Steel Rule Die for Custom Gasket Cutting

Often when people hear “custom” and think high cost; special setup charges, and tooling charges. In reality custom gaskets can be custom made for relatively low cost. If volumes warrant die cutting (often 500+ pcs) a steel rule tool can be made. A die for a six inch square window gasket with fastener holes at each corner can be made for less than $200. When amortized over a few thousand pieces, tooling cost quickly become pennies/per part.

Steel ruled dies are often made by accurately laser burning the part geometry into engineered, dimensionally stable plywood. Then a long steel blade (almost like a razor blade) is precisely bent and press fitted into the wood. Holes are made by pressing punch sets into the plywood. Tools in the 12” x 12” range can hold a tolerance of less that .012”.

Stockwell uses steel rule dies to cut Poron urethane foam, silicone foam, silicone sponge, and neoprene sponge. It is important to know that softer and thicker foam or sponges tend to have wider tolerances because the material compresses before it is cut through. Solid silicone gaskets, thermal gasket, emi gaskets can also be cut with steel rule dies.

Gaskets and pads can be made many ways. Stockwell takes into consideration gasket material type, gasket thickness and quantity to determine the production method that is most cost effective. Very tight tolerance gaskets or low volume gaskets can be waterjet cut with no tooling charge.

For more information about gaskets or gasket materials cut with steel rule dies, visit http://www.stockwell.com/ or call 215-335-3005.

Why Stockwell is a Sensible Strategic Partner in this Rough Economy

Stockwell Elastomerics’ business model has been centered around low to mid volume runs, quality and speed. For companies practicing Lean Manufacturing this business model makes good sense. Stockwell maintains stock in its core product lines such as Silicone Foams, Silicone Sponge, Solid Silicone, Poron, Thermal products, EMI gasketing materials, and Pressure Sensitive Adhesives (PSA). This stock along with quick changeovers and semi-automated production equipment (Die Cutting, Water Jet Cutting, Slitting and Laminating) allows for fast turns on low to mid-volume runs.

In the current economic climate, overproduction and inventory are much more of a liability than they were a year ago. With some customers relying on lines of credit and banks being more cautious, the risk of orders being cancelled and OEM’s being left holding the bag is much greater. Having a fast turn supplier such as Stockwell who can run smaller batch sizes and still meet long term production needs with scheduled releases allows OEM’s to have less “skin in the game”.

For more information on how Stockwell can meet your production needs, please contact us at 215-335-3005, service@stockwell.com or visit our website http://www.stockwell.com/.

THICK EMI GASKET & EMI GASKET OPTIONS

Stockwell Elastomerics provides custom EMI gaskets regularly for a wide range of customers. Each application is a bit different; some can be cut from “off the shelf” sheets of nickel graphite filled silicone and others may require special fluorosilicone compounds or silver plated particle filled silicone for more conductivity. Generally materials are .062” thick or thinner with a few conductive compounds available up to .125” thick. So what are the options for thicker EMI / NEMA seals? Below are a few pros and cons for different manufacturing techniques for EMI gaskets.

Option 1 – Mold the Gasket
Pros: You can control your design; sealing beads and 3 dimensional shapes are possible. Material savings; EMI compounds cost more that unfilled non-conductive compounds. Compression molding minimizes raw material waste.
Cons: Molds are more costly than tools used in die cutting, and molded parts have longer production lead times than die cut or water jet cut gaskets.

Option 2 – Mold Sheets and Water Jet Cut
Pros: If a part is smaller or there is little center waste, molding sheets from a standard sheet mold and then waterjet cutting the part geometry may be most feasible. This option offers flexibility in material thickness (.020” to .500”), conductive adhesive backings, and there is no tooling charge for the waterjet cutting process if a CAD file is provided. Lead times for this option are relatively short based on using our in-house 12” x 12” sheet tooling.
Cons: Geometries are limited to 2 dimensions and there is some edge and center waste.

