Tuesday, August 31, 2010

Glue Assists- Tricks of The Trade

Written By Mark Batson Baril

"If the glued part of the product ever fails then we are not selling boxes, we are selling flat pieces of nicely printed paper." Quote from a very determined folding carton Glue Department Manager.

WHY do glue assists work better when they run across the grain as opposed to with the grain? Most people say they just work better - most don't know why - they just do. Is there anything written down explaining why?

Let's start this answer with another question -
WHAT is a glue assist?
A glue assist is well known in the folding carton and printing industries and rather unknown in most of the rest of the diecutting and converting industry. Glue assists were developed as a method to break through the clay coating, varnish coatings, UV coatings etc… of paperboard so that the water soluble glue could penetrate the soluble fibers of the inner core of the board. A series of knives are placed into the die (usually in the glue flap area). These knives are set at a height typically 30% of the overall stock thickness lower than the through cut knives. This partial cut gives the glue more adhesion between the two glued surfaces. If the board is pulled apart, the top layers of the carton board (covered by the slick coating) must tear apart before the carton surfaces will separate.

The penetration of the knife also adds to the actual surface area that the glue has to adhere to. This exposed area must be formed in a way that exposes fibers and stays open through the gluing process. A cross grain cut will tend to stay open were a with grain cut will tend to close. By running the specialty rule that is forming the glue assist pattern across the grain, we force more fibers to be exposed. For example if you were to take a piece of pine, lets say 1/2" thick, and break it with the grain then the woods' cellulose fibers break in long strings. Should you take the same piece of wood and break it across the grain the cellulose fibers will splinter in longer slivers and expose more of the interior of the wood. The same happens with the paper board. By penetrating the material across the grain the pressure on the inner fibers forces the same cellulose fibers to break and splinter exposing the inner fibers to the soluble glue allowing for greater adhesion.

One concern is that a number of companies add glue assists to the flaps of their seal end cartons and then seal the carton using hot melt non-porous glue in their cartoning process. Although not as big a help as with a penetrating glue, glue assists still help in that the hot melt glue will form around the broken and exposed fibers. The general rule is that unless the product is being spot glued in only a couple of small areas, the use of glue assists will help the strength of the box, not hurt it.

Most die shops and diecutting shops have a very specific pattern they use that they know is better than the competitions'. This is to say that there are many patterns that are common and each has it's own reason for effectiveness. Some shops use a simple straight perforating rule that cuts in just one direction. Others use wave perfs or half a zipper rule that cuts in both directions to the grain. Whatever the case may be in your shop, keep in mind the cross grain factor to help make your decision.

Tuesday, August 24, 2010

Applying Phenolic Counterplates

Written By Mark Batson Baril

Phenolic CounterPlates On-Press Application for Spray-on Glued Plates
Get the Press ready:
    1.Get the press ready with a cleaned cutting plate locked in place with the spot sheet and any other make-ready in place. Make sure the cutting plate is locked in and in ready for the entire run position. No movement is allowed in this location.
    2.Set up the steel rule die ready for the run, locked into the chase, spot sheets, etc..., all in place.
    3.The counterplates must be applied to the cutting plate before any bringing up of impression or patch-up has started.
Get the Counter Plates Ready:
    4.Put the registration pins on the plates with the rubber seaters on the pins. Pins and rubber go on the side with the channel cuts. Make sure you know how the orientation works and where the plates attach to the die.
    5.Set-up a spraying area (paper sheet) so that all the plates can be sprayed at one time. This area needs to be close to the die when it has been slid out of the press. Place the counterplates pin side toward the sheet, flat side up ready to be sprayed with 3M #77 glue. Make sure the plates are oil and debris free.
    6.Spray all the plates at one time with the glue. Be careful to get enough glue on but not too much. Too much glue will allow the plates to move and shift after they have been stuck to the cutting plate. The glue will stay tacky for quite a while so don't panic that they will dry too soon.
Apply the Counterplates to the Die:
    7.Touch the edges of the plates only and locate the plates to the die using the pins to start the line-up. Use a small ball peen hammer to tap the counterplates into the die as evenly as possible. Tap only on the locating pins as damage to the plates is possible if they are hit directly. A very small amount of water or saliva on the tip of the hammer will stop the glue from becoming a problem when hammering.
    8.The plates need to be tapped down as close to the die as possible in order to clear the press when the die is slid back into the press. The plates should not be tapped down to the point where they start to buckle or bend due to contact with parts of the die. If they do curl up not only will they hit the press upon sliding the tool back in but they are likely to pop away from the locating pins causing a non-accurate line up.
Apply the Counterplates to the Cutting Plate:
    9.Slide the die back into the press. Lock the die in place where it will sit every time it is slid back in. No movement in this registration is allowed.
    10.Bring the impression up and leave it on for approx. one minute. Bring the impression off.
    11.Slide out the cutting plate and using a block of wood or plastic and a hammer, gently tap all the plates in place to make sure the glue has set and there are no parts of any plates that are curling away from the cutting surface. Applying Tape to the lead edge is an option but should not be needed if the counterplates have been made with a skived lead edge.
    12.Return the cutting plate to its original position and start the make ready process.
    13.As an option, the die and plate can be dusted with a small amount of printers powder in order to stop any excess glue from adhering to the sheet.
  • Depending on the size of the tool and the number on, the entire process above can be broken down into sections or parts of the image to be applied. This may allow better control over the drying of the glue.

