Thursday, April 29, 2010

Guide to Selecting the Best Steel Cutting Rule

Written By Mark Batson Baril

Cut Smart has compiled the information presented here as an aid to businesses trying to make decisions on what types of steel cutting rules may fit their needs. All of the tangible factors presented here must be mixed with the intangible effects that present themselves like, relationships and loyalty, customer service and commitment to improvements. It is through this mix that a good decision can be made.

1999-2001 Rule Manufacturers Technical Data
(Being Updated During June 2004)

Who Is Making The Rules These Days?

Steel Rule Diemakers - have you been approached by your customers about trying a new rule or perhaps by another rule manufacturer claiming their rule is better than what you are using now?
Diecutters - how well do you know the type of rule that is going into your tools and do you really need to know? Could that job have perhaps cut longer or faster or with less dust or with less make-ready if you had specified a different rule?
End Product Buyers - should you know what goes into the tools that make your products? What will you specify on that next job and how detailed do you really need or want to get?

In today's aggressive converting market, the sea of information is vast and the nets used to gather and compile that information are often full of holes. Our intention with this Rule Guide is to compile the information our research has shown is important to rule buyers and rule users within a very specific, but large market. We feel that the presentation of this information in a condensed, straight forward, and unbiased format will save readers lots of time and will help to educate those in the industry that are lost in the sea of information.

Our concentration for this guide is for 2 point - .0282 (.71mm) thick Center Bevel cutting rules used within the converting industry for a vast number of applications like; folding cartons, gaskets, labels, nameplates, membrane switches, medical applications, plastics, etc… . According to all the rule manufacturers, this 2 point standard cutting rule is by far the largest volume item produced and is by far where the largest amount of marketing and research dollars go. At the time of this article, we have found that there are eleven rule manufacturers that concentrate on this market, worldwide.

We will focus on the following areas within this guide, first by discussion of the areas then by presenting our gathered information from all the rule manufacturers. The information gathered is to the best of our knowledge and the manufacturers, accurate and correct. Line items like minimum bend radius and hardnesses have been tested by the manufacturer and can be expected to perform to that level. The following areas are the most important factors in knowing what makes a steel cutting rule work for you.

  • Edge construction method
  • Bevel Angles
  • Body Hardness
  • Cutting Edge Hardness
  • Body Coatings
  • Edge Coatings
  • Decarburization thickness
  • Minimum bend radius and angle
  • Standard Heights and availability
  • Height tolerances, general tolerances
  • Special Notes
  • Pricing
Edge Construction Method:
There are two methods used within the industry to put the cutting edge on a flat strip of steel rule.
Grinding (Ground Edge) This method uses a series of grinding wheels to grind the edge on the rule as it passes through the production line. The wheels typically grind in a perpendicular direction to the length of the blade. They can be turned in some cases to create an angled grind direction.
Shaving (Shaved Edge) This method uses a series of hardened solid tools to peel back or shave away the steel in order to create the cutting edge.

Grinding gives you a sharper edge than shaving. The grinding process leaves a very sharp edge that has thousands of microscopic points per inch, almost like a serrated edge rule. Because of this inherent sharpness, the rule cuts very well in situations where aggressive materials like plastics are being converted. If you are cutting gaskets, labels, membrane switches, nameplates, laminated folding cartons, etc…. there is no question that you will produce better parts more quickly with ground edge rule.

One disadvantage of grinding - Grinding the rule leaves microscopic grooves in the edge that can cause stress fractures when trying to create a very tight radius bend. Grinding at an angle instead of perpendicular to the length of the blade can help to eliminate this effect. Shaved edge rules can usually achieve slightly tighter radius bends without cracking.

Shaving the edge is typically faster than grinding and therefore the rule is usually less expensive. Up until recently, shaving has delivered a smoother edge finish resulting in less dusting especially when cutting recycled paperboards. New production methods in grinding are delivering as smooth finishes on most ground edge rules by all manufacturers. The concentration for reducing dusting and poor edge finishes in the final product has very quickly been re-focused within the industry from the construction method to the cutting edge bevel angle.

Bevel Angles:
The basics are these - The steeper the angle the less pressure needed to cut and the more shearing effect you get. More shearing effect will allow for smoother less fragmented cuts eliminating or reducing dusting and chipping.
The steeper the angle, the weaker the rule. Although there is less cutting pressure needed to penetrate the material, there is less strength in the rule (especially the cutting edge) to absorb the punishing effects of the impression. There are three bevel angles commonly in use around the world today.

