Method for manufacturing a composite work piece for a drug delivery device and composite work piece for a drug delivery device

A method for manufacturing a composite work piece for a drug delivery device, comprising the steps:

• A) providing a first work piece part and a second work piece part,
• B) arranging both work piece parts with respect to each other in such a way that both work piece parts are in mechanical contact with one another in a contact area,
• C) irradiating a surface of the first work piece part with electromagnetic radiation, thereby softening the first work piece part and/or the second work piece part in a region adjacent to the contact area, wherein a surface of the first work piece part is irradiated which is on that side of the first work piece part remote from the second work piece part, and
• D) joining the first work piece part to the second work piece part in the contact area for the composite work piece,
• wherein for the first work piece part a part is used which is impervious for the electromagnetic radiation of step C) and absorbs the electromagnetic radiation of step C) to an extent sufficient for softening the first work piece part and/or the second work piece part.

A drug delivery device comprising:

• a composite work piece, wherein the composite work piece comprises:
• a first work piece part, wherein the first work piece part is impervious to an electromagnetic radiation,
• a second work piece part,
• wherein the first work piece part comprises a semi-tubular shaped spring comprising a first and a second slot contact area,
• and the second work piece part comprises a semi-tubular shaped spring comprising a first and second wing,
• wherein the first work piece part and the second work piece part are in mechanical contact with one another in a contact area by an elastic force that is exerted by one of the work piece parts on the other one of the work piece parts by way of an elastic deformation,
• such that the first and second wings of the second work piece part are pressed on the first and second slot contact areas of the first work piece part, respectively, by the elastic force,
• wherein the contact area comprises a weld, which permanently connects the first work piece part to the second work piece part,
• and wherein the contact area comprises an unwelded sub-area adjacent to the weld,
• wherein in the unwelded sub-area the first and the second part are under elastic residual stress,
• wherein a residual elastic restoring force is exerted by one of the work piece parts onto the other one of the work piece parts on account of a residual elastic deformation of one of the work piece parts.