There are numerous characteristics pertaining to needle design that must be considered to produce a more effective needle for a given customer or application. However the four main areas that should be considered:

BLADE SHAPE
Standard triangular bladed needles have been produced since before the turn of the century. They continue to be used in the vast majority of needlepunch operations worldwide. When higher strengths are a requirement we recommend Pinch Blade, or Star Blade needles. Pinch Blade needles have a diamond shape cross section and the Star Blade has barbs on four apexes rather than the three of a triangular blade. Generally speaking, both styles produce higher strengths than triangular bladed needle styles.

BARB SHAPE
The barbs are the single most important element of a felting needle. It's important to consider the barb shape and its impact on nonwoven physical properties. Some of the barb characteristics we can vary are as follows:

Formed Barb or "Cut" Barb - All needle manufacturers produce what are called rounded barb styles. These barbs are produced so that all edges are rounded. Thus as fibers are engaged only rounded smooth edges engage fiber - minimizing fiber damage caused by the barbs themselves. In total contrast to the Rounded Barb Styles are "Cut" barbs. "Cut" barbs are made with a chisel like tool which cuts into the blade's edge forming a sharp barb. As fibers are engaged by this barb style, fibers must lay across one flat surface and two sharp edges. As a result, fiber damage is much more common. There are very few instances where we would recommend a "Cut" barb over a rounded Formed barb since the rounded barb styles will out perform cut barbs in almost all cases.

BARB SPACING
Many years ago the overwhelming majority of all needle styles produced were Regular Barb spaced needles. Today however, barb spacings have become more diverse so we are better able to match the proper barb spacing to the desired product specification. I'll get into why we recommend the various barb spacings a bit later.

NEEDLE LENGTH
Obviously this is a rather cut and dry area. Most often needle length is determined by the loft of the material entering the needling zone as well as the finished thickness of the needled product. Another factor is the stroke length of the needle loom - which has become shorter over the years. As a general rule, the shorter the needle the better in terms of reduced needle deflection and needle breakage.

So given that characteristics such as needle blade shape, barb shape, barb spacing and needle length are the main areas of a needle that can be specified, I would now like to review the factors we consider when making a needle recommendation. They are:

1. The end product
2. Fiber type and finished weight
3. Key physical properties
4. Geography
5. Needling equipment in use

END PRODUCT
We base much of our needle selection on the type of product one is needlepunching. It is not surprising that while Foster produces hundreds of different needle styles within a certain product category such as "filtration," those needles we recommend are fairly similar.

Now I would like to illustrate how we would custom design a felting needle for various needlepunched products and briefly explain why we would make such a recommendation.

SUGGESTED NEEDLE RECOMMENDATIONS - GEOTEXTILES

• Blade Shape - Star Blade. With geotextiles one of the most critical product specifications are tensile strength, burst strength, trapezoid tear, etc. Thus, we try to recommend a needle that will provide the maximum fiber entanglement. At this time we feel the Star Blade shape provides for best tensile properties of all other blade shapes and designs. The Star Blade is more efficient than a triangular bladed needle. This is because the blade of the Star needle encompasses four barbed apexes versus only three with a triangular bladed needle. This extra edge allows for a more efficient felting needle.
      
• Barb Shape - Rounded barb style, no kickup with 20 degree barb angle. Again, because tensile properties are of paramount importance we would recommend the rounded barb style that minimizes fiber damage caused by the barbs themselves. No kickup (kickup is the projection of the barb above the edge into which it is formed) should be used as kickup can literally rake and break fibers thus lowering the fabric's physical properties. While kickup does increase fiber carrying capacity, it does not increase fiber interlocking and this is an important distinction. For products that require high tensiles, kickup should be avoided. However, for paddings and waddings that do not require a high degree of interlocking some kickup is ideal. When producing geotextiles we recommend a barb angle of 20 degrees. The barb angle is the amount of degrees which the fiber engaging surface is displaced from a vertical position. Barb angles can range from zero through 20 degrees. Lower barb angles allow for fiber slippage as the needle penetrates the web. Fabric made with lower barb angles will be more lofty and thick and they will have a better hand and be of lesser strength than if higher barb angles had been used. Higher barb angles however do not allow the fibers to slip off the barb face during penetration. As a result, fabrics made with 20 degree barb angles, such as with most geotextile related products, will be stronger and more dense than if barb angles had been lower.
      
• Needle Length - This will vary from mill to mill depending on the equipment in use. Again 3 inch needles are best suited and result in less needle breakage compared to 3.5 inch needles.
      
