Context
A client asked me to design a key and its packaging in 3D. The brief set the steel blade, carried over from an existing profile, and the requirement that everything fit inside a presentation box together with the cylinder, three keys, the ring and its fixing screw. The head itself was still open. The client wanted a shape of his own, recognisable on a shelf, and still producible in series. That drawing never comes out right on the first try, it is built through back and forth, and every round had to fit the announced deadline.
Approach / Solution
I modelled in Autodesk Inventor with one simple rule I picked up from my teacher M. J. Fritsch, never leave a sketch under-constrained. Every dimension is driven by a constraint or a parameter, so reworking the head after a review means changing a value instead of rebuilding the part. Five versions followed one another that way, each one born from client feedback, until a head he liked and the workshop could produce. None of them required starting over. The packaging is a machined foam block, 120 mm long and 25 mm thick. A 9 mm pocket holds the key and the ring, a second one at 17.4 mm holds the cylinder, whose seat is 93 mm long. Four shims (three of 10 mm, one of 20 mm) adapt that seat to the length of the cylinder supplied, which avoids a new mould for every reference. The head pocket reuses the radii of the part itself, R5, R14 and R15, so the key sits with no visible gap. The cylinder uses the European profile covered by EN 1303, so the same foam takes any reference on the market as long as the length stays within the range of the shims. Drawings go out dimensioned to ISO 129-1, with ISO 2768 general tolerances and a standard title block, and the fastener is off the shelf, an ISO 10642 M5x50 for the fixing. A manufacturer can quote and start without calling me back. For each version I printed the head in 3D to check the dimensions by hand, the fit on the blade and the clearance for the ring, before sending anything out. The client always received the same package, the STEP for the design office, the DWG and the dimensioned PDF for the workshop, the STL to reprint on their side.
Results
The project went to the manufacturer with the dimensioned drawings of the assembly and the material notes, an overmoulded head on the steel blade and the packaging foam. Five iterations to converge on a head that is both distinctive and producible, no model rebuilt from scratch, and every delivery on time. What I keep from it is a working method more than a part. Fully constraining a sketch costs ten minutes up front and saves hours by the third revision. I also learned to hand over a package a client can open without me, and to discuss tolerances and materials with the people who actually make the thing.