  • For those press operators familiar with make ready using matrix with common plastic locators, the general application of phenolic counterplates is nearly identical in every way but the gluing stage.

  • Phenolic counterplates are now available with self adhesive tape already in place in order to save a bit of time and to make the process more convenient. The disadvantage of this type of plate is that they are a bit harder to make and using the plates a second time around is harder due to hard to remove adhesives.

  • Tuesday, August 17, 2010

    Non Stick Diecutting

    Written By Mark Batson Baril

    That job needs to be running at 145 strokes per minute, your parts are stuck in the die on every third impression, and the job is getting hotter by the minute. Now what!

    Everyone has the problem, and everyone admits it at one time or another. Whether it is to your fellow worker, your customer, or to your boss, we have all had to admit that we just can’t get the parts to come out of that tooling fast and clean enough. It’s quite a dilemma. Tons of money has been put into planning materials, and printing, and tooling, and the right press, and the right operator, and when the time comes to put it all together we just can’t get the parts to do what they’re supposed to do. There are many ways to set-up ejection. In fact there probably should be a different way of setting up ejection for every material there is out there. Ejection rubber comes in every durometer, cell type, surface emboss style, recovery rate, thickness, and color the mind can imagine but sometimes there is another piece to the puzzle that rubber just doesn’t cover. Let’s tackle a couple of parts to this puzzle that many of us have either never tried or have never heard of.

    Puzzle Part # 1

    DriCote by Bostik – It’s not too often that we talk about a specific product but what the heck, this stuff may be the miracle drug for the cutting press operator. Spray this product on your cutting blades and the parts will just fly out of the press.

    DriCote is a Blade and Bit cutting lubricant that is sprayed on. It’s most typical application is in the woodworking industry where it is sprayed onto saw blades, router bits, joiner blades, etc…. . It adheres and dries in just seconds and depending on the material you are cutting, it can create a wide variety of advantages. By spraying it on cutting blades in a typical diecutting operation – steel rule and specialty tooling - it will have some of the same effects expected in the woodworking field. It will prevent resin/glue build-ups from just about any source. It can extend blade life due to reduced friction. It reduces the heat effects caused by friction and it contains no silicone or petroleum oil making it safe for many applications. We don’t recommend DriCote for medical and food products but for your run of the mill adhesives and foams it is nearly contaminant free. It can also reduce the tonnage needed to cut. Most of all though, in a difficult die cutting situation, it can enhance the quick ejection of the parts from the tool and in many cases will keep that residue build-up from happening at all.

    In particular I have had a recent exposure in the foam cutting field where the normal drag caused by residue build-up from repeat cutting on medium density open cell foam was virtually eliminated. A fast moving press that had been brought to its’ knees several times per hour for tool cleaning is now operating at non-stop full capacity with two applications per day of this lubricant. Given the right situation, this product can work wonders.

    Puzzle Part # 2

    Feed-Thru Punches on Steroids - How many times has the speed of your press, the waste free quality of your parts, or the length of time needed to set-up your job been effected by a specialty material not working well with the feed thru punches you just bought off the shelf? If this is a problem, even every once in a while, keep reading.

    Recently I have encountered specialty feed-thru punches. Yes, I found out that not only can I order special diameters on the cut edge, the base size and the ejection bore, but a feed thru can be specially ordered to work well for certain materials. The last items that can be specially ordered are the exterior cut angle(s) (bevel angles), the interior “grab the waste” lengths, and the interior bevel angles for cutting. By combining these factors with tough to feed material specs, a sometimes difficult situation can be made easier or possible. Ask your current supplier about these special order items the next time you are having troubles or anticipate a problem with a new material or shape.

