Wednesday, December 29, 2010

Cutting Registration to Printed Fabric Materials

Written By Mark Batson Baril

A brief question:
I am in the promotional product's business. Currently I am preparing to manufacture a product where I will need to cut sheets of fabric, such as neoprene and ultraseude (polyurethane) into (140) 3 inch (76.2mm) X 1/2 inch (12.7mm) printed strips. I have contacted various die cutting facilities but there are potential accuracy problems since the sheets may not be perfectly shaped and may not align perfectly. I am assuming that some form of laser guided cutting would illiminate this concern?

And a brief answer:
Right off the bat I can think of a few ways to approach the project you are talking about. The fact that your printing may wander and not be in accurate/consistent registration to any corner of the sheet is the main problem.

Registration marks could be printed at the same time as your main printing. These could be designed as either simple slash marks or simple target type circles. This then opens up your options.

    1. Use the registration marks to align your materials in any type of cutting machine. Diecutting, guillotine, and laser immediately come to mind. A simple retractable and clear overlay that has been pre-struck acts as your line-up. Each individual sheet of material to be cut is lined up under the retractable sheet. Once the part is aligned and fixed to the cutting bed the clear overlay is moved away and the impression is made for a near perfect cut every time. 2. Other tooling methods would include using see through tools that could be registered one at a time on press by the operator. A clear Polycarbonate (*Lexan) or Acrylic based steel rule die or clicker type die may be your best bet. 3. Circle type registration marks can be used with a *Spartanics type machine that will automatically pre-punch a perfect hole at the mark. This can then be used in conjunction with a tool that has retractable registration pins. This method is used all the time in the membrane switch and flex-circuit industry.Optical registration is also an option on many diecutting machines and may be a good method for your particular job.

Each of these methods will result in accuracy of ± .010"-.015" (.254mm) depending on the operator. These ideas are slow but luckily your quantities are small. If you increase your quantities you will have to inquire about better ways to register to the flexible material you are using.

Wednesday, December 15, 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!

  • Wednesday, December 1, 2010

    Laser Cutting

    Written By Mark Batson Baril

    (LASER) Light Amplification by Stimulated Emission of Radiation

    Lasers come in many different shapes and sizes. They range in usage from the standard supermarket scanner to those being developed as part of military defensive systems. The laser has existed in usable form since the mid 1960's.

    The type used almost exclusively for cutting a wide range of materials is the CO2 gas laser. Hole drilling is typically done with solid state YAG lasers.

    A laser beam is created by the introduction of gas and electric current to a sealed chamber. As the electricity breaks down the gas an energy is released and resonates between mirrors within the chamber. As it resonates it increases in intensity and at it's optimum is released through a partially transmissive mirror. The beam is then directed to a focusing lens and is further intensified. At this point the laser beam becomes a usable cutting device.

    Some advantages of cutting with lasers include, the ability to cut incredibly complex shapes with no tooling or set-ups. This makes them perfect for production or prototype runs for a huge variety of different products.

    Laser cutting systems cut quickly and very accurately through a wide range of materials. In general, for steel, laser cutting lies between cutting with wire EDM, which is more precise but slower, and plasma, which is less precise but faster. They go well beyond the range of these other methods as well in that they can cut through just about anything within certain thicknesses.

    Given the right material and type of system, tolerances can be held to ±.0005"(.0127mm). Lasers can be found most commonly being used to cut:

    • Most types of steel and aluminum. Large lasers will cut up to 1"(25.4mm) steel and .250"(6.35mm) in aluminum.
    • Paper
    • Wood, plywood, hardwoods
    • Rubber
    • Most Plastics - Acrylic

    When matched to a suitable motion control system, laser cutting provides extremely accurate cuts with a high degree of repeatability over a wide range of materials and shapes.