Folding-carton die cutting: Five fundamentals

Want to increase efficiency? Focus on these pre press and on press make ready issues.

By James Banister,
Cutting Process Manager, Rock-Tenn Co.

Efficiency is the focus of the folding-carton industry today. Converters are faced daily with the need to cut costs. An efficient die cutting press, for example, should average about 88 percent run-time. To achieve this level of productivity, short make-readies are a must.

The problem facing converters is not how fast the manager can push the operator to put a job on and get it running but what is actually accomplished--or not accomplished, prior to the on-press make ready

Experience has shown that 80 percent of an efficient on-press make ready is really out of the operator's control and actually takes place before the job even gets pre-madeready. This article looks at five fundamental aspects of efficient folding-carton die cutting Each represents a percentage of importance to the overall task.

These include:

• Carton design--20%
• Production layout--30%
• Die and tooling--30%
• Pre-press set up--10%
• On-press makeready--10%.

By concentrating on the efficiency of each aspect, not only will your operation reduce downtime, but a machine-makeready average of only one hour for a whole month is achievable. I can personally attest to that.

Carton Design -- ±20%
How can a carton's design play a part in speeding die cutting? As brevity is the soul of wit, so are a carton's simplicity and the die to cut it the key to easier production. Three areas should be questioned.

Combination Rule: Is it really needed, or is it used as a crutch? Instead, try alternative types of scoring, such as reduced bead creasing.

Hairpin Slots: These are highly labor-intensive for both pre-makeready and make ready In addition, they can leave scrap in the load and can trip electric eyes. Eliminate hairpin slots, if possible.

Special Features and Their Location: Opening features, glue assists, reverse cuts, embossing and debossing may all be necessary to a carton's design but add time, cost and potential die cutting problems down the line.
The following design-related suggestions can go a long way to smoothing production.

• Each department manager prior to the final customer approval must sign off on all designs going into production, keeping in mind the rules of simplicity. (Make the design miter- and machine-friendly.)
• If a designer has to rush something to a customer, place a label on the design that reads, "This Design is Pending Approval by Production Personnel. Any necessary changes will be made, and a new design will be generated for your approval."
• Don't buy into your salesman's line, "We can't change this design because the customer has already approved it."
• Impose a CAD number to the individual carton design so that die side and printed side are consistent in your facility.

Production Layout -- ±30%
Five aspects of the carton's production layout are critical to the die cutting process. They will either make or break your efficiency.

The layout needs to be generated at the Estimating or Design Sign-off Stage: Make sure the estimating layout is approved by cutting before it is used for quotational purposes. It isn't a matter of how many cartons we can get on a sheet, regardless if it can blank or not, but getting the most items on a sheet that will run quickly and effectively. Knowing the number of cartons per sheet and actual sheet size helps capture a true price while estimating.

Use blanker operator input: Customer service, the estimator and employees not directly involved in blanking should consult the blanker operator to help prevent problems before they happen. The operator will feel included and want to make the layout a success when it hits the press. Such cooperation also promotes an important Team Atmosphere.

Visualize the sheet/layout through each phase of the cutting press: How will it travel through the stripper? What things can catch? Does the female stripper need carrier rule in it? How will it blank? What areas will catch on the grid or flat top? How much offset on the female blanking grid will be needed for single/double-knife?

If your company has blankers and non-blankers, lay out the job with breaker knives so you can sheet blank-it for the air hammer if needed. Prepare ahead of time for those rush jobs.

Use the paper's grain direction and double-knifing to eliminate internal stripping and assist in blanking: Grain direction is more critical to die cutting than it is to printing. Double-knifed jobs require special attention to the layout. Most often, a stiff grain sheet will be the only effective option. If you don't have to strip, don't. This is a labor-intensive part of the make ready process.

Generate a vinyl or Mylar of the production layout: This can help the die room or pre-makeready get started on making in-house tooling, if necessary.

Die and Tooling -- ±30%
Although the die and tool constitute about 30 percent of the on-press make ready, about 75 percent of the pre-press and pre-makeready efficiencies lie in the folding-carton die and tooling. Here, three areas should be examined.

Do your homework: Ask your salesman about run quantities and estimated number of production orders per year. Investigate as to what die and tooling costs are actually being built into the estimate?

Place timely orders. This helps reduce the cost of shipping. Some suppliers will offer free shipping with five working days notice. Enough time is also available then to assemble "burned only" tooling in-house.

Laser tools versus handmade and universal tooling: Know the benefits and drawbacks of each to help determine the best choice for the new size and style going into production. (Refer to chart.)

Know what types of tools to order: Steel, maple or Rayform dies; Strip Clip, regular or Power strippers; steel, flat-top, universal or Rayform blankers; and matrix, phenolic, steel or hand-cut Female Counter Plates are some of the choices.

Pre-Press Set Up -- ±10%
Pre-press set up constitutes the other 25 percent of pre-press and pre-makeready efficiencies. A variety of easily-accessible equipment and an organized method to accomplish set up are vital.

These items include a counter-transfer machine; an Easy-Set table; extra storage cassettes; a hoist and systematic storage with humidity control.

A lift cart is an essential element to maintain a one-man crew for pre-press set up as well as worker safety.
Finally, a Centerline system allows dies, strippers and male blankers to be set almost exactly in frames with minimal adjustments (if any).

As to method, nothing beats organization: A place for all components and all components in their place. File folders should be kept with saved job information for both diecutter operators and pre-makeready personnel. Also, cleanliness and accuracy must be the watchwords throughout.

On-Press Make ready±10%
An efficient die cutting operation now moves into the final stages. For on-press make ready, four areas stand out in need to special attention.

Job-setting histories: Knowing the proper information about a job will only speed on-press make ready when the job is run again. This data includes feeder, tonnage and delivery load settings; Bernoulli (Air) bar between platen and stripper, and the stripper and blanker; and the location of the extra knife and counters.

Employ the Pit Stop Concept: Have a neighboring pressman set the feeder while two others take the die-tools out of the press. Then, have the same pressman set swords and perform line clearance while the diecutter operator and assistant are inserting the next job's tooling.

Keep all necessary tools at hand: This list encompasses Allen and crescent wrenches; die and nick grinder; spot-up tape (self-adhesive); a toolbox; make ready knife; and tape (masking and two-sided).

Use available machine and tooling alignment techniques: For tools, these might include T-Rails; plastic bolts for male and female strippers; 1-mm plate micro adjusters; and a Centerline system (the same unit previously used in pre-press set up).

The Quicklock System from The Bobst Group is one new piece of technology that will help eliminate 95 percent of all press adjustments, thus saving precious time on the make ready, and virtually eliminates the need for pre-makeready.

Proper preventative maintenance, along with records of diecutting-press footprinting or press leveling to use as a basis of operation, wrap up the on-press make ready requirements.

Other Resources
To make a folding-carton die cutting operation as efficient as possible, keep in mind and make use of these other important information resources: Expertise of machine manufacturers,information and advice from die and tool suppliers; the Bobst ABCq book and other training manuals, independent consultants and trade associations such as IADD and its associated die cutting and diemaking seminars.
Q 2001 Intl. Assn. of Die cutting and Diemaking, Crystal Lake, Ill.

Die & Tooling Choices: Laser vs. Universal

Source: Rock-Tenn Co.

Copyright © 1992- Packaging Graphics. All rights reserved. James Banister. No part may be reproduced without prior written approval.