Option 3 – Non-conductive sponge or foam with a bonded conductive wire mesh
Pros: This option offers another range of flexibility. Stockwell uses its core silicone foams and silicone sponge products (with or without adhesive backing) and bonds a Monel (Nickel/Copper alloy) wire mesh to the inside or outside edge of a gasket. This option offers lower compression forces, UL94 V0 foam option, closed cell sponges and a variety of thicknesses cut from standard, readily available roll or sheet stocks. Waste is less costly due to the non-conductive and expanded polymer. Lead time for smaller or initial volumes is relatively quick.
Cons: Geometries are limited to 2 dimensions. There is some assembly which may require scheduled shipments. Heavy compression and release cycles may disturb the mesh to polymer bond.

For more information about EMI gaskets, custom EMI gasket, silicone gaskets or other Stockwell products call 215-335-3005, email service@stockwell.com or visit our website at stockwell.com.

Rubber? - Rubber Gasket, Rubber Seals, Rubber Pads…

It is interesting how the word “rubber”, which historically has referred to Natural Rubber (also known as isoprene) has become a general term for elastomeric materials. Natural rubber is the original elastomer; however, over the years there have been many more synthetic polymers developed, each with its own unique property.

From an engineering standpoint it is important to know the demands and environmental conditions to which a “rubber” component will be exposed. Many of us have seen a black, flaking, cracking gasket essentially at a failure state. For a critical water seal the cracking could allow leaks causing damage to expensive electronics. For pads, excessive compression set (when the elastomer fails to rebound) may be the mode of failure, ultimately transferring mechanical shock or vibration to the device. Many of these common failures can be avoided with proper material selection. Temperature, UV, ozone, and chemicals all play a role in how well a “rubber” part will survive. Stockwell helps customers with material selection and in most cases will provide samples at no charge for testing.

For more information about materials contact visit Stockwell Elastomerics at stockwell.com or call 215-335-3005

Adhesive Backed Gasket

For decades Stockwell has been applying pressure sensitive adhesive backings onto gasketing materials. Adhesive backed gaskets are very appealing to our customers for several reasons. More often engineers and designers are specifying adhesive backings for gaskets. A peel and stick gasket (or peel and stick vibration pad) offers some nice features that plain or non-adhesive backed gaskets don’t have, below is a list of a few. (Link: Stockwell adhesive offerings)

Ease of installation – a peel and stick gasket allows operators and assembly technicians to install a gasket or pad quickly and easily. The time saved by having an adhesive backing justifies the additional cost.

Gasket Positioning – when an adhesive backed gasket is installed and “stuck” in place it stays in place when the lid or mating surfaces are compressed. Without being fixed in place the motion of the mating faces could move or twist the gasket cause a leakage.

Kiss-cutting - adhesive backed gaskets are able to be kiss-cut (see blog posting Oct. 12, 2007). Manufacturing engineers like this because parts are presented to the operators on neat roll and parts are removed from the liner versus individual parts requiring tedious liner removal

Bolt hole position – a supported adhesive backing or double coated adhesive (see blog posting July 30, 2007) gives a gasket that has a series of bolt holes dimensional stability. Essentially the thin P.E.T. layer does not let the gasket stretch in the X and Y dimensions. Without this support layer the gasket may stretch during installation and the holes will not line up.

Stockwell offers a wide range of adhesive backed gaskets. Adhesive backings are applied to the vast majority of materials. These include Poron urethane foam, silicone foam, silicone sponge, solid silicone, Neoprene sponge, electrically conductive gasket materials, thermal pads to name a few. Adhesives such as 3M’s Low Surface Energy (LSE) adhesives, transfer adhesives, double coated (or supported adhesives), thermally conductive adhesives and electrically conductive adhesives are available.

Stockwell is not limited to applying silicone adhesive to silicone rubber. With several proprietary processes, Stockwell is capable of bonding a wide range of quality adhesives including acrylics and silicones. (Stockwell adhesive offerings)

For more information regarding adhesive backed gaskets, grades of adhesive, peel and stick or adhesive offerings, please contact us at service@stockwell.com or 215-335-3005.

New Stockwell Brochure!

Over the last few months Bill Stockwell has been working on a new brochure that highlights Stockwell Elastomerics core products and service. I thought it would be interesting to show a couple pages from an archive brochure. I’m guessing this brochure is from the 1940 – 1950’s. Think about what may have been involved with that brochure. No digital pictures or computers back then!

