Perfecting on 40gsm problems!!

Pwa

Member
Hi All,
We need to do perfecting on 40gsm using SM CD 74. the first job we ran went alright with no problems, but after that every job we run on 40gsm, the sheets keep dropping after the perfecting unit(same paper size and setting as the previous job). I've tried changing the air setting, didn't work. The grippage was 4-5mm. Has anyone had this or similar issues. any help/suggestions is highly appreciated.
Thanks
Patrick
 
Thanks Asif,
Yes,I've tried different gripper margins as well no luck. How do you check the pincer grippers? I've done a general check to see if the open and close on time and hold the sheets tight.
 
By "after the perfecting unit", do you mean it's dropping between storage drum and reversing drum...or reversing drum and impression cylinder? I would assume at storage drum, in which case my focus would be sufficient blow down to tail suckers and sufficient vacuum at tail suckers, give you've proven sheet length is set correctly. You mention a visual check looks good, so are you able to inch the sheets through ok, but at speed they drop? Asif mentioned checking pincer bar...you should grab the fixed (lower) gripper and see how much "play" is in the tube radially, same for the spring loaded grippers.
 
Thanks junker1984, it's all fixed, the air-settings were to high also the rotators needed to come on manually.
 

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