Every minute, 90 parts fall from the fineblanking press onto the conveyor belt with the triple-feed follow-on tool. Each of the steel parts, which are 70 millimetres round in diameter and six millimetres thick, has a precise smooth cut, as is usual in fineblanking. Nevertheless, there are still burrs that need to be removed. This means that they cannot yet be passed on to the customer, who then produces the final contour in a high-pressure forming process. Later, they will be important parts of the seat adjuster, as found in every car.

Burrs also occur despite smooth cutting

First the burrs have to be removed, then the parts have to be washed, dried and demagnetized before they are packed in boxes ready for shipping. They also have to be checked. A scale decides whether they are OK or not. The round part should weigh 150 grams; quality management tolerates a deviation of one percent. All processes run quickly and reliably in a connected production line. No process may be slower than the one with the greatest added value - i.e. fineblanking. The line must be synchronized with all processes.

The DA300P brush deburring machine deburrs parts quickly and reliably and ensures high surface quality. © Surfinsys

In the past, the parts were moved around more than they were processed. After each process, they were loaded into boxes, driven away, temporarily stored, retrieved, driven to the next process, and so on. Line production eliminates unproductive times. The core process of the subsequent processes is deburring. Here, Schiess has opted for the latest DAP machine generation from the Swiss company Surfinsys. It removes burrs that occur during punching, sintering or fine blanking.

The six millimeter thick raw material is fed from the coil via a straightening machine into the fineblanking press and thus into the line. A Surfinsys DA300P is integrated directly after the fineblanking process. It works with two units, each with five integrated abrasive brushes with a diameter of 150 millimeters. The planetary brushes are driven directly via the central unit using gear wheels. This means that no additional gearbox is required. The brushes are simply mounted on short shafts and can be changed in seconds thanks to the quick-change mechanism. This allows primary and secondary burrs to be removed with high power density.

Remove primary and secondary burrs

The orbital movement of the central unit and the additional planetary rotation of the five brushes produce optimum sanding results on belts up to 340 millimetres wide. The double rotary movement removes the burrs that occur during the pre-process. The process has an advantage over the widely used vibratory grinding process because the deburring process is more defined. It ensures even rounding of round or pointed contours, pockets and chucks as well as the smallest bores. While the removal rate of mass finishing stones is reduced by around ten percent in a very short time and then decreases continuously by a further 20 percent over the next one hundred hours, with brush deburring it increases slightly but continuously over the course of the tool life. In addition, the deburring tools work so thoroughly that even massive burr roots, chipping and embossed burrs are removed and evenly rounded edges are created.

Another important advantage is particularly evident with small bores. If bores can be narrowed during mass finishing because either material is driven into them or the burr is only bent over instead of being cut, the brushes remove burrs reliably, reliably and with repeat accuracy. This also applies to parts weighing more than 100 grams, which can be damaged during vibratory finishing if the filling is not reduced. However, process reliability is more decisive. Measurements have shown that the deviations in geometric accuracy with the DA300P are within a small range compared to a significantly larger range with mass finishing.

Defined parts transport

Parts can be transported along the line in a more defined manner via the deburring machine. The workpieces can be guided on the belt in such a way that after deburring on one side, they can be fed through the DA300P again using cleverly designed reverse loops and thus also deburred on the other side. They are held magnetically. But even if the workpieces were made of stainless steel or non-ferrous metals, they could be guided in guide rails or pockets. A combination with magnetic force is also possible. Even impact-sensitive parts can be guided and turned safely and without damage and thus deburred on both sides.

Once the workpieces have been deburred on both sides, it's time for cleaning. At a pressure of 60 bar, the water jet removes any oil and dirt that has been carried over and prepares the parts for the final work steps. Now it's time to dry, weigh and check the quality, and off they go into the shipping boxes. pb