Impulse Sealer

Impulse against constant heat

The alternative is a constant-heat machine, where a bar or a pair of heated blocks is held at temperature all the time. A hot bar sealer and a continuous band sealer both work this way.

Constant heat wins where the material is thick, laminated, or simply stubborn, and wherever the volume means the machine never gets to cool down anyway. Impulse wins on a bench, on thin film, on safety, and on power.

If your pouch seals inconsistently on an impulse machine - closed at one end of the seal and open at the other, or sealed but peeling apart - that is usually the material asking for constant heat rather than a fault in the machine.

Setting one up so it seals properly

Most complaints about impulse sealers are settings rather than machines, and they are worth knowing before you blame the supplier.

• Time too short - the film is warmed but not fused, and the seal peels apart cleanly when pulled.
• Time too long - the film burns through or thins so much that the seal tears at the line, which looks like a strong seal until it fails.
• A worn PTFE strip - film sticks, the seal is ragged, and the operator starts pulling bags off the bar. Replacing the strip fixes more machines than anything else.
• Bag mouth not flat - a wrinkle in the film is a channel, and a bag with a channel in its seal is an open bag.

Which formats are impulse machines

The hand, foot and table top sealers are impulse machines. A continuous band sealer is not, and a hot bar sealer is not. That is why the choice between formats and the choice of heating method are really the same decision made once.

Consumables you should plan for

The element and the PTFE strip are consumed by ordinary use. On a machine that runs every day, keeping one of each on the shelf turns a failure into a five-minute job instead of a lost afternoon. Ask what a machine's element and strip cost before you buy it, not after.

Cutting and sealing in one press

Some impulse machines carry a cutting wire alongside the sealing element, so the same press seals the bag and trims the excess film above the seal in one action.

It sounds like a convenience and on the right bench it is a real one. If you are working from a roll of layflat tubing rather than from pre-made bags - which many hardware, component and garment units do, because it is cheaper per bag and one roll covers several lengths - then sealing and cutting together is the difference between one operation and three.

It is not free. There is a second consumable to keep, the cut edge has to be set so it does not fray, and on a bench that only ever seals pre-made bags it is a part that wears for no benefit.

The question to ask yourself is simply where your bags come from. Pre-made bags, and you do not need it. A roll of tubing, and you probably do - say so at the enquiry rather than discovering it afterwards.