60 Degree - The American StandardSteep
52 Degree - The European StandardSteeper
42 Degree - New for Dust reductionSteepest

Most manufacturers produce at or around these angles. Some of the other angles companies produce are listed within their section of the technical guide. The advantage to staying with a standard is that the tools used to cut and miter the rule are typically set-up to work with only one angle. The best joints and ruling job will be done with tooling that matches the rule angle exactly. Although you can get away with slight differences in angle of rule to tooling matches, it is best to stay at least close to the angle the tool is meant to cut. Changing the machines can be expensive and time consuming and this has always been one of the big resistance's to change within the diemaking industry around the world.

Body Hardness:
Because most rule manufacturers are now hardening the cutting edges of at least some of their rules, you must be careful in making the distinction between the body hardness and the cutting edge hardness. Both are very important!

All manufacturers are using the Rockwell C scale to measure hardness. Although each has their own method of testing, the measurement can generally be used as a good comparison. The only areas we have found where the Rockwell measurements have not helped in comparison is within certain rules made from specialty materials that bend extremely tight radii yet have fairly hard Rockwell comparisons. These rules are noted in the "Special Notes" section of some manufacturers list of rules. Keep in mind also that the body hardness is a measurement of the inner part of the body and it does not include the softer decarburization layers that most rules have.

The body hardness effects a number of things. The softer the rule is the easier it is to bend consistently, especially multiple bends in auto benders. The softer the rule is the tighter radius you can bend with it. The harder the body is the better it will stand up to the punishment of the cut. Be careful when choosing rules with a drastic difference in cutting edge vs. body hardness. In some cases the body can collapse or shrink before the cutting edge does. In cylinder presses especially, where the rule not only has a downward pressure exerted on it but has a sideways push, the hardest possible body should be used.

Cutting Edge Hardness and Methods Used:
The harder the rule the longer it will last. That's the basic rule. Of course the harder the rule the harder it is to work with too. This means there must be compromise when choosing the right rule to use for each project. It used to be that all rules had the same hardness in the cutting edge that they had in the body. This is still the case in many rules that work excellent for today's various markets. Many rule producers however are now offering the service of edge hardening their rules. Laser, Plasma, High Frequency, and Induction are some of the methods used to concentrate energy on the cutting edge that results in the effected area becoming harder than the rest of the rule. To this date there has not been a great deal of marketing or research to say that one method is better than the other. Expect that anytime! We have included the hardening method in our technical guide for those manufacturers willing to tell us how they do it.

The reasoning behind hardening just the edge is to try and keep some of the benefits of the softer body while having the long lasting edge. Be careful again as the harder that edge is made the more cracking you will get on the tighter radii. If a manufacturer shows that no hardening has taken place it means that the entire rule has been through hardened and the body and the cutting edge are the same rockwell.

Body Coatings:
Most manufacturers are coating their rules with some type of protection from the elements. Often times this is merely to prevent rust from taking over. Most are using some type of petroleum based product that is put on as the last step in the process, while others use no coatings at all. One of the major factors in the coatings area is how they react to automatic processing equipment. Not only is the grabbing power of the machinery effected, the residue left within the machine can help in some cases and hurt in others. Be sensitive to the maintenance requirements and internal workings of your particular machine when choosing a rule. Other specialty coatings like Teflon are sometimes used for specialty applications, but are uncommon as stock items.

Edge Coatings:
Edge coatings are different than body coatings in that they concentrate on and try to help the effectiveness of the cutting operation. Although they are uncommon and add greatly to the cost of the rule, they are offered by several manufacturers as specialty items and by a few as stock items.
Molybdenum and Titanium are two of the more common coatings. In interviews with several manufacturers the actual make-up of the coatings is either proprietary or unavailable. These coatings perform a couple of functions. They fill voids and tend to smooth the cutting edge thus reducing dusting and cracking and make for a generally smoother cut. They also create a very hard cutting edge that can extend the life of the rule. These coated rules tend to be used in only very special circumstances where the material being cut is very abrasive or the finished part edge finish is absolutely critical.

