Extruders: output capacity, sizes and what kg/h means

What the data sheet actually tells you

An extruder is usually specified by its maximum welding rate in kg of melted rod per hour, the rod diameters it runs, and the sheet thicknesses and seam widths it is designed for. These three figures are interconnected: a larger extruder provides a higher output rate, but also requires more heat, more air and more power.

The rate is specified for PP and varies with material, rod diameter and temperature. Consider it a figure for comparison between models, not a guarantee of how many metres of seam you will weld per hour – this depends on the substrate, accessibility and the operator.

In practice, preheating is more important. An extruder with integrated hot air preheats the pipe or sheet immediately ahead of the shoe, ensuring the melt bonds to a warm substrate. Without sufficient preheating, you get a seam that looks neat, but pulls apart.

Size classes and typical data

The table summarises typical levels for hand extruders with integrated hot air. The weight includes cable and hose – i.e. the weight you hold in your hand all day.

How to select the extruder

For repairs, small fillet welds and thin sheets, a small extruder using 3 and 4 mm rod is quick to handle and easy to manoeuvre in confined spaces. For thick-walled pipes, large tanks and long seams, a larger machine is required to supply enough melt to maintain a consistent speed throughout the seam.

Select based on the thickest joint you realistically will be making – and on how long you need to weld at a time. A large extruder is heavy to guide, and in a confined workspace, the small one can produce a better seam because you can hold it steady.

The rod diameter must match the welding shoe and feed mechanism: 4 and 5 mm rod requires a shoe that can feed it, and a preheating nozzle that covers the width of the seam. If you need to switch between 3 and 4 mm, check that both feed roller and shoe match.

Materials and temperature

Standard materials are PP, PE and PVDF, with other materials requiring manufacturer approval. Melt and air temperatures are controlled separately, and it is precisely this combination that determines weld quality: excessively low air temperature results in a cold seam, while excessively high melt temperature degrades the polymer, causing bubbles and odour.

Hot machine parts can reach up to approx. 350 °C. Never set the extruder down on the pipe or substrate while hot, and use the included stand or holder. Allow the machine to cool down with air supply running before packing it away.

Cold-start protection and start-up timers are available on several models: they ensure that the melt and preheating air have reached temperature before the rod is fed. This feature is worth insisting on if the machine will be operated by different workers.

Power on site

A hand extruder typically draws 2-3,6 kW, with hot air accounting for the largest share. When running on a generator, the generator must be sized to at least four times the rated power of the extruder – here, a mobile power bank with a stable sine wave voltage is a quiet alternative, see power on site. A 3 kW machine therefore requires an approx. 12 kW generator to run stably through an entire seam.

Extension cable at 230 V: up to approx. 19 m requires at least 2,5 mm², and 20-40 m requires 4,0 mm². Longer cables cause voltage drops, causing the temperature to fall halfway through the seam. See also power on site.

If the machine is to be used outdoors, ensure a welding tent or shelter is used, and keep plugs and connections dry. Rain falling on the seam results in uneven preheating and reduces quality.

Maintenance and calibration

Clean the melt channel and welding shoe after use while the machine is manageable, and check the heating element and air flow regularly. A clogged nozzle results in a lower output rate and uneven melt, which often first appears as a seam lifting on one side.

Have the extruder calibrated alongside the rest of your equipment so that temperature readings can be documented. See service and maintenance for the standard routine. Execution and inspection of the seam itself are described in extrusion welding in practice.

Vedligehold af varmluftværktøj

Rengør smeltekanalen efter brug, kontroller varmelementer og luftmængde (air flow) regelmæssigt, og lad maskinen kalibreres en gang om året. En kalibreret maskine dokumenteres også bedre over for bygherren.

Vedligehold og kalibrering

Rengør smeltekanal og dyse efter brug, mens maskinen er håndterbar, og kontrollér varmeelement og luftmængde regelmæssigt. En tilstoppet dyse giver lavere rate og ujævn smelte, og det ses ofte først som en søm, der slipper i den ene side.

Lad ekstruderen kalibrere sammen med resten af udstyret, så temperaturvisningen kan dokumenteres. Se service and maintenance for den faste rutine. Selve udførelsen og kontrollen af sømmen er beskrevet i extrusion welding in practice.