• Barb Spacing - Most geotextile fabrics fall into the 3-5 oz/yd² range. Also, most geotextile lines will incorporate looms that needle from top and bottom. If this is then the case, close barb spacing is recommended. Close Barb spacing will allow all six barbs of the Pinch Blade to penetrate the fabric with a fairly shallow penetration of eleven millimeters. Close Barb spacing enables the use of a minimal penetration depth resulting in the blades of the needles spending less time in the fabric. The less time the blades spend in the fabric, the better off you are in terms of reduced draft in the needle loom, improved fabric properties and lower needle breakage. Spreading the barbs over a wider distance really doesn't make any sense when you’re dealing with such a low overall weight such as 3-5 oz/yd². Using Regular Barb spacing and penetrating the same six barbs would require a penetration depth of 19mm. Nineteen millimeters of penetration depth using Regular Barb spacing on a 3-5 oz/yd² product would result in needling most of the fiber right through the bottom of the fabric. So, for thinner, lighter weight products such as this, closer spaced barbs will provide the best results.

FIBER-TYPE, ORIENTATION, WEIGHT
We do consider the fiber type, denier, length, as well as orientation of the fibers within the web (usually this means, the web is airlaid or carded and crosslapped). Also considered is the overall weight of the product as well as if a support scrim is used. Basically the finer the denier, the finer the needle; the coarser the denier, the coarser the needle. Below are some guidelines as to what needle we recommend for various denier polyester, polypropylene, nylon and acrylic fibers:

These needle gauge recommendations should serve as a guideline only. The above situation is only true for certain fibers. The rules of needle gauge, relating to denier change when working fibers such as aramids, natural fibers and various other fibers.

Needle recommendation as it pertains to fiber orientation also should be noted. Time does not permit great detail in the subject but it is possible to utilize special needle designs to change fiber orientation within the web itself. For instance some airlaid webs will have a MD to XMD strength ratio of 2 to 1 or even 3 to 1 after needling. This is because the fibers are orientated more in the MD than the XMD. However by utilizing a Pinch Blade needle with the barb oriented in the XMD we can work and reorient the fibers more into the XMD and achieve more isotropic strengths in both directions.

IF A WOVEN SCRIM IS BEING USED
Needling into a woven scrim, as is commonly done in the filtration industry, special consideration in needle recommendation is required. It is most important when needling into a woven support scrim to minimize damage to the warp and fill yarns of this support structure.

We can avoid damage to the woven support by orienting the barbs so that they are at 45 degrees to the warp and fill yarns. This can be done by utilizing barbs on only one edge of a triangular bladed needle. However this method has its disadvantages since the fiber carrying capacity of the needle is severely limited since only one apex has barbs. More intense needling can be accomplished by utilizing a Pinch Blade needle and orienting the two rows of the needles so they are 45 degrees to the warp and fill.

KEY PHYSICAL PROPERTIES
Important or key physical properties of a particular needled fabric are of the most important considerations upon recommending a needle style. Certain needled fabrics can have properties that are of paramount importance for performance reasons. Some of the more common key physical properties we consider are as follows:

We have the ability to recommend needle styles that can enhance these and other physical properties in a needled fabric. I'll now explain in some detail needle recommendations as it pertains to three of these key physical properties.

Tensile - We have already discussed how we can increase tensile in a fabric by recommending certain barb and blade configurations. Of all physical properties it seems tensile improvements are always being sought after.

Thickness - It's surprising how many times I'm asked to recommend a needle that will increase tensile and thickness by say 10-20%. Unfortunately, there is no easy way to increase both tensile and thickness as increasing or decreasing one tends to adversely affect the other. However, increasing or decreasing thickness in and of itself can be done with various needle designs.

Increasing thickness can be accomplished without changing needle design by lowering the level of PPSI and/or lower penetration depths. The problem with this procedure can be delamination or poor needling on the backside of the fabric. In terms of needles, the following can be tried to increase thickness:

• Smaller and or fewer barbs
• Lower barb angles
• RB spacing

Changing to a needle style with smaller barbs can help increase product thickness. In addition, smaller barbs can actually help prevent delamination on the back side of the product by allowing for adequate PPSI and penetration depth levels. And in addition to increased thickness, smaller barbs can reduce overall needle breakage. This is because the smaller barbs will carry fewer fibers per stroke, resulting in lower loads on the needle's blade section. Lowering the load will increase the stability of the needle and reduce the tendency for needle breakage.

