{"id":142,"date":"2020-05-12T14:47:27","date_gmt":"2020-05-12T14:47:27","guid":{"rendered":"http:\/\/www.tthk.ee\/inlearcs\/?page_id=142"},"modified":"2020-09-13T14:39:36","modified_gmt":"2020-09-13T14:39:36","slug":"3-bending-process-execution-in-a-robot-bending-cell","status":"publish","type":"page","link":"https:\/\/www.tthk.ee\/inlearcs\/3-bending-process-execution-in-a-robot-bending-cell\/","title":{"rendered":"4.\tBending process execution in a robot-bending cell"},"content":{"rendered":"

Basic<\/strong><\/p>\n

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The press brake contains an upper tool called the punch and lower tool called the die between which the sheet metal is placed.<\/p>\n

Bending is performed by a press brake machine that can be automatically or manually loaded. Press brakes are available in a variety of different sizes and lengths (20-200 tons) depending on the process requirements.<\/p>\n

Bending is a process whereby a force is applied to sheet metal which causes it to bend at an angle and form the desired shape. Bends can be short or long depending on what the design requires. The sheet is placed between the two and held in place by the backstop. The bend angle is determined by the depth that the punch forces the sheet into the die. This depth is precisely controlled to achieve the required bend.<\/p>\n

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Bend line<\/span><\/strong>\u2013 The straight line on the surface of the sheet, on either side of the bend, that defines he end of the level flange and the start of the bend.<\/span><\/p>\n

Bend radius<\/span><\/strong> \u2013 The distance from the bend axis to the inside surface of the material, between the bend lines.<\/span><\/p>\n

Bend angle<\/span><\/strong> \u2013 The angle of the bend, measured between the bent flange and its original position, or as the included angle between perpendicular lines drawn from the bend lines. Sometimes specified as the inside bend radius. The outside bend radius is equal to the inside bend radius plus the sheet thickness.<\/span><\/p>\n

Neutral axis<\/span><\/strong> \u2013 The location in the sheet that is neither stretched nor compressed, and therefore remains at a constant length.<\/span><\/p>\n

K-factor<\/span><\/strong> \u2013 The location of the neutral axis in the material, calculated as the ratio of the distance of the neutral axis T, to the material thickness t. The K-factor is dependent upon several factors (material, bending operation, bend angle, etc.) and is greater than 0.25, but cannot exceed 0.50. K factor = T\/t<\/span><\/p>\n

Bend allowance<\/span><\/strong> \u2013 The length of the neutral axis between the bend lines or the arc length of the bend. The bend allowance added to the flange lengths is equal to the total flat length.<\/span><\/p>\n

The K-factor is the ratio between the the neutral axis to the thickness of the material.<\/p>\n

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Importance of the K-factor in sheet metal design<\/strong><\/p>\n

The K-factor is used to calculate flat patterns because it is related to how much material is stretched during bending. Therefore it is important to have the value correct in CAD software. The value of the K-factor should range between 0 \u2013 0,5. To be more exact the K-factor can be calculated taking the average of 3 samples from bent parts and plugging the measurements of bend allowance, bend angle, material thickness and inner radius into the following formula:<\/p>\n

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In sheet metal bending, a flat part is bent using a set of punches and dies. The punch and the die are mounted on a press-brake, which controls the relative motion between the punch and tie, and provides the necessary bending pressure.<\/p>\n

Sheet metal bending process consists from the following stages:<\/p>\n