Frequently Asked Questions

Impulse or Constant Heat
An impulse sealer is usually used for a single web type material such as polythene (polyethylene) where the material is melted to seal it but has to be left to cool down and set before the jaws of the machine are opened.
Hence the use of the word impulse which means there is a brief impulse of heat sufficient to melt the product followed by a cool period to allow the material to set before the jaws open again. When the machine is not performing a seal the jaws are cold and no energy is being used.
A constant heat sealer is used when sealing laminate type materials or pouches where the outer layer melts at a much higher temperature than the inner one, this allows the jaws of the machine to be set constantly at the correct temperature to seal the inner layers together.
These sort of jaws can be fitted to bar sealers with accurate temperature controls or in rotary sealers where the material in transported through the machine using motorised guide belts.
Generally constant heat type sealing is a quicker method than impulse, but of course it cannot be used on polythenes.
Pneumatically Operated or Solenoid Operated Sealer

In both cases the jaws of the machine will close and automatically create a dependable seal by simply pressing a footswitch meaning there is no effort required by the operator and therefore no possibility of fatigue or repetitive strain issues.
Pneumatically Operated Machines.
These machines will obviously require compressed air for their operation which could be from either an existing compressed air system on site or if not available could be operated using a small stand alone portable compressor which are available which are now acceptably quiet in use.
Air (pneumatically) operated machines use an air cylinder to bring the jaws together and with accurate timers they are held together for the required time to create a perfect seal each time.
Air operation can be used on both Impulse Sealers and Constant Heat Sealers and one of its great benefits is the control of the speed that the jaws come together which adds to the repetitive quality of the seals and the life of the sealer.
When Impulse sealers are operated by air there is a low pressure system to bring the jaws together making it completely safe for the operator.
Solenoid Operated Machines
Sometimes it is not possible to provide an air supply or it maybe not allowed in some medical of food related applications.
These machines use electromagnetic solenoids to close the sealing jaws together meaning there is no requirement for compressed air.
After pressing the footswitch the jaws will close and accurate timer processors will ensure a perfect seal each time. Safety features are built into the processor to ensure that the machine is both safe for the operator and dependable in its operation.
It should be noted that only impulse type machines can be solenoid operated.


Bar Sealer or Rotary Sealer

Bar sealers

This term generally refers to machines fitted with a pair of flat jaws, of varying lengths where the user will bring the bag or material to the sealer, place it between the sealing jaws and bring the jaws together to effect the seal.
Bar sealers can be impulse or Constant heat, and also can be manually operated, air operated and solenoid operated. They range from quite small inexpensive table top hand operated machines similar to a stapler is size through to floor mounted semi automatic machines and on to long beam type sealer which can seal up to three metres.
There is a large range of types of bar sealer available as standard and of course, special purpose machines designed to a customer’s specific requirements can also be supplied.
Rotary Sealers
This term is used to refer to machines which are motorised and usually run continuously allowing the operator to feed the material or bags/pouches constantly.
This type of machine is generally used for higher production rates around the 10metres per minute and faster in some cases.
There are versions available for sealing polythene type materials and laminate materials, but it is important to specify this when enquiring.
Depending on the size and weight of the product being sealed it is sometimes necessary to have a speed matched conveyor running underneath the sealer to support the product as it travels through the machine to keep the seal even and presentable.
These machines are available in a variety of sizes and throughput speeds to suit most applications from small pouches and packets up to large multi-walled sacks.
Repair of machines
If your machine stops working or is not sealing as well as previous then obviously it may be time for maintenance.
Astrapac can supply most parts for their own manufactured units and also supply a great many parts for other makes of machines, and a phone call will give you advice where possible on diagnosing the problem and help in how to repair the device yourself.
If the problem is beyond your capabilities then Astrapac have a repair department who can give an estimate of cost if necessary and repair the machine to full working order, just arrange to get the machine back to us and we will do the rest.
If the machine cannot be sent back for any reason then Astrapac can arrange to send an engineer to your site to effect the repair, this would obviously incur travelling costs on top of the actual repair.