For even more thickness, lower barb angles can be used. Lower barb angles will allow for fiber slippage off of the barb face during penetration through the fiber web. The lower barb angles will also benefit in improving the smoothness, or hand, on the face side of the fabric. The only disadvantage that is possible using lower barb angles in this application can be on heavier weight fabrics. Delamination on the bottom portion of the product is more likely using lower barb angles than with higher barb angles. This possibility results from the fiber slippage associated with this barb design. The lower barb angles may be better suited for medium to lower weight fabrics and in those cases where fabric density is not so much a concern.

In terms of barb spacing, Regular Barb (RB) spacing is recommended for increasing thickness. RB spacing spreads the barbs over a greater distance providing for more uniform distribution of fibers. RB spacing becomes more essential with fabrics 3/8" thick or greater.

Decreasing fabric thickness is really less complicated and involved than decreasing thickness. Depending on the situation, decreasing thickness can be done with the existing needle by increasing PPSI and/or penetration depth. However the following needle designs can be used to decrease product thickness:

• Larger barbs and/or more barbs
• Higher barb angles
• Close Barb (CB) or High Density Barb (HDB) spacing

Permeability - is a key physical property associated with products such as geotextiles, filtration, paperfelts, and others. Air permeability can be measured by a device that calculates the amount of air that flows through the needled fabric. A similar test can be done with liquids instead of air.

To increase permeability we can recommend the following general needle characteristics:

• Coarser gauge blade
• Larger barbs
• Higher kickup
• The Open Barb

The above needle characteristics will result in producing larger than normal "channels" through the needled web. These channels will cause less resistance to air and liquid movements through the web thus increasing permeability and in many cases reduce the filtering efficiency of the fabric.

To decrease permeability in the fabric the following general needle characteristics can be recommended:

• Finer gauge blade
• Smaller barbs
• No kickup

Lower permeability is more difficult to achieve than higher permeability. However, if the above mentioned needle characteristics are used in combination with adequate needling technique, lower permeability can be maintained. The key to lower permeability ratings in a fabric, is to "close" the felt up as much as possible. The more the felt is "closed" (in other words, needled tightly and as densely as possible) the lower the permeability.

Surface Smoothness - Surface smoothness is important with many needled nonwovens. Products such as automotive headliners, synthetic leather, felts for vinyl substrates, and others, require very smooth fabric surfaces. Many of these fabrics require surfaces that have a face side void from needle hole marks and by using the proper fiber, needling equipment, needling technique and of course felting needles, it is possible to accomplish this.

The following needle characteristics can be used to enhance surface smoothness in a needled fabric:

• Regular barb spacing
• Finer gauge needles
• Triangular blade design
• No kickup barbs
• Blades with barbs on only one or two apexes

The proper needlepunching technique is equally important as the proper felting needle in this application. Depending on fabric density, needling from top and bottom is highly recommended for the best results. Also, preneedling is just as important as finished needling. Any needle holes put into the fabric during preneedling will not be totally removed in finished needling. So the proper needle selection is important for both pre-needling and finished needling.

RB spacing is recommended for smooth surface, over CB spacing. CB spacing can create surface linearity caused by the needle carrying large tufts of fiber bundles through to the back side of the web. RB spacing spreads the barbs over a greater distance, and this provides for a finished fabric with a cleaner - less linear look.

Earlier I suggested a rule of thumb "the finer the denier, the finer the needle." This is especially true when trying to achieve ultra smooth surfaces. The smaller the diameter of metal entering the web, the less likely you notice needle holes on the fabric surface.

Triangular needles are an excellent choice for smooth surface applications. They are better than Pinch Blade needles because they are less aggressive carrying fiber. Less aggressive is better than more aggressive when seeking a needle for smooth surfaces. An aggressive needle like the Pinch Blade can mark the surface with a more noticeable needle hole pattern than a less aggressive triangular needle style.

From what we've heard earlier we know that kickup should be avoided in this situation. No kickup barbs provide for the smoothest fabric surfaces. Kickup will rake fibers and create a much poorer fabric surface than barbs with no kickup.

Needle holes tend to close easier and less noticeably when we leave one or even two apexes of a triangulated needle with no barbs at all. One of the best needles we recommend for smooth surfaces is a two barbed needle. This needle has one barb per apex with the third apex being barbless. Instead of fibers being pulled in from all three sides - which is common for a standard triangular bladed needle, the two barbed needle will pull in fiber from only two sides and this will result in much less noticeable needle holes on the fabric's surface.

