Calculating Die Cutting Tonnage Continued...

Let’s Get Really Technical:
 
A couple of us have actually talked about developing an on-line tonnage calculating website. It would be comprised of a database that held values and asked questions like; Strength values (Tensile) for most common materials (A), Shear strength values for several processes/rule types/ejection, etc…(B), Number of inches being cut (C), Thickness of the material (D). A X B X C X D = Tons 2,000

In fact, this is exactly how many software stress analysis programs work. They take a set of very obvious variables and make a simple calculation based on these (and other) numbers. It gives you a very consistent way of looking at every project you take on. Right or wrong, the answer is a base number to start with, and that is what we have gathered is the trick to determining proper starting tonnage numbers. Once you have this standard formula in place and trust that it will give you that base number, you can then depend on it and translate it to work in different machinery on your shop floor. Perhaps you have a string of ten punch presses and they all cut a little different. One is hydraulic, one is pneumatic, one is mechanical off a simple small cam while another throws off a giant flywheel that was welded back together by Uncle Joe a few years back. They all cut differently but they all have a factor you can use as a multiplier against that base number we just calculated out. It’s beautifully simple really, it just takes some time to develop and work out in your own shop, on your own equipment. Once you have that number, everyone can plan around the equipment you have vs. the projects you have with more confidence.

So then the formula may look like this;
(A X B X C X D) F = Tons (Where F is a press factor based on experience and/or a manufacturers guidelines.) 2,000 Putting this into a real life situation may look something like this; I have a ten up steel rule die cutting and creasing .018” paperboard. There are 1,000 total inches of cutting, creasing, stripping, support knives etc… I am using modern ejection materials. I am cutting on a platen style press.
17000(A) X 1(B) X 1,000(C) X .018(D) X 1(F) = 153 Tons. 2,000
Simple Formulas from above; C/6.5 = Tons (1,000 / 6.5 = 153.8 Tons) or (C X 400) / 2,000 = Tons (1,000 X 400) / 2,000 = 200 Tons

Both formulas work and give us a range that is safe and a good starting point.

Now Let’s Get Really Simple:
 
What seems to happen with all this fancy calculating in real world situations is that the base theory gets boiled down to simple formulas that work for similar situations. Most of us deal in very similar tooling and materials everyday and having a very fast and simple way of coming up with a safe base number is natural. If you are always working in paperboard in about the same caliper, taking the total periphery and dividing by a single proven number is a fantastic way to approach tonnage calculating. The same goes for plastic, steel, leather, or anything else you cut on a regular basis.

So, this article is not going to give a catch-all formula for determining tonnage for all materials on all press types, with all tools, because there are too many factors involved and nobody would ever use it in real life. What we can do is offer a base calculation where you plug in your own numbers based on experience. Your own situation will provide the best formula for you.

That base calculation would look like this;
Total Periphery to Convert X Material Factor / 2,000 = Tons Needed

Developing a living chart of MATERIAL FACTORS will then be the key to making this work in your business. We’ve been using paperboard a good deal in our discussions and it seems that a starting point for a folding carton manufacturer on a Flatbed style press would be a MATERIAL FACTOR of 300. The heavier gauge the material is the bigger the Material Factor. (1,000 Inches X 300) / 2,000 = 150 Tons Keep in mind that if your cutting process changes, maybe it’s as simple as going to a harder rubber or steeper bevel rule, you will have to use a multiplier to compensate for this change.

There is no trick of the trade in calculating the tonnage you need for a project but as you develop a more and more sophisticated list of materials and how they process on your equipment, you will have an estimating and production tool that will help you predict with greater accuracy how well a job will run, where it should run, how many up it can run, and whether or not it will run at all. You will have a leg up on the competition that is still shooting from the hip and this will really put the pressure on them…..

We’d like to thank all of the operators out there that are trying to improve their production techniques and came to The TECHTEAM with their questions!

Calculating Die Cutting Tonnage

Compiled & Written by The IADD TECHTEAM

Knowing How Much Pressure It Will Take To Convert Your Product Is One More Key To Success
 
Here on the TECHTEAM we sometimes see the same question more than once. The question of “how much tonnage will it take to cut this product?” is the most common, and also one of the hardest to answer because of the complexities involved in calculating a perfect number. In fact the question should probably be, “is it possible to calculate exactly the tonnage it will take to cut a specific product, in a specific material, on a specific press?” This article outlines the basic theory of calculating tonnage needed to cut and will give most readers a base starting point they can feel comfortable with for their business.

Here’s my problem with the idea of tonnage. It’s an intangible sort of a concept that really has no place at all in my business. It seems to change and move and act quite slippery and I really just don’t think I need to deal with it. That is true until I find out that the machine I just planned a job for in a very specific factory, on a very specific machine, on a very specific tool, in a very specific material, will not run because the machine doesn’t have the guts to get the job done. Then it becomes a factor that I should have paid allot more attention to right from the get go.