Decarburization Thickness:
Decarburization is the decrease of the carbon content at the surface of a steel due to interactions with the environment at elevated temperatures. Carbon has a huge influence on the mechanical properties of steel and decreasing carbon content causes a degradation of these properties. The decarburized layer in steel rule is the weakened outer layer on both flat surfaces of the rule. The only significance we feel that this has to selection of the right rule for your application is again related to bending and in particular to automatic rule processing machines. This "decarb" layer is what tends to be scraped off during processing. In many cases it is what the machine or bending tool is able to grab onto and therefore its thickness and consistency can effect your final results. Build up of this debris along with the coatings mentioned earlier should be taken note of by operators and maintenance people as well as those involved with calibrating the equipment. The thickness of this "decarb" layer also has a direct impact on the bendability within most rules. Since this outer skin is softer and weaker than the inner body, the thicker the layer is the easier it is to bend.

Minimum Bend Radius and Angle:
This measurement is for the smallest bend a rule can take without
suffering a stress crack at that corner. Most of today's rules are
capable of much more than what most applications need for a
minimum radius. The charts for each manufacturer show the smallest radius they guarantee their rule will take on a consistent basis. The line below this radius shows how deep you can go with this bend (the maximum angle) before it will crack.

With the most bendable of today's rules, a bend can be made that will actually allow the rule to be completely folded over on itself at 180°. Even when this bend is made with the sharpest of tools, like a Standard Helmold X3 hand bender die, the minimum radius that can actually be achieved, past 90° in depth, is somewhere between .0152(.381mm) and .0282(.711mm). In order to get a smaller radius on these deeper angle bends, steel must be removed at the bend location. Removal of this steel is called "broaching." Broaching the rule means that a section of the face of the rule is taken away in order to relieve the corner where the bend will be made. This will usually allow for a very tight, flat bend to be made at the cost of slightly weakening the rule. Some manufacturers rules will bend to a tighter radius than the typical minimum we just talked about. In these cases it must be noted that broaching may be necessary to get this extreme from the rule.

Standard Heights and Availability:
The industry standard height is .937" (23.8mm). Other very common heights are the old type high .918" (23.3mm) and the conventional cylinder press height of .923" (23.44mm). Depending on the application and the type of press, rule heights can and will vary greatly. Most rule producers will offer at least the three heights mentioned here as stock items in at least a couple of their rule types. Expect to be able to find the .937" (23.8mm) height available in just about all categories of rule in just about any quantity needed.

Purchasing rule in strips has been the most common way for many years. These strips vary in length from the American standard of 30" to the 1 meter standard used around the world. Coils of varying length are now very common with the more common use of rule processing machines. Less waste and speed of processing are both keys to the coils new found popularity. All rule manufacturers are now making their rule available in both strips and coils. For this reason we have not made this part of our technical charts. The one area to be careful of is to make sure your manufacturer can easily coil in the proper direction for your operation. Clockwise feed means that with the cutting edge facing up the rule feeds the same way the hands of a clock would move. Counterclockwise means the opposite. Most manufacturers can coil both ways. There is a movement now to try to standardize the coil direction and packaging for all rules and machines - we say, good luck!

Height Tolerances / General Specifications:
In general, all of the manufacturers of rule involved with this guide meet or exceed the tolerances and recommended specifications set forth by the IADD (International Association of DieCutters and Diemakers) for cutting rules of this type. These specifications control height, thickness, temper, cut edge fidelity, cut angle fidelity, camber, dish, twist, and coil set. We have included height tolerances in our guide as it is often used as a measure of quality and comparison. Holding the best possible height tolerance is becoming more and more important as today's presses and make-ready systems become more sophisticated. If extremely tight tolerances are needed, talk to your manufacturer about their tolerances within a specific single batch of rule. It is usually the case that within a batch, the rule will be extremely uniform in height and being able to segregate that batch will allow extreme close tolerances to be held for particular customers or jobs.

This is an interesting area to tackle. For the large production user of steel rule, pricing can and should be one of the large factors in deciding on a rule. Quality should not be sacrificed for a good price, yet in many cases the lower priced rules may be sufficient to get the job done well. Often times a lower price doesn't mean the rule is of lower quality or feature, it may simply mean that the rule is produced in such high volume that the price is able to be reduced. As your volume of rule used goes up it becomes more and more important to know all the factors involved, including price!

Pricing becomes complicated as many factors are involved. There are exchange rates to deal with as well as the flexibility your particular distributor or salesperson has with regards to your final pricing. Because of this we have set up a system for a very general comparison of pricing. Final pricing will be very much based upon your volumes used, your ability to negotiate, and the ability of the manufacturer to produce.

