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CREASING MATRIX
- Details
- Written by Robert Larson
Using a self-locating creasing matrix is the most economical, most accurate and fastest method of makeready for the die-cutting, folding carton and corrugated box industries--for most runs shorter than 1 million impressions.
The folding carton industry, like many other industries in this country and all over the world, has undergone many changes in the last 30 years.
With the introduction of Bobst automatic platen cutting presses in the 1950's, most companies began to realize the possibilities of shorter makereadies and running hours. In those early days, die and counter plates were pulled and strikes were made so the pressman could hand cut his counter while his press was running a production run. This was a big improvement over hand cutting while the press was down.
Self-locating creasing matrix was originated in England. The company of Frederick Squire Limited was founded in 1847 and was located in an area of London which was highly populated with printers and boxmakers. It was not surprising that the company, well respected for precision engineering, became deeply involved with the packaging industry. It was in the early 1950's that Mr. Harold Frederick Squire, the great grandson of the company's founder, began work on the matrix system, and by 1956 he had fully developed and patented the process. Although the present matrix bears little resemblance to the original product, the idea of incorporating steel into the matrix has never changed.
This type of self-locating, pre-formed matrix strip has obviously been available for a long time. Perhaps at some period, many companies have tried the product with less-than-satisfactory initial results. But at many companies this system has been used 100% for over 20 years. The system is ideal for Bobst presses on runs ranging from 25 M to 225 M sheet runs, and up to 1 million impressions.
We have one company with 100 makereadies per month; the average cost of matrix material is $5.60 per job, with savings in makeready time that exceed 100 M per year.
Most companies in the carton converting area will generally use material between the calipers of .014 and .028. The size of the available matrix does not provide sufficient variation if the company is following the usual converting process of using a material as nearly equal to the stock caliper as possible (that is, with a narrower creasing line in the direction of the grain than that used across the grain).
With this requirement in mind, the product line has been expanded. If we look at the new chart showing the present range as now supplied by Shreiner Creasing Matrix, it can be seen that the varieties now available to cover the same material range do give sufficient alternatives required by a discerning, quality-conscious folding carton converter.
One of the biggest problems facing the converter is the machine downtime during the makeready. With the conventional handcut matrix, it is necessary either to have the die ready early, which is not always possible, or to stop the machine to take an impression so the operator can cut out the scores while producing his present job.
Alternatively, expensive P.M.R. machinery can be purchased, which usually involve setting up a P.M.R. department. With a self-locating matrix, neither of these are necessary. As soon as the die is available, the operator or his assistant can locate the matrix easily and quickly, without interrupting production. Operators do this automatically, P.M.R. is easily achieved and downtime for this operation is almost eliminated.
The same procedure is possible with preformed, one-piece laser counters by the laser die manufacturers. But except for the special or awkward styles--where matrix strips are not effective--the cost of a laser counter plate is much higher than matrix strips.
V3 -- GT
As with all methods of conversion, there are advantages and disadvantages, and this system is no exception. With most matirx strips, it is usually necessary to tape the back edge of the matrix strip in the machine direction so that the sheets do not catch and break up after impression. However, this step has been eliminated with the introduction of the new G.T. with rounded edges. It is also better to consider another method when the crease length is 3/8" or less. There is not enough surface on that small a matrix strip to assure it will adhere to the cutting plate.
HERE ARE THE ADVANTAGES IN USING THE MATRIX STRIP SYSTEM
1. Easy and quick to use -- Savings up to 25% over hand cut methods
2. Cost effective -- In terms of time when compared to hand cut, and actual cost when compared with
laser counter plates
3. Comprehensive range of choice -- Over 35 color-keyed sizes to choose from with one matrix strip
manufacturer.
4. Saves on machine downtime -- Makeready completed on the die, out of the press
5. Easy to replace damaged pieces -- Peel off damaged piece and insert replacement piece
6. Gives equal results in quality and number of impressions as laser system -- Recently run
successfully to over 700,000 impressions
7. Outlasts hand cut system -- Two-to-three times the impressions of a hand cut matrix
8. Automatic for pre-makeready -- Can be completed by the machine operator or assistant while the is
Running another job
9. Eliminates the use and expense of pre-makeready machine for cutting out the matrix or for taking
pulls on the machine -- Makeready completed outside of press right on the die
10. Reduces capital equipment costs -- Extra plates to keep jobs lifted
HOW TO USE THE MATRIX STRIP SYSTEM:
The matrix strip system is easy to use. First, with the die out of the press, measure the creasing rules in preparation for cutting the matrix. In most cases, the measurements can be taken from plans used in making the die.
The second step is to cut the matrix strips into their required lengths. This can be done with hand-held mitering pliers or with a mitering bench press. The bench press is designed to cut two ends of the matrix at one time.
In the third step, you simply place the locator strip on the creasing rule. If you have any problem because the rule has rusted, you can wax the rule with a candle to remedy the situation.
Once you've placed the matrix on the die, you then remove the protective strip to expose the adhesive on the matrix. Next, lock the die into the press and cycle the press once. This causes the matrix strips to adhere to the cutting plate.
All that remains is to remove the locator strips, which will leave the matrix ready to run in accurate register with the creasing rule.
The range of matrix strips currently available accommodates most calipers of board used today. Reverse bend, double crease, off centers, together with special deep matrixes, complete the line.
The following problems sometimes arise during a run on today's high-speed die-cutting machines:
1. The die is usually in excess of "20-up", and after initial 'cut' the board is extremely flimsy to hold
together.
2. Frequently it is too delicate and "breaks up" during the actual impression, the result being that
the "whole" board cannot move forward as one piece to the secondary operation of stamping out
and waste removal. The machine is stopped, the damaged board removed. Usually the machine is
then slowed down, say from 5,500 to 4,500 iph, or even less. The net result: A dramatic cost
increase in operating.
3. Additionally, the user has to insert more "nicks" in the cutting blades to allow the board to remain
whole and intact while still at lower speed.
4. Even when production completed, these nicks are still showing when finished cartons are supplied
to customer, frequently causing complaints.
5. With ordinary ejection rubber, they have to insert more nicks to hold board together, and run at
slower speeds than originally recommended by the machine manufacturer. This is not desirable
and very costly.
6. With ordinary rubber they also have to carefully measure the 1mm gab between rubber and blade,
and after frequent impressions this becomes even more difficult.
These problems can be controlled by using Shreiner Euro-Rubba, a special hardness profiled rubber.
The 1mm lip allows instant and accurate measurements along the required cutting rule. The rubber is positioned carefully, and the special hardness means that the rubber just "kisses" the board, allowing the nicks to remain completely intact.
This then means that the machine can be run at the speed recommended by the manufacturer for full cost-efficiency--without the nicks breaking. It also means that where users were previously putting in more nicks to hold the board together, this is no longer necessary, and the number of nicks can usually be cut by 50%, say from 6 to 3.
Profitability greatly increased by improving production flow by some 20% and no stoppages for "break up" to be released. Additionally, this technique cuts down on form-making costs by having dies made without rubber on those areas specified (from experince) or by instructing die-makers to use Euro Rubba on those areas.
There is room for the use of all three methods of production in most converting companies, with each company setting its own ratio depending on its work content. At the same time, companies which produce folding cartons within the range of board calipers indicated could convert as much as 80% of their production to the matrix strip system. They would experience savings in time and dollars with the self-locating matrix strips, while maintaining the quality required by the industry for cartons to work successfully on high-speed packing machinery.