    A recent experience led me to the KEN KUTS-ALL PUNCH. In this particular case the punch was built as a specialty item for the abrasives industry. Because the tooling must cut through two very different types of material and then grab and pull off the cutting plate a thick and tough to cut material, the angles, depths and hardness had to be changed to make the punches work well. The result is now an in-stock item that cuts longer, grabs better, and sets-up faster than the standard punch for the abrasives industry. You will pay more, but in the right situation they are worth their weight in gold.

    Filling your pockets full of tricks makes you a specialist in your field, so keep in-tune with the latest and please share some when you can. We'll look forward to hearing your tricks of the trade!

    Tuesday, August 10, 2010

    Pre-Press Counter Plate Validation

    Written By Mark Batson Baril

    What is the best way to validate the accuracy of the counter plates produced, to the die, without the benefit of a press or XY coordinate inspection machine?

    There are several parts of a typical counter plate that need to be checked before it goes to press. Those parts include:
    • The thickness of the counter plate material
    • The width of the channel that was cut
    • The depth of the channel that was cut
    • The size of the locating holes that were cut
    • The actual image that was cut
    • The size of the image that was cut

    How each of the parts is passed through Quality Control varies from shop to shop. The most common are outlined here. Specifications for each tool set must pass with the tooling through the QC process. Your quality control people are only as good as the information they are provided with. Training in what's important to inspecting a counter plate is also vital to the quality control.

    The thickness of the counter material
    This is very important as the overall thickness controls the overall emboss we get when the creasing rule enters the counter. Typically a spot check is made of two or three points on each counter with a vernier. ±.001" (±.025mm) is the standard thickness deviation allowed within the industry.

    The width of the channel that was cut
    The width will typically vary with the grain of the board you are working with. Both the with the grain and against the grain width should be at least spot checked within the counter plate. Again a vernier is typically used to check this width. The channel width should fall within ±.002" (.052mm) of the nominal dimension.

    The depth of the channel that was cut
    Again an extremely important factor in how well a tool set will work together. More than any other variable, this is the one that may be out of tolerance. Any up and down movement of the material during production will produce results that may not work. Unlike the width of the channel where the constant tool produces a fairly constant channel, the depth relies on the up and down tolerancing of the machine head and the ability of the machine to hold the material in place. Spot checking the depth with a micrometer is standard practice. Typical tolerancing is ± 10 % of the overall depth of the channel.

    The size of the locating holes that were cut
    Here's a simple one that really matters to the press person. If the holes are to small it's a nightmare to get your pins in the plates. Nobody wants to have to take the time to ream out the holes in pre-make ready or worse yet, on press! If they are too big you'll have to be a magician to get them to stay with the die long enough to make that first impression. You can use a vernier to measure but that's tough to be accurate with a round hole. One of the actual pins that will be used on press is often the best bet for a great and practical QC. Spot check all your plates. The standard deviation allowed is ±.002" ( .052mm). Another excellent measuring device to use is a standard gauge pin. This especially works well if you are a commercial shop and your various customers use various sources for their pins. Set-up the size you need to give them and go with it based on the gauge pin.

    The actual image that was cut
    The actual image we refer to here means differentiating between creasing / cutting / perfing / cut scoring / etc.... Making sure that there are no channels missing and that all of your cut backs stay far enough away from the cutting areas. Again spot checking is most commonly used by putting in few locating pins and actually laying the plate on top of the knifed die (it's easier before the die is rubbered). Check that everything that should be there is there and that areas that should not be there are not. There's no standard tolerancing on this, it's either right or wrong.

    The size of the image that was cut
    An XY Coordinate measuring machine is a great tool to have in your shop for many reasons - measuring counter plates is not one of the reasons. The amount of time and effort that would be spent measuring each and every counter plate would slow your inspection department to a halt and there are not too many customers that would be willing to pay for this service. So how do we get comfortable with the fact that we really are not checking each and every channel in our plates?

  • Calibrate your Counter plate machine as you would your laser, your bending machine, or your XY coordinate measuring machine. When you're comfortable with the fact that your laser and your counter plate cutter are cutting within tolerance, then you can start to relax about you final product.

