There are essentially two processes: - Impulse Heat and Constant Heat.
Impulse Heat Sealers
Impulse heat is typically used to weld like-for-like thermo-plastic films (usually, but not always polythene.)
Standard impulse sealers weld up to 1000 Gauge (250 micron) polythene film without difficulty. Special purpose double- element machines are available for repetitive sealing of heavier gauge and gusseted polythene. Other thermo-plastic materials such as nylon laminates, polypropylene, polyurethane and some PVC's are sealable but should be tested first. We will happily test samples for you prior to the purchase of any heat sealer.
Impulse heat sealers use low voltage element wires that heat up rapidly to a temperature that welds in seconds. The element then cools, allowing the seal to set under pressure.This makes this type of sealer very ecconomical to run as the power is only used during the sealing cycle.
All Hulme Martin impulse sealers are fitted with electronic timers to accurately control the welding period. Our Duo models are fitted with a higher specification timer that also indicates the cooling period, helping to control the quality and consistency of seals. The welding and cooling periods are independently adjusted to suit the type and thickness of material being used.
Cutters are available on many models to trim surplus material or to make bags from lay-flat polythene tubing. Modified wide seal elements and cut-and-seal elements can be specified on selected machines.
Constant Heat Sealers
This process is normally used to seal laminated materials made from layers of thermo-plastic film having different properties and melting points, such as foils, coated papers, cellophane and polypropylene laminates.
Constant heat sealers use temperature controllers to maintain the element bar at as stable and precise temperature. This seals the inner layer (or coating) without distortion of the backing material. To avoid de-lamination the seal is 14mm wide and crimped for added strength.
There are basically two types of vacuum sealers - chamber vacuum sealers, to vacuum seal smaller products and Probe vacuum sealers for larger products which require vacuum sealing.
Chamber Vacuum sealers are simple to use and offer very consistant results. They all offer digital controls and have stainless steel chambers so are commonly used to vacuum seal food, engineering products and electronic products. Chamber vacuum sealers can be used to vacuum seal some liquids.
Probe vacuum sealers are more versitile and can seal most solid products. Probe vacuum sealers can be manufactured with jaws which allow the product to be sealed in the upright position so are idea for larger sacks, or with support trays for larger products. Product holders can be made which enable the vacuum sealing of composte and larger sacks to form a "brick shape" if required. Probe vacuum sealers can not be used for liquids and powders.