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Mittwoch, 28. August 2013

Quality defects of copied sewing machine parts

Using the example of a sewing foot for topstitching of closing seams

Copied wear and tear parts for industrial sewing machines often show severe quality deficits and lead to bad sewing results. We want to show such problems using the example of a presser foot:

1. Bad fastening elements lead to wrong foot position

At the copied part, the fastening screw pushes on the left side of the foot bar (see picture 1). When tightening the screw, a flat area on the foot bar will evolve from this. If the first foot was positioned incorrectly, this cannot be corrected anymore. The next foot will slide into the wrong position also which results in a continuously bad seam quality. It may be necessary to change the foot bar, which leads to additional cost.
The fastening element of the original presser foot encloses the foot bar completely so that the round shape of the foot bar will persist. Thus, the presser foot position can be easily and correctly adjusted at any time.
Picture 1: Copied versus original sewing machine spare part

2. Bad seam center guide damages the material

The seam center guide protrudes a lot to the bottom at the copied part (see picture 2). Since the pressure of the guide is high, the sewing material (e.g. leather) or the seam below the guide is often damaged.
At the genuine part, the guide protrudes only a little with an appropriate pressure to avoid this.

Picture 2: Copied versus genuine industrial sewing machine spare part

3. Side tolerance of the guide is too high

The seam center guide of the copied part is not only very long, but has a big side tolerance (see following video). The material cannot be guided straightforward. The seams will not be parallel to the center, resulting in a bad seam appearance.

The guide of the original part has no tolerance to ensure best seam quality (see following video).

4. Missing finger guard

The copied part has no finger guard resulting in dangerous operation.(see picture 3).

Abb. 3: Danger by missing finger guard at copied part compared to Dürkopp Adler foot with finger guard

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