good luck

Mike

 

[bspillai78]

Thanks mike & rapid,

i will check & come back

 

[turbotom1052]

try setting your headstops on both sides to the middle position... then set a sheet into the headstops and let in go into the press. stop press with access to gripper of sheet while its still in impression cylinder grippers to make sure sheet bite is to spec and even on both sides. this is a good place to start.