What is the difference between an impulse and fixed-temperature welding machine?

Impulse or "hot bar"? Which type of sealing machine is better suited to your line?

Wondering what the difference is between an impulse and fixed-temperature welder and when to choose each? Below you will find a practical comparison of operating principle, performance, weld quality, cost and typical applications - in the form of quick answers to specific questions.

How does an impulse welder work and how does a fixed-temperature welder work?

• Does the impulse heats only at the moment of welding?

  Yes - the element (wire/resistive tape) heats up with current only for the duration of the welding, after which it quenches and goes into cooling under pressure. This gives it lower power consumption and a shorter warm-up time for operation.

• What does fixed-temperature work involve?

  "Hot bar" or belt welding machine keeps the jaws/belts at a constant, preset temperature. The material passes through a heating zone and then through a cooling zone (often continuously, as the material moves).

Quality and aesthetics of the weld - what makes the difference between these technologies?

• Does impulse produce sufficiently strong but narrower welds?

  Usually yes - ideal for LDPE/PP bags and short lengths. Width and texture depend on heating strip and Teflon, joints are even but less 'decorative'.

• Does fixed-temperature provide a wider and more 'premium' edge?

  Yes - stable 'hot bars' and heating strips produce a wide, aesthetically pleasing weld (smooth or knurled), valued in cosmetics, pharmaceuticals and display packaging.

Materials and thicknesses - which one 'likes' better?

• Does impulse handle PE/PP monomaterials best?

  Yes - it has a wide process window for PE/PP and many laminates with a PE/CPP sealing layer. With very thick laminates it can sometimes be slower.

• Does fixed-temperature better "push through" thicker, multilayer films?

  Often yes - the constant temperature and longer contact make it easier to weld stiffer barrier laminates with high repeatability.

Line performance and tact - which works faster?

• Does impulse reduce the rate through the cooling stage?

  Usually yes - the cycle includes heating, sealing and cooling under pressure. It's great for short runs and variable formats, but less so for ultra-fast lines.

• Does fixed-temperature allow continuous operation at high speed?

  Yes - especially band sealers in HFFS/VFFS systems achieve tens/hundreds of seals per minute.

Energy, commissioning, TCO - what about cost and service?

• Does pulsed use less energy and take off 'instantly'?

  Yes - no constant heating means lower power consumption and virtually zero 'warm-up' time.

• Does fixed-temperature require a stable power supply and have a higher consumption?

  As a rule, yes - it maintains the temperature all the time, but in return it gives a constant process readiness and higher throughput.

• How about service and operation?

  Pulsed: more frequent replacement of PTFE belts and wires, but simple and cheap. Fixed-temperature: control of belts, bearings and temperature calibration, higher cost of parts, longer intervals.

Process safety and tolerance to 'contamination' - who wins?

• Is impulse more forgiving with slight differences in thickness?

  Often yes - the short energy pulse reduces the risk of edge overheating. However, it still requires cleanliness of the overlap.

• Does fixed-temperature give the most even temperature across the width?

  Yes - it's an asset when aesthetics and repeatability are required; when stopping on 'hot' jaws, you have to be careful not to overheat the film.

Example applications - where does what work?

• Where to choose impulse?

  Shipping bags, PE/PP bags, short runs, variable formats, manual/semi-automatic stations, retail packaging on scales/tables.

• Where to bet on fixed-temperature?

  HFFS/VFFS lines in food, cosmetics and pharmaceuticals, doypacks, sticks, pillow-bags, when speed and a 'salon-like' weld are a priority.

Process settings - how to select parameters?

• Are timing and pressure key in impulse?

  Yes - start with film recommendations, increase time/dwell and pressure while keeping the temperature pulse as low as possible; cooling under pressure is critical.

• In fixed-temperature, do you set the temperature and speed first?

  Yes - choose a constant 'hot bar/bar' temperature and then correct the transport speed and clamping force, keeping an eye on stable cooling.

Quick comparison - how to decide?

• Need flexibility in formats and low entry costs?

  Select impulse sealer.

• Does throughput and top weld aesthetics count?

  Select fixed temperature welding machine (hot bar/band sealer).

• Do you have thick or stiff laminates and long runs?

  More often fixed-temperature.

• Do you mainly pack PE/PP on demand?

  Bet on impulse.

FAQ - short answers?

• Is pulsed suitable for continuous operation?

  Yes, but with a lower clock speed; for very fast lines, a fixed-temperature would be better.

• Does the fixed-temperature start faster when switched on?

  No - it needs a warm-up; impulse is ready almost immediately.

• Does the difference in energy affect bills?

  Yes - pulsed tends to use less energy per cycle, but at high volumes the fixed-temperature speed advantage can make up the difference in cost per unit.

Summary

Welder impulse is flexibility, lower energy consumption and excellent compatibility with PE/PP for smaller/alternate batches. Welder fixed-temperature is the speed, repeatability and aesthetic weld desired on continuous lines with laminates and premium packaging. Match the technology to the material, line tact and visual requirements - then the weld will be both strong and cost-effective.