elna sewing machine gear driving grip wheel

thingiverse

Older type Elna sewing machines drive the grip wheel (the sharp pointed wheel that takes up the upper thread and winds it around the lower thread) with a continuously rotating rod fitted with a plastic gear wheel. At Gered Gereedschap in Groningen, the Netherlands (saved tools , a charity refurbishing tools and sewing machines for projects in developing countries) we see often machines that are almost beyond repair because plastic gears are broken. Replacements are hard to get and expensive. The cause is generally that a sewing machine gets stuck because of a loose thread blocking movement of the grip wheel. 3D printed replacement wheels are a good solutions, especially because the forces acting on the gears are perpendicular to the Z axis. In this direction the strength of the extruded plastic is optimal. I use PETG for these wheels. In SCAD these wheels are quite easy to define because gear wheels are easy to describe mathematically and powerful commands such as linear extrusion with a twist generate gear wheels with very little coding.