{"id":3793,"date":"2023-03-10T00:00:43","date_gmt":"2023-03-10T00:00:43","guid":{"rendered":"https:\/\/www.swd-technology.com\/?p=3793"},"modified":"2024-10-20T09:46:14","modified_gmt":"2024-10-20T09:46:14","slug":"differences-in-bonding-technology-explained","status":"publish","type":"post","link":"https:\/\/www.swd-technology.com\/en\/differences-in-bonding-technology-explained\/","title":{"rendered":"Differences in bonding technology explained"},"content":{"rendered":"
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The technologies for bonding electrical sheet are different and have a major impact on the stator and rotor stacks.<\/strong><\/p>\n<\/div>\t<\/div>\n<\/div>\n<\/div><\/div>

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Every manufacturer of bonded lamination stacks has developed their own technologies and processes for bonding electrical sheet coated with bonding varnish (Backlack)<\/a>. At its core, bonding varnish (Backlack)<\/a> is an epoxy resin that is mixed with hardener before coating so that it chemically hardens under pressure, temperature, and time. This ensures high-strength bonding of the electrical sheet over the entire surface. The manufacturers of the bonding varnish (Backlack)<\/a> specify a processing window that indicates the duration of the application as a function of the temperature. The higher the temperature, the shorter the curing time of the bonding varnish (Backlack)<\/a>. Sufficient pressure is required to ensure that the bonding varnish (Backlack) layers flow together evenly.<\/p>\n<\/div>\t<\/div>\n<\/div>\n\n\t\n\t

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Batch oven<\/h2>\n

The most well-known and widespread technology is bonding in the oven. Electrical sheets are stacked and placed under (bonding) pressure in bonding tools with springs. The bonding tools with the electrical sheets are then bonded in the oven at 200 \u00b0C for 2 hours and cooled down to room temperature for approx. 30 minutes. The springs are now released and the bonded stator and rotor stacks are removed. This process is reproducible and established. However, the process is not suitable for series manufacturing, as the cycle times are around 3 hours<\/strong> and even longer for large tools.<\/p>\n<\/div>\t<\/div>\n<\/div>\n\n\t\n\t

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Further development: the continuous furnace<\/h2>\n

The continuous furnace is the further development of the aforementioned batch furnace. The tools are identical. The continuous furnace consists of a furnace section and a cooling section. The tools are moved through the furnace on conveyor elements. High air velocities and special nozzles speed up heating, which reduces cycle times. However, due to the faster heat input, the electrical sheets heat up faster on the outside than on the inside, which leads to an asymmetrical temperature distribution in the stator and rotor stacks. As a result, the bond is not always identical, and even warping can occur in the component. This can have a very negative effect on flatness, for example. In addition, the effect of the temperature difference outside to inside is further intensified by the geometry (e.g. a rotor assembly with magnetic pockets, where the magnetic pockets represent heat barriers). Although the process enables shorter cycle times (approx. 1.5 hours), good quality can only be achieved by optimizing the process and the furnace to the existing geometry<\/strong>.<\/p>\n<\/div>\t<\/div>\n<\/div>\n

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Interested?<\/h2>

Then contact us without obligation. We look forward to talking to you.<\/p>\n<\/div>Start inquiry<\/a><\/div><\/div>\n\n<\/div>\n\n\t\n\t

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Bonding in the tool<\/h2>\n

Another technology is bonding directly in the punching die. A heating unit is installed directly under the punching die. After punching, the laminations are guided through this heating unit, heat up, and are subjected to counterpressure. After a certain number of laminations, either a release layer is bonded on or the pile is ejected to create individual, separate stacks.<\/p>\n

This leads to several conflicting objectives:<\/p>\n