You may think that a two barb needle will not yield good product strengths compared to a standard 6 or 9 barb needle. However on a 3-6 oz/yd² fabric, a two barbed needle can provide as much or more product strength as a 9 barb needle. Why? Firstly, while most needles have 6 or 9 barbs, most mills utilize a penetration depth that commonly engages only 50% of these barbs - depending on barb spacing. Secondly, the first 3 barbs of a 9 barb needle carry about 75-85% of the total fibers available to that needle. So very little needling capacity is lost by going to a needle with only 2 barbs, and a great deal is gained with such a needle style in terms of providing superior fabric surfaces.

GEOGRAPHIC LOCATION
Geography plays a role in our needle recommendation but is a lesser role than the factors discussed previously. In certain tropical, seaside areas for instance it may be required to nickel plate all needle styles to protect against rust. Also, various countries tend to seek out the new, technical needle styles while other locations are interested only in the basic needle designs. Since roughly 50% of our products are exported to other countries, location, geography and cultural business practices do play some part in the needle recommendation.

THE MILL'S NEEDLING EQUIPMENT
Yet another area of consideration when recommending a needle style is the type and condition of the equipment in use.

The age of the needle loom plays a big role in the needle recommendation. Needlepunching a 2 denier 9 oz/yd² fabric on a 20 year old needle loom will require a different needle than the same product needled on a new Dilo, Fehrer, or Asselin. On fairly new equipment, a 40 gauge needle can be recommended to produce such a product. However a 40 gauge will not stand up to the vibration and poor needle alignment associated with many older looms. Thus, a heavier 38 or 36 gauge needle might be required in this situation. Having said this, it’s obvious that the filtration media produced with the 40 gauge needle on the new line will have superior physical properties such as air permeability, than the filter media produced with the 38 or 36 gauge needle on the older line. This is because the heavier bladed needles will cause larger needle holes than the finer gauge needles.

Yet another consideration in our needle recommendation is the total available needle density of the customer's line as it pertains to the needled product. The total needle density of a line is the density of all the needle boards in a line.

For example, lets say we have two customers both producing the same generic product - a 9 oz/yd² geotextile fabric. Customer A has a fairly new line consisting of a single board downpunch needle loom followed by a top and bottom quadro punch (double board) needle loom. Total needle density of the line is 25,000 needles per linear meter. (Assuming that each needle loom has boards with a needle density of 5,000 needles per linear meter).

Customer B has a line consisting only of an older single board downpunch machine with a needle density of 3,000 needles per linear meter of width. Thus total needle density of the line is then 3,000 needles per linear meter.

Even though both customers produce the same general product, totally different needles are required for each line. Customer A with the higher needle density can utilize a fine gauge needle such as 38 or 40 gauge Close Barb with barbs that have no kickup. Such a needle will produce a product with very high strength. A fairly high number of PPSI is required but that's okay since the line has plenty of needle density so throughput speeds can be fairly fast. The barbs with no kickup will create maximum strengths in the fabric by interlocking and carrying small bundles of fiber with each stroke and thus minimizing fiber damage.

Customer B does not have the luxury to put in the high PPSI as Customer A. To do so would mean he would have to run his line so slow that profitability would be impossible. Thus we must utilize a needle that is more efficient than the needle in Customer A's line. For Customer B we would recommend a slightly coarser gauge needle of perhaps 36 or even 32 gauge. The barbs should be larger and more aggressive since they must do a great deal of needling at a lower PPSI level compared to Customer A. Customer B can also utilize the Open Barb. The Open Barb is produced by eliminating the metal preceding the barb face, creating a barb with an open throat area for more ready fiber accessibility. By removing this material the throat of the barb is fully open and free from fiber loading restrictions. This barb style can help Customer B by increasing needling efficiency without reverting to a barb with higher kickup that can be more damaging to the fiber.

So with Customer B the needle recommendation actually becomes more critical. We must recognize the limitations of the line given the low needle density, and design a needle that is as aggressive as possible in order to keep throughput speeds at a profitable level. Yet not overly aggressive to cause excessive fiber damage. Recommending this same Open Barb aggressive needle for Customer A would be a disaster. Given the high needle density of his line this needle would create massive amounts of fiber damage and result in a totally unacceptable product.

Hopefully this example illustrates how we must look at each customer's line and recommend a needle for his particular and unique requirements.

SUMMARY
I hope to have shed some light on how the needle producers in the business make their needle recommendations and how their recommendations can affect the needled nonwoven. The needlepunching industry has become much more technical and this trend is continuing. No longer is a 9 barb Regular Barb needle adequate. While such a needle will do an adequate job on the majority of needled fabrics, there are better, more advantageous needle styles available that can give the nonwoven producer the competitive edge he needs. Are you using the right needle style? Hopefully you gained enough information today to answer this question.

Thank you.