  • Most companies again perform a spot check by laying the finished plate over the finished die. You will be able to see whether it lines up or if it's questionable. This is done at the same time you are looking for discrepancies in the image that was to be cut. Again this is the fast down and dirty method for checking your tooling.

    Two other methods used in practice include:
    1). Produce a one up vinyl of the carton or product to be produced and use it as an overlay to check the plates. Make sure you are comfortable with your plotter accuracy by calibrating it along with the rest of your equipment.
    2). Take the laser cut die board before it is knifed and lay it on a light table. Take the counter plates and fit them to the die board. Because phenolic counter plates are see-through at the cut channel, you will be able to see whether the light coming through the die is locating to the plates. This method only works for steel counter plates if you have Superman working in your QC department. The only company that we have been able to find that has this ability is Metropolis Die Company.

    We hope this has helped in your quest for the best possible checks on your system. As always, quality leads the way in being the best at anything.

  • Tuesday, August 3, 2010

    Rotary Steel Rule Diecutting Hard Anvil

    Written By Mark Batson Baril

    I recently read a press release that said that a rotary steel rule die could be used cutting against a hard steel anvil. I thought that you could only cut into a soft blanket with this type of die? Could you give a brief explanation of the benefits vs. soft anvil, differences in the tool/press, make-ready differences or comparisons to flatbed steel-on-steel and anything else that could clue me into this new technology? Is it new technology?

    This is not new technology. It has been around at least 20 years. Marumatsu Company manufactured a 1350mm & 1700mm (53" & 67") diameter bottom cutter with a stripping section. United Machine has also made a 1.700mm (66") S-S top cutter with a stripping section.

    The die is built in some ways similar to a flat die with extra considerations such as the straight rule is always mitered to curved and curved cut pieces are usually no longer than 10 inches. Soft anvil rule is serrated in order to penetrate the urethane blanket where as the S–S rule is a continuous bevel (non-serrated). The rule used in S-S cutting is 4pt center bevel edge hardened with a soft base. The idea here is to run-the-rule-in so that it levels itself off before actual diecutting begins. Rule heights around the cylinder vs. across the cylinder are varied by about ,075mm to ,127mm (.003" to .005") and the final heights are established during the run-in process on press. The hard anvil cutting surface is made out of an 85+ Rockwell steel and stands up to a great deal of pressure. As you can imagine, much of the success you achieve with this process comes from good maintenance of the press and well made and maintained tooling. The rule must be consistently perpendicular to the base surface and that tool base material must be able to maintain a perfect curvature. Excellent tool building and on-press “tricks” account for the success or failure of this process.

    The benefits over soft anvil rotary cutting are that you can achieve the same rotary speed with the accuracy and cut quality of flat-bed diecutting. Because the surface you are cutting against is consistent, you avoid the dimensional variance that you get during soft anvil diecutting. Recent improvements in blanket re-surfacing and tool calibration to the soft cutting surface during prodcution have improved finished part tolerances, however there is still a big difference between the two processes.

    Typically a stripping blanket is manufactured with each cutting die. The blanket is made from a ,75mm (.030") mounting material with "T" and "L" shaped stripping pieces attached to push off scrap in a section immediately after diecutting.

    Because the cylinders run 1:1 in their gearing (opposite to a soft anvil cutting where the soft blanket cylinder will strike the cutting blades in a different spot every turn), the make-ready process can be made in several ways. Upon running the die and beginning the diecutting process and after achieving 80 percent good cutting, make-ready tape is applied to the die cut anvil in the non-cutting areas. This raises the substrate and helps the cutting in the non-cutting areas. Some companies will also make-ready under the die for fine tuning. This is typically the wrong way to go when making ready in flatbed applications but because there is no secondary steel cutting plate on top of the cutting cylinder, behind the die may be the only choice. The tricks here are in choosing a rule that will self-level and having an operator that is level headed enough to make it self-level. The 1:1 gearing/cylinder ratio also lends itself well to using matrix or other counter materials to form the scores.

    From what we can see out there, this process seems to be a fairly rare one. Not many presses were made with this capability and the tricks of the trade needed to be successful seem to have taken a toll on its popularity. The companies that are using steel to steel rotary with SRD’s are enjoying some terrific benefits!

    Some of the stories that helped answer this question and put together this summary were told by;

  • Thomas A. Sporleder – Printron

  • Mike Porter – The Rayner Company

  • Tommy Moore – Stafford Cutting Dies

    Thanks Guys!

    Please contact Cut Smart if you would like more information on this subject.