Rewinding and Doctoring Machines

Print inspection and rewinding machines have by now, found their way into most converting companies due to their multiple role in quality assurance, optimum utilization of lamination and slitting equipment at their full rated speed and saving of downstream raw materials such as secondary substrates and adhesives.

Since these machines are more in the nature of quality assurance, cost reduction and supporting apparatus rather than those that add value to the product, it needs to be kept in mind that while selecting this equipment, the add on cost of these operations are kept to the bare minimum to keep the impact on the per kg cost of laminate at the least possible level.

Thus the advent of reversible print inspection and rewinding machines which confer the following benefits over the traditional uni directional machines-

• Inspection rewinding reverses the arrow mark direction of the substrate, making it necessary to restore the substrate to the original direction for downstream lamination and slitting operations. Accordingly, on a traditional uni- directional machine, full size jumbo reels produced on the printing press after the inspection and editing process on the rewinding machine have to be unloaded from the rewinder and re- loaded onto the unwinder, making the changeover exercise time consuming and labor intensive. Some convertors try to circumvent this by making the required changes on the printing cylinders, so that the substrate is printed in the wrong direction and restored to the correct direction while Inspection rewinding. This practice however pre-supposes 100% inspection of printed reels and requires that each and every reel is inspected, irrespective of whether it has unacceptable defects. In either case, valuable resources of time, labor and power are lost. With a reversible machine for the inspection process, the reels to be inspected can be selectively edited while rewinding in the forward direction and thereafter the defect free reel in the correct direction for the onward processes can be obtained by reverse running the machine at full rated speed.
• An additional advantage with reversible inspection rewinding machines is that the operator instead of having to be extremely attentive and stop the machine in the instantaneous made, would press the defect button, which would slow down the machine speed and parallelly reset the meter counter to start counting the meterage of the defective material passing. The operator could then closely monitor the passing substrate for defects and stop the machine precisely where the defect ends. He would then mark the web at this position and run the machine in the reverse direction and, guided by the meterage indicator, stop the machine at the precise point where the defect started. Then, depending on the length of defective material which has passed, he could either cut out the material at the main rewinder or rewind it on the (Optional) auxiliary rewind unit provided. Once the defective material is removed in either manner, he would resume normal machine operation.
• The reversible Web inspection rewinder offered by SP ULTRAFLEX can on request be made suitable for incorporation of an on line 100% defect detection system or even carry out the required actions on the basis of the output provided by such system fitted on the printing press, thereby totally eliminating the chances of lapses due to human error.

Doctoring and re-reeling machines are used to salvage badly rewound coils produced on Slitting and rewinding machines which would otherwise be liable for rejection due to reasons such as telescoping, loose winding and bad edge finish.

The following is a summary of the benefits of reversible Doctoring and re- reeling machines over the traditional uni directional machines-

• Rewinding badly wound reels produced on the Slitter rewinder reverses the arrow mark direction of the substrate, making it necessary to restore the substrate to the original direction to comply with the customer’s specifications. On traditional doctoring machines, the material, after winding for the first time has to be taped, off loaded from the rewinder, replaced by a fresh empty core, inserted again on the rewinder, threaded again and taped on to the fresh empty core before re- starting to reverse the direction. This activity is time consuming and labor intensive. As against this, the unwind and rewind sections on a reversible doctoring machine are functionally identical, so the material can be reversed and restored to the original direction without off loading the reel from the machine.
• It often so happens that most of the reel is good and simply to restore a few layers near the surface of the reel, the entire reel has to be wound not just once but two times. On a reversible machine you simply need to rewind the reel till the bad portion is unwound, then reverse the machine direction to obtain the finished reel.

Standard features of the DRM REV include :

• Air shafts for unwind and rewind sections, suited for 76 mm and ID cores
• Vector driven servo motors for unwind and rewind sections
• Speeds of upto 400 m/min