Typical prices range from the low end of $.28/ft.(USD) to the high end of $3.00/ft. (USD). Our system differentiates between the following as a basic guide. Please consult with your local distributor for precise pricing details.

LOW PRICE.......$
HIGH PRICE......$$$

In the real world steel rule diemakers like to choose one or two rules that work for most of their basic workload within a given market. It makes sense from all standpoints including the customers to do this. Substantial savings are made by; buying in volume, reducing set-up times for all machinery involved, and controlling of quality and tracability.

One more major item to keep in mind when choosing a rule is that all of the factors found in our comparison charts can be mixed and matched if your volume is big enough. The standard volume needed to try something new, just for you, is approx. 5,000 feet (1,500 meters).

Special Notes:
This is the area where room was made for those facts that couldn't be explained in the rest of the chart.

Cut Smart Engineering & Manufacturing's Part In This:

Cut Smart is proud to play a part in an ever evolving industry! With more than twenty-five years of experience in the diemaking and diecutting field I have learned that good information is the most important factor in growing a profitable business. Finding that good information is also one of the hardest things to do, especially if your business is growing fast! How involved you as an individual or company get depends upon how much time you have and how much you are willing to trust in the information presented by others. We hope this information helps you and your customers perform to the highest level.

Thursday, April 22, 2010

Best Cutting Method Process Calculator

Good Morning Everyone!

 It is really exciting that more people have stumbled upon our Blog! I hope everyone that has been here so far has been able to take some new knowledge with them! 

 This week I'm not going to be posting an article but instead I am going to introduce our  Method Process Calculator. 

  "Whether you are engineering parts for R & D, or engineering for production quantities, start the process by knowing the best quality, fastest, and least costly way to produce. The Method Calculator uses a database of constantly updated industry engineering information to show you an accurate picture of possibilities, right now!"

Click Here to Check Out the Calculator 

Thank you everyone who has taken a look at our website and I hope you did enjoy it!
Remember if you have any questions ever feel free to shoot us an email or check out our website


Thursday, April 15, 2010

Polycarbonate Cutting

Written By Mark Batson Baril

How would we best cut 1.2mm (.047") polycarbonate (50,000 sheets) using a conventional flatbed - platen style machine? The sheet size is 1,524 x 762 (60" x 30"). The part is a simple rectangular shape with rounded corners, but with 32 keyhole shaped cut outs. These keyholes are 9.52mm x 12.7mm (3/8" x 1/2"). What would be the best type of rule, etc... to use? We are used to cutting paper...

Polycarbonate, very commonly known in the US by its trade name Lexan, is a very diecuttable material. It is used constantly in the nameplate, membrane switch and sign industries due to its toughness, ability to be printed on, electrical non-conductivity, and general availability.

We would make just a few suggestions that may make your life a bit easier going from paper to Polycarbonate.

  • Feed the sheets and strip the waste the same way you would treat similar shaped paper products.

  • Use fewer nicks to start with than you normally would and try to get away with just the natural nicks caused by the rule joints. The material will tend to stay with itself even though it has been cut and it can be a real bear to separate if it has not cut all the way through or if too big a nick has been made to get it through the press.

  • Use 3 point sideface rule with a ground edge. Face the bevel to the waste. Test cut your keyholes with long bevel and sideface before you make them all, especially if their size is critical. A simple one up test die may save you a great deal of time.

  • Use 3/4" base material (assuming .937" high rule) to support the rule as high as you can. Under the strain of this thickness of this material, the rule will want to move with a thinner base material. Movement will make it more difficult to make-ready and maintain ready. Etch away the front of the board if need be to make way for any feed devices like gripper bars.

    Other than that, you shouldn’t have too many problems. It will make one heck of a POP when it cuts compared to paper, but that is normal.

    Depending on your quantities you may want to take a look at laser cutting, waterjet cutting and perhaps even routing the parts.
  • Wednesday, April 7, 2010

    Polypropylene Cutting

    Written By Mark Batson Baril

    Prepare Yourself for a Mind Teaser!
    This one has presented itself as a real technical dilemma, not only for the questioning company but for a large group of technical experts. It's a work in progress and may be for a while to come!

