The present invention pertains to an approach to facilitating an efficient order change in the dry end conversion of a corrugated paperboard web.
In a corrugator dry end, the corrugated paperboard web is longitudinally scored and slit into multiple parallel out put webs (or “outs”). The outs are directed through one or more downstream cut-off knives which cut the output webs into selected sheet lengths. When two cut-off knives are used, they are vertically separated and each is capable of cutting the full corrugator width web. A web selector, positioned downstream of the slitter scorer divides the outs into two groups, one of which is directed to the upper cut-off knife and the other to the lower cut-off knife. Order changes must be effected while the upstream corrugator web end continues to product and deliver the continuous web to the slitter scorer. After an order change is completed, the slit and score tools must be repositioned or “set-up” for the next order. The time required for the set-up is a critical parameter related to the minimum length of order that can be run for a certain class of slitter scorers.
Prior art has developed two basic slitter scorer configurations.
With this type of single station slitter scorer, the minimum order length can be very short because the individual head motors can be reprogrammed in a control sense to effectuate another head move with very short time delay. The speed at which order changes can be made is restricted by the time that it takes to move the heads from a current running position to the new running position in the gap 15. The order change speed is a function also of the gap pulling space, and the acceleration rate of the knife 30 controlling the tailout web 40. For reasonable gap pulling speeds and knife accelerations, order change speeds on single station slitter scorers of the type shown in
For this and other reasons, the dual station slitter scorer of
One embodiment of the dual station design is shown in
Another embodiment of the dual station slitter is shown in
The invention relates to a method of using order look ahead and analysis to achieve dry end order change that is very efficient in terms of minimizing recovery time after an order change as well as minimizing waste associated with an order change. In accordance with the present invention, a quick recovery of a slitter scorer is accomplished by use of an automatic auxiliary (or second) score axis on one or both stations of the slitter scorer and the use of order look ahead to partially set up the slit tools and fully setting up the score tools on the unused automatic auxiliary score axis on the station running a current order.
Assume the current running order is positioned in the order queue immediately preceding a short order. This short order necessitates quick recovery after order change from the currently running slitter scorer station to a slit/score head position required for the order after the short order. To achieve this, non-used slit tools on the station associated with the current running order are set up at the positions associated with the order after the short order, to the extent they can be, consistent with not interfering in position with the currently running slit heads. The score tools on the unused auto auxiliary axis of the station running the current order are set up for the order after the next (short) order. Lastly, the quick recovery approach will utilize, to the extent possible with the working web width, asymmetric trim so that the trim slit head on one side of the currently running slitter will remain in its currently running position to accomplish the set-up for the order following the short order. This will eliminate the requirement of the robot to reposition this slit tool in the order setup process and thereby substantially reduce the recovery time.
In accordance with the present invention, a quick recovery of a slitter scorer is accomplished on a slitter with one or more redundant score axes. The dual station slitter concept requires a minimum of one slit axis 21 and one score axis 22 for each station. Automatic auxiliary score axes 22a are added to one or both stations of the slitter scorer, as shown in
A typical sequence of orders using the present invention is shown in
At the end of order “0” in Sequence A, an order change occurs to Sequence B of
Immediately after order change to Sequence B, the first score axis 22 of Station I will begin to be set up for the third order after (order “3”) after the running the order on Station II. The unused score axis 22a on Station II had previously been set up for the third order after the running order of Sequence A. This setup is now for the second order after the running order of Sequence B.
The Sequence B short order on Station II completes transitioning to Sequence C, also a short order. In Sequence C, the current order “0” runs on Station I and the setup continues on the unused score axis 22 of Station I for the second order after the Sequence C running order. The setup is completed while running the short order of Sequence C. On Station II, the robot begins to set up for the order three ahead on the unused score axis 22.
To continue the analysis of
With the other look-ahead concept of the current invention, it would be possible to halve the required recovery time of the slitter for efficient running of short orders. For example, all the orders from Sequence B onward could be 20 second back-to-back orders if score head placement times for all orders were less than 40 seconds.
On the slit head recovery, orders from each alternate sequence must be run on a given station, so slit head recovery must occur within the duration of the run of a short order. A critical aspect of the current invention regarding slit head placement is that unused slit heads are set up between running positions of other slit heads, on the same axis, consistent with physical aspects of head interference. Yet, a second critical aspect of slit head recovery is that the trim slit head on one side of the machine stays engaged in its current running position during an order change with asymmetric trim after the order change. This will be possible as long as the resulting trim width adjustment on the opposite trim slit head is not less than the minimum slit width that can be run on the slitter. Since there are half as many slit heads as score heads, it is likely that the combinations of pre-positioning unused slit heads and taking asymmetric trim will allow quick slit head recovery. All move distances for slit heads will be very short as only physical interference of heads will preclude pre-position.
There are times when both score axes must be used to run an order due to close score spacing requirements. This situation is shown in
This application relates to and claims priority from U.S. Provisional Application Ser. No. 61/224,554 filed on Jul. 10, 2009.
Number | Date | Country | |
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61224554 | Jul 2009 | US |