For most of us, the machines we plan around have all the tonnage we’ll ever need for 99% of the jobs we will ever see. I’d bet most estimators never even look at this factor when they plan a job. For many diecutters the advantage of knowing how to accurately calculate tonnage needed makes the biggest difference in faster make-readies, and that alone is well worth the effort of knowing how to at least get a good starting number. For some of us it will only make a difference when we are planning an usual job that needs to run perfectly the first time around, and that alone is also worth knowing exactly what you are talking about.

So, where on Earth do we start? How about a bit of theory? The tonnage needed to cut/emboss a material is strictly a function of the strength of the material, the shear power of the process being used to cut, the size of the image to cut, and other factors like flex in the machinery, ejection materials, air pressure build-up’s, etc… That being the case then we should be able to use a simple formula that says – This is the amount of image I have to cut/crease/emboss/etc. that has value A. This is how thick the material is and it has value B. This is the material that I am cutting and it has value C. Calculate them all out and I get an exact number that works every time. Answer D.

Straight from the from Machinery's Handbook 25th ED. P1924 “P = periphery x thickness x tensile strength(PSI) where P is cutting force in pounds.” That was easy! And in fact for many cases it may be a number that is good enough to get started. The problem lies in the fact that there are many different processes and techniques for cutting and each holds a different value that must be factored in, and there must be a starting value for the material you are cutting.

Over the past year we’ve been answering tonnage calculating questions and it’s really interesting to take a look at all the formulas being used out there. Here’s a typical and really great question. "Thanks for taking my call. Here is my question. I need to be able to figure if my die cutting press has enough tonnage for different jobs that we produce. We die cut anything from 10 pt to 100 pt. paper in different shapes and sizes. Sometimes they are 1 up, sometimes they are 100 up. Is there a formula that I can use to determine if I can run a job 2 up as oppose to 5 or 6 up? Something like 1 ton of press is equal to 6 in of cutting rule when cutting 18 pt. and 5 in of rule when cutting 24 pt. This would greatly help when trying to quote jobs knowing that I can't die cut as many up as I print. Thanks in advance for your help.”

Here’s a sampling of formulas and answers that worked for this and other applications;

• 6.5 inches of cut rule with ejection = 1 ton pressure This should be good for paper up to .030 thick for thickness .031 - .050 reduce the inch count by 10% for thickness .051 - .070 reduce the inch count by by 20% for thickness .071 - .100 reduce the inch count by by 30%
• Total inches x thickness x (some material strength factor you know to be correct) /2,000 is one way to get total tonnage needed.
• For each inch of rule, you will need 300 lbs of pressure and for each square inch of rubber; you will need approximately 50 lbs of pressure. So if a die has 1000 inches of cutting rule and is rubbered in strips of ½” wide on each side of the knife, it will calculate to 1000 x 300 and 1000 x 50 or 350,000 lbs of pressure or 175 tons.
• We use a factor of 400 pounds per linear inch of rule up to 500 pound per inch depending upon material being cut. Paper is 400 pounds. Ejection rubber can add up to 20% more pressure needed, depending upon amount of rubber in die.
• I have looked over the information you supplied me and I feel fairly confident your 50 ton press would be able to cut your material to the size and # up you are considering. The most basic formula many of us in the industry use is 6.5 inches of cut knife requires 1 ton of cutting pressure to cut and eject a paper sheet .018 thick. Considering other factors such as the die area, serrated rule and the fact that I feel that a press can be called upon from time to time to cut up to 110% of its tonnage rating. If I didn't know for sure that it did not have the ability to cut to this pressure I would take a chance and build this die and use it as a "benchmark" as what the press is capable of cutting. If you would like me to go into further detail please contact me.

Case Study: Snow Shoe Cutting

Written By Mark Batson Baril

On this particular project we were asked to visit, and so we did. The following is a gathering of facts as seen from the manufacturers viewpoint...

A few quotes gathered during that visit;
"We dread the busy season this year. We make snow shoes and one of our major operations includes diecutting. We currently have twenty-eight different shoe models and each model averages five different cut shapes. These five parts will often be of at least three different materials all of which are fairly tough to cut multiple layer synthetics. We produced approx. 5,000 of each model during last year. About every two to three years the models change and so we must at least partially re-tool. Some of the models have an overlap of parts allowing us to combine diecutting runs. We currently use clicker/forged dies, steel rule dies, and specialty machined dies."

"Our problems include the following:"

• Sales of our product are increasing fast. They are also unpredictable in regards to which model will sell best and what the actual quantities will be.
• We are running two clicker type presses full time on two shifts and can barely keep pace. We plan to go to a third shift this year during the busy season.
• We believe that the diecut parts of our product will become obsolete within 5 - 10 years.
• Prototypes are needed by R & D, quickly and accurately from our CAD files. We have no way of doing this well.
• Yield is critical because our materials are so expensive. All our material comes in rolls. They vary from 36" (915mm) wide to 60"(1,524mm) wide. Currently we must slit and sheet everything to size and then make our cuts, not always enjoying a no-waste situation.

