Requirements of the domestic industry on washing machine and dryer drums
- High product quality
- Low material costs
- Clean and smooth seam surface
- No cracks in the material due expanding
The washing drum is a key element of the washing machine, and is surrounded by a detergent container. Although washing machines generally use the same design principle, the materials used here may vary.
The detergent container is often made of plastic, although some manufacturers prefer stainless steel detergent containers.
Drums are designed using a perforated, honeycomb or corrugated texture that helps optimise the interactions between water, detergent, run time and washing effectiveness. The metal sheets used to build the drum, with perforations and openings punched from the inside to the outside, are not flat.
Metal sheets are butt-welded into a cylinder using laser welding, and the final drum shape is then created through expanding and attaching the front base and bottom disc.
Both sides of the sheet metal edges must be trimmed before the laser welding process to ensure a secure welded seam connection (l-seam).
The revolutions of the washing drum play a key role. In the past, some spin cycles used a speed of 1800 revolutions per minute; today, most washing machines run at 1600 revolutions per minute. Although approx. 5 kg of laundry was used in the past as the standard for sizing washing drums, today 8 to 9 kg is the standard. Machines with a 10 kg capacity are already being produced today (2019).
Larger fill quantities per wash place the materials under a heavier load, and the unbalanced forces created during spin cycles are enormous. Although the metal plates used to build drums used to be connected with a folded joint, in some cases this joint would come undone during the spin cycle.
Later, resistance welding was used to create a more solid connection that could stand up to higher spin cycle speeds.
Today, laser welding has become the established choice for applications involving > 1400 revolutions per minute.
The sheets cut using a cross-cutting shear or laser are fed into a bending station, shaped into a tube, and then pushed into the welding station. There, the tube is butt-welded using a laser (l-seam). The weld seam quality is checked by an optical sensor. Only properly welded tubes are fed into drum production by a transport system.
When a laser welding source is used, the butt-welded sheets inside the washing drum have no weld spatter (the seam root is on the outside of the drum) and pass the so-called “nylon stocking test”. The weld seam itself is “blank,” almost invisible, and stands up to the subsequent expanding process.
Only a very small amount of heat enters the material during laser welding. This results in visually perfect welded components that are free of warpage and stand up to high mechanical loads.
Typically, reworking such welded seams is unnecessary.
Advantages of laser welding technology
- Small amount of heat enters the material, creating almost no component warpage
- Small heat-affected zone
- Slim welded seams
- Aesthetic, high-quality, “blank” welded seams
As part of a drum manufacturing line, weil technology concentrates on the intermediate product of washing machine or dryer drums: forming the cylinder with textured surface and laser welding it in cycles.
We offer a variety of fully and semi-automatic solution concepts for manufacturing drums.
In all of these solutions, welding guarantees the following properties for the drum interior
- a high surface quality ("smooth seam surface") and no need to cover the welded seam.
- Laser butt welding provides perfect seam strength from the start of the seam to the end, resulting in no seam cracks during expanding.
- Multiple modules for trimming, transportation, molding and welding allow for a wide variety of production options.