September 2016

Custom Gasket Cutting

At Hennig we provide custom gasket cutting services. If the material is in stock we can usually get a new gasket shipped out the day it was ordered.

The key to this rapid turnaround is cutting process flexibility. With flash, die and water jet cutting equipment on-site we’re able to select the fastest and most cost-effective process for your order. Whether you need one gasket or one thousand, prototype or production runs, we have a process that works.

Accuracy and appearance are important considerations too. A gasket that fits poorly or has rough, uneven edges leaves a negative impression of the equipment it’s installed on, and probably won’t last as long. Our cutting processes provide a range of finishes to suit your needs.

Flash Cutting Services

Flash cutting uses a  gantry machine that moves an oscillating knife over sheet material up to 60” x120”. The knife cuts straight edges or curves in material up to 1/2” thick, leaving smooth vertical edges. Knife motion is computer-controlled with the cutting path programmed directly from a CAD file, and nesting software maximizes material utilization.

Die Cutting Services

A die cutter uses a metal blade shaped to the profile of the gasket and embedded into a wood block or panel. With die cutting it’s possible to cut to a precise depth, which is useful when you don’t want to separate individual pieces from the sheet. Technically described as “kiss-cutting,” this allows gaskets to be kept together on a sheet or roll and peeled off as needed. It’s a good method for producing gasket kits.

Unless a die already exists, die cutting will incur a tooling charge along with some lead time. However, it is a fast and repeatable process, which makes it economical for quantity orders. We can die cut gaskets as large as 36” x 72” from sheet material. Cut edges are smooth although thicker material may show a small degree of curvature.

Water Jet Cutting Services

Also a gantry-style machine, water jet cutting cuts with a jet of fast-moving water just 0.010” wide. The thin jet means minimal material waste, and tolerances as tight as +/-0.007” can be maintained. Depending on the material, it’s possible to cut up to 6” thicknesses and the largest size we can produce is 72” x 96”.

Like flash cutting, a water jet is programmed directly from a CAD file of the gasket required. One strength of water jet is that there’s no material deformation during the cut, which improves edge appearance.

Ask about custom gaskets

Many sealing applications need a custom gasket. At Hennig we have a range of equipment for cutting sheet gasket material and this lets us provide a rapid turnaround. Many custom gaskets ship the day they were ordered.

Why Use PTFE Seals in Food Industry Applications?

Commercial cooking kettles used for boiling and preparing foods usually have a food grade gasket around the lid. By creating a good seal this helps the vessel build and retain pressure. This raises the boiling point of water, shortening cooking time while also destroying pathogens. A defective gasket can result in food not reaching the required temperature, potentially creating a health hazard. Additionally, the gasket itself can provide places for bacteria to become established.

This gasket leads a hard life. Not only must it withstand the heat and pressure of cooking, but it’s also expected to go through multiple cleaning cycles. In addition, it’s essential that it not transfer anything or impart any taint to the food being cooked. Several materials are available for such gaskets, but in many situations the best sealing option is PTFE.

A Versatile Sealing Material

Polytetrafluoroethylene, or PTFE, better known by it’s DuPont tradename of Teflon, has a number of properties that make it an excellent choice for a food grade gasket. At the atomic level it consists of a long chain of carbon atoms, each one of which links to two fluorine atoms. This linkage is so strong that PTFE won’t bond to anything else, hence its non-stick properties.

PTFE doesn’t melt until 635°F and is usable at temperatures up to 260°F. At lower temperatures it remains flexible well below freezing, as low as -100°F or even lower, depending on formulation. It’s also a good electrical insulator. Of particular relevance for food industry gasket applications, it doesn’t absorb water and it’s biologically inert. It does however resist attack by almost all chemicals, including aggressive cleaning and disinfecting agents like chlorine dioxide.

PTFE Seal Alternatives

Other materials have properties that are close or superior to PTFE in some regards. Silicone for example is flexible at low temperature, has good compressibility and a higher upper temperature limit. However, silicone does not fare well with steam, which is found in many food preparation environments. It also lacks resistance to acids, alkalies and chlorinated solvents, so is limited in its potential as a food grade gasket.

FDA Approved Seal Material

Gaskets & Seals made entirely of PTFE are covered by 21 CFR 177.1550, meaning they have FDA approval for food industry use. (PTFE incorporating filler material may not meet FDA requirements.) At Hennig we can supply PTFE sealss in thicknesses ranging from 0.015″ to 0.50″. Call or email for further information.