"The question is - Is there a better way, and what is it?"

A Better Way:

After gathering some facts from the outside, we have put together the following possibilities followed by a recommendation.

Put on the third shift and continue as you have been. This has the advantage of simplicity, very little capital cost and no additional space needed for production. Your operators are already trained and new ones will be easy to bring up to speed. Disadvantages include having to hire more people, no yield improvements, and no prototype abilities. The costs of doing this may prove to be the highest of all of the solutions mentioned here.

Put in another clicker press and keep the production to just two shifts. A good clicker type press can be purchased for under $8,000.00 USD and will save you a lot of money in the cost of actually setting up a temporary third shift. This doesn’t solve all the problems but it may be a good cheap fix for this year. Long term this still has the yield problem nipping at your heals. As we all know in the diecutting business, material is where the money can be made or lost!

Choose several of your common large quantity parts and have a diecutting manufacturer produce these parts for you. You can still control the materials and the timing for deliveries while someone else absorbs the cost of the machinery needed to do the job quickly and efficiently. You may be surprised at the overall cost of the purchased parts compared to your actual costs of cutting them yourself. The current manufacturer of your materials may even be able to provide you with this service and with today’s quick turn-around times, your unpredictable sales volumes will not be a problem. Your company can continue to produce the specialty and low volume parts in-house while having the stress of the high volume parts passed on to someone else.

Plan to purchase a new type of press. The perfect type of press for your situation would be a traversing head press with a belt delivery system that feeds from a roll. These presses can also be purchased with computer controls that allow for a best yield for material based on your CAD file. The head can turn in any direction as it travels in order to get the perfect nest and the fastest cut. These machines also have the advantage of being able to store into memory each part or job and to be able to recall this information at the touch of a button. Between this technology and tooling matched to it, set-up times would be very short. You would, more than likely, be able to use most of your current supply of dies. Cost would be around $ 80,000 USD. You would be able to eliminate your slitting and sheeting operations and should gain enough time to be able to reduce your full time cutting staff from four people to two. This combined with material gains may make it a very logical choice. The gains would outweigh the costs over the course of a few years, and should beat the obsolescence of your product by a wide margin. You may even be able to cut products for other companies in your area. The only area it misses is the prototypes!

We talked about waterjet cutting, CNC routing, and other computer driven cutting machines at our meeting. The advantages they all have are that they would enable you to produce prototypes, would allow you to get a great yield from the material, and would eliminate any tooling costs associated with your constantly changing models. They would also eliminate the slitting and sheeting of materials. The two big disadvantages they have are that they are slow compared to punching parts out with tooling, and they all are very expensive to purchase, possibly reaching past the $125,000 mark without blinking an eye. Typical running speeds on any of these machines will be between 30 and 200 inches per minute depending on the material and how intricate the cuts are, where as a tool with 30 to 200 inches of cutting surface can make an impression many times during that same minute.

From this group of five possible solutions it seems as though the traversing head press purchase is the most logical with prototypes being cut by an outside vendor. A closer look may uncover that a combination of the above suggestions may be your best choice.

Our recommendation at this point would be to gather together and take a closer look at your costs, especially those costs associated with wasted materials. Is it really possible to gain a significant amount of money by cutting materials to a better yield? How much time and money will you really save by not having to convert the rolls before they are die cut? What does your labor really cost you over the course of a year and does it make sense to try and reduce the labor cost? What are the sales predictions for the next five years and have they been accurate over the past five years?

The final conclusion set this company on a course that continued some production in-house while developing an outside source that cut finished parts and prototypes. A great solution for a semi-complicated situation.

Diecutting from an outsiders view

Hello Everyone.

First off let me say if you are reading this you better be a follower and if you are not then you should start!

As you might be able to tell this blog is new and we are trying to keep it as exciting as possible. If you have any questions about diecutting feel free to send us a message and maybe we can create a blog about it. Or feel free to go to our website - www.cutsmart.com .

We really do appreciate any feedback that could make us a better site.

My name is Samantha and before I worked with Cut Smart I admit I knew really nothing about diecutting, laser cutting, waterjet cutting, even now it is a still a little confusing. But there is so many things that we use in our daily life that has something to with one of them! Even in the last article about diecutting food!? Didn't even know that was possible. If you are just sitting on your couch can you even count the things that have been through the diecutting process? It is really interesting how these little things, like your TV remote, has been through some sort of process like that. Those things that you don't think about normally but if you thought about it for a moment it could actually be pretty interesting to learn how such things are made. 

I hope you all enjoyed my little post, I will try to post again.

And again please feel free to leave feedback, or even become a follower! 

Have a great week everyone!