    The Case Started with this question;

    We are a manufacturer of a non-oriented polypropylene material. We have a fairly new product line that involves cutting holes in our raw material and delivering this finished product in roll form. We have had a flatbed machine built to perform the diecutting operation and are having problems delivering the material through the machine with zero waste left in the areas where the holes are cut. The material is being used extensively in the reinforcement of boat bodies and other hard shell consumer good products. Do you have any suggestions?

    After a few phone calls and a visit to the facility, the following additional information started to gel:
    • The raw material is produced, and final cut product will be delivered, in rolls. These rolls vary from 16" to 24" (406mm - 607mm) wide. The raw material is about the consistency of bathroom tissue and varies in thickness from .005" to .050" (.127mm - 1.27mm) thick. It has more pulling strength than bathroom tissue because of the micro-strands of polypropylene. These micro-strands are a major part of the cutting and waste hang problem.
    • The pattern of cutting resembles that of a grid of holes that are approx. 3.00" (76.2mm) on center, cover the entire width and length of the material and range in size from 1/4" (6.35mm) to 1/2" (12.7mm) in diameter.
    • The annual volume of goods is now approx. 700,000 lineal feet (214,000 meters) and is expected to get bigger.
    • The press that was made specifically for this project is a flatbed style press with multiple, and individually air actuated, male/female stations. The separate feed and take up mechanisms are a constant feed and pull set of rollers. The male pins cut with a ball into a correct diameter female type set-up (very strange).
    • The non-cleared reject rate is currently close to 40% but this converted material is used because this is the best available. There are currently no training or routine maintenance plans in action.

    After checking out the process, a few thoughts on how to proceed to improve the process started to become obvious. Cut Smart answered the question this way.

    Because of the rather large investment already made in equipment, I think it will make sense to continue to produce the parts/finished material in-house with most of the equipment already in place.

    In order to do this you will have to make the following changes/improvements in this order of priority.

  • Try a new type of die punch male and female set-up. This is absolutely key! The punches we saw in operation and the ones given to me as samples are out of the ordinary and seem dysfunctional for the material to be cut. I don't think that this ball and cut mechanism is helping in the slightest and may really be throwing everything off. I would talk to one of the well known male/female punch experts to get their opinions on a reproducible and well thought out set-up for your press. By making this your first step, you may save a tremendous amount of time and effort in what other changes, if any, you make to your machinery.

    SIDE NOTE - We discussed and talked to three of the big punch guys out there and nobody had seen anything like this nor did it look like these punches should work.

  • Change your feed mechanism from a constant pull to a pull and stop for each impression. No matter how fast your impression is made, the web is still moving and in theory you will get some of the pulling, tearing, and poor cutting results in the material just as you are getting now. This may be easier said than done especially in your thinner materials but is necessary for good cutting results in a flatbed operation like you are running. Your overall rate of production will probably be slowed by this stop and start but it will allow you to control the impression and eliminate a possible cause of your problem.

  • Connect both your unwind and rewind machines/systems to your diecutter. The fact that there are three units in operation and none of them are solidly connected, (plus the diecutter is on wheels) is not helping your consistency of set-ups or cutting. At least, any new feeder must be attached to the diecutter.

    Once the above items are changed and can be proved to work individually and together, just in R & D or sampling, you should proceed with the following before you can expect consistently good results.

    • Control the air temperature and humidity in the cutting area so they are both constant at all times.
    • Develop a make-ready and changing punch procedure that is documented.
    • Develop a system that tracks when in the life cycle the cutting dies are wearing out. Follow the answers from this documentation to replace or sharpen the cutting tools exactly when they need it. For a 100% perfect product, like you are hoping for, you will have to error on the side of caution when it comes to replacement.
    • Train all your operators in these systems.

    Putting all of these ideas into use, with a few more that I'm sure will be gathered along the way, will result in better and perhaps a perfect product using the same basic method you are using now.

    The one possible problem I see with correcting these problems and spending the time, money, and effort to do so is that the flatbed cutting method may be too slow to make it cost effective in the long run. If this products' volumes will continue to increase, as they have been over the last year, you may find that rotary cutting is the fastest and cheapest alternative. By gathering some pricing not only for machines but for finished product via rotary converting you will probably find that rotary cutting is the first alternative to look at for your in-house operation.

    Throwing good money after bad makes no sense - but finding a route to determining whether a method is doomed can be very frustrating. We hope this helps open up a new possibility or two or even a new line of thinking on this very difficult cutting problem. Good Luck!