How to die, perfectly - The Noel D'Cunha Sunday Column

A die-makers task is to produce a cutting die which can create custom boxes – cut out to the exact shape and dimension. Many packagers may know this, but how many know or understand the process of making a perfect die?

In this Sunday Column, Biren Naykpura of Son N Naykpura demystifies die-making

22 Dec 2019 | By Noel D'Cunha

What is a die-cutting tool?
It’s a combination of wood, steel blade (rules) and rubber, which is put into a specific shape and structure such that when compressed, the substrate material cuts or crease to create specific shaped boxes.

What kind of machines are required to produce dies?
The basic machines are laser or router or jigsaw for cutting the ply or other base material and automatic, semi-automatic or manual benders to process the rules. Other equipment like milling machine to produce counters and plotter machine to cut rubber. which can be added depending on what other services a die-maker is providing.

What are the trends in material-use for producing dies?
It’s a quest for stability. It's a never-ending search for the ultimate piece of material over the years. All the materials have evolved. Today, the converters are producing carton or corrugated boxes on high-speed die-cutting machines. There is a demand for dies which have few on-press problems, as a result, one needs to use more stable die-board.

What is key to making a good die – technique or material?
The definition of technique – performance of artistic work or procedure varies from die-maker to die-maker. But choosing the correct material is key to producing a good die.

(L) Biren Naykpura with sons Brijesh (sitting left) and Keyur (standing)

What is the role of software – CAD/CAM, and such? What’s the time taken to design a die-board?
Good software can help complete the work faster, but it is also important that the die-maker has a good command over the software, he is using.

Today, the process is digital and automated. Die-board designs are computer-generated according to the box or packaging shape design. Using software, the printer's design file is automatically translated into a part program with all necessary machine instruction. Depending on the die-board design, the typical die-board design can be completed within an hour or less.

In a world where cost-cutting is the norm, what’s the impact on the quality of dies?
The only way to cut cost while making dies is, lower the grade of material. For everything else in production cost – labour, time and machines, there’s no change. Lower the grade of material can impact the quality of die, and subsequently the boxes.

What is broaching, and what are the benefits?
Broaching is simply the machining of a channel in the side of the cutting knife for the purpose of eliminating cracking of the face or edge of the knife and eliminating knife-edge distortion. What it does is, allows a minimum radius to be achieved, reduces makeready time on the press, consistent die-cut part quality and aids in achieving greater press productivity.

Using laser Vs CNC for producing plates for making dies?
Using laser and CNC (routing/milling) for producing has its own benefits and drawbacks. With CNC, the main advantage is easy control of kerfs’ width to hold knives but it’s a time taking and labour consuming process. Speed is laser’s USP as it will burn the full wood in one pass, but the challenge is in controlling kerfs.

There’s a demand for sandwich dies – What is sandwich die?
Sandwich dies are now facelifted – previously with two plywood, now with fibre reinforced with steel, which tends not to absorb moisture, more durable, precise, had a longer life span, and can be re-knifed multiple times.

CNC is predominantly used to produce sandwich dies. Why?
As informed previously, the CNC process has the benefit of controlling the width of kerfs which gives more dimensional stability and resistance to environmental factors. 

Why is rubbering such an important element of dies?
It’s the only product that is constantly moving on a cutting die. As I always say rubbers are more than just an ejector. Don’t ignore them. I would say rubbering was a long-term frustration but now it’s unique customer service. Previously it was done by machine operator/helper at the printer’s place but now the situation has completely changed. Packagers are getting pre-rubberised dies from die-makers. So, the machine can be up for further processing of makeready in no time.

How does it affect speed, and runs?
There are all sorts of machines, running at different speeds. They function differently and deliver the product with various methods. Not only speed and runs but many problems can be solved with proper techniques of rubbering. Proper rubbering can prevent angle hairs and flaking.

Can a die produced to use at a speed of say, 5,000iph be run at 8,000iph speed?
No, it can’t. The rules, the depth and width of the kerf, and the rubbering would be different for different speeds.  As mentioned in the trend of material, the need for a stable die-board becomes important.

Soft creasing – the impact of matrix and channel lines?
It’s all about choosing, using and troubleshooting. There are many options available for creasing makeready nowadays. For example, creasing matrix, characterised by their flexibility and quick operational readiness. The Pertinax offers a higher quality than the matrix. This is a custom-made counter plate with engraved channels. Always ready-to-use and easily re-usable. Then there’s the Steel Counter Plate. This variant of creasing makeready may be used for long runs and as well as for repeat jobs. The advantages are high machine speed and excellent creasing results in high precision from first to the last impression.

There are dies for stripping and dies for blanking.  What kind of precision is required while producing dies that are run on the same machine?
All good tool materials are in vain if the toolmaker lacks the understanding and know-how for the optimum application. Of all the converting tools, the blank separating tool probably has the greatest influence on the layout of blanks. This means that jobs must be carefully studied to see if they correspond to the requirements of the punching machine.

One pass – punching and stripping – Why?
For a high level of production, good flexibility, and assured quality – it’s a fact that everybody knows. The quality of the stripping technology is a major factor in maximising production efficiencies and reducing setup times in the die-cutter. It saves a lot of time at the post-press level.

Delivery of dies – speed-to-market is key? How do you handle it?
It’s all about planning. Well planned production will lead to timely delivery. We plan production in such a way that we can achieve maximum output from production along with a high quality of standards.

Die-punching machines have moved from manual to automatic. How has that changed the way in which you first produced dies, to now? Has it become easy or difficult?
Nowadays value addition is key to the next level. Converters are trying various paper boards, new substrates, a different combination of coating, etc. Die, it’s not just about plywood and cutting-creasing rules. It takes a lot of other things to make it work. It is difficult to provide a good die without having knowledge of all these things. With new automatic technology, we must update ourselves. We do that.

Expectations of customers and your challenges?
Expectations of customer are super-fast service. Some jobs cannot be done within a few hours. Complicated jobs take time. One cannot treat all jobs in the same way.

Most of the packagers underestimate the process of die-making. Another challenge is pricing. The customer wants quality, but they also want to remain economical. But as a supplier to the industry, quality is about being repeatable and durable and about having a product that is available. Being economical doesn't always end up being the right decision for that job. It's a choice that is made by understanding the entire process, including the end-use of the product.