It’s remarkable how some things remain the same and others do not. As an example on the inside cover of the 1940ish brochure the slogan reads “What we really SELL is SERVICE” this very much holds true for Stockwell today. The old Stockwell Rubber Company sold everything “rubber” whereas today Stockwell Elastomerics is focused on high performance materials (such as silicone, Poron urethane foam, thermal and electrically conductive rubber), custom manufacturing (waterjet cutting, die cutting, slitting, and molding. Quick reliable service is still at the core of Stockwell's business model.

The New 2008 Stockwell Elastomerics Brochure:

For a copy of our New Brochure or more information on our products and services, please contact us at service@stockwell.com or by phone at 215-335-3005.

Large Custom Gaskets

Every so often we receive inquiries for large custom gasket. In some case they are extreme such as the one shown below. In many cases they are for NEMA enclosures (commonly NEMA 4). A single piece gasket generally offers the best seal, however many gaskets exceed the width of the material. In this case a jointed corner may be an option.

Single Piece - a single piece gasket will offer consistent deflection force around the gasket. The con to a large single piece gasket is the center waste. If engineer are making multiple gaskets they can create an assembly level drawing that show several gaskets nested.

Joint and Bond – when a single piece is required but the gasket dimensions exceed the material dimensions, a jointed and bonded gasket may be an option. In most cases this is a die or water jet cut male/female dove tail that is then UV bonded. This type of gasket needs to be evaluated to see that the extra labor of bonding does not exceed the material savings. Also, for foams and sponges the corners will be firmer than the gasket material.

Joint (no bonding) – similar to the Jointed and Bonded gasket, a male/female dove tail is die or water jet cut. In this case the gasket is provided in 4 pieces and is mated during installation. In some cases a bond is never required. This is most dependant on the enclosure configuration and the level of sealing required.

Materials most commonly used for large custom gaskets are silicone foam and silicone sponge. Since the sealing area is relatively large (i.e. square inches) the soft nature of these materials allow for lower closure forces to get proper deflection for sealing.

For more information please feel free to contact us at service@stockwell.com or 215-335-3005.

Silicone Gasket

Stockwell carries a wide range of materials so that we can meet the demands of most application. Over the years silicone has grown to be our core product. We are seeing more and more engineers specifying silicone products into their design because of its unique properties. Today Stockwell keeps in stock sheet good materials and compounds for custom molded silicone parts.

Key properties:
• High Operating Temperature
• Low Operating Temperature
• UV resistant
• Ozone resistant
• Excellent compression set resistance (rebound)

Silicone offerings include:
• Silicone Foam - that is UL94 V0 rated, excellent for electrical enclosure
• Closed Cell Silicone Sponge - for soft water gaskets such as IP 66, IP 67, and NEMA 4
• Solid Silicone – for water tight seals where higher closure forces are available
• Custom Molded Silicone – standard 20 durometer thru 70 durometer
• Electrically Conductive Silicone – for EMI and ESD gaskets
• Thermally Conductive – for gap pads and press pads for thermal management
• Adhesive Backed Silicone – Stockwell applies pressure sensitive adhesives (acrylic and silicone) to most materials in stock

For more information regarding silicone gaskets or other product offerings, please contact Stockwell at service@stockwell.com or call 215-335-3005.

What is kiss cutting and a kiss cut gasket?

Kiss cutting is a die cutting process where a gasket or pad is supplied rolled up on the adhesive liner. If you were able to watch the cutting process in slow motion you would see the die penetrate the gasket or pad material, then continue through the thin adhesive layer and cut partially into the adhesive liner. The gasket or pad must have a Pressure Sensitive Adhesive (PSA or “peel and stick”) backing for kiss-cutting to be possible.

Kiss cutting has several advantages over individually cut through parts. Kiss-cut gaskets the parts to be rolled up, parts on rolls are easier to handle can and can be set up neatly and dispensed in a paper towel like fashion at assembly work stations. Also, peeling the part off the release liner is considerably easier than removing the release liner from an individual part, this helps increase production throughput.

Stockwell regularly kiss-cuts gaskets and pads from solid silicone, silicone sponge, silicone foam, and Poron. Other materials include foam adhesives such as 3M VHB’s and thermal pads. Note, not all materials and parts can be kiss-cut, for more